Absorption by Gaseous Helium in the Extreme Ultraviolet

X-Ray Interactions: Photoabsorption, Scattering, Transmission, and Reflection at E = 50-30,000 eV, Z = 1-92

“…Because TJ~/ E-is very small as compared with unity (see, for example, Parratt and Hempstead [46] ) the first integral becomes simply equal to gq, the total oscillator strength of this electron in the n, 1 -subshell.…”

“…i't = (1/m)ln(Io/I) = JJ.+Jl.inc (46) where m is the mass per unit area (gm/cm 2 ) of the foil and p. and P.inc are the photoabsorption and incoherent scattering cross sections respectively. We may then obtain the mass photoabsorption cross section by: (47) where the correction for incoherent scattering, Jl.inc/ p., may be obtained from the appended tables for Jl.inc and p. as has been discussed in Sect.…”

Theoretical description of the ionization processes with a discrete basis set representation of the electronic continuum

“…Computationally the topic of photoionization of the helium atom is heavily exploited. We choose to compute this quantity in order to test our approximation method for the simplest many-electron system, for which there are rich experimental data available [75][76][77][78]. The experimental results were consolidated by Marr and West [79], later by Samson, Yin and Haddad [80] with an accuracy of 2 % and Bizau and Wuilleumier [81].…”