Charge transfer and association of Na+ with 87Rb atoms from extremely low to intermediate energies

The nonradiative charge-transfer processes in Na+ + Rb-87(5s) collisions have been investigated by using the quantum-mechanical molecular-orbital close-coupling method and the two-center atomic-orbital close-coupling method for the energy range of 10(-4)-5 and 0.3-100 keV/u, respectively. The radiative charge-transfer, radiative-decay, and radiative-association processes have been investigated by using the fully quantum, optical-potential, and semiclassical methods for the energy range of 10(-18)-0.2 eV/u. The nonradiative charge-transfer processes dominate the collisions for energies above 0.2 eV/u and radiative-decay processes dominate in the lower-energy region. At the very low collision energies of 10(-18)-10(-3) eV/u, the radiative-association process is more important than the radiative charge-transfer process. Most importantly, it is found that the radiative cross sections exhibit Langevin behavior as E-1/2 for energies less than 10(-2) eV/u.