Plasma-screening effects on direct 1s→2p± electron endash ion collisional excitation rates in dense plasmas

Plasma-screening effects are investigated on the 1s→2p- (m=-1) and 1s→2p+ (m=+1) electron endash ion collisional excitation rates in dense plasmas. The excitation rates are calculated using the semiclassical excitation cross sections obtained by the classical straight-line trajectory approximation with the nonspherical Debye endash Hueckel potential. The results show that the ratio of the 1s→2p+ to 1s→2p- excitation rates is found to be a slowly varying function of the temperature. Including the plasma-screening effects for hydrogenic ions, the ratio is found to be a monotonically increasing function of the parameter (Z2Ry/kT)1/2. However, without the plasma-screening effects, the ratio becomes a monotonically decreasing function. The plasma-screening effects appreciably enhance the 1s→2p- excitation rates and reduce the 1s→2p+ excitation rates. copyright 1996 American Institute of Physics