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Wiberg KB, Rablen PR. Re-Examination of Some Carbocations. Structures, Energies, and Charge Distributions. J Org Chem 2020; 85:11741-11749. [PMID: 32808777 DOI: 10.1021/acs.joc.0c01469] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chemists have had a long-standing interest in reactive intermediates such as carbenes, carbon radicals, carbanions, and carbocations. Carbocations are an interesting part of this group because of their tendency to undergo rearrangement, sometimes forming bridged ions, as well as their ability in many cases of spreading out the positive charge over several atoms. We have re-examined some of these cases using high-level compound procedures, W1BD and G4, as well as by considering the charge distributions making use of the Hirshfeld method that has been shown to uniquely correlate with several types of experimental data.
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Affiliation(s)
- Kenneth B Wiberg
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Paul R Rablen
- Department of Chemistry, Swarthmore College, Swarthmore, Pennsylvania 19081, United States
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2
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Porterfield JP, Bross DH, Ruscic B, Thorpe JH, Nguyen TL, Baraban JH, Stanton JF, Daily JW, Ellison GB. Thermal Decomposition of Potential Ester Biofuels. Part I: Methyl Acetate and Methyl Butanoate. J Phys Chem A 2017; 121:4658-4677. [PMID: 28517940 DOI: 10.1021/acs.jpca.7b02639] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two methyl esters were examined as models for the pyrolysis of biofuels. Dilute samples (0.06-0.13%) of methyl acetate (CH3COOCH3) and methyl butanoate (CH3CH2CH2COOCH3) were entrained in (He, Ar) carrier gas and decomposed in a set of flash-pyrolysis microreactors. The pyrolysis products resulting from the methyl esters were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by matrix infrared absorption spectroscopy. Pyrolysis pressures in the pulsed microreactor were about 20 Torr and residence times through the reactors were roughly 25-150 μs. Reactor temperatures of 300-1600 K were explored. Decomposition of CH3COOCH3 commences at 1000 K, and the initial products are (CH2═C═O and CH3OH). As the microreactor is heated to 1300 K, a mixture of CH2═C═O and CH3OH, CH3, CH2═O, H, CO, and CO2 appears. The thermal cracking of CH3CH2CH2COOCH3 begins at 800 K with the formation of CH3CH2CH═C═O and CH3OH. By 1300 K, the pyrolysis of methyl butanoate yields a complex mixture of CH3CH2CH═C═O, CH3OH, CH3, CH2═O, CO, CO2, CH3CH═CH2, CH2CHCH2, CH2═C═CH2, HCCCH2, CH2═C═C═O, CH2═CH2, HC≡CH, and CH2═C═O. On the basis of the results from the thermal cracking of methyl acetate and methyl butanoate, we predict several important decomposition channels for the pyrolysis of fatty acid methyl esters, R-CH2-COOCH3. The lowest-energy fragmentation will be a 4-center elimination of methanol to form the ketene RCH═C═O. At higher temperatures, concerted fragmentation to radicals will ensue to produce a mixture of species: (RCH2 + CO2 + CH3) and (RCH2 + CO + CH2═O + H). Thermal cracking of the β C-C bond of the methyl ester will generate the radicals (R and H) as well as CH2═C═O + CH2═O. The thermochemistry of methyl acetate and its fragmentation products were obtained via the Active Thermochemical Tables (ATcT) approach, resulting in ΔfH298(CH3COOCH3) = -98.7 ± 0.2 kcal mol-1, ΔfH298(CH3CO2) = -45.7 ± 0.3 kcal mol-1, and ΔfH298(COOCH3) = -38.3 ± 0.4 kcal mol-1.
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Affiliation(s)
| | - David H Bross
- 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.,Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - James H Thorpe
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
| | - Thanh Lam Nguyen
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
| | | | - John F Stanton
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States.,Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States
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3
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Buckingham GT, Porterfield JP, Kostko O, Troy TP, Ahmed M, Robichaud DJ, Nimlos MR, Daily JW, Ellison GB. The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical. J Chem Phys 2016; 145:014305. [DOI: 10.1063/1.4954895] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Grant T. Buckingham
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden Colorado 80401, USA
| | - Jessica P. Porterfield
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA
| | - Oleg Kostko
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Tyler P. Troy
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - David J. Robichaud
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden Colorado 80401, USA
| | - Mark R. Nimlos
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden Colorado 80401, USA
| | - John W. Daily
- Department of Mechanical Engineering, Center for Combustion and Environmental Research, University of Colorado, Boulder, Colorado 80309-0427, USA
| | - G. Barney Ellison
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA
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4
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Lu Z, Gao H, Xu YT, Yang L, Lam CS, Benitez Y, Ng CY. High-Resolution Threshold Photoelectron Spectroscopy by Vacuum Ultraviolet Laser Velocity-Map-Imaging Method. CHINESE J CHEM PHYS 2016. [DOI: 10.1063/1674-0068/29/cjcp1512247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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5
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Porterfield JP, Nguyen TL, Baraban JH, Buckingham GT, Troy TP, Kostko O, Ahmed M, Stanton JF, Daily JW, Ellison GB. Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor. J Phys Chem A 2015; 119:12635-47. [DOI: 10.1021/acs.jpca.5b10984] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jessica P. Porterfield
- Department
of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - Thanh Lam Nguyen
- Department
of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Joshua H. Baraban
- Department
of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - Grant T. Buckingham
- Department
of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - Tyler P. Troy
- Chemical
Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, California 94720, United States
| | - Oleg Kostko
- Chemical
Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, California 94720, United States
| | - Musahid Ahmed
- Chemical
Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, California 94720, United States
| | - John F. Stanton
- Department
of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - John W. Daily
- Center
for Combustion and Environmental Research, Department of Mechanical
Engineering, University of Colorado, Boulder, Colorado 80309-0427, United States
| | - G. Barney Ellison
- Department
of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
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Krechkivska O, Wilcox C, O’Connor GD, Nauta K, Kable SH, Schmidt TW. Ionization Energies of Three Resonance-Stabilized Radicals: Cyclohexadienyl (dn, n = 0, 1, 6, 7), 1-Phenylpropargyl, and Methylcyclohexadienyl. J Phys Chem A 2014; 118:10252-8. [DOI: 10.1021/jp508985s] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Olha Krechkivska
- School
of Chemistry, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Callan Wilcox
- School
of Chemistry, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Gerard D. O’Connor
- School
of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Klaas Nauta
- School
of Chemistry, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Scott H. Kable
- School
of Chemistry, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Timothy W. Schmidt
- School
of Chemistry, UNSW Sydney, Sydney, New South Wales 2052, Australia
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Ng CY. State-to-State Spectroscopy and Dynamics of Ions and Neutrals by Photoionization and Photoelectron Methods. Annu Rev Phys Chem 2014; 65:197-224. [DOI: 10.1146/annurev-physchem-040412-110002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Cheuk-Yiu Ng
- Department of Chemistry, University of California, Davis, California 95616;
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8
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Tian Z, Lis L, Kass SR. Carbon–Hydrogen Bond Dissociation Energies: The Curious Case of Cyclopropene. J Org Chem 2013; 78:12650-3. [DOI: 10.1021/jo402263v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhixin Tian
- Department
of Chemistry, Tongji University, Shanghai 200092, China
| | - Lev Lis
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Steven R. Kass
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Fischer KH, Hemberger P, Bodi A, Fischer I. Photoionisation of the tropyl radical. Beilstein J Org Chem 2013; 9:681-8. [PMID: 23616813 PMCID: PMC3629033 DOI: 10.3762/bjoc.9.77] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 03/13/2013] [Indexed: 11/23/2022] Open
Abstract
We present a study on the photoionisation of the cycloheptatrienyl (tropyl) radical, C7H7, using tunable vacuum ultraviolet synchrotron radiation. Tropyl is generated by flash pyrolysis from bitropyl. Ions and electrons are detected in coincidence, permitting us to record mass-selected photoelectron spectra. The threshold photoelectron spectrum of tropyl, corresponding to the X+ 1A1’ ← X2E2” transition, reveals an ionisation energy of 6.23 ± 0.02 eV, in good agreement with Rydberg extrapolations, but slightly lower than the value derived from earlier photoelectron spectra. Several vibrations can be resolved and are reassigned to the C–C stretch mode ν16+ and to a combination of ν16+ with the ring breathing mode ν2+. Above 10.55 eV dissociative photoionisation of tropyl is observed, leading to the formation of C5H5+ and C2H2.
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Affiliation(s)
- Kathrin H Fischer
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland Süd, 97074 Würzburg, Germany
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10
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Affiliation(s)
- Michael A. Duncan
- Department
of Chemistry, University of Georgia, Athens, Georgia 30602, United
States
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11
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Gao H, Lu Z, Yang L, Zhou J, Ng CY. Communication: A vibrational study of propargyl cation using the vacuum ultraviolet laser velocity-map imaging photoelectron method. J Chem Phys 2012; 137:161101. [PMID: 23126688 DOI: 10.1063/1.4764306] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
By employing the vacuum ultraviolet (VUV) laser velocity-map imaging photoelectron (VUV-VMI-PE) method, we have obtained a vibrationally resolved photoelectron spectrum of gaseous propargyl radical [C(3)H(3)(X(2)B(1))] in the energy range of 0-4600 cm(-1) above its ionization energy. The cold C(3)H(3) radicals were produced from a supersonically cooled radical beam source based on 193 nm ArF photodissociation of C(3)H(3)Cl. The VUV-VMI-PE spectrum of C(3)H(3) thus obtained reveals a Franck-Condon factor (FCF) pattern with a highly dominant origin band along with weak vibrational progressions associated with excitations of the C-C ν(5)(+)(a(1)) and C≡C ν(3)(+)(a(1)) symmetric stretching modes and the CCH ν(7)(+)(b(1)) out-of-plane bending mode of C(3)H(3)(+)(X(1)A(1)). The ν(5)(+)(a(1)) vibrational frequency of 1120 cm(-1) determined in the present study is lower than the value deduced from the recent Ar-tagged infrared photodissociation study by 102 cm(-1), confirming the highly accurate vibrational frequency predictions obtained by the most recent state-of-the-art ab initio quantum calculations. The observation of the FCF disallowed ν(7)(+)(b(1)) mode is indicative of vibronic interactions. The discrepancy observed between the FCF pattern determined in the present study and that predicted by a recent high-level quantum theoretical investigation can be taken as evidence that the potential energy surfaces used in the latter theoretical study are in need of improvement in order to provide a reliable FCF prediction for the C(3)H(3)/C(3)H(3)(+) photoionization system.
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Affiliation(s)
- Hong Gao
- Department of Chemistry, University of California, Davis, California 95616, USA
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12
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Lau KC, Ng CY. Note: Accurate ab initio predictions of ionization energies of propargyl and allyl radicals: Revisited. J Chem Phys 2011; 135:246101. [DOI: 10.1063/1.3673443] [Citation(s) in RCA: 7] [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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13
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Gao H, Xu Y, Yang L, Lam CS, Wang H, Zhou J, Ng CY. High-resolution threshold photoelectron study of the propargyl radical by the vacuum ultraviolet laser velocity-map imaging method. J Chem Phys 2011; 135:224304. [DOI: 10.1063/1.3664864] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Trevitt AJ, Soorkia S, Savee JD, Selby TS, Osborn DL, Taatjes CA, Leone SR. Branching Fractions of the CN + C3H6 Reaction Using Synchrotron Photoionization Mass Spectrometry: Evidence for the 3-Cyanopropene Product. J Phys Chem A 2011; 115:13467-73. [DOI: 10.1021/jp208496r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Adam J. Trevitt
- School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Satchin Soorkia
- Departments of Chemistry and Physics, University of California, Berkeley, California 94720, United States
| | - John D. Savee
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551, United States
| | - Talitha S. Selby
- Department of Chemistry, University of Wisconsin—Washington County, West Bend, Wisconsin 53095, United States
| | - David L. Osborn
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551, United States
| | - Craig A. Taatjes
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551, United States
| | - Stephen R. Leone
- Departments of Chemistry and Physics, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
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15
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Troy TP, Chalyavi N, Menon AS, O'Connor GD, Fückel B, Nauta K, Radom L, Schmidt TW. The spectroscopy and thermochemistry of phenylallyl radical chromophores. Chem Sci 2011. [DOI: 10.1039/c1sc00247c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Shuman NS, Stevens WR, Lower K, Baer T. Heat of Formation of the Allyl Ion by TPEPICO Spectroscopy. J Phys Chem A 2009; 113:10710-6. [DOI: 10.1021/jp906691a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicholas S. Shuman
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - William R. Stevens
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Katherine Lower
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Tomas Baer
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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Gasser M, Schulenburg AM, Dietiker PM, Bach A, Merkt F, Chen P. Single-photon and resonance-enhanced multiphoton threshold ionization of the allyl radical. J Chem Phys 2009; 131:014304. [DOI: 10.1063/1.3157185] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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18
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Xing X, Wang P, Reed B, Baek SJ, Ng CY. Infrared Vacuum-Ultraviolet Laser Pulsed Field Ionization-Photoelectron Study of CH3Br+(X̃2E3/2). J Phys Chem A 2008; 112:9277-82. [DOI: 10.1021/jp8019649] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- X. Xing
- Department of Chemistry, University of California, Davis, Davis, California 95616, USA
| | - P. Wang
- Department of Chemistry, University of California, Davis, Davis, California 95616, USA
| | - B. Reed
- Department of Chemistry, University of California, Davis, Davis, California 95616, USA
| | - S.-J. Baek
- Department of Chemistry, University of California, Davis, Davis, California 95616, USA
| | - C. Y. Ng
- Department of Chemistry, University of California, Davis, Davis, California 95616, USA
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Xing X, Reed B, Bahng MK, Baek SJ, Wang P, Ng CY. Infrared–vacuum ultraviolet–pulsed field ionization–photoelectron study of CH3I+ using a high-resolution infrared laser. J Chem Phys 2008; 128:104306. [DOI: 10.1063/1.2888557] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Douberly GE, Ricks AM, Schleyer PVR, Duncan MA. Infrared spectroscopy of gas phase C3H5+: The allyl and 2-propenyl cations. J Chem Phys 2008; 128:021102. [DOI: 10.1063/1.2828553] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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