Abstract
Through the use of Fourier-transform spectroscopy, the electron-impact optical cross sections for the infrared emissions from the and levels of the helium atom have been measured for gas pressures between 3 and 50 mTorr and incident electron energies from threshold to 200 eV. The very strong pressure dependence of these measured emission cross sections at different energies is in excellent quantitative agreement with the mechanism of excitation transfer from the levels through collisions with ground-state helium atoms. From our data, we determine the electron-impact cross sections for excitation into the and levels. The effects of the singlet-triplet mixing in the nF states on the excitation cross sections are discussed. The excitation data of the level are compared with those of and We have also obtained the collisional excitation transfer cross sections for
- Received 29 June 1998
DOI:https://doi.org/10.1103/PhysRevA.58.4572
©1998 American Physical Society