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Photodissociation transition states characterized by chirped pulse millimeter wave spectroscopy. Proc Natl Acad Sci U S A 2020; 117:146-151. [PMID: 31852828 DOI: 10.1073/pnas.1911326116] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The 193-nm photolysis of CH2CHCN illustrates the capability of chirped-pulse Fourier transform millimeter-wave spectroscopy to characterize transition states. We investigate the HCN, HNC photofragments in highly excited vibrational states using both frequency and intensity information. Measured relative intensities of J = 1-0 rotational transition lines yield vibrational-level population distributions (VPD). These VPDs encode the properties of the parent molecule transition state at which the fragment molecule was born. A Poisson distribution formalism, based on the generalized Franck-Condon principle, is proposed as a framework for extracting information about the transition-state structure from the observed VPD. We employ the isotopologue CH2CDCN to disentangle the unimolecular 3-center DCN elimination mechanism from other pathways to HCN. Our experimental results reveal a previously unknown transition state that we tentatively associate with the HCN eliminated via a secondary, bimolecular reaction.
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2
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Suas-David N, Thawoos S, Suits AG. A uniform flow-cavity ring-down spectrometer (UF-CRDS): A new setup for spectroscopy and kinetics at low temperature. J Chem Phys 2019; 151:244202. [PMID: 31893907 DOI: 10.1063/1.5125574] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The UF-CRDS (Uniform Flow-Cavity Ring Down Spectrometer) is a new setup coupling for the first time a pulsed uniform (Laval) flow with a continuous wave CRDS in the near infrared for spectroscopy and kinetics at low temperature. This high resolution and sensitive absorption spectrometer opens a new window into the phenomena occurring within UFs. The approach extends the detection range to new electronic and rovibrational transitions within Laval flows and offers the possibility to probe numerous species which have not been investigated yet. This new tool has been designed to probe radicals and reaction intermediates but also to follow the chemistry of hydrocarbon chains and PAHs which play a crucial role in the evolution of astrophysical environments. For kinetics measurements, the UF-CRDS combines the CRESU technique (French acronym meaning reaction kinetics in uniform supersonic flows) with the SKaR (Simultaneous Kinetics and Ring-Down) approach where, as indicated by its name, the entire reaction is monitored during each intensity decay within the high finesse cavity. The setup and the approach are demonstrated with the study of the reaction between CN (v = 1) and propene at low temperature. The recorded data are finally consistent with a previous study of the same reaction for CN (v = 0) relying on the CRESU technique with laser induced fluorescence detection.
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Affiliation(s)
- N Suas-David
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - S Thawoos
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - A G Suits
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
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Reza MA, Telfah H, Xu R, Liu J. Room-Temperature Cavity Ring-Down Spectroscopy of Methylallyl Peroxy Radicals. J Phys Chem A 2019; 123:3510-3517. [PMID: 30939007 DOI: 10.1021/acs.jpca.9b01233] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report room-temperature cavity ring-down (CRD) spectra of the à ← X̃ electronic transition of 1-, 2-, and 3-methylallyl peroxy (MAOO•) radicals produced by 193 nm photolysis of methyl-substituted allyl chlorides in the presence of O2. Vibronic structure of experimentally observed spectra was simulated using calculated relative populations of MAOO• conformers, their electronic transition frequencies and oscillator strengths, as well as their vibrational frequencies and Franck-Condon factors of the à ← X̃ electronic transition. The reaction intermediate for the production of 1- and 3-MAOO• radicals, CH3CHCHCH2, is a resonance-stabilized free radical. CRD spectra of 1- and 3-MAOO• radicals obtained using different precursors suggest that allylic rearrangement between the two resonance structures (CH3CH=CHCH2• and CH3CH•CH=CH2) is significantly faster than oxygen addition. Branching ratio between terminal and nonterminal oxygen addition was predicted to be 52:48 on the basis of calculated spin densities, which agrees qualitatively with the experimental CRD spectra of 1- and 3-MAOO• radicals.
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Affiliation(s)
| | | | | | - Jinjun Liu
- Conn Center for Renewable Energy Research , University of Louisville , Louisville , Kentucky 40292 , United States
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4
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Lewis T, Heard DE, Blitz MA. A novel multiplex absorption spectrometer for time-resolved studies. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:024101. [PMID: 29495797 DOI: 10.1063/1.5006539] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A Time-Resolved Ultraviolet/Visible (UV/Vis) Absorption Spectrometer (TRUVAS) has been developed that can simultaneously monitor absorption at all wavelengths between 200 and 800 nm with millisecond time resolution. A pulsed photolysis laser (KrF 248 nm) is used to initiate chemical reactions that create the target species. The absorption signals from these species evolve as the composition of the gas in the photolysis region changes over time. The instrument can operate at pressures over the range ∼10-800 Torr and can measure time-resolved absorbances <10-4 in the UV (300 nm) and even lower in the visible (580 nm) 2.3 × 10-5, with the peak of sensitivity at ∼500 nm. The novelty of this setup lies in the arrangement of the multipass optics. Although appearing similar to other multipass optical systems (in particular the Herriott cell), there are fundamental differences, most notably the ability to adjust each mirror to maximise the overlap between the probe beam and the photolysis laser. Another feature which aids the sensitivity and versatility of the system is the use of 2 high-throughput spectrographs coupled with sensitive line-array CCDs, which can measure absorbance from ∼200 to 800 nm simultaneously. The capability of the instrument is demonstrated via measurements of the absorption spectrum of the peroxy radical, HOCH2CH2O2, and its self-reaction kinetics.
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Affiliation(s)
- Thomas Lewis
- School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Dwayne E Heard
- School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Mark A Blitz
- School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom
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Codd T, Chen MW, Roudjane M, Stanton JF, Miller TA. Jet cooled cavity ringdown spectroscopy of the A˜2E″←X˜2A2′ transition of the NO3 radical. J Chem Phys 2015; 142:184305. [DOI: 10.1063/1.4919690] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Terrance Codd
- Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210, USA
| | - Ming-Wei Chen
- Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210, USA
| | - Mourad Roudjane
- Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210, USA
| | - John F. Stanton
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Terry A. Miller
- Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210, USA
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Chhantyal-Pun R, Chen MW, Miller TA. Laser induced fluorescence study of the - transition of FCH2CH2O. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2012.11.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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8
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Prozument K, Shaver RG, Ciuba MA, Muenter JS, Park GB, Stanton JF, Guo H, Wong BM, Perry DS, Field RW. A new approach toward transition state spectroscopy. Faraday Discuss 2013; 163:33-57; discussion 117-38. [DOI: 10.1039/c3fd20160k] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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9
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Tanner CM, Quack M. Reinvestigation of the ν2 + 2ν3subband in the overtone icosad of12CH4using cavity ring-down (CRD) spectroscopy of a supersonic jet expansion. Mol Phys 2012. [DOI: 10.1080/00268976.2012.702934] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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10
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Kline ND, Miller TA. Analysis of the A∼–X∼ electronic transition of the 2,1-hydroxypropylperoxy radical using cavity ringdown spectroscopy. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.01.056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Chen MW, Just GMP, Codd T, Miller TA. Spectroscopic studies of the ÖX̃ electronic spectrum of the β-hydroxyethylperoxy radical: Structure and dynamics. J Chem Phys 2011; 135:184304. [DOI: 10.1063/1.3656835] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Dupré P. Axis-switching in the vibrationless Ã←X̃ transition of the jet-cooled deuterated methyl peroxy radical CD3O2. J Chem Phys 2011; 134:244308. [PMID: 21721631 DOI: 10.1063/1.3599953] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The jet-cooled high resolution spectrum of the vibrationless Ã←X̃ transition of the deuterated species of the methyl peroxy radical has been recently published in this journal (S. Wu, P. Dupré, P. Rupper, and T. A. Miller, J. Chem. Phys. 127, 224305 (2007)). The spectrum was analyzed using a rigid-rotor model with quadratic spin-rotation coupling. The analysis was based on the fit of ∼350 partially resolved line positions and was quite satisfactory. However, the full simulation of the spectral intensity clearly identifies a lack of ability to reproduce relatively small line clumps ("extra" lines) located between the two main central Q branches. This is indicating of an incomplete initial analysis. In the present paper we reanalyze this electronic transition by considering a reference-frame axis-switching resulting from the nuclear rearrangement associated to the electronic transition (spectra obtained at two different temperatures are considered). The potential energy hypersurfaces of the two electronic states are sufficiently dissimilar to induce changes in the molecule geometry, particularly, the angle COÔ, which induces a rotation (∼1.7°) of the principal axes of inertia located in the molecule symmetry plane. The present analysis is supported by a global fitting of the spectrum intensity and gives rise to a slightly different set of molecular constants. Attention is paid to the wavefunction symmetry assignment of a non-orthorhombic molecule. Couplings due to the torsion of the methyl group are discussed in the following paper (P. Dupre, J. Chem. Phys. 134, 244309 (2011)).
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Affiliation(s)
- Patrick Dupré
- The University of York, Department of Chemistry, Heslington, York, United Kingdom.
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Gao B, Jiang W, Liu AW, Lu Y, Cheng CF, Cheng GS, Hu SM. Ultrasensitive near-infrared cavity ring-down spectrometer for precise line profile measurement. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:043105. [PMID: 20441323 DOI: 10.1063/1.3385675] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A cavity ring-down (CRD) spectrometer is built with a continuous-wave Ti:sapphire ring laser. Using a pair of R approximately 0.999 95 high-reflective mirrors, the noise-equivalent minimum detectable absorption loss reaches 7 x 10(-11)/cm over the spectral range of 780-830 nm. A thermal-stabilized Fabry-Perot interferometer is applied to calibrate the CRD spectrum with an accuracy of 1 x 10(-4) cm(-1). The quantitative measurement is carried out for the line profile measurements of some overtone absorption lines of C(2)H(2) near 787 nm. Doppler determined line shape has been observed with milli-Torr acetylene gas in the ring-down cavity. The instrumental line width is estimated from the line profile fitting to be <1 x 10(-4) cm(-1). It demonstrates that the CRD spectrometer with extremely high sensitivity is also very suitable for quantitative measurements including precise line profile studies in the near-infrared.
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Affiliation(s)
- Bo Gao
- Department of Chemical Physics, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
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Just GMP, Rupper P, Miller TA, Meerts WL. High-resolution cavity ringdown spectroscopy of the jet-cooled propyl peroxy radical C3H7O2. Phys Chem Chem Phys 2010; 12:4773-82. [DOI: 10.1039/b924323b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Just GMP, Rupper P, Miller TA, Meerts WL. High-resolution cavity ringdown spectroscopy of the jet-cooled ethyl peroxy radical C2H5O2. J Chem Phys 2009; 131:184303. [PMID: 19916600 DOI: 10.1063/1.3262612] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have recorded high resolution, partially rotationally resolved, jet-cooled cavity ringdown spectra of the origin band of the A-X electronic transition of both the G and T conformers of the perproteo and perdeutero isotopologues of the ethyl peroxy radical, C(2)H(5)O(2). This transition, located in the near infrared, was studied using a narrow band laser source (< or approximately 250 MHz) and a supersonic slit-jet expansion coupled with an electric discharge allowing us to obtain rotational temperatures of about 15 K. All four spectra have been successfully simulated using an evolutionary algorithm approach with a Hamiltonian including rotational and spin-rotational terms. Excellent agreement with the experimental spectra was obtained by fitting seven molecular parameters in each ground and the first excited electronic states as well as the band origin of the electronic transition. This analysis unambiguously confirms the assignment of the lower frequency origin band to the G conformer and the higher frequency one to the T conformer.
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Affiliation(s)
- Gabriel M P Just
- Department of Chemistry, Laser Spectroscopy Facility, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210, USA
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Zolot AM, Nesbitt DJ. Crossed jet reactive scattering dynamics of F+H2O→HF(v,J)+OH:HF(v,J) product quantum state distributions under single-collision conditions. J Chem Phys 2008; 129:184305. [DOI: 10.1063/1.2998524] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Sharp EN, Rupper P, Miller TA. The structure and spectra of organic peroxy radicals. Phys Chem Chem Phys 2008; 10:3955-81. [DOI: 10.1039/b800954f] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Wu S, Dupré P, Rupper P, Miller TA. The vibrationless Ã←X̃ transition of the jet-cooled deuterated methyl peroxy radical CD3O2 by cavity ringdown spectroscopy. J Chem Phys 2007; 127:224305. [DOI: 10.1063/1.2802202] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Wong DM, Dagdigian PJ. Comparison of IR and UV cavity ring-down spectroscopy detection of transient intermediates: pyrolysis of methyl azide to form methyleneimine. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2007; 67:1019-24. [PMID: 17088097 DOI: 10.1016/j.saa.2006.09.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 09/15/2006] [Accepted: 09/18/2006] [Indexed: 05/12/2023]
Abstract
Mid-infrared cavity ring-down spectroscopy (CRDS) has been employed in this study to examine the hydride stretching region of methyl azide and its pyrolysis product methyleneimine. The absorption spectrum of methyl azide over 2835-3085 cm(-1) was recorded, and the integrated absorption cross section was determined. The pyrolysis of methyl azide and subsequent production of methyleneimine was observed at various wavenumbers. Using IR CRDS, we were able to observe vibrational transitions of methyleneimine without interference from the methyl azide precursor. Our previous UV CRDS study showed that electronic transitions of methyleneimine overlapped with those of methyl azide. IR CRDS should thus be useful for the detection of polyatomic transient intermediates without interference from precursors.
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Affiliation(s)
- Diane M Wong
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218-2685, USA
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Herman M, Didriche† K, Hurtmans D, Kizil B, Macko P, Rizopoulos A, Poucke PV. FANTASIO: a versatile experimental set-up to investigate jet-cooled molecules. Mol Phys 2007. [DOI: 10.1080/00268970601063820] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Dupré P, Miller TA. Quasi-Fourier-transform limited, scannable, high energy titanium-sapphire laser source for high resolution spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:033102. [PMID: 17411173 DOI: 10.1063/1.2670804] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A tunable injection seeded Ti:sapphire laser source has been developed and tested. Slave-master tandem cavity and ramp-lock-and-fire concepts have been implemented and fully controlled by a digital signal processor. A Fourier-transform-based analysis, as well as direct measurements, have demonstrated spectral linewidths in the range of 3.5-15 MHz (HWHM), with potential tunability over the entire Ti:sapphire lasing range. A quasi-Fourier-transform limited spectral linewidth is demonstrated assuming a secant hyperbolic shape of the electromagnetic field. Output energies >100 mJ have been reached with approximately 300 mJ of pump energy. The highest spectral purity is obtained using the quadruple pumping scheme.
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Affiliation(s)
- Patrick Dupré
- Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA.
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Rupper P, Sharp EN, Tarczay G, Miller TA. Investigation of Ethyl Peroxy Radical Conformers via Cavity Ringdown Spectroscopy of the Ã-X̃ Electronic Transition. J Phys Chem A 2007; 111:832-40. [PMID: 17266223 DOI: 10.1021/jp066464m] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Both stable conformers, trans (T) and gauche (G), of the ethyl peroxy radical and its perdeutero analogue have been observed via cavity ringdown spectroscopy (CRDS) of the A2A'-X2A' ' electronic transition in the near-IR. Assignments of specific spectral lines to the electronic transition origin (T00), to observed vibrational hot bands, and to the COO bend and the O-O stretch vibrations are given with the help of equation of motion (EOMIP) quantum chemical calculations. In particular, spectral information for the previously unknown/unassigned T conformer of ethyl peroxy is given in this study for the first time and compared to the data for the previously observed G conformer. The conformer assignment is confirmed by an analysis of the partially resolved rotational structures. The electronic origins for the T and G conformers of C2H5O2 are located at 7362(1) and 7592(1) cm-1, respectively.
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Affiliation(s)
- Patrick Rupper
- Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 West 18th Avenue, Columbus, Ohio 43210, USA
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Miller TA. Spectroscopic probing and diagnostics of the geometric structure of the alkoxy and alkyl peroxy radical intermediates. Mol Phys 2006. [DOI: 10.1080/00268970600747746] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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