Quantum-mechanical phase interference and optical polarization in low-energyNa+-Ne inelastic collisions

Abstract

Pronounced oscillatory structure and strong optical polarization effects have been observed in emission cross sections for the production of optical radiation measured as a function of energy in low-energy (100 eV to 6 keV) ${\mathrm{Na}}^{+}$-Ne atomic collisions. Highly regular oscillatory structure found in the energy dependence of the emission cross sections for ten $\mathrm{NeI}(3p\ensuremath{\rightarrow}3s)$ optical transitions is observed to be in antiphase with similar structure in two $\mathrm{NaI}(3p\ensuremath{\rightarrow}3s)$ optical emission cross sections. In addition, large polarization effects have been observed in optical radiation from excited $J\ensuremath{\ne}0$ states. In one particular case involving a $J=1$ to $J=0$ transition, oscillations in the excitation function appear to arise exclusively from the polarization component of the radiation perpendicular to the beam direction. These observations indicate strong sublevel-state selection processes associated with collisional quantum-mechanical phase-interference phenomena. A simple model is presented which allows us to uniquely determine for the first time the quasimolecular states responsible for such oscillatory structure and consequently associated with each polarization component. Analysis based on the model for the case of the ${\mathrm{Na}}^{*}(3p)$ radiation data indicates that the oscillatory structure is not attributable to interactions between simple single-electron diabatic states as believed previously. Similar analysis of the ${\mathrm{Ne}}^{*}(3p)$ radiation data uniquely identifies the $^{1}\ensuremath{\Pi}(\ensuremath{\Omega}=\ifmmode\pm\else\textpm\fi{}1)$ and $^{3}\ensuremath{\Pi}(\ensuremath{\Omega}=\ifmmode\pm\else\textpm\fi{}2)$ molecular states as the major contributors.