Photolysis and spectroscopy of vibrationally excited C-H overtones of CHFCl2 Academic Article uri icon

abstract

  • Photodissociation of jet-cooled vibrationally excited CHFCl2 coupled with mass spectroscopic detection of 35Cl (2P3/2) [Cl], 35Cl (2P1/2) [Cl*], 37Cl (2P3/2), 37Cl (2P1/2), and H photofragments was performed. It enabled determination of Cl*/Cl and H/[Cl* + Cl] branching ratios and measurement of the action spectra of the N = 3, N = 7/2, and N = 4 CH stretch−bend polyads. Enhanced C−Cl and C−H bond breaking was observed for all the initially prepared C−H stretch−bend states demonstrating that energy is not preserved in the initial state but rather flows into the other part of the molecule. The yield of Cl* photofragments was found to be about half that of Cl for ∼235 nm photolysis of vibrationally excited CHFCl2. The action spectra are significantly narrower than the room-temperature photoacoustic spectra due to reduction of the rotational inhomogeneous structure. The action spectra also enabled one to resolve the components arising from the different isotopomers of the precursor and a resonance splitting attributed to a local resonance of the 7/21 polyad component with a combination of the 7/23 component and the ClCCl bending. This splitting reflects a ∼3 ps period for the vibrational redistribution and indicates that the coupling of the stretch−bend mixed state to the rest of the molecule is weaker than the stretch−bend coupling itself.

publication date

  • January 1, 2000