VIBRATIONAL SPECTRA AND AB-INITIO CALCULATIONS FOR THE STUDY OF INTRAMOLECULAR VIBRATIONAL REDISTRIBUTION IN THE CH-CHROMOPHORE IN {$\mathrm{CHD_2I}$}
Loading...
Date
2007
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Intramolecular vibrational energy redistribution (IVR) on the femto- to picosecond time scale is a central primary process in unimolecular chemical reaction dynamics. There are two main approaches towards its understanding. One is the analysis of the highly resolved vibrational spectra of polyatomic molecules} (ed. by J. Manz and L. Woeste), Verlag Chemie, Weinheim, 781 (1995); M. Quack, Chimia, 55 (10), 753 (2001) and references therein.}${}^{,}$} combined with {\em ab initio} calculations. Another approach consists in time resolved femtosecond (fs) pump-probe experiments, which we have recently carried out for a series of alkyliodides} including {$\mathrm{CHD_2I}$}. For the latter molecule we present here results for IVR processes within the CH-chromophore. The infrared absorption spectrum of {$\mathrm{CHD_2I}$} from 500 to 12000 cm$^{-1}$ has been recorded with a Bomem Fourier transform infrared spectrometer equipped with a White type multi reflection cell and resolutions of 0.10 and 0.15 cm$^{-1}$. The CH-chromophore bands dominate the vibrational overtone spectrum of {$\mathrm{CHD_2I}$} and we have assigned 24 of them. Vibrational variational calculations were carried out for the overtone spectrum of the CH-chromophore based on a 3-dimensional {\em ab initio} potential energy and electric dipole moment surface in normal coordinates. The anharmonic resonance structure between the CH-stretching and bending modes was investigated via an effective Hamiltonian for both experimental and theoretical spectra. Finally, we have calculated the time dependent dynamics on the fs time scale}.
Description
Author Institution: Laboratorium fur Physikalische Chemie, ETH Zurich, CH-8093, Zurich, Switzerland