Photodissociation and intramolecular dynamics of vibrationally excited CHF2Cl Academic Article uri icon

abstract

  • Photodissociation of jet-cooled, vibrationally excited CHF2Cl molecules was studied in a time-of-flight mass spectrometer to elucidate bond rupture and intramolecular dynamics. The molecules were first excited with infrared photons to the N=3, N=7/2, and N=4 C–H stretch-bend polyad components, representing stretch-bend mixed states. They were then dissociated via promotion to excited electronic states by ∼235 or 243.135 nm photons, which also tagged 35Cl(2Pj) and 37Cl(2Pj) or H photofragments, respectively, by (2+1) resonantly enhanced multiphoton ionization. Comparison of the photofragment yield spectra to the simultaneously measured room-temperature infrared absorption spectra revealed significant narrowing of the former due to the reduction of rotational inhomogeneous structure. These spectra, and particularly the band contraction, afforded observation of resonance splitting in the vicinity of the 31, 34, 41, and 44 components, reflecting redistribution times in the range of 1–18 ps. These times manifest the vibrational redistribution of the mixed states to other states of the molecule and are longer than those for the coupling of the stretch-bend. The initial vibrational excitation enhanced C–Cl and C–H bond cleavage with the former producing both ground-, Cl 2P3/2[Cl], and excited-, Cl 2P1/2[Cl∗], spin-orbit states. The branching ratio of Cl∗/Cl was ∼0.5 and of H/[Cl∗+Cl]∼0.1, independent on the initially prepared state, signifying preferential production of Cl photofragments and energy flow from the initially excited bond. © 2002 American Institute of Physics.

publication date

  • January 1, 2002