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Crabtree KN, Westerfield JH, Dim CA, Meyer KS, Johansen SL, Buchanan ZS, Stucky PA. Rotational spectroscopy of methyl tert-butyl ether with a new Ka band chirped-pulse Fourier transform microwave spectrometer. Phys Chem Chem Phys 2024; 26:13694-13709. [PMID: 38666410 DOI: 10.1039/d4cp00797b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2024]
Abstract
Chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is a powerful tool for performing broadband gas-phase rotational spectroscopy, and its applications include discovery of new molecules, complex mixture analysis, and exploration of fundamental molecular physics. Here we report the development of a new Ka band (26.5-40 GHz) CP-FTMW spectrometer that is equipped with a pulsed supersonic expansion source and a heated reservoir for low-volatility samples. The spectrometer is built around a 150 W traveling wave tube amplifier and has an instantaneous bandwidth that covers the entire Ka band spectral range. To test the performance of the spectrometer, the rotational spectrum of methyl tert-butyl ether (MTBE), a former gasoline additive and environmental pollutant, has been measured for the first time in this spectral range. Over 1000 spectroscopic transitions have been measured and assigned to the vibrational ground state and a newly-identified torsionally excited state; all transitions were fit using the XIAM program to a root-mean-square deviation of 22 kHz. The spectrum displays internal rotation splitting, nominally forbidden transitions, and an intriguing axis-switching effect between the ground and torsionally excited state that is a consequence of MTBE's extreme near-prolate nature. Finally, the sensitivity of the spectrometer enabled detection of all singly-substituted 13C and 18O isotopologues in natural abundance. This set of isotopic spectra allowed for a partial r0 structure involving the heavy atoms to be derived, resolving a structural discrepancy in the literature between previous microwave and electron diffraction measurements.
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Affiliation(s)
- Kyle N Crabtree
- Department of Chemistry, University of California, Davis, Davis, CA, USA.
| | - J H Westerfield
- Department of Chemistry, University of California, Davis, Davis, CA, USA.
| | - Chisom A Dim
- Department of Chemistry, University of California, Davis, Davis, CA, USA.
| | - Kelly S Meyer
- Department of Chemistry, University of California, Davis, Davis, CA, USA.
| | - Sommer L Johansen
- Department of Chemistry, University of California, Davis, Davis, CA, USA.
| | - Zachary S Buchanan
- Department of Chemistry, University of California, Davis, Davis, CA, USA.
| | - Paul A Stucky
- Department of Chemistry, University of California, Davis, Davis, CA, USA.
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2
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Triumph Z, Vyas S. Chemical bonding in potential PFAS products from the thermal degradation of energetic devices, a DFT analysis. CHEMOSPHERE 2023; 345:140363. [PMID: 37802475 DOI: 10.1016/j.chemosphere.2023.140363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 10/02/2023] [Accepted: 10/03/2023] [Indexed: 10/10/2023]
Abstract
This work investigates stability and chemical bonding in possible per- and polyfluoroalkyl substances (PFAS) generated through the disposal of munitions in controlled detonations and open burns. Density functional theory (DFT) calculations were used to determine bond dissociation enthalpies (BDEs), activation energies, and other chemical properties. Calculated parameters were used to determine the functional groups most likely to be present based on the level of fluorination and the position of fluorines. In compounds that form C-O bonds, the presence of α-fluorines significantly strengthens the C-O bond by ∼4-18 kcal/mol. The results of this study indicate that fluoroalkyl alcohols are a very likely product of the disposal of munitions. This work was designed to expedite the analytical process of confirming that PFAS are created from current disposal methods of energetic devices by providing insight as to of what types of compounds should be expected. The PFAS generated in such reactions are expected to contain some functional groups (i.e., nitro and nitrite) that have not been known to exist as a result of the environmental degradation of industrially relevant PFAS, therefore, they may have been overlooked before. These initial results imply that PFAS with nitro functionalities may be formed in these conditions considering the abundance of NO2 radicals expected to be present as well as the strength of the C-N bond that can form (∼40-50 kcal/mol) whereas with nitroso functionalities are not expected to be found since the bonds formed are much weaker (∼25-35 kcal/mol), and nitrosoalkanes are known to decompose under mild conditions. Although these results are promising, analytical work is needed to assess the conclusions of this study in real systems.
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Affiliation(s)
- Zachary Triumph
- Department of Chemistry, Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA
| | - Shubham Vyas
- Department of Chemistry, Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA.
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3
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Liu R, Zhang Z, Yan L, Yang X, Zhu Y, Su P, Song H, Wang Z. The Influence of Hydrogen Bonds on the Roaming Reaction. J Phys Chem Lett 2023; 14:9351-9356. [PMID: 37820388 DOI: 10.1021/acs.jpclett.3c02133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Roaming bypasses the conventional transition state and is a significant reaction pathway due to the unusual energy distributions of its products; however, its reaction pathway under external environmental interactions remains unclear. Herein, we report for the first time the roaming process of nitrobenzene, which is influenced by the hydrogen bonds (H-bonds) between nitro- and phenyl radicals and water molecules in the gas phase. Notably, despite the fact that the single water structure produces a higher but narrower barrier, whereas the double water structure leads to a lower but wider barrier, the roaming reaction still occurs. The underlying mechanism responsible for these influences of H-bonds is ascribed to the dramatically changed polarization and correlation interactions between the roaming radicals. The reaction rates and thermal perturbation probabilities are also remarkably influenced due to the presence of the H-bonds, by approximately 2 orders of magnitude. It is anticipated that this work will encourage the promising feasibility of introducing environmental molecules to modulate the roaming reaction.
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Affiliation(s)
- Rui Liu
- Key Laboratory of Material Simulation Methods & Software of Ministry of Education, College of Physics, Jilin University, Changchun 130012, China
| | - Zhiyuan Zhang
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Longxiang Yan
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Xinrui Yang
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
| | - Yu Zhu
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
- College of Physics and Electronic Engineering, Hainan Normal University, Haikou 571158, China
| | - Peifeng Su
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Huajie Song
- Beijing Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
| | - Zhigang Wang
- Key Laboratory of Material Simulation Methods & Software of Ministry of Education, College of Physics, Jilin University, Changchun 130012, China
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
- Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130023, China
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4
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Senanayake PS, Syrlybaeva RR, Talipov MR. Unusual In-plane Aromaticity Facilitates Intramolecular Hydrogen Transfer in Long-Bonded cis-Isonitrosyl Methoxide. J Phys Chem A 2022; 126:6826-6833. [PMID: 36049165 DOI: 10.1021/acs.jpca.2c03315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hydrogen-atom transfer from methoxy radical to nitric oxide, leading to the formation of formaldehyde and nitroxyl, represents a secondary reaction of photodissociation of methyl nitrite, which is used as rocket fuel. In this study, we explored the potential energy profile of the hydrogen-atom transfer using the electronic structure calculations at the DLPNO-CCSD(T)/aug-cc-pVTZ level of theory for two isomeric forms (cis and trans) of the pre-reaction complex. The cis-oriented pre-reaction complex has a weak elongated O─O bond, which gets further elongated in the hydrogen transfer transition state. This O─O bond stabilizes the pre-reaction complex by 32.9 kJ/mol. The O─O-induced stabilization is even greater for the transition state (48.2 kJ/mol), which was unexpected because of the larger O─O distance in the transition state structure. To address this paradox, we performed the electronic structure analysis of the reaction participants using the valence bond (VB) theory, natural resonance theory, topological analysis of the electron density and its derivatives, and analysis of the electron localization function distribution. This combined analysis led to the conclusion that the cis-transition state for hydrogen transfer, instead of being directly stabilized by the O─O interaction, gained substantial stabilization from the in-plane five-center six-electron aromaticity.
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Affiliation(s)
- Punhasa S Senanayake
- Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Raulia R Syrlybaeva
- Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Marat R Talipov
- Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, United States
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5
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Analysis of the roaming trajectories from the dynamic and kinematic perspectives – A representative study of triatomic systems. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.138599] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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6
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Mishra P, Fritz SM, Herbers S, Mebel AM, Zwier TS. Gas-phase pyrolysis of trans 3-pentenenitrile: competition between direct and isomerization-mediated dissociation. Phys Chem Chem Phys 2021; 23:6462-6471. [PMID: 33729262 DOI: 10.1039/d1cp00104c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The flash pyrolysis of trans 3-pentenenitrile (3-PN, CH3-CH[double bond, length as m-dash]CH-CH2-CN) was studied by combining the results of VUV photoionization mass spectra with broadband microwave spectra recorded as a function of the temperature of the pyrolysis tube. The two separated functional groups (vinyl and nitrile) open up isomerization as an initial step in competition with unimolecular dissociation. Primary products were detected by keeping the 3-PN concentration low and limiting reaction times to the traversal time of the gas in the pyrolysis tube (∼100 μs). The reaction is quenched and products are cooled by expansion into vacuum before interrogation over the 8-18 GHz region using chirped-pulse broadband methods. 118 nm VUV photoionization of the same reaction mixture provides a means of detecting all products with ionization potentials below 10.5 eV with minimal fragmentation. These results are combined with a detailed computational investigation of the C5H7N and related potential energy surfaces, leading to a consistent picture of the unimolecular decomposition of 3-PN. Loss of two H-atoms to form a 79 amu product is proven from its microwave transitions to contain trans-Z-2,4-pentadienenitrile, while no pyridine is observed. Methyl loss, HCN loss, and breaking the central C(2)-C(3) bond all occur following isomerization of the position of the double bond, thereby opening up low-energy pathways to these decomposition channels.
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Affiliation(s)
- Piyush Mishra
- Department of Chemistry, Purdue University, West Lafayette, IN 47907-1393, USA
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7
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Zaleski DP, Sivaramakrishnan R, Weller HR, Seifert NA, Bross DH, Ruscic B, Moore KB, Elliott SN, Copan AV, Harding LB, Klippenstein SJ, Field RW, Prozument K. Substitution Reactions in the Pyrolysis of Acetone Revealed through a Modeling, Experiment, Theory Paradigm. J Am Chem Soc 2021; 143:3124-3142. [PMID: 33615780 DOI: 10.1021/jacs.0c11677] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The development of high-fidelity mechanisms for chemically reactive systems is a challenging process that requires the compilation of rate descriptions for a large and somewhat ill-defined set of reactions. The present unified combination of modeling, experiment, and theory provides a paradigm for improving such mechanism development efforts. Here we combine broadband rotational spectroscopy with detailed chemical modeling based on rate constants obtained from automated ab initio transition state theory-based master equation calculations and high-level thermochemical parametrizations. Broadband rotational spectroscopy offers quantitative and isomer-specific detection by which branching ratios of polar reaction products may be obtained. Using this technique, we observe and characterize products arising from H atom substitution reactions in the flash pyrolysis of acetone (CH3C(O)CH3) at a nominal temperature of 1800 K. The major product observed is ketene (CH2CO). Minor products identified include acetaldehyde (CH3CHO), propyne (CH3CCH), propene (CH2CHCH3), and water (HDO). Literature mechanisms for the pyrolysis of acetone do not adequately describe the minor products. The inclusion of a variety of substitution reactions, with rate constants and thermochemistry obtained from automated ab initio kinetics predictions and Active Thermochemical Tables analyses, demonstrates an important role for such processes. The pathway to acetaldehyde is shown to be a direct result of substitution of acetone's methyl group by a free H atom, while propene formation arises from OH substitution in the enol form of acetone by a free H atom.
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Affiliation(s)
- Daniel P Zaleski
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Department of Chemistry, Colgate University, Hamilton, New York 13346, United States
| | - Raghu Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Hailey R Weller
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Nathan A Seifert
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - David H Bross
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Branko Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Kevin B Moore
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Sarah N Elliott
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Andreas V Copan
- Emmanuel College, Natural Sciences Department, Franklin Springs, Georgia 30639, United States
| | - Lawrence B Harding
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Stephen J Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Robert W Field
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Kirill Prozument
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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8
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Abstract
Roaming reactions were first clearly identified in photodissociation of formaldehyde 15 years ago, and roaming dynamics are now recognized as a universal aspect of chemical reactivity. These reactions typically involve frustrated near-dissociation of a quasibound system to radical fragments, followed by reorientation at long range and intramolecular abstraction. The consequences can be unexpected formation of molecular products, depletion of the radical pool in chemical systems, and formation of products with unusual internal state distributions. In this review, I examine some current aspects of roaming reactions with an emphasis on experimental results, focusing on possible quantum effects in roaming and roaming dynamics in bimolecular systems. These considerations lead to a more inclusive definition of roaming reactions as those for which key dynamics take place at long range.
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Affiliation(s)
- Arthur G. Suits
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
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9
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Jocher A, Vandewiele NM, Han K, Liu M, Gao CW, Gillis RJ, Green WH. Scalability strategies for automated reaction mechanism generation. Comput Chem Eng 2019. [DOI: 10.1016/j.compchemeng.2019.106578] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Hernandez-Castillo AO, Abeysekera C, Robicheaux F, Zwier TS. Propagating molecular rotational coherences through single-frequency pulses in the strong field regime. J Chem Phys 2019; 151:084312. [PMID: 31470710 DOI: 10.1063/1.5099049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the weak-field limit in which microwave spectroscopy is typically carried out, an application of a single-frequency pulse that is resonant with a molecular transition will create a coherence between the pair of states involved in the rotational transition, producing a free-induction decay (FID) that, after Fourier transform, produces a molecular signal at that same resonance frequency. With the advent of chirped-pulse Fourier transform microwave methods, the high-powered amplifiers needed to produce broadband microwave spectra also open up other experiments that probe the molecular response in the high-field regime. This paper describes a series of experiments involving resonant frequency pulses interrogating jet-cooled molecules under conditions of sufficient power to Rabi oscillate the two-state system through many Rabi cycles. The Fourier-transformed FID shows coherent signal not only at the applied resonant frequency but also at a series of transitions initially connected to the original one by sharing an upper or lower level with it. As the duration of the single-frequency excitation is increased from 250 to 1500 ns, the number of observed off-resonant, but dipole-allowed, molecular coherences grow. The phenomenon is quite general, having been demonstrated in Z-phenylvinylnitrile, E-phenylvinylnitrile (E-PVN), benzonitrile, guaiacol, and 4-pentynenitrile. In E-PVN, the highest power/longest pulse duration, coherent signal is also present at energetically nearby but not directly connected transitions. Even in molecular samples containing more than one independent species, only transitions due to the single species responsible for the original resonant transition are present. We develop a time-dependent model of the molecular/photon system and use it in conjunction with the experiment to test possible sources of the phenomenon.
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Affiliation(s)
| | - Chamara Abeysekera
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA
| | - F Robicheaux
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907-2084, USA
| | - Timothy S Zwier
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA
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11
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Grinberg Dana A, Moore KB, Jasper AW, Green WH. Large Intermediates in Hydrazine Decomposition: A Theoretical Study of the N3H5 and N4H6 Potential Energy Surfaces. J Phys Chem A 2019; 123:4679-4692. [DOI: 10.1021/acs.jpca.9b02217] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alon Grinberg Dana
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Kevin B. Moore
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Ahren W. Jasper
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - William H. Green
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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12
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Lou M, Swearer DF, Gottheim S, Phillips DJ, Simmons JG, Halas NJ, Everitt HO. Quantitative analysis of gas phase molecular constituents using frequency-modulated rotational spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:053110. [PMID: 31153269 DOI: 10.1063/1.5093912] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 04/29/2019] [Indexed: 06/09/2023]
Abstract
Rotational spectroscopy has been used for decades for virtually unambiguous identification of gas phase molecular species, but it has rarely been used for the quantitative analysis of molecular concentrations. Challenges have included the nontrivial reconstruction of integrated line strengths from modulated spectra, the correlation of pressure-dependent line shape and strength with partial pressure, and the multiple standing wave interferences and modulation-induced line shape asymmetries that sensitively depend on source-chamber-detector alignment. Here, we introduce a quantitative analysis methodology that overcomes these challenges, reproducibly and accurately recovering gas molecule concentrations using a calibration procedure with a reference gas and a conversion based on calculated line strengths. The technique uses frequency-modulated rotational spectroscopy and recovers the integrated line strength from a Voigt line shape that spans the Doppler- and pressure-broadened regimes. Gas concentrations were accurately quantified to within the experimental error over more than three orders of magnitude, as confirmed by the cross calibration between CO and N2O and by the accurate recovery of the natural abundances of four N2O isotopologues. With this methodology, concentrations of hundreds of molecular species may be quantitatively measured down to the femtomolar regime using only a single calibration curve and the readily available libraries of calculated integrated line strengths, demonstrating the power of this technique for the quantitative gas-phase detection, identification, and quantification.
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Affiliation(s)
- Minghe Lou
- Department of Chemistry, Rice University, Houston, Texas 77005, USA
| | - Dayne F Swearer
- Department of Chemistry, Rice University, Houston, Texas 77005, USA
| | - Samuel Gottheim
- Department of Chemistry, Rice University, Houston, Texas 77005, USA
| | - Dane J Phillips
- IERUS Technologies, 2904 Westcorp Blvd., Suite 210, Huntsville, Alabama 35805, USA
| | - Jay G Simmons
- U.S. Army Combat Capabilities Development Command, Aviation and Missile Center, Redstone Arsenal, Alabama 35898, USA
| | - Naomi J Halas
- Department of Chemistry, Rice University, Houston, Texas 77005, USA
| | - Henry O Everitt
- U.S. Army Combat Capabilities Development Command, Aviation and Missile Center, Redstone Arsenal, Alabama 35898, USA
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13
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Suits AG. Invited Review Article: Photofragment imaging. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:111101. [PMID: 30501356 DOI: 10.1063/1.5045325] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 10/25/2018] [Indexed: 06/09/2023]
Abstract
Photodissociation studies in molecular beams that employ position-sensitive particle detection to map product recoil velocities emerged thirty years ago and continue to evolve with new laser and detector technologies. These powerful methods allow application of tunable laser detection of single product quantum states, simultaneous measurement of velocity and angular momentum polarization, measurement of joint product state distributions for the detected and undetected products, coincident detection of multiple product channels, and application to radicals and ions as well as closed-shell molecules. These studies have permitted deep investigation of photochemical dynamics for a broad range of systems, revealed new reaction mechanisms, and addressed problems of practical importance in atmospheric, combustion, and interstellar chemistry. This review presents an historical overview, a detailed technical account of the range of methods employed, and selected experimental highlights illustrating the capabilities of the method.
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Affiliation(s)
- Arthur G Suits
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
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14
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Dias N, Joalland B, Ariyasingha NM, Suits AG, Broderick BM. Direct versus Indirect Photodissociation of Isoxazole from Product Branching: A Chirped-Pulse Fourier Transform mm-Wave Spectroscopy/Pulsed Uniform Flow Investigation. J Phys Chem A 2018; 122:7523-7531. [PMID: 30165738 DOI: 10.1021/acs.jpca.8b04713] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The UV photodissociation of isoxazole (c-C3H3NO) is studied in this work by chirped-pulse Fourier transform mm-wave spectroscopy in a pulsed uniform Laval flow. This approach offers a number of advantages over traditional spectroscopic detection methods due to its broadband, sub-MHz resolution, and fast-acquisition capabilities. In coupling this technique with a quasi-uniform Laval flow, we are able to obtain product branching fractions in the 193 nm photodissociation of isoxazole. Five dissociation channels are explored through direct detection of seven different photoproducts. These species and their respective branching fractions (%) include the following: HCN (53.8 ± 1.7), CH3CN (23.4 ± 6.8), HCO (9.5 ± 2.3), CH2CN (7.8 ± 2.9), CH2CO (3.8 ± 0.9), HCCCN (0.9 ± 0.2), and HNC (0.8 ± 0.2). Guided by previous electronic structure and dynamics simulations, we are able to elucidate the dissociation dynamics that govern the final product branching fractions observed in this work, which differ significantly from previous reports on the thermal decomposition of isoxazole. Interestingly, both direct and indirect dynamics contribute to its dissociation, and clear signatures of both are manifested in the relative branching ratios obtained. Consistent with previous studies on the unimolecular dissociation of isoxazole, our findings also suggest the importance of the open-shell singlet diradicaloid species vinylnitrene in the dissociation dynamics, regardless of the initially populated excited state. This work, taken together with previous investigations, provides a global picture of the complex dissociation pathways involved in the photodissociation of isoxazole.
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Affiliation(s)
- Nureshan Dias
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Baptiste Joalland
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Nuwandi M Ariyasingha
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Arthur G Suits
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Bernadette M Broderick
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
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15
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Fritz SM, Hays BM, Hernandez-Castillo AO, Abeysekera C, Zwier TS. Multiplexed characterization of complex gas-phase mixtures combining chirped-pulse Fourier transform microwave spectroscopy and VUV photoionization time-of-flight mass spectrometry. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:093101. [PMID: 30278727 DOI: 10.1063/1.5046085] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 08/14/2018] [Indexed: 06/08/2023]
Abstract
We report details of the design and operation of a single apparatus that combines Chirped-Pulse Fourier Transform Microwave (CP-FTMW) spectroscopy with vacuum ultraviolet (VUV) photoionization Time-of-Flight Mass Spectrometry (TOFMS). The supersonic expansion used for cooling samples is interrogated first by passing through the region between two microwave horns capable of broadband excitation and detection in the 2-18 GHz frequency region of the microwave. After passing through this region, the expansion is skimmed to form a molecular beam, before being probed with 118 nm (10.5 eV) single-photon VUV photoionization in a linear time-of-flight mass spectrometer. The two detection schemes are powerfully complementary to one another. CP-FTMW detects all components with significant permanent dipole moments. Rotational transitions provide high-resolution structural data. VUV TOFMS provides a gentle and general method for ionizing all components of a gas phase mixture with ionization thresholds below 10.5 eV, providing their molecular formulae. The advantages, complementarity, and limitations of the combined methods are illustrated through results on two gas-phase mixtures made up of (i) three furanic compounds, two of which are structural isomers of one another, and (ii) the effluent from a flash pyrolysis source with o-guaiacol as the precursor.
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Affiliation(s)
- Sean M Fritz
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA
| | - Brian M Hays
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA
| | | | - Chamara Abeysekera
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA
| | - Timothy S Zwier
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA
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16
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Smart SE, Scrape PG, Butler LJ, Mazziotti DA. Using reduced density matrix techniques to capture static and dynamic correlation in the energy landscape for the decomposition of the CH2CH2ONO radical and support a non-IRC pathway. J Chem Phys 2018; 149:024302. [DOI: 10.1063/1.5024512] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Scott E. Smart
- The James Franck Institute and Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
| | - Preston G. Scrape
- The James Franck Institute and Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
| | - Laurie J. Butler
- The James Franck Institute and Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
| | - David A. Mazziotti
- The James Franck Institute and Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
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17
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Zaleski DP, Harding LB, Klippenstein SJ, Ruscic B, Prozument K. Time-Resolved Kinetic Chirped-Pulse Rotational Spectroscopy in a Room-Temperature Flow Reactor. J Phys Chem Lett 2017; 8:6180-6188. [PMID: 29193976 DOI: 10.1021/acs.jpclett.7b02864] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Chirped-pulse Fourier transform millimeter-wave spectroscopy is a potentially powerful tool for studying chemical reaction dynamics and kinetics. Branching ratios of multiple reaction products and intermediates can be measured with unprecedented chemical specificity; molecular isomers, conformers, and vibrational states have distinct rotational spectra. Here we demonstrate chirped-pulse spectroscopy of vinyl cyanide photoproducts in a flow tube reactor at ambient temperature of 295 K and pressures of 1-10 μbar. This in situ and time-resolved experiment illustrates the utility of this novel approach to investigating chemical reaction dynamics and kinetics. Following 193 nm photodissociation of CH2CHCN, we observe rotational relaxation of energized HCN, HNC, and HCCCN photoproducts with 10 μs time resolution and sample the vibrational population distribution of HCCCN. The experimental branching ratio HCN/HCCCN is compared with a model based on RRKM theory using high-level ab initio calculations, which were in turn validated by comparisons to Active Thermochemical Tables enthalpies.
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Affiliation(s)
- Daniel P Zaleski
- Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Lawrence B Harding
- Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Stephen J Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Branko Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Kirill Prozument
- Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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18
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Jones PJ, Riser B, Zhang J. Flash Pyrolysis of t-Butyl Hydroperoxide and Di-t-butyl Peroxide: Evidence of Roaming in the Decomposition of Organic Hydroperoxides. J Phys Chem A 2017; 121:7846-7853. [PMID: 28956925 DOI: 10.1021/acs.jpca.7b07359] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thermal decomposition of t-butyl hydroperoxide and di-t-butyl peroxide was investigated using flash pyrolysis (in a short reaction time of <100 μs) and vacuum-ultraviolet (λ = 118.2 nm) single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) at temperatures up to 1120 K and quantum computational methods. Acetone and methyl radical were detected as the predominant products in the initial decomposition of di-t-butyl peroxide via O-O bond fission. In the initial dissociation of t-butyl hydroperoxide, acetone, methyl radical, isobutylene, and isobutylene oxide products were identified. The novel detection of the unimolecular formation of isobutylene oxide, as supported by the computational study, was found to proceed via a roaming hydroxyl radical facilitated by a hydrogen-bonded intermediate. This new pathway could provide a new class of reactions to consider in the modeling of the low temperature oxidation of alkanes.
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Affiliation(s)
- Paul J Jones
- Department of Chemistry and ‡Air Pollution Research Center, University of California , Riverside, California 92521, United States
| | - Blake Riser
- Department of Chemistry and ‡Air Pollution Research Center, University of California , Riverside, California 92521, United States
| | - Jingsong Zhang
- Department of Chemistry and ‡Air Pollution Research Center, University of California , Riverside, California 92521, United States
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19
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20
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Hansen N, Wullenkord J, Obenchain DA, Graf I, Kohse-Höinghaus K, Grabow JU. Microwave spectroscopic detection of flame-sampled combustion intermediates. RSC Adv 2017. [DOI: 10.1039/c7ra06483g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Microwave spectroscopy was used to detect and identify combustion intermediates after sampling out of laboratory-scale model flames.
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Affiliation(s)
- N. Hansen
- Combustion Research Facility
- Sandia National Laboratories
- Livermore
- USA
| | - J. Wullenkord
- Department of Chemistry
- Bielefeld University
- D-33615 Bielefeld
- Germany
| | - D. A. Obenchain
- Institut für Physikalische Chemie & Elektrochemie
- Gottfried-Wilhelm-Leibniz-University Hannover
- D-30167 Hannover
- Germany
| | - I. Graf
- Department of Chemistry
- Bielefeld University
- D-33615 Bielefeld
- Germany
| | | | - J.-U. Grabow
- Institut für Physikalische Chemie & Elektrochemie
- Gottfried-Wilhelm-Leibniz-University Hannover
- D-30167 Hannover
- Germany
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21
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Scrape PG, Roberts TD, Lee SH, Butler LJ. Dissociation Pathways of the CH2CH2ONO Radical: NO2 + Ethene, NO + Oxirane, and a Non-Intrinsic Reaction Coordinate HNO + Vinoxy Pathway. J Phys Chem A 2016; 120:4973-87. [PMID: 27124098 DOI: 10.1021/acs.jpca.5b12669] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We first characterize the dissociation pathways of BrCH2CH2ONO, a substituted alkyl nitrite, upon photoexcitation at 193 nm under collision-free conditions, in a crossed laser-molecular beam scattering apparatus using vacuum ultraviolet photoionization detection. Three primary photodissociation pathways occur: photoelimination of HNO, leading to the products HNO + BrCH2CHO; C-Br bond photofission, leading to Br + CH2CH2ONO; and O-NO bond photofission, leading to NO + BrCH2CH2O. The data show that alkyl nitrites can eliminate HNO via a unimolecular mechanism in addition to the commonly accepted bulk disproportionation mechanism. Some of the products from the primary photodissociation pathways are highly vibrationally excited, so we then probe the product branching from the unimolecular dissociation of these unstable intermediates. Notably, the vibrationally excited CH2CH2ONO radicals undergo two channels predicted by statistical transition-state theory, and an additional non-intrinsic reaction coordinate channel, HNO elimination. CH2CH2ONO is formed with high rotational energy; by employing rotational models based on conservation of angular momentum, we predict, and verify experimentally, the kinetic energies of stable CH2CH2ONO radicals and the angular distribution of dissociation products. The major dissociation pathway of CH2CH2ONO is NO2 + ethene, and some of the NO2 is formed with sufficient internal energy to undergo further photodissociation. Nascent BrCH2CHO and CH2Br are also photodissociated upon absorption of a second 193 nm photon; we derive the kinetic energy release of these dissociations based on our data, noting similarities to the analogous photodissociation of ClCH2CHO and CH2Cl.
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Affiliation(s)
- Preston G Scrape
- The James Franck Institute and Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States
| | - Trevor D Roberts
- The James Franck Institute and Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States
| | - Shih-Huang Lee
- National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan, Republic of China
| | - Laurie J Butler
- The James Franck Institute and Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States
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22
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Park GB, Field RW. Perspective: The first ten years of broadband chirped pulse Fourier transform microwave spectroscopy. J Chem Phys 2016; 144:200901. [DOI: 10.1063/1.4952762] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- G. Barratt Park
- Institute for Physical Chemistry, University of Göttingen, Tammannstraße 6, 37077 Göttingen, Germany
- Max Planck Institute for Biophysical Chemistry, Göttingen, Am Faßberg 11, 37077 Göttingen, Germany
| | - Robert W. Field
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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23
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Fernando R, Ariyasingha NM, Suits AG. Imaging NO elimination in the infrared multiphoton dissociation of nitroalkanes and alkyl nitrites. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2015.12.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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24
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Abeysekera C, Zack LN, Park GB, Joalland B, Oldham JM, Prozument K, Ariyasingha NM, Sims IR, Field RW, Suits AG. A chirped-pulse Fourier-transform microwave/pulsed uniform flow spectrometer. II. Performance and applications for reaction dynamics. J Chem Phys 2015; 141:214203. [PMID: 25481137 DOI: 10.1063/1.4903253] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in pulsed uniform flows. Here we detail the development and testing of a new K(a)-band CP-FTMW spectrometer in combination with the pulsed flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys. 141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.
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Affiliation(s)
- Chamara Abeysekera
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - Lindsay N Zack
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - G Barratt Park
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Baptiste Joalland
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - James M Oldham
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - Kirill Prozument
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - Nuwandi M Ariyasingha
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
| | - Ian R Sims
- Institut de Physique de Rennes, UMR CNRS-UR1 6251, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042, Rennes Cedex, France
| | - Robert W Field
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Arthur G Suits
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA
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25
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Annesley CJ, Randazzo JB, Klippenstein SJ, Harding LB, Jasper AW, Georgievskii Y, Ruscic B, Tranter RS. Thermal Dissociation and Roaming Isomerization of Nitromethane: Experiment and Theory. J Phys Chem A 2015; 119:7872-93. [DOI: 10.1021/acs.jpca.5b01563] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher J. Annesley
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - John B. Randazzo
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Stephen J. Klippenstein
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Lawrence B. Harding
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Ahren W. Jasper
- Combustion
Research Facility, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - Yuri Georgievskii
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Branko Ruscic
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Robert S. Tranter
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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26
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Maksyutenko P, Muzangwa LG, Jones BM, Kaiser RI. Lyman α photolysis of solid nitromethane (CH3NO2) and D3-nitromethane (CD3NO2) – untangling the reaction mechanisms involved in the decomposition of model energetic materials. Phys Chem Chem Phys 2015; 17:7514-27. [DOI: 10.1039/c4cp05759g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Solid nitromethane and D3-nitromethane ices were exposed to Lyman α photons to investigate the mechanism involved in the decomposition of energetic materials in the condensed phase.
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