1
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Liu T, Lester MI. Roaming in the Unimolecular Decay of syn-Methyl-Substituted Criegee Intermediates. J Phys Chem A 2023; 127:10817-10827. [PMID: 38109698 DOI: 10.1021/acs.jpca.3c05859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
Alkene ozonolysis generates transient carbonyl oxide species, known as Criegee intermediates, which are a significant nonphotolytic source of OH radicals in the troposphere. This study demonstrates that unimolecular decay of syn-methyl-substituted Criegee intermediates proceeds via 1,4 H atom transfer to vinyl hydroperoxides, resulting in OH fission to O-O products or, alternatively, OH roaming to hydroxycarbonyl products. Newly generated Criegee intermediates are shown to yield hydroxycarbonyls with sufficient internal excitation to dissociate via C-C fission to acyl and hydroxymethyl (CH2OH) radicals. The stabilized Criegee intermediates and unimolecular products are rapidly cooled in a pulsed supersonic expansion for photoionization detection with time-of-flight mass spectrometry. CH2OH products are identified by 2 + 1 resonance-enhanced multiphoton ionization via the 3pz Rydberg state upon unimolecular decay of CH3CHOO, (CH3)2COO, (CH3)(CH3CH2)COO, and (CH3)(CH2═CH)COO (methyl vinyl ketone oxide). The stabilized Criegee intermediates are separately detected using 10.5 eV photoionization. This study provides the first experimental evidence of roaming in the unimolecular decay of isoprene-derived methyl vinyl ketone oxide and extends earlier studies that reported stabilized hydroxycarbonyl products.
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Affiliation(s)
- Tianlin Liu
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States
| | - Marsha I Lester
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States
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2
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Walmsley T, Unwin J, Allum F, Bari S, Boll R, Borne K, Brouard M, Bucksbaum P, Ekanayake N, Erk B, Forbes R, Howard AJ, Eng-Johnsson P, Lee JWL, Liu Z, Manschwetus B, Mason R, Passow C, Peschel J, Rivas D, Rolles D, Rörig A, Rouzée A, Vallance C, Ziaee F, Burt M. Characterizing the multi-dimensional reaction dynamics of dihalomethanes using XUV-induced Coulomb explosion imaging. J Chem Phys 2023; 159:144302. [PMID: 37823458 DOI: 10.1063/5.0172749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 09/27/2023] [Indexed: 10/13/2023] Open
Abstract
Site-selective probing of iodine 4d orbitals at 13.1 nm was used to characterize the photolysis of CH2I2 and CH2BrI initiated at 202.5 nm. Time-dependent fragment ion momenta were recorded using Coulomb explosion imaging mass spectrometry and used to determine the structural dynamics of the dissociating molecules. Correlations between these fragment momenta, as well as the onset times of electron transfer reactions between them, indicate that each molecule can undergo neutral three-body photolysis. For CH2I2, the structural evolution of the neutral molecule was simultaneously characterized along the C-I and I-C-I coordinates, demonstrating the sensitivity of these measurements to nuclear motion along multiple degrees of freedom.
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Affiliation(s)
- T Walmsley
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - J Unwin
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - F Allum
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - S Bari
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - R Boll
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - K Borne
- J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA
| | - M Brouard
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - P Bucksbaum
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - N Ekanayake
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - B Erk
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - R Forbes
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - A J Howard
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - P Eng-Johnsson
- Department of Physics, Lund University, 22100 Lund, Sweden
| | - J W L Lee
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Z Liu
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - B Manschwetus
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - R Mason
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - C Passow
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - J Peschel
- Department of Physics, Lund University, 22100 Lund, Sweden
| | - D Rivas
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - D Rolles
- J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA
| | - A Rörig
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - A Rouzée
- Max-Born-Institute, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - C Vallance
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - F Ziaee
- J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA
| | - M Burt
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
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3
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Roy TK, Liu T, Qian Y, Sojdak CA, Kozlowski MC, Lester MI. A five-carbon unsaturated Criegee intermediate: synthesis, spectroscopic identification, and theoretical study of 3-penten-2-one oxide. Chem Sci 2023; 14:10471-10477. [PMID: 37800006 PMCID: PMC10548502 DOI: 10.1039/d3sc03993e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 09/03/2023] [Indexed: 10/07/2023] Open
Abstract
Biogenic alkenes, such as isoprene and α-pinene, are the predominant source of volatile organic compounds (VOCs) emitted into the atmosphere. Atmospheric processing of alkenes via reaction with ozone leads to formation of zwitterionic reactive intermediates with a carbonyl oxide functional group, known as Criegee intermediates (CIs). CIs are known to exhibit a strong absorption (π* ← π) in the near ultraviolet and visible (UV-vis) region due to the carbonyl oxide moiety. This study focuses on the laboratory identification of a five-carbon CI with an unsaturated substituent, 3-penten-2-one oxide, which can be produced upon atmospheric ozonolysis of substituted isoprenes. 3-Penten-2-one oxide is generated in the laboratory by photolysis of a newly synthesized precursor, (Z)-2,4-diiodopent-2-ene, in the presence of oxygen. The electronic spectrum of 3-penten-2-one oxide was recorded by UV-vis induced depletion of the VUV photoionization signal on the parent m/z 100 mass channel using a time-of-flight mass spectrometer. The resultant electronic spectrum is broad and unstructured with peak absorption at ca. 375 nm. To complement the experimental findings, electronic structure calculations are performed at the CASPT2(12,10)/aug-cc-pVDZ level of theory. The experimental spectrum shows good agreement with the calculated electronic spectrum and vertical excitation energy obtained for the lowest energy conformer of 3-penten-2-one oxide. In addition, OH radical products resulting from unimolecular decay of energized 3-penten-2-oxide CIs are detected by UV laser-induced fluorescence. Finally, the experimental electronic spectrum is compared with that of a four-carbon, isoprene-derived CI, methyl vinyl ketone oxide, to understand the effects of an additional methyl group on the associated electronic properties.
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Affiliation(s)
- Tarun Kumar Roy
- Department of Chemistry, University of Pennsylvania Philadelphia PA 19104-6323 USA
| | - Tianlin Liu
- Department of Chemistry, University of Pennsylvania Philadelphia PA 19104-6323 USA
| | - Yujie Qian
- Department of Chemistry, University of Pennsylvania Philadelphia PA 19104-6323 USA
| | - Christopher A Sojdak
- Department of Chemistry, University of Pennsylvania Philadelphia PA 19104-6323 USA
| | - Marisa C Kozlowski
- Department of Chemistry, University of Pennsylvania Philadelphia PA 19104-6323 USA
| | - Marsha I Lester
- Department of Chemistry, University of Pennsylvania Philadelphia PA 19104-6323 USA
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4
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Ji YT, Lee YP. Dynamics of Reaction CH 3CHI + O 2 Investigated via Infrared Emission of Products CO, CO 2, and OH. J Phys Chem A 2021; 125:8373-8385. [PMID: 34524829 DOI: 10.1021/acs.jpca.1c05610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction CH3CHI + O2 has been commonly employed in laboratories to produce a methyl-substituted Criegee intermediate CH3CHOO, but the detailed dynamics of this reaction remain unexplored. We carried out this reaction by irradiating a flowing mixture of CH3CHI2 (∼70 mTorr) and O2 (∼4 and 8 Torr) at 308 or 248 nm and observed infrared emission of the products with a step-scan Fourier-transform spectrometer. Upon irradiation at 248 nm with O2 ∼4 Torr, a Boltzmann distribution of CO (v ≤ 4, J ≤ 25) with average vibrational energy (12 ± 2) kJ mol-1 and of OH (v = 1, J ≤ 5.5) were observed and assigned to be produced from the decomposition of CH3C(O)OH* to form CO + CH3OH and OH + CH3CO, respectively. The observed broadband emission of CO2 was simulated with two vibrational distributions of average energies (42 ± 3) and (114 ± 6) kJ mol-1 and assigned to be produced from the decomposition of CH3C(O)OH* and (methyl dioxirane)*, respectively. The results upon irradiation of the sample at 308 nm are similar, likely indicating a small fraction of energy partition into these products and rapid thermalization of CH3CHI*. Compared with reaction CH2I + O2, the title reaction yielded products with much less internal excitation, consistent with the expectation that these observed products receive much less fraction of available energy upon fragmentation when an additional methyl moiety was present in the parent. The large-v component of CO observed in experiments of CH2I + O2 at 248 nm, produced from secondary reaction HCO + O2, was absent in this work because the corresponding secondary reaction CH3CO + O2 in decomposition of CH3CHOO* produces α-lactone + OH or H2CO + CO + OH.
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Affiliation(s)
- Ya-Tsang Ji
- Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan
| | - Yuan-Pern Lee
- Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan.,Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan.,Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106319, Taiwan
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5
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Lin Y, Lin JJ. A new approach to determine the absolute photodissociation cross section of molecules in a cell. J CHIN CHEM SOC-TAIP 2021. [DOI: 10.1002/jccs.202100336] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Yen‐Hsiu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica Taipei Taiwan
| | - Jim Jr‐Min Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica Taipei Taiwan
- Department of Chemistry National Taiwan University Taipei Taiwan
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6
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Chen TY, Lee YP. Dynamics of the reaction CH 2I + O 2 probed via infrared emission of CO, CO 2, OH and H 2CO. Phys Chem Chem Phys 2020; 22:17540-17553. [PMID: 32808958 DOI: 10.1039/d0cp01940b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction CH2I + O2 has been widely employed recently for the production of the simplest Criegee intermediate CH2OO in laboratories, but the detailed dynamics of this reaction have been little explored. Infrared emission of several products of this reaction, initiated on irradiation of CH2I2 and O2 (∼8 Torr) in a flowing mixture at 308 or 248 nm, was recorded with a step-scan Fourier-transform spectrometer; possible routes of formation were identified according to the observed vibrational distribution of products and published theoretical potential-energy schemes. Upon irradiation at 308 nm, Boltzmann distributions of CO (v ≤ 5, J ≤ 19) with an average vibrational energy of 32 ± 3 kJ mol-1 and OH (v ≤ 3, J ≤ 5.5) with an average vibrational energy of 29 ± 4 kJ mol-1 were observed and assigned to the decomposition of HCOOH* to form CO + H2O and OH + HCO, respectively. The broadband emission of CO2 was simulated with two vibrational distributions of average energies (91 ± 4) and (147 ± 8) kJ mol-1 and assigned to be produced from the decomposition of HCOOH* and methylene bis(oxy), respectively. Upon irradiation of samples at 248 nm, the emission of OH and CO2 showed similar distributions with slightly greater energies, but the distribution of CO (v ≤ 11, J ≤ 19) became bimodal with average vibrational energies of (23 ± 4) and (107 ± 29) kJ mol-1, and branching (56 ± 5) : (44 ± 5). The additional large-v component is assigned to be produced from a secondary reaction HCO + O2 to form CO + HO2; HCO is a coproduct of OH. The branching between CO and OH is (50 ± 5) : (50 ± 5) at 308 nm and (64 ± 5) : (36 ± 4) at 248 nm, consistent with the mechanism according to which an additional channel to produce CO opens at 248 nm. Highly internally excited H2CO was also observed. With O2 at 16 Torr, the extrapolated nascent internal distributions are similar to those with O2 at 8 Torr except for a slight quenching effect.
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Affiliation(s)
- Ting-Yu Chen
- Department of Applied Chemistry and Institute of Molecular Science National Chiao Tung University, Hsinchu 30010, Taiwan.
| | - Yuan-Pern Lee
- Department of Applied Chemistry and Institute of Molecular Science National Chiao Tung University, Hsinchu 30010, Taiwan. and Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 30010, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
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7
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Barber VP, Esposito VJ, Trabelsi T, Hansen AS, McHenry TA, Francisco JS, Lester MI. Experimental and computational investigation of vinoxy and 1-methylvinoxy radicals from the unimolecular decay of alkyl-substituted Criegee intermediates. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.137478] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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Kapnas KM, Murray C. Mode-specific vibrational predissociation dynamics of (HCl) 2 via the free and bound HCl stretch overtones. J Chem Phys 2020; 152:194301. [PMID: 33687237 DOI: 10.1063/5.0003652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Velocity-map ion imaging has been used to study the vibrational predissociation dynamics of the HCl dimer following infrared (IR) excitation in the HCl stretch overtone region near 1.77 Å. HCl monomer predissociation products were detected state-selectively using 2 + 1 resonance-enhanced multiphoton ionization spectroscopy. The IR action spectrum shows the free HCl stretch (2ν1), the bound HCl stretch (2ν2), and a combination band involving the intermolecular van der Waals stretching mode (2ν2 + ν4). Fragment speed distributions extracted from ion images obtained for a range of HCl(v = 0, 1; J) levels following vibrational excitation on the 2ν1 and 2ν2 bands yield the correlated product pair distributions. All product pairs comprise HCl(v = 1) + HCl(v = 0) and show a strong propensity to minimize the recoil kinetic energy. Highly non-statistical and mode-dependent HCl product rotational distributions are observed, in contrast to that observed following stretch fundamental excitation. Predissociation lifetimes are also mode-dependent: excitation of the free HCl leads to τVP = 13 ± 1 ns, while the bound stretch has a shorter lifetime τVP ≤ 6 ns. The dimer dissociation energy determined from energy conservation (D0 = 397 ± 7 cm-1) is slightly smaller than the previously reported values. The results are discussed in the context of previous observations for (HF)2 and (HCl)2 after excitation of HX stretch fundamentals and models for vibrational predissociation.
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Affiliation(s)
- Kara M Kapnas
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, USA
| | - Craig Murray
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, USA
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9
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Toulson BW, Borgwardt M, Wang H, Lackner F, Chatterley AS, Pemmaraju CD, Neumark DM, Leone SR, Prendergast D, Gessner O. Probing ultrafast C-Br bond fission in the UV photochemistry of bromoform with core-to-valence transient absorption spectroscopy. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2019; 6:054304. [PMID: 31649963 PMCID: PMC6800284 DOI: 10.1063/1.5113798] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 09/12/2019] [Indexed: 06/10/2023]
Abstract
UV pump-extreme UV (XUV) probe femtosecond transient absorption spectroscopy is used to study the 268 nm induced photodissociation dynamics of bromoform (CHBr3). Core-to-valence transitions at the Br(3d) absorption edge (∼70 eV) provide an atomic scale perspective of the reaction, sensitive to changes in the local valence electronic structure, with ultrafast time resolution. The XUV spectra track how the singly occupied molecular orbitals of transient electronic states develop throughout the C-Br bond fission, eventually forming radical Br and CHBr2 products. Complementary ab initio calculations of XUV spectral fingerprints are performed for transient atomic arrangements obtained from sampling excited-state molecular dynamics simulations. C-Br fission along an approximately C S symmetrical reaction pathway leads to a continuous change of electronic orbital characters and atomic arrangements. Two timescales dominate changes in the transient absorption spectra, reflecting the different characteristic motions of the light C and H atoms and the heavy Br atoms. Within the first 40 fs, distortion from C 3 v symmetry to form a quasiplanar CHBr2 by the displacement of the (light) CH moiety causes significant changes to the valence electronic structure. Displacement of the (heavy) Br atoms is delayed and requires up to ∼300 fs to form separate Br + CHBr2 products. We demonstrate that transitions between the valence-excited (initial) and valence + core-excited (final) state electronic configurations produced by XUV absorption are sensitive to the localization of valence orbitals during bond fission. The change in valence electron-core hole interaction provides a physical explanation for spectral shifts during the process of bond cleavage.
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Affiliation(s)
- Benjamin W. Toulson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Mario Borgwardt
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Han Wang
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | | | | | - C. D. Pemmaraju
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Stanford, California 94025, USA
| | | | | | | | - Oliver Gessner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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10
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Horton SL, Liu Y, Forbes R, Makhija V, Lausten R, Stolow A, Hockett P, Marquetand P, Rozgonyi T, Weinacht T. Excited state dynamics of CH 2I 2 and CH 2BrI studied with UV pump VUV probe photoelectron spectroscopy. J Chem Phys 2019; 150:174201. [PMID: 31067867 DOI: 10.1063/1.5086665] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We compare the excited state dynamics of diiodomethane (CH2I2) and bromoiodomethane (CH2BrI) using time resolved photoelectron spectroscopy. A 4.65 eV UV pump pulse launches a dissociative wave packet on excited states of both molecules and the ensuing dynamics are probed via photoionization using a 7.75 eV probe pulse. The resulting photoelectrons are measured with the velocity map imaging technique for each pump-probe delay. Our measurements highlight differences in the dynamics for the two molecules, which are interpreted with high-level ab initio molecular dynamics (trajectory surface hopping) calculations. Our analysis allows us to associate features in the photoelectron spectrum with different portions of the excited state wave packet represented by different trajectories. The excited state dynamics in bromoiodomethane are simple and can be described in terms of direct dissociation along the C-I coordinate, whereas the dynamics in diiodomethane involve internal conversion and motion along multiple dimensions.
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Affiliation(s)
- Spencer L Horton
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Yusong Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Ruaridh Forbes
- Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada
| | - Varun Makhija
- Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada
| | - Rune Lausten
- National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| | - Albert Stolow
- Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada
| | - Paul Hockett
- National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| | - Philipp Marquetand
- Faculty of Chemistry, Institute of Theoretical Chemistry, University of Vienna, Währinger Str. 17, 1090 Wien, Austria
| | - Tamás Rozgonyi
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok Körútja 2, Budapest 1117, Hungary
| | - Thomas Weinacht
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
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11
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Pan C, Zhang Y, Lee JD, Kidwell NM. Imaging the Dynamics of CH2BrI Photodissociation in the Near Ultraviolet Region. J Phys Chem A 2018; 122:3728-3734. [PMID: 29600858 DOI: 10.1021/acs.jpca.7b12268] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Changen Pan
- Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187-8795, United States
| | - Yi Zhang
- Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187-8795, United States
| | - Joseph D. Lee
- Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187-8795, United States
| | - Nathanael M. Kidwell
- Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187-8795, United States
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12
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Borin VA, Matveev SM, Budkina DS, El-Khoury PZ, Tarnovsky AN. Direct photoisomerization of CH 2I 2vs. CHBr 3 in the gas phase: a joint 50 fs experimental and multireference resonance-theoretical study. Phys Chem Chem Phys 2018; 18:28883-28892. [PMID: 27722308 DOI: 10.1039/c6cp05129d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Femtosecond transient absorption measurements powered by 40 fs laser pulses reveal that ultrafast isomerization takes place upon S1 excitation of both CH2I2 and CHBr3 in the gas phase. The photochemical conversion process is direct and intramolecular, i.e., it proceeds without caging media that have long been implicated in the photo-induced isomerization of polyhalogenated alkanes in condensed phases. Using multistate complete active space second order perturbation theory (MS-CASPT2) calculations, we investigate the structure of the photochemical reaction paths connecting the photoexcited species to their corresponding isomeric forms. Unconstrained minimum energy paths computed starting from the S1 Franck-Condon points lead to S1/S0 conical intersections, which directly connect the parent CHBr3 and CH2I2 molecules to their isomeric forms. Changes in the chemical bonding picture along the S1/S0 isomerization reaction path are described using multireference average coupled pair functional (MRACPF) calculations in conjunction with natural resonance theory (NRT) analysis. These calculations reveal a complex interplay between covalent, radical, ylidic, and ion-pair dominant resonance structures throughout the nonadiabatic photochemical isomerization processes described in this work.
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Affiliation(s)
- Veniamin A Borin
- Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio, USA.
| | - Sergey M Matveev
- Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio, USA.
| | - Darya S Budkina
- Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio, USA.
| | - Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, P. O. Box 999, Richland, WA 99352, USA
| | - Alexander N Tarnovsky
- Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio, USA.
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13
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Marggi Poullain S, Chicharro DV, Navarro E, Rubio-Lago L, González-Vázquez J, Bañares L. Photodissociation dynamics of bromoiodomethane from the first and second absorption bands. A combined velocity map and slice imaging study. Phys Chem Chem Phys 2018; 20:3490-3503. [PMID: 29335697 DOI: 10.1039/c7cp07077b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ion imaging is applied to disentangle the selective bond cleavage in the photodissociation of bromoiodomethane from the two first absorption bands.
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Affiliation(s)
- Sonia Marggi Poullain
- Departamento de Qumica Fsica I
- Facultad de Ciencias Qumicas
- Universidad Complutense de Madrid
- 28040 Madrid
- Spain
| | - David V. Chicharro
- Departamento de Qumica Fsica I
- Facultad de Ciencias Qumicas
- Universidad Complutense de Madrid
- 28040 Madrid
- Spain
| | - Eduardo Navarro
- Departamento de Qumica Fsica I
- Facultad de Ciencias Qumicas
- Universidad Complutense de Madrid
- 28040 Madrid
- Spain
| | - Luis Rubio-Lago
- Departamento de Qumica Fsica I
- Facultad de Ciencias Qumicas
- Universidad Complutense de Madrid
- 28040 Madrid
- Spain
| | - Jesús González-Vázquez
- Departamento de Qumica
- Módulo 13
- Facultad de Ciencias
- Universidad Autónoma de Madrid
- 28049 Madrid
| | - Luis Bañares
- Departamento de Qumica Fsica I
- Facultad de Ciencias Qumicas
- Universidad Complutense de Madrid
- 28040 Madrid
- Spain
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14
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Kapnas KM, Toulson BW, Foreman ES, Block SA, Hill JG, Murray C. UV photodissociation dynamics of CHI 2Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate. Phys Chem Chem Phys 2017; 19:31039-31053. [PMID: 29160321 DOI: 10.1039/c7cp06532a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photolysis of geminal diiodoalkanes in the presence of molecular oxygen has become an established route to the laboratory production of several Criegee intermediates, and such compounds also have marine sources. Here, we explore the role that the trihaloalkane, chlorodiiodomethane (CHI2Cl), may play as a photolytic precursor for the chlorinated Criegee intermediate ClCHOO. CHI2Cl has been synthesized and its UV absorption spectrum measured; relative to that of CH2I2 the spectrum is shifted to longer wavelength and the photolysis lifetime is calculated to be less than two minutes. The photodissociation dynamics have been investigated using DC slice imaging, probing ground state I and spin-orbit excited I* atoms with 2 + 1 REMPI and single-photon VUV ionization. Total translational energy distributions are bimodal for I atoms and unimodal for I*, with around 72% of the available energy partitioned in to the internal degrees of freedom of the CHICl radical product, independent of photolysis wavelength. A bond dissociation energy of D0 = 1.73 ± 0.11 eV is inferred from the wavelength dependence of the translational energy release, which is slightly weaker than typical C-I bonds. Analysis of the photofragment angular distributions indicate dissociation is prompt and occurs primarily via transitions to states of A'' symmetry. Complementary high-level MRCI calculations, including spin-orbit coupling, have been performed to characterize the excited states and confirm that states of A'' symmetry with highly mixed singlet and triplet character are predominantly responsible for the absorption spectrum. Transient absorption spectroscopy has been used to measure the absorption spectrum of ClCHOO produced from the reaction of CHICl with O2 over the range 345-440 nm. The absorption spectrum, tentatively assigned to the syn conformer, is at shorter wavelengths relative to that of CH2OO and shows far weaker vibrational structure.
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Affiliation(s)
- Kara M Kapnas
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA.
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Toulson BW, Kapnas KM, Fishman DA, Murray C. Competing pathways in the near-UV photochemistry of acetaldehyde. Phys Chem Chem Phys 2017; 19:14276-14288. [DOI: 10.1039/c7cp02573d] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Time-resolved ion imaging measurements have been performed to explore the photochemistry of acetaldehyde at photolysis wavelengths spanning the range 265–328 nm.
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Affiliation(s)
| | - Kara M. Kapnas
- Department of Chemistry
- University of California, Irvine
- Irvine
- USA
| | | | - Craig Murray
- Department of Chemistry
- University of California, Irvine
- Irvine
- USA
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Toulson BW, Murray C. Decomposing the First Absorption Band of OCS Using Photofragment Excitation Spectroscopy. J Phys Chem A 2016; 120:6745-52. [PMID: 27552402 DOI: 10.1021/acs.jpca.6b06060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photofragment excitation spectra of carbonyl sulfide (OCS) have been recorded from 212-260 nm by state-selectively probing either electronically excited S((1)D) or ground state S((3)P) photolysis products via 2 + 1 resonance-enhanced multiphoton ionization. Probing the major S((1)D) product results in a broad, unstructured action spectrum that reproduces the overall shape of the first absorption band. In contrast, spectra obtained probing S((3)P) products display prominent resonances superimposed on a broad continuum; the resonances correspond to the diffuse vibrational structure observed in the conventional absorption spectrum. The vibrational structure is assigned to four progressions, each dominated by the C-S stretch, ν1, following direct excitation to quasi-bound singlet and triplet states. The S((3)PJ) products are formed with a near-statistical population distribution over the J = 2, 1, and 0 spin-orbit levels across the wavelength range investigated. Although a minor contributor to the S atom yield near the peak of the absorption cross section, the relative yield of S((3)P) increases significantly at longer wavelengths. The experimental measurements validate recent theoretical work characterizing the electronic states responsible for the first absorption band by Schmidt and co-workers.
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Affiliation(s)
- Benjamin W Toulson
- Department of Chemistry, University of California, Irvine , Irvine, California 92697, United States
| | - Craig Murray
- Department of Chemistry, University of California, Irvine , Irvine, California 92697, United States
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