Probing spin-orbit quenching in Cl (²P) + H₂ via crossed molecular beam scattering

Abstract.

In our previous work we investigated electronically non-adiabatic effects in $\rm Cl~(^{2}P_{3/2,1/2})+D_{2}$ using crossed molecular beam scattering coupled with velocity mapped ion imaging. The prior experiments placed limits on the cross-section for electronically non-adiabatic spin-orbit excitation $\rm Cl~(^{2}P_{3/2})+D_{2} \to Cl^*~(^{2}P_{1/2})+D_{2}$ and electronically non-adiabatic spin-orbit quenching $\rm Cl^*~(^{2}P_{1/2})+D_{2}\to Cl~(^{2}P_{3/2})+D_{2}$. In the present work, we investigate electronically non-adiabatic spin-orbit quenching for $\rm Cl^*~(^{2}P_{1/2})+H_{2}$ which is the required first step for the reaction of Cl^* to produce ground state HCl+H products. In these experiments we collide Cl (²P) with H₂ at a series of fixed collision energies using a crossed molecular beam machine with velocity mapped ion imaging detection. Through an analysis of our ion images, we determine the fraction of electronically adiabatic scattering in Cl^* +H₂, which allows us to place limits on the cross-section for electronically non-adiabatic scattering or quenching. We determine the following quenching cross-sections σ _quench(2.1 kcal/mol) = 26 ±  21 Å², σ _quench(4.0 kcal/mol) = 21 ±  49 Å², and σ _quench(5.6 kcal/mol) = 14 ±  41 Å².