Least-squares variational treatment of positron (electron)-diatomic molecule scattering

A computer code based on the least-squares variational method (LSVM) is developed for the treatment of the collisions of positrons and electrons with diatomic molecules. The code was tested and employed for the investigation of the elastic scattering of positrons and electrons by hydrogen molecules within the framework of the adiabatic approximation. The system is described by a set of prolate spheroidal coordinates which is the most suitable representation of diatomic molecules. Reliable convergence of the scattering phaseshifts has been achieved by optimizing the nonlinear parameters and increasing the number of L² components of the trial wavefunctions. The cross section of the lowest partial wave is calculated at energies varying from 0.136 eV to 13.6 eV, under the assumption that positronium formation, exchange interactions, and all excitation channels are closed. A comparison is presented between our results and those determined by other authors.