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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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Chang YC, Lam CS, Reed B, Lau KC, Liou HT, Ng CY. Rovibronically Selected and Resolved Two-Color Laser Photoionization and Photoelectron Study of the Iron Carbide Cation. J Phys Chem A 2009; 113:4242-8. [DOI: 10.1021/jp810797v] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Y.-C. Chang
- Department of Chemistry, University of California, Davis, Davis, California 95616, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, and Department of Biochemistry and Chemistry, City University of Hong Kong, Kowloon, Hong Kong
| | - C.-S. Lam
- Department of Chemistry, University of California, Davis, Davis, California 95616, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, and Department of Biochemistry and Chemistry, City University of Hong Kong, Kowloon, Hong Kong
| | - B. Reed
- Department of Chemistry, University of California, Davis, Davis, California 95616, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, and Department of Biochemistry and Chemistry, City University of Hong Kong, Kowloon, Hong Kong
| | - K.-C. Lau
- Department of Chemistry, University of California, Davis, Davis, California 95616, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, and Department of Biochemistry and Chemistry, City University of Hong Kong, Kowloon, Hong Kong
| | - H. T. Liou
- Department of Chemistry, University of California, Davis, Davis, California 95616, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, and Department of Biochemistry and Chemistry, City University of Hong Kong, Kowloon, Hong Kong
| | - C. Y. Ng
- Department of Chemistry, University of California, Davis, Davis, California 95616, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, and Department of Biochemistry and Chemistry, City University of Hong Kong, Kowloon, Hong Kong
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Hou Y, Woo HK, Wang P, Xing X, Ng CY, Lau KC. Vacuum ultraviolet pulsed field ionization-photoelectron and infrared-photoinduced Rydberg ionization study of trans-1,3-butadiene. J Chem Phys 2008; 129:114305. [DOI: 10.1063/1.2973635] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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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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Lau KC, Woo HK, Wang P, Xing X, Ng CY. Vacuum ultraviolet laser pulsed field ionization-photoelectron study ofcis-dichloroethene. J Chem Phys 2006; 124:224311. [PMID: 16784278 DOI: 10.1063/1.2207610] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The vacuum ultraviolet (VUV) laser pulsed field ionization photoelectron (PFI-PE) spectrum of cis-dichloroethene (cis-ClCH[Double Bond]CHCl) has been measured in the energy region of 77 600-79 500 cm(-1). On the basis of the semiempirical simulation of the origin PFI-PE band, we have obtained the IE(cis-ClCH[Double Bond]CHCl) to be 77 899.5+/-2.0 cm(-1) (9.658 39+/-0.000 25 eV). The assignment of the vibrational bands resolved in the VUV-PFI-PE spectrum are guided by high-level ab initio calculations of the vibrational frequencies for cis-ClCH[Double Bond]CHCl(+) and the Franck-Condon factors for the ionization transitions. Combining the results of the present VUV-PFI-PE measurement and the recent VUV-infrared-photoinduced Rydberg ionization study, the vibrational frequencies for eleven of the twelve vibrational modes of cis-ClCH[Double Bond]CHCl(+) have been experimentally determined: nu(1) (+)(a(1))=181 cm(-1), nu(2) (+)(a(2))=277 cm(-1), nu(3) (+)(b(2))=580 cm(-1), nu(4) (+)(b(1))=730 cm(-1), nu(5) (+)(a(1))=810 cm(-1), nu(6) (+)(a(2))=901 cm(-1), nu(8) (+)(a(1))=1196 cm(-1), nu(9) (+)(b(2))=1348 cm(-1), nu(10) (+)(a(1))=1429 cm(-1), nu(11) (+)(b(2))=3067 cm(-1), and nu(12) (+)(a(1))=3090 cm(-1)). These values are compared to theoretical anharmonic vibrational frequencies obtained at the MP2/6-311G(2df,p) and CCSD(T)/6-311G(2df,p) levels. The IE prediction for cis-ClCH[Double Bond]CHCl has also been calculated with the wave function based CCSD(T)/CBS method, which involves the approximation to the complete basis set (CBS) and the high-level correlation corrections. The theoretical IE(cis-ClCH[Double Bond]CHCl)=9.668 eV thus obtained is found to have a deviation of less than 10 meV with respect to the experimental IE value.
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Affiliation(s)
- K-C Lau
- Department of Chemistry, University of California, Davis, Davis, California 95616, USA
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C. Lau K, Ng CY. Accurate ab initio Predictions of Ionization Energies and Heats of Formation for Cyclopropenylidene, Propargylene and Propadienylidene. CHINESE J CHEM PHYS 2006. [DOI: 10.1360/cjcp2006.19(1).29.10] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lau KC, Ng CY. Accurate ab initio predictions of ionization energies and heats of formation for the 2-propyl, phenyl, and benzyl radicals. J Chem Phys 2006; 124:044323. [PMID: 16460178 DOI: 10.1063/1.2148950] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ionization energies (IEs) for the 2-propyl (2-C(3)H(7)), phenyl (C(6)H(5)), and benzyl (C(6)H(5)CH(2)) radicals have been calculated by the wave-function-based ab initio CCSD(T)/CBS approach, which involves the approximation to the complete basis set (CBS) limit at the coupled cluster level with single and double excitations plus quasiperturbative triple excitation [CCSD(T)]. The zero-point vibrational energy correction, the core-valence electronic correction, and the scalar relativistic effect correction have been also made in these calculations. Although a precise IE value for the 2-C(3)H(7) radical has not been directly determined before due to the poor Franck-Condon factor for the photoionization transition at the ionization threshold, the experimental value deduced indirectly using other known energetic data is found to be in good accord with the present CCSD(T)/CBS prediction. The comparison between the predicted value through the focal-point analysis and the highly precise experimental value for the IE(C(6)H(5)CH(2)) determined in the previous pulsed field ionization photoelectron (PFI-PE) study shows that the CCSD(T)/CBS method is capable of providing an accurate IE prediction for C(6)H(5)CH(2), achieving an error limit of 35 meV. The benchmarking of the CCSD(T)/CBS IE(C(6)H(5)CH(2)) prediction suggests that the CCSD(T)/CBS IE(C(6)H(5)) prediction obtained here has a similar accuracy of 35 meV. Taking into account this error limit for the CCSD(T)/CBS prediction and the experimental uncertainty, the CCSD(T)/CBS IE(C(6)H(5)) value is also consistent with the IE(C(6)H(5)) reported in the previous HeI photoelectron measurement. Furthermore, the present study provides support for the conclusion that the CCSD(T)/CBS approach with high-level energy corrections can be used to provide reliable IE predictions for C(3)-C(7) hydrocarbon radicals with an uncertainty of +/-35 meV. Employing the atomization scheme, we have also computed the 0 K (298 K) heats of formation in kJ/mol at the CCSD(T)/CBS level for 2-C(3)H(7)/2-C(3)H(7) (+) ,C(6)H(5)/C(6)H(5) (+), and C(6)H(5)CH(2)/C(6)H(5)CH(2) (+) to be 105.2/822.7 (90.0/806.4), 351.4/1148.5 (340.4/1138.8), and 226.2/929.0 (210.3/912.7), respectively. Comparing these values with the available experimental values, we find that the discrepancies for the 0 and 298 K heats of formation values are < or =2.6 kJ/mol for 2-C(3)H(7)/2-C(3)H(7) (+),< or =4.1 kJ/mol for C(6)H(5)/C(6)H(5) (+), and < or =3.2 kJ//mol for C(6)H(5)CH(2)C(6)H(5)CH(2) (+).
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Affiliation(s)
- K-C Lau
- Department of Chemistry, University of California, Davis, California 95616, USA
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Lee M, Kim H, Lee YS, Kim MS. Vibrational assignment and Franck-Condon analysis of the mass-analyzed threshold ionization (MATI) spectrum of CH2ClI: the effect of strong spin-orbit interaction. J Chem Phys 2005; 122:244319. [PMID: 16035769 DOI: 10.1063/1.1948384] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Detailed analysis of the one-photon mass-analyzed threshold ionization (MATI) spectrum of CH(2)ClI is presented. This includes the determination of the ionization energy of CH(2)ClI, complete vibrational assignments, and quantum-chemical calculations at the spin-orbit density-functional-theory (SODFT) level with various basis sets. Relativistic effective core potentials with effective spin-orbit operators can be used in SODFT calculations to treat the spin-orbit term on an equal footing with other relativistic effects and electron correlations. The comparison of calculated and experimental vibrational frequencies indicate that the spin-orbit effects are essential for the reasonable description of the CH(2)ClI(+) cation. Geometrical parameters and thus the molecular shape of the cation are greatly influenced by the spin-orbit effects even for the ground state. Calculated geometrical parameters deviate substantially for different basis sets or effective core potentials. In an effort to derive the exact geometrical parameters for this cation, SODFT geometries were further improved utilizing Franck-Condon fit of the MATI spectral pattern. This empirical fitting produced the well-converged set of geometrical parameters that are quite insensitive to the choice of SODFT calculations. The C-I bond length and the Cl-C-I bond angle show large deviations among different SODFT calculations, but the empirical spectral fitting yields 2.191 +/- 0.003 Angstroms for the C-I bond length and 107.09 +/- 0.09 degrees for the Cl-C-I angle. Those fitted geometrical parameters along with the experimental vibrational frequencies could serve as a useful reference in calibrating relativistic quantum-chemical methods for radicals.
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Affiliation(s)
- Mina Lee
- National Creative Research Initiative Center for Control of Reaction Dynamics and School of Chemistry, Seoul National University, Korea
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Lau KC, Ng CY. Accurate ab initio predictions of ionization energies of hydrocarbon radicals: CH2, CH3, C2H, C2H3, C2H5, C3H3, and C3H5. J Chem Phys 2005; 122:224310. [PMID: 15974671 DOI: 10.1063/1.1926274] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ionization energies for methylene (CH2), methyl (CH3), ethynyl (C2H), vinyl (C2H3), ethyl (C2H5), propargyl (C3H3), and allyl (C3H5) radicals have been calculated by the wave-function-based ab initio CCSD(T)/CBS approach, which involves the approximation to the complete basis set (CBS) limit at the coupled-cluster level with single and double excitations plus a quasiperturbative triple excitation [CCSD(T)]. When it is appropriate, the zero-point vibrational energy correction, the core-valence electronic correction, the scalar relativistic effect correction, the diagonal Born-Oppenheimer correction, and the high-order correlation correction have also been made in these calculations. The comparison between the computed ionization energy (IE) values and the highly precise experimental IE values determined in previous pulsed field ionization-photoelectron (PFI-PE) studies indicates that the CCSD(T)/CBS method is capable of providing accurate IE predictions for these hydrocarbon radicals achieving error limits well within +/-10 meV. The benchmarking of the CCSD(T)/CBS IE predictions by the PFI-PE experimental results also lends strong support for the conclusion that the CCSD(T)/CBS approach with high-level energy corrections can serve as a valuable alternative for reliable IE determination of radicals, particularly for those radicals with very unfavorable Franck-Condon factors for photoionization transitions near their ionization thresholds.
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Affiliation(s)
- K-C Lau
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, USA
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Woo HK, Wang P, Lau KC, Xing X, Ng CY. Vacuum Ultraviolet (VUV) Pulsed Field Ionization−Photoelectron and VUV−IR Photoinduced Rydberg Ionization Study of trans-Dichloroethene. J Phys Chem A 2004. [DOI: 10.1021/jp040250s] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- H. K. Woo
- Department of Chemistry, University of California at Davis, One Shields Avenue, Davis, California 95616
| | - P. Wang
- Department of Chemistry, University of California at Davis, One Shields Avenue, Davis, California 95616
| | - K. C. Lau
- Department of Chemistry, University of California at Davis, One Shields Avenue, Davis, California 95616
| | - X. Xing
- Department of Chemistry, University of California at Davis, One Shields Avenue, Davis, California 95616
| | - C. Y. Ng
- Department of Chemistry, University of California at Davis, One Shields Avenue, Davis, California 95616
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