Primer on Collisions
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II) Electron-Impact Excitation out of the ground state of Atoms

D. Pressure Effects

Collision Transfer in He(41D)

Besides the value of the apparent cross section increasing with pressure, the shape of the excitation function changes from a sharply peak to a broad maxima. As with the 33D level, the 41D level's pressure effects are due to cascades from the nF levels. Whose own pressure effects are due to collisional transfer from n1P levels.

1.7 mTorr33 mTorr 130 mTorr
41D Cross section (in arbitrary units) versus Electron energy (in eV).

Theory of Collision Transfer of Excitation in Helium Chun C. Lin, and Richard G. Fowler, Annal of Physics 15 (1961) 461-469.

Collisional Excitation Transfer to the 41D State in Helium by Multiple State Mechanism Chun C. Lin, and Robert M. St. John, Physical Review 128 (1962) 1749-1753.
last updated: May-18-1997