The generalized oscillator strengths for the valence shell excitations in helium by fast electron impact

The generalized oscillator strengths (GOSs) for the valence shell excitations of 21S, 31S, 31P + 31D, 41S, 41P + 41D, 51S + 51P + 51D, and 61S + 61P + 61D in helium were measured by a high-resolution angular-resolved fast-electron energy loss spectrometer at the incident energy of 2500 eV and the value of the momentum transfer square from K2 = 0.07 to 3.6 a.u. In the present measurement, the impact energy was higher, and the momentum transfer was higher except for 21S. The first Born approximation was reached for these transitions under the present experimental condition. The GOS of 41S was measured for the first time.