Günter Grossmann

The effect of the core hole on X-ray emission spectra in simple metals

Shows that one-particle calculations of X-ray spectra with and without the core hole can give drastically different results, indicating a breakdown of one-particle theory. Only emission spectra obtained in the absence of the core hole consistently show a close resemblance to experiment. The authors show, that this fact can be explained by the many-body theory of Nozieres and DeDominicis (1969). They are then able to give the first interpretation of the L2,3 satellite spectrum of sodium.(17 refs)

Dynamical calculations of X-ray absorption and emission spectra

The authors have previously shown that one-particle calculations of X-ray spectra in simple metals give very different results depending on whether the core hole is taken into account or not. Guided by experiment and the dynamical theory of X-ray spectra developed by Nozieres and DeDominicis (ND) (1969) the authors have, however, also established the rule that rather realistic spectra can be obtained from a one-particle calculation provided final state wavefunctions are used in the transition matrix elements. They report on direct numerical evaluations of the dynamical ND theory for several different cases including the case where a bound state appears. In all cases the results support their final state rule. They also give arguments in support of the procedure used to extract threshold exponents and asymmetry indices from X-ray absorption and emission spectra and X-ray photoemission spectra.(18 refs) (Less)

Transition Metal Excited States in Silicon

Recent absorption and photoconductivity studies of deep transition-metal impurities in silicon are discussed, with emphasis on optical transitions from the deep ground state to shallow Coulomb excited states. The P 3/2 line spectra of the deep Au and Pt acceptors closely resemble those of group II acceptors in silicon, whereas the P 1/2 lines show resonance effects due to interaction with the valence band continuum. Behavior under uniaxial stress is compatible with D 2d or C 2y point-group symmetry for the Au and Pt acceptors. A line spectrum in g-dopes Si can be attributed to excitations to shallow donor states since the phononassisted Fano resonances involve characteristic inter-valley phonons. Both the Ag donor spectrum and the corresponding Au spectrum are dominated by excited s-state transitions. Thus, the traditional fingerprint of a donor in silicon, i.e. the effective-mass like p-state series, is missing or at best observed weakly

Highly excited states of donor centres in silicon

Abstract We report the observation under appropriate conditions of odd-parity absorption lines in the spectra of two S-related centres in silicon, associated with very low binding energies. Most of these levels can be identified by extension of the effective mass calculations. One level near 0.43 meV is attributed to 10 f± - 10 h± and the shallowest one (0.34 meV) cannot be attributed presently with any certainty.

GOLD IN SILICON AND OTHER ANALOGOUS DONORS AND ACCEPTORS

Abstract Recent results on the substitutional Au and interstitial Fe deep-level impurities in silicon are discussed in some detail. Their excitation spectra are due to transitions from a deep ground state to shallow states. The good understanding of the electronic structure of the shallow states as well as their response to external perturbations, i.e., uniaxial stress and magnetic field, allows for a detailed investigation of the electronic structure of the deep states.

Excited State Spectroscopy of Deep Defects in Silicon

The shallow excited states associated with some deep impurities in silicon are studied in absorption and photoconductivity measurements. From these sharp line spectra one may infer novel information on the electronic structure and local symmetry of deep defects. In combination with Photo-EPR measurements, these studies may further reveal the chemical identity of the center. For a detailed understanding of the spectra, finally, many-electron effects and electron-phonon coupling have to be considered.