State-resolved differential scattering in open-shell collisions: Cl(2P3/2)+HCl from high-resolution infrared-laser Dopplerimetry

Abstract

Time- and frequency-resolved IR-laser absorption methods are used to probe state-resolved collisional energy transfer in open-shell collisions of Cl(2P3/2) radicals with HCl(J) in the near single-collision regime. Translationally ‘‘hot’’ Cl(2P3/2) radicals are formed by excimer laser photolysis of Cl2, which then collide with a room-temperature distribution of HCl peaked at J≂3. Final-state distributions of the HCl are monitored via transient absorption detection of a cw IR probe laser by the collisionally populated states (J=4, 5, 6,...,12). In previous work [J. Chem. Phys. 102, 7046 (1995)], these transient signals are used to extract absolute integral collisional cross sections for state-resolved rotational energy transfer into final J states. In the present study, high-resolution IR Dopplerimetry with the single-mode probe laser is used to measure translational distributions of the collisionally populated HCl(J) as a function of final J state. Analysis of these translational distributions leads to state-resolved differential scattering cross sections for rotational energy transfer, which exhibit a strong propensity for forward scattering into all levels observed (J≤12). These results are compared with quasiclassical trajectory calculations (QCT) on a recently modified potential energy surface of Schatz and Gordon. The theoretical analysis is in good agreement with experiment, with the angular distribution dominated by forward scattering for most of the final HCl rotational states. However, for the very highest J states collisionally populated, the QCT calculations predict a shift from predominantly forward to more isotropic scattering that is not evident in the experimental results.

Librational Control of Photochemical Reactions in Small Clusters

“…[23][24][25][26][27][28][29][30] The van der Waals region of the system, corresponding to the Cl‚‚‚HCl cluster, has been mapped in terms of potentials and vibrational/librational eigenstates. 31 It follows from this analysis that the Cl‚‚‚HCl cluster should be more stable than its thoroughly investigated closed-shell Ar‚‚‚HCl analogue, and the possibility of the isolation of the Cl‚‚‚HCl species under supersonic jet conditions has been considered.…”

“…The ClHCl species has been intensively studied both theoretically and experimentally in connection with the symmetric hydrogen exchange reaction Cl + HCl → HCl + Cl and the strongly exothermic Cl 2 + H → HCl + Cl exchange reaction. − The van der Waals region of the system, corresponding to the Cl···HCl cluster, has been mapped in terms of potentials and vibrational/librational eigenstates . It follows from this analysis that the Cl···HCl cluster should be more stable than its thoroughly investigated closed-shell Ar···HCl analogue, and the possibility of the isolation of the Cl···HCl species under supersonic jet conditions has been considered …”

Infrared Spectroscopy and Inelastic Recoil Dynamics of OH Radicals in Complexes with ortho- and para-D2

“…Both of these channels may contribute to the rate of decay of vibrationally activated H 2 −OH. The reactive decay channel may also influence the inelastic scattering dynamics, as some nonreactive encounters may be “frustrated” attempts at chemical reaction. − …”

11 State-to-state rotational inelastic scattering of free radicals

“…Nesbitt and co-workers have used Doppler analysis in infrared laser absorption spectroscopy to explore the inelastic scattering in the XMB 31,32 and in a cell. 32 Using the pump-probe scheme with two high-resolution ring dye lasers, McCaffery and his co-workers 33 performed measurements of velocity-dependent SR-DCS for RIS of alkali metal dimers in a cell. A narrow-band pump laser prepared a single quantum state and a particular velocity component of the molecules in an electronically excited state.…”