A. von dem Borne

Resonant inner-shell photoelectron spectra of ground-state and laser-excited Cr atoms

Photoelectron spectra and partial cross sections of ground-state and laser-excited Cr atoms in the range of the excitations are presented. The experimental spectra are compared with results obtained by calculations within the spin-polarized random-phase approximation with exchange (SP RPAE), in which the dynamic relaxation upon core hole creation is taken into account.

LINEAR DICHROISM IN PHOTO-INDUCED AUGER ELECTRON EMISSION FROM ALIGNED CR ATOMS

We report the first observation of linear dichroism in the photo-induced Auger electron emission from aligned atoms. The linear dichroism in the Cr Auger spectrum shows striking similarity to the corresponding linear dichroism in the 3p photoelectron spectrum. The theoretical analysis presented here proves that the linear dichroism in the Auger spectrum depends on the same dynamical parameters as the linear dichroism in direct photoionization.

Linear dichroism in the core-resonant photoelectron spectra of laser-aligned Cr atoms

The linear dichroism in the intensity of the electrons (LD) emitted by laser-aligned ground state and excited-state Cr atoms has been exploited in order to characterize the prominent 3p core resonances. The experimental spectra are compared to calculations based on theoretical partial cross sections.

A new method for the investigation of the angular distribution of photoelectrons from laser-aligned core-excited atoms

Abstract A new method for photoionization experiments with the combined use of laser and synchrotron radiation is introduced. It consists in determination of the intensity modulation of the photoelectron signal caused by rotation of the direction of polarization of the laser radiation. Compared with the usual determination of the angular distribution of photoelectrons by rotation of the spectrometer, this method offers the advantage of being insensitive to smaller mis-alignments of apparatus and independent of the numerical value of the atomic alignment and absolute count rates produced by the laser pumping. The method is applied to the investigation of core-excited Ca 3p5 3d4s4p resonances with two different detector configurations (angle resolved electron spectrometer and cylindrical mirror 180° analyzer). The results are discussed in connection with theoretical predictions and are used for the determination of the asymmetry coefficient β.

Measurement of the absolute 4d-photoabsorption cross section of atomic barium

The absolute photoabsorption cross section of atomic barium in the region of the 4d-giant resonance (80-140 eV) has been determined. The vapour density in the absorbing metal vapour column, required for the determination of the absolute cross sections was measured quasi-simultaneously with the absorption using a Mach-Zehnder interferometer. Our data show good agreement in terms of spectral signature with existing relative photoabsorption measurements. The measured absolute cross section corroborates the results of recent many-body calculations.

High resolution spectroscopy of 2p6→2p53d resonantly excited atomic Ca

Abstract Free calcium atoms were excited in the energy region about 10 eV below the 2p thresholds. For the excitation, synchrotron radiation from the high resolution undulator beamline BW3 (HASYLAB, Hamburg) equipped with a SX-700 monochromator was used. The excited atoms were studied by means of ion as well as electron spectroscopy. Two lines could be resolved within one of the two dominating features of the 2 p →3 d resonance. Resonance enhanced 3 p −1 photoelectron spectra resolving the 2 P 1 2 and 2 P 3 2 lines are presented.