The low energy collision between metastable Ne*(3 P 0,2) and He(1 S 0): ab initio potentials, differential cross sections and polarization effects

Abstract

Potential energies for molecular states dissociating into Ne*(1P1,3P0,1,2) + He(1S0) have been calculated ab initio within the distance range 4–100a0. The SCF energy (without spin-orbit interaction) is optimized on the lowest3Σ state. After CI, the four Λ-states (1,3Σ,1,3Π)are obtained. They dissociate into Ne*(1,3P) + He(1S). All of them are repulsive atR ≲ 8a0, they exhibit shallow wells around 12a0 and have a correct asymptotic behaviour (∼ -R−6). The spin-orbit interaction is introduced, using the Cohen-Schneider scheme, and adiabatic Ω-potentials are derived. The collision at low energy (E ≦ 124 meV) is described in the frame of a fragment-state basis. By means of a deflation procedure, it is shown that states dissociating into Ne*(1P1) + He can be eliminated, which lead to a 9 × 9 interaction matrix dynamically equivalent to the original 12 × 12 matrix, in the subspace of interest. Collision channels are defined by angular momenta,J (total),j (of Ne*) andl (of the relative motion). Scattering radial equations are solved by the algorithm of Gordon and theS matrix is derived. Two sets of physically meaningful scattering amplitudes (and differential cross sections) are constructed, referred to the incident axis or to the initial and final directions of the internuclear axis. Polarization effects are discussed. The case of a quantization axis perpendicular to the collision plane is also mentioned.