Collisional rates and cooling within atomic hydrogen plasmas

The experimental cross section is convolved with a Maxwellian distribution of electronic energies to evaluate accurate collisional rates for electron impact ionization of the ground state of atomic hydrogen. An extension of previous work on 1s-2s and 2s-2p scattering rates is reported. These results are supplemented by semiempirical collisional rates for other excitation processes to yield the cooling rate for optically thin hydrogen plasmas. The present numerical results are evaluated for temperatures ranging from 2000 to 100-million K and are fitted to simple analytic formulas designed to be easily incorporated into computer programs.