Moments of dipole oscillator-strength distribution for the helium sequence

Abstract

The moments S(mu) for -6 < or = mu < or = 2 and L(mu) for mu = 0, 1 and 2 are calculated for the helium sequence for atomic numbers Z up to 30 under a screened hydrogenic model. In this model, one describes the atom by single-particle hydrogenic wavefunctions and treats the initial and the final state as characterised by two different effective charge parameters Zi and Zf, respectively. An asymptotic expansion is made of the differential oscillator strength of the screened hydrogenic model. Assuming the value 287.6 for the coefficient of the term epsilon -7/2 for helium atom as given by Salpeter and Zaidi, the parameter Zf is determined for the helium sequence. This approach has resulted in values which are in reasonable agreement with the various moment values of other authors.

Single-differential and integral cross sections for electron-impact ionization for the damage of carbon clusters irradiated with x-ray free-electron lasers

“…(4), as a function of x-ray flux photons/(pulse mm 2 ) in pulses of 10 fs and 6 keV, 10 fs and 12 keV, and 1 fs and 20 keV, respectively. The effect of photoionization decreases with increase in the x-ray energy since the photoionization cross section decreases in proportion to E −3.5 [33], where the E is the photoelectron energy. We must select higher energy x rays to suppress the "primary damage."…”