Radiative association of He(23P) with lithium cations

Abstract

Formation of HeLi+ molecular ion by radiative association of metastable helium atoms with lithium ions is investigated on the triplet-Sigma manifold. Energy dependent cross-sections are calculated for He(23P) colliding with Li+ in the continuum of the c3Σ+ electronic state and undergoing radiative transition into one of the rotational-vibrational states of the lower electronic states a3Σ+,b3Σ+, or c3Σ+ of HeLi+. Evaluation of the cross-sections is based on the fully quantal approach taking into account all possible state-to-state transitions at thermal energies (spontaneous association) or at higher background temperatures (stimulated association). The corresponding rate coefficients are presented as functions of temperature. Calculations show that the rate coefficients for two-state processes c→a and c→b are several orders of magnitude larger than the rate coefficient for the c-state formation. The rate coefficient for the c→a radiative association reaches 10-15cm3s−1 at low temperatures. As expected stimulation of the radiative association by black-body background radiation has a noticeable effect only on the one-state c→c process.