Excitation of spectral lines of the principal series of the helium atom and ion in electron-atom collisions

In electron-atom collisions, VUV emission spectra of He I (50--60 nm) and He II (20--30 nm) were studied, and the excitation functions were measured for spectral lines corresponding to the 1snp--1s2 He I and np--1s He II (n< or =4) transitions in the energy range from the excitation threshold to 500 eV. Absolute values of the excitation cross sections of the lines studied were estimated. The law of decrease of the cross sections (at the maximum) within the series with an increase in the principal quantum number of the initial line level was established