Close-coupled calculation of field-free collisions of cold metastable helium atoms

A quantum-mechanical close-coupled calculation of field-free collisions of cold metastable helium atoms has been performed. Theoretical predictions of the rate coefficients for elastic processes and losses due to the Penning and associative ionization processes are reported for temperatures ranging from 1 μK to 1 K. The sensitivity of the rate constants to uncertainties in the molecular potentials and autoionization widths has been investigated. The total ionization loss rates were found to be sensitive to the short-range form of the 1Σg+ molecular potential and the autoionization widths, while the total elastic rate constants exhibit greater sensitivity to the short-range 5Σg+ molecular potential