Collisional rates and cooling within atomic hydrogen plasmas

Accurate collisional rates for electron impact ionization of the ground state of atomic hydrogen are evaluated by convolving the experimental cross section with a Maxwellian distribution of electronic energies. An extension of previous work on 1s-2s and 1s-2p scattering rates is also reported. These results are supplemented by semiempirical collisional rates for other excitation processes to yield the cooling rate for optically thin hydrogen plasmas. The numerical results are evaluated for temperatures ranging from 2 × 10 3 K to 1 × 10 8 K and fitted to simple analytic designed to be easily incorporated into computer programs