Abstract
We have determined limits on the cross section for both electronically nonadiabatic excitation and quenching in the Cl (Pj2) + D2 system. Our experiment incorporates crossed-molecular-beam scattering with state-selective Cl (P 12,32 2) detection and velocity-mapped ion imaging. By colliding atomic chlorine with D2, we address the propensity for collisions that result in a change of the spin-orbit level of atomic chlorine either through electronically nonadiabatic spin-orbit excitation Cl (P 32 2) + D2 → Cl* (P 12 2) + D2 or through electronically nonadiabatic spin-orbit quenching Cl* (P 12 2) + D2 →Cl (P 32 2) + D2. In the first part of this report, we estimate an upper limit for the electronically nonadiabatic spin-orbit excitation cross section at a collision energy of 5.3 kcalmol, which lies above the energy of the reaction barrier (4.9 kcalmol). Our analysis and simulation of the experimental data determine an upper limit for the excitation cross section as σNA ≤0.012 Å2. In the second part of this paper we investigate the propensity for electronically nonadiabatic spin-orbit quenching of Cl * following a collision with D2 or He. We perform these experiments at collision energies above and below the energy of the reaction barrier. By comparing the amount of scattered Cl* in our images to the amount of Cl* lost from the atomic beam we obtain the maximum cross section for electronically nonadiabatic quenching as σNA ≤ 15 -15 +44 Å2 for a collision energy of 7.6 kcalmol. Our experiments show the probability for electronically nonadiabatic quenching in Cl* + D2 to be indistinguishable to that for the kinematically identical system of Cl* +He.