LAUSR

The potential energy surface (PES) for the CP(X2Σ+)$\mathrm{CP}(\mathrm{X}^{2}\varSigma^{+})$-He(1S)$\mathrm{He}(^{1}S)$ complex has been calculated at the RCCSD(T)-F12/VTZ-F12 level of theory. The analytic fit of the PES was obtained by using global analytical method. The fitted PES was used subsequently in the close-coupling approach for the computation of the state-to-state collisional excitation cross sections of the fine-structure levels of the CP-He complex. Collision energies were taken up to 1500 cm−1 and they yield after thermal averaging, state-to-state rate coefficients up to 200 K. The propensity rules between the lowest fine-structure levels were studied. These rules show, on one hand, a strong propensity in favour of even ΔN$\Delta N$ transitions, and the other hand, that cross sections and collisional rate coefficients for Δj=ΔN$\Delta j =\Delta N$ transitions are larger than those for Δj≠ΔN$\Delta j\neq \Delta N$ transitions.