Jb. Boffard et al., Electron-impact-excitation cross sections out of the 2 S-3 metastable level of helium at high energies, PHYS REV A, 59(5), 1999, pp. 4079-4082
In this paper we report experimental measurements of the electron-impact-el
;citation cross sections out of the 2 S-3 metastable level of helium into h
igher excited levels, with emphasis on measurements at high electron energi
es. The agreement between our metastable results and recent theoretical cal
culations is comparable to the agreement between experimental and theoretic
al values for excitation from the ground state. [S1050-2947(99)09905-9].