Energies and widths of atomic core-levels in liquid mercury

High-resolution measurements of the photoinduced X-ray emission of liquid mercury were performed, using a transmission DuMond-type crystal spectrometer for transitions above 11 keV and a reflection von Hamos-type crystal spectrometer for transitions below 11 keV. The target X-ray fluorescence was produced by irradiating the sample with the Bremsstrahlung from X-ray tubes. The energies and natural linewidths of 6 K-shell, 26 L-shell and 2 M-shell X-ray transitions were determined. Using a least-squares-fit method to solve the two sets of equations derived from the observed transition energies and transition widths the binding energies of the subshells K to M5 and O1 and the level widths of the subshells K to N5 and O1 could also be determine

Lifetimes of doubly K -shell ionized states

The present work provides a reliable interpretation of the Khα₁/Khα₂ intensity ratios and an explanation of the lifetime values for K-shell hollow atoms based on an advanced theoretical analysis (using extensive multiconfiguration Dirac–Fock calculations with the inclusion of the transverse Breit interaction and quantum electrodynamics corrections). It was found that, as a result of closing the Khα₁ de-excitation channel in the pure LS coupling scheme, the Khα₁/Khα₂ intensity ratio changes with the atomic number from small values (for the LS coupling limit at low Z) to about 1.5– 1.6 (for the j–j coupling limit at high Z). However, closing the Khα₁ de-excitation channel (due to the domination of the pure LS coupling for the low-Z atoms) does not enlarge the lifetimes of hollow atoms

High energy resolution off-resonant spectroscopy for X-ray absorption spectra free of self-absorption effects

X-ray emission spectra recorded in the off-resonant regime carry information on the density of unoccupied states. It is known that by employing the Kramers-Heisenberg formalism, the high energy resolution off-resonant spectroscopy (HEROS) is equivalent to the x-ray absorption spectroscopy (XAS) technique and provides the same electronic state information. Moreover, in the present Letter we demonstrate that the shape of HEROS spectra is not modified by self-absorption effects. Therefore, in contrast to the fluorescence-based XAS techniques, the recorded shape of the spectra is independent of the sample concentration or thickness. The HEROS may thus be used as an experimental technique when precise information about specific absorption features and their strengths is crucial for chemical speciation or theoretical evaluation

Physical mechanisms and scaling laws of K-shell double photoionization

We report on the photon energy dependence of the K-shell double photoionization (DPI) of Mg, Al, and Si. The DPI cross sections were derived from high-resolution measurements of x-ray spectra following the radiative decay of the K-shell double vacancy states. Our data evince the relative importance of the final-state electron-electron interaction to the DPI. By comparing the double-to-single K-shell photoionization cross-section ratios for neutral atoms with convergent close-coupling calculations for He-like ions, the effect of outer shell electrons on the K-shell DPI process is assessed. Universal scaling of the DPI cross sections with the effective nuclear charge for neutral atoms is revealed

Double K-shell photoionization of low-Z atoms and He-like ions

We report on the investigation of the photon energy dependence of double 1s photoionization of light atoms and compare the cross sections for hollow atom and He-like ion production. Measurements of the Kα hypersatellite x-ray spectra of Mg, Al, and Si were carried out using the Fribourg high-resolution x-ray spectrometer installed at the ID21 and ID26 beam lines at the ESRF. The double-to-single photoionization cross section ratios were derived as a function of the incident photon beam energy and compared to convergent close-coupling (CCC) calculations for He-like ions. The dynamical electron-electron scattering contribution to the DPI cross-sections was found to be more important for neutral atoms than for the He isoelectronic serie

Theoretical and experimental determination of LL-shell decay rates, line widths, and fluorescence yields in Ge

Fluorescence yields (FYs) for the Ge L shell were determined by a theoretical and two experimental groups within the framework of the International Initiative on X-Ray Fundamental Parameters Collaboration. Calculations were performed using the Dirac-Fock method, including relativistic and QED corrections. The experimental value of the L3FYωL3 was determined at the Physikalisch-Technische Bundesanstalt undulator beamline of the synchrotron radiation facility BESSY II in Berlin, Germany, and the Lα1,2 and Lβ1 line widths were measured at the Swiss Light Source, Paul Scherrer Institute, Switzerland, using monochromatized synchrotron radiation and a von Hamos x-ray crystal spectrometer. The measured fluorescence yields and line widths are compared to the corresponding calculated values

Back-to-back emission of the electrons in double photoionization of helium

We calculate the double differential distributions and distributions in recoil momenta for the high energy non-relativistic double photoionization of helium. We show that the results of recent experiments is the pioneering experimental manifestation of the quasifree mechanism for the double photoionization, predicted long ago in our papers. This mechanism provides a surplus in distribution over the recoil momenta at small values of the latter, corresponding to nearly "back-to-back" emission of the electrons. Also in agreement with previous analysis the surplus is due to the quadrupole terms of the photon-electron interaction. We present the characteristic angular distribution for the "back-to-back" electron emission. The confirmation of the quasifree mechanism opens a new area of exiting experiments, which are expected to increase our understanding of the electron dynamics and of the bound states structure. The results of this Letter along with the recent experiments open a new field for studies of two-electron ionization not only by photons but by other projectiles, e.g. by fast electrons or heavy ions.Comment: 10 pages, 2 figure