MOMENTUM-TRANSFER IN PHOTOIONIZATION PROCESSES

Photo-ionization of an atom by a photon of energy hv involves absorpti on of momentum h nu/c, where c is the speed of light. That momentum is shared between the ion produced and the electron ejected. In order to calculate the fraction of the momentum given to the electron it is ne cessary to allow for interference between the dipole and quadrupole ph otoionization amplitudes. Results for H 1s states were given by Sommer feld in 1930. The present paper gives similar results for H 1s, 2s, 3s , 2p, 3p and 3d. These results are of interest in connection with calc ulations of selective radiation pressures which lead to diffusive sepa rations of chemical elements in stars.