Photoionization of helium: study of He+H nu =He⁺(n=2)+e

Simultaneous excitation and ionization of helium to the n=2 state has been studied between 100 and 200 eV, at angles theta =54 degrees 44' and theta =90 degrees between photon and photo-electron. The cross section ratio ( sigma 2s+ sigma 2p)/ sigma 1s agrees well with the theoretical prediction by Jacobs and Burke; also the theoretical values of sigma 1s/ sigma 2p and asymmetry parameter beta 2p are consistent with experimental data.