Four-vector correlation experiment onNe(3p)+Hecollisions: Measurements on intramultiplet mixing

Abstract

Intramultiplet mixing collisions have been investigated using polarized $\mathrm{Ne}(3p)$ atoms with a well-defined initial relative velocity, i.e., two initial-state vectors. By analyzing the final-state center-of-mass velocity with a (Doppler-detuned) probe laser with a well-defined polarization and detecting the laser-induced fluorescence we measure the differential cross section and the polarization of the final state, i.e., two final-state vectors. Measurements have been done at a collision energy $E=70\mathrm{meV},$ for both the ${\ensuremath{\alpha}}_{7}$ and ${\ensuremath{\alpha}}_{9}$ (Paschen numbering) initial states. For the elastic ${\ensuremath{\alpha}}_{7}\ensuremath{\rightarrow}{\ensuremath{\alpha}}_{7}$ collisions the experimental results are strongly hindered by the undesired response on elastic scattering of the metastable $\mathrm{Ne}{(3s,}^{3}{P}_{0})$ state. Inelastic collisions have been investigated for the ${\ensuremath{\alpha}}_{9}$ state, that forms a closed level system with the metastable $\mathrm{Ne}{(3s,}^{3}{P}_{2})$ state. For the ${\ensuremath{\alpha}}_{9}\ensuremath{\rightarrow}{\ensuremath{\alpha}}_{8}$ transition experimental results are presented for both parallel and perpendicular orientations of the polarizations of the pump and probe laser, respectively, as well as for circular polarized $({\ensuremath{\sigma}}^{+},{\ensuremath{\sigma}}^{+})$ and $({\ensuremath{\sigma}}^{+},{\ensuremath{\sigma}}^{\ensuremath{-}})$ configurations. The experiments are compared to a full quantum-mechanical coupled channels calculation of the scattering process, using the model potentials of Hennecart and Masnou-Seeuws as input. The output of this calculation is combined with a density matrix description of the initial- and final-state polarization. Both shape of the differential cross sections and their relative scaling for different laser polarizarion configurations agree well with experiment. This gives strong support for the quality of the model potentials used.