REMPI-TOF studies of the translational anisotropy and the polarization of the O (1D2) photofragment angular momentum following ozone photolysis at 298 nm

Abstract

The translational anisotropy and the polarization of the electronic angular momentum of the O (¹D₂) fragment produced from the 298 nm photodissociation of ozone have been determined using resonance enhanced multiphoton ionization (REMPI) in conjunction with time-of-flight mass spectrometry (TOFMS). The translational anisotropy parameter β, which is necessarily averaged over the O₂ co-fragment rotational distribution, is measured to be 1.08 ± 0.04. This is consistent with that expected for the ¹B₂ ← ¹A₁ transition within an impulsive model if the tangential velocity associated with the zero point motion of the bend is constricted to opening the bond angle. Molecular frame polarization parameters of rank up to k = 4 have been extracted for the O (¹D₂) fragment and the calculated m_J populations show a strong preference for the |m_J| = 1 states. A small coherence term is also observed, a manifestation of the nuclear geometry of the dissociating molecule and the existence of possible non-adiabatic processes in the exit channel. The orientation associated with the mapping of the photon helicity onto the O (¹D₂) electronic angular momentum distribution was observed to have been quenched. However, the parameter γ₁′, which describes the contribution to the orientation from a coherent superposition of a parallel and perpendicular excitation where the photofragment angular momentum lies perpendicular to both the recoil velocity and to the transition dipole moment, was determined to be −0.06.