Helium oscillator strengths

Figure 1 Generalized oscillator strength for the 1 transition in helium obtained by Lassettre...

Figure 11 A Platzman plot, the ratio of the experimental single differential cross section for electron emission from helium by 1-MeV protons to the corresponding Rutherford cross sections plotted as a function of RjE. The experimental cross sections are from Ref. 54 and the differential oscillator strength is taken from Ref. 43.

The pioneering studies of electron-ion coincidence at small momentum transfer by Van der Wiel and his co-workers provided the first approximate data for dipole oscillator strengths for the multiple ionization of helium and neon,8-11 argon,149 and krypton and xenon141 in both valence... 

The absorption oscillator strength for CH4 was obtained24 from the forward scattering. The absolute ionization efficiency was then obtained by normalizing the quotient of the relative oscillator strength for ionization and absorption on a few absolute points obtained by a calibration procedure using a mixture of helium and neon. The ionization efficiency is unity from about 5 eV above threshold to the limit of the data at 80 eV. 

Abstract. We have calculated the scalar and tensor dipole polarizabilities (/3) and hyperpolarizabilities (7) of excited ls2p Po, ls2p P2- states of helium. Our theory includes fine structure of triplet sublevels. Semiempirical and accurate electron-correlated wave functions have been used to determine the static values of j3 and 7. Numerical calculations are carried out using sums of oscillator strengths and, alternatively, with the Green function for the excited valence electron. Specifically, we present results for the integral over the continuum, for second- and fourth-order matrix elements. The corresponding estimations indicate that these corrections are of the order of 23% for the scalar part of polarizability and only of the order of 3% for the tensor part... 

J.R. Sabin, J. Oddershede, G.H.F. Diercksen, Moments of the Dipole Oscillator Strength Distribution and Mean Excitation Energies of Helium, Phys. Rev. A 42 (1990) 1302. 

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