### Abstract

Photodissociation of vibrationally excited CH_{3}I is studied using a time-dependent quantum mechanical formalism based on the fast Fourier transform (FFT) method. The dissociation dynamics is modeled with two active degrees of freedom, i.e., the dissociation coordinate and the C-H_{3} umbrella coordinate. The ground state vibrational wave functions are calculated using a time-dependent relaxation method proposed by Kosloff and Tal-Ezer. Two coupled excited states are explicitly considered in this model and the potential energy functions are taken from a previous study that was able to reproduce experiments for photodissociation of the CH_{3}I ground state. We investigate the dissociation dynamics of the system after initial vibrational excitation, with particular attention paid to nonadiabatic transitions during the dissociation process. Our calculations show that vibrational excitation can significantly change the product I*/I branching ratio. In particular, it is found that there are significant dips in the I* yield at energies associated with minima in the absorption spectrum. These dips can be attributed to differences in Franck-Condon factors associated with the two excited state potential surfaces. Other observables of the dissociation process, such as the absorption spectrum and fragment vibrational state distributions, have also been investigated.

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

Pages (from-to) | 6562-6568 |

Number of pages | 7 |

Journal | Journal of Chemical Physics |

Volume | 94 |

Issue number | 10 |

Publication status | Published - 1991 |

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### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

### Cite this

_{3}I.

*Journal of Chemical Physics*,

*94*(10), 6562-6568.

**Quantum nonadiabatic effects in the photodissociation of vibrationally excited CH _{3}I.** / Guo, Hua; Lao, Kai Qin; Schatz, George C; Hammerich, Audrey Dell.

Research output: Contribution to journal › Article

_{3}I',

*Journal of Chemical Physics*, vol. 94, no. 10, pp. 6562-6568.

_{3}I. Journal of Chemical Physics. 1991;94(10):6562-6568.

}

TY - JOUR

T1 - Quantum nonadiabatic effects in the photodissociation of vibrationally excited CH3I

AU - Guo, Hua

AU - Lao, Kai Qin

AU - Schatz, George C

AU - Hammerich, Audrey Dell

PY - 1991

Y1 - 1991

N2 - Photodissociation of vibrationally excited CH3I is studied using a time-dependent quantum mechanical formalism based on the fast Fourier transform (FFT) method. The dissociation dynamics is modeled with two active degrees of freedom, i.e., the dissociation coordinate and the C-H3 umbrella coordinate. The ground state vibrational wave functions are calculated using a time-dependent relaxation method proposed by Kosloff and Tal-Ezer. Two coupled excited states are explicitly considered in this model and the potential energy functions are taken from a previous study that was able to reproduce experiments for photodissociation of the CH3I ground state. We investigate the dissociation dynamics of the system after initial vibrational excitation, with particular attention paid to nonadiabatic transitions during the dissociation process. Our calculations show that vibrational excitation can significantly change the product I*/I branching ratio. In particular, it is found that there are significant dips in the I* yield at energies associated with minima in the absorption spectrum. These dips can be attributed to differences in Franck-Condon factors associated with the two excited state potential surfaces. Other observables of the dissociation process, such as the absorption spectrum and fragment vibrational state distributions, have also been investigated.

AB - Photodissociation of vibrationally excited CH3I is studied using a time-dependent quantum mechanical formalism based on the fast Fourier transform (FFT) method. The dissociation dynamics is modeled with two active degrees of freedom, i.e., the dissociation coordinate and the C-H3 umbrella coordinate. The ground state vibrational wave functions are calculated using a time-dependent relaxation method proposed by Kosloff and Tal-Ezer. Two coupled excited states are explicitly considered in this model and the potential energy functions are taken from a previous study that was able to reproduce experiments for photodissociation of the CH3I ground state. We investigate the dissociation dynamics of the system after initial vibrational excitation, with particular attention paid to nonadiabatic transitions during the dissociation process. Our calculations show that vibrational excitation can significantly change the product I*/I branching ratio. In particular, it is found that there are significant dips in the I* yield at energies associated with minima in the absorption spectrum. These dips can be attributed to differences in Franck-Condon factors associated with the two excited state potential surfaces. Other observables of the dissociation process, such as the absorption spectrum and fragment vibrational state distributions, have also been investigated.

UR - http://www.scopus.com/inward/record.url?scp=0001243960&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001243960&partnerID=8YFLogxK

M3 - Article

VL - 94

SP - 6562

EP - 6568

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 10

ER -