### Abstract

The molecular structure, intramolecular rearrangement and dissociation energy of C_{2}H_{3} have been studied with high-level ab initio calculations using ACES II and MOLCAS-2 programs. In the structural calculations of C_{2}H_{3}, the optimized geometry and vibrational frequencies of X̃ ^{2}A′, the vertical electronic transition energies (Ã ^{2}A″ ← X̃ ^{2}A′ and B̃ ^{2}A′ ← X̃ ^{2}A′), the vertical ionization potential and the permanent dipole moment of X̃ ^{2}A′ have been computed. The harmonic vibrational frequencies and infrared intensities of C_{2}H_{3} X̃ ^{2}A′ obtained from this calculation will help the spectroscopic observation for the vibrational modes, most of which are unobserved. The calculated vertical transition energy, 25529 cm^{-1} for Ã ^{2}A″ ← X̃ ^{2}A′, and the vertical ionization potential, 8.33 eV from an MRCI method with atomic natural orbitals, are in excellent agreement with the experimental values of 24815 cm^{-1} and 8.25 eV, respectively. The vertical transition of B̃ ^{2}A′ ← X̃ ^{2}A′, predicted to be 43910 cm^{-1} from this work, will facilitate the experimental search for the undiscovered B̃ state of C_{2}H_{3} through spectroscopic observation. In calculating the intramolecular rearrangement in C_{2}H_{3} X̃ ^{2}A′, using CCSD(T)/Dunning's triple zeta polarizations, the non-classical structure with a hydrogen atom bridged between the C=C bond has been found to lie at least 47 kcal/mol above the classical equilibrium structure. The calculation also indicates that the non-classical C_{2}H_{3} X̃ ^{2}A′ is an unstable isomer, corresponding to a transition state. The computed barrier for the tunnelling of α-H in C_{2}H_{3} X̃ ^{2}A′ is also in excellent agreement with the upper bound limit of < 1500 cm^{-1} determined from high-resolution infrared spectroscopy. The dissociation energy of C_{2}H_{3} → C_{2}H_{2} + H and the energy difference between the isomers of acetylene and vinylidene, calculated in the present study, are also consistent with experimental measurements.

Original language | English |
---|---|

Pages (from-to) | 43-56 |

Number of pages | 14 |

Journal | Chemical Physics |

Volume | 206 |

Issue number | 1-2 |

DOIs | |

Publication status | Published - 1996 May 15 |

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### ASJC Scopus subject areas

- Physics and Astronomy(all)
- Physical and Theoretical Chemistry

### Cite this

_{2}H

_{3}.

*Chemical Physics*,

*206*(1-2), 43-56. https://doi.org/10.1016/0301-0104(95)00441-6

**Theoretical study of isomeric structures and low-lying electronic states of the vinyl radical C _{2}H_{3}.** / Wang, Jeng Han; Chang, Hung Chang; Chen, Yit Tsong.

Research output: Contribution to journal › Article

_{2}H

_{3}',

*Chemical Physics*, vol. 206, no. 1-2, pp. 43-56. https://doi.org/10.1016/0301-0104(95)00441-6

_{2}H

_{3}. Chemical Physics. 1996 May 15;206(1-2):43-56. https://doi.org/10.1016/0301-0104(95)00441-6

}

TY - JOUR

T1 - Theoretical study of isomeric structures and low-lying electronic states of the vinyl radical C2H3

AU - Wang, Jeng Han

AU - Chang, Hung Chang

AU - Chen, Yit Tsong

PY - 1996/5/15

Y1 - 1996/5/15

N2 - The molecular structure, intramolecular rearrangement and dissociation energy of C2H3 have been studied with high-level ab initio calculations using ACES II and MOLCAS-2 programs. In the structural calculations of C2H3, the optimized geometry and vibrational frequencies of X̃ 2A′, the vertical electronic transition energies (Ã 2A″ ← X̃ 2A′ and B̃ 2A′ ← X̃ 2A′), the vertical ionization potential and the permanent dipole moment of X̃ 2A′ have been computed. The harmonic vibrational frequencies and infrared intensities of C2H3 X̃ 2A′ obtained from this calculation will help the spectroscopic observation for the vibrational modes, most of which are unobserved. The calculated vertical transition energy, 25529 cm-1 for Ã 2A″ ← X̃ 2A′, and the vertical ionization potential, 8.33 eV from an MRCI method with atomic natural orbitals, are in excellent agreement with the experimental values of 24815 cm-1 and 8.25 eV, respectively. The vertical transition of B̃ 2A′ ← X̃ 2A′, predicted to be 43910 cm-1 from this work, will facilitate the experimental search for the undiscovered B̃ state of C2H3 through spectroscopic observation. In calculating the intramolecular rearrangement in C2H3 X̃ 2A′, using CCSD(T)/Dunning's triple zeta polarizations, the non-classical structure with a hydrogen atom bridged between the C=C bond has been found to lie at least 47 kcal/mol above the classical equilibrium structure. The calculation also indicates that the non-classical C2H3 X̃ 2A′ is an unstable isomer, corresponding to a transition state. The computed barrier for the tunnelling of α-H in C2H3 X̃ 2A′ is also in excellent agreement with the upper bound limit of < 1500 cm-1 determined from high-resolution infrared spectroscopy. The dissociation energy of C2H3 → C2H2 + H and the energy difference between the isomers of acetylene and vinylidene, calculated in the present study, are also consistent with experimental measurements.

AB - The molecular structure, intramolecular rearrangement and dissociation energy of C2H3 have been studied with high-level ab initio calculations using ACES II and MOLCAS-2 programs. In the structural calculations of C2H3, the optimized geometry and vibrational frequencies of X̃ 2A′, the vertical electronic transition energies (Ã 2A″ ← X̃ 2A′ and B̃ 2A′ ← X̃ 2A′), the vertical ionization potential and the permanent dipole moment of X̃ 2A′ have been computed. The harmonic vibrational frequencies and infrared intensities of C2H3 X̃ 2A′ obtained from this calculation will help the spectroscopic observation for the vibrational modes, most of which are unobserved. The calculated vertical transition energy, 25529 cm-1 for Ã 2A″ ← X̃ 2A′, and the vertical ionization potential, 8.33 eV from an MRCI method with atomic natural orbitals, are in excellent agreement with the experimental values of 24815 cm-1 and 8.25 eV, respectively. The vertical transition of B̃ 2A′ ← X̃ 2A′, predicted to be 43910 cm-1 from this work, will facilitate the experimental search for the undiscovered B̃ state of C2H3 through spectroscopic observation. In calculating the intramolecular rearrangement in C2H3 X̃ 2A′, using CCSD(T)/Dunning's triple zeta polarizations, the non-classical structure with a hydrogen atom bridged between the C=C bond has been found to lie at least 47 kcal/mol above the classical equilibrium structure. The calculation also indicates that the non-classical C2H3 X̃ 2A′ is an unstable isomer, corresponding to a transition state. The computed barrier for the tunnelling of α-H in C2H3 X̃ 2A′ is also in excellent agreement with the upper bound limit of < 1500 cm-1 determined from high-resolution infrared spectroscopy. The dissociation energy of C2H3 → C2H2 + H and the energy difference between the isomers of acetylene and vinylidene, calculated in the present study, are also consistent with experimental measurements.

UR - http://www.scopus.com/inward/record.url?scp=0030559308&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030559308&partnerID=8YFLogxK

U2 - 10.1016/0301-0104(95)00441-6

DO - 10.1016/0301-0104(95)00441-6

M3 - Article

AN - SCOPUS:0030559308

VL - 206

SP - 43

EP - 56

JO - Chemical Physics

JF - Chemical Physics

SN - 0301-0104

IS - 1-2

ER -