T. LeBrun

Electron-ion-X-ray spectrometer system

Abstract We describe a spectrometer system developed for electron, ion, and X-ray spectroscopy of gas-phase atoms and molecules following inner-shell excitation by tunable synchrotron radiation. The instrumentation and experimental methods are discussed, and examples are given of electron spectra and coincidence spectra between electrons and fluorescent X-rays.

The X-ray photoabsorption spectrum of potassium near the K-edge

The authors have used a heat-pipe target in an X-ray beam to obtain photoabsorption spectra of potassium at the K- and KM-edges, in the photon energy range 3,600 to 3,650 eV. Preliminary identifications of most of the peaks observed are made using Dirac Hartree-Fock calculations. They compare these results with those obtained previously in closed-shell rare gas absorption spectra.

The VUV spectrum from fast heavy-ion induced excitation of

We have measured the spectrum of vacuum ultraviolet radiation (500 - 1700 A) arising from the impact of 625 MeV xenon ions with . The spectral features are due primarily to emission from neutral and ionized carbon atoms. These photons mask sensitivity to either the giant dipole resonance or to excited dimers. We compare with data obtained in collisions of xenon ions with methane and isobutane. Decay times of several of the lines were also measured. Some of the lines persist for times long compared to the lifetimes of the corresponding states in neutral and ionized carbon.

Nondipolar photoelectron angular distributions

The deviations of photoelectron angular distributions from the simple, highly symmetric shapes predicted within the electric-dipole approximation are investigated. The admixture of an electric-quadrupole component in the photon-atom interaction causes an asymmetry in the angular distribution with respect to the direction of photon propagation. The reported measurement of the angular distributions of argon 1s, krypton 2s, and krypton 2p photoemission within 2–3 keV above their respective thresholds reveal pronounced asymmetries which are present even at low electron kinetic energies. The measured asymmetry parameters are in good agreement with recent predictions from nonrelativistic calculations.