Photo-Ionization of Krypton Between 300 and 1500 eV. Relative Subshell Cross Sections and Angular Distributions of Photoelectrons

Abstract

Energy spectra of electrons ejected from $M$ and $N$ subshells of krypton by characteristic x rays of 300 to 1500 eV energy have been measured with an electrostatic analyzer. Krypton was irradiated in the gas phase and electrons were detected perpendicular to the x-ray beam. From these spectra, relative subshell contributions to the photo-ionization cross section were obtained for single-electron emission and for double-electron emission, the latter involving simultaneous transitions of $M$ and $N$ electrons. Angular distributions of photoelectrons from $3s$, $3p$ and $3d$ shells of krypton and $1s$ shell of neon also have been determined at excitation energies from about 200 to 1100 eV above the respective ionization thresholds. Data on relative cross sections for single photo-ionization corroborate a theoretical model which uses a Herman-Skillman central potential (Cooper and Manson in the following article). Angular distributions agree satisfactorily with calculations by the same model; this means theory makes dependable predictions regarding the asymmetry parameter and the effect of retardation. Data on double photo-ionization disagree with results of the electron shakeoff theory which accounts for only about half the observed intensities. This suggests that electron-electron correlation plays an important role.