| 1. |
- Almbladh, Carl-Olof, et al.
(författare)
-
Comments on core-hole lifetime effects in deep-level spectroscopies
- 1978
-
Ingår i: Physical Review B. - 1550-235X. ; 17:2, s. 929-939
-
Tidskriftsartikel (refereegranskat)abstract
- he effects of a finite core-hole lifetime on deep-level spectra in solids have recently attracted much interest. We here present a solvable model which enables a detailed analysis of lifetime effects. For x-ray photoemission and x-ray absorption, our analysis gives support for the usual convolution approach where the infinite lifetime spectrum is convoluted with a Lorentzian lifetime broadening. In particular, we demonstrate the inadequacy of a recent intuitive approach which predicts a suppression of the phonon broadening for short core-hole lifetimes. This is done by testing the different theories on our model. We also show that a straightforward diagrammatic analysis leads to the same conclusion. Finally, we discuss the phonon response to the total process of core-hole creation and subsequent annihilation in an x-ray or Auger emission event. It is explained in some detail that the lifetime independence of the shake-up connected with the first step in this process is in no contradiction with the fact that the phonon system is uneffected by the total deep-level process in the limit of short core-hole lifetimes. We also analyze the process of 1s hole creation and subsequent Auger K-LL emission and give explicit expressions for this process.
|
|
| 2. |
- Almbladh, Carl-Olof, et al.
(författare)
-
Screening of a proton in an electron gas
- 1976
-
Ingår i: Physical Review B. - 1550-235X. ; 14:6, s. 2250-2254
-
Tidskriftsartikel (refereegranskat)abstract
- Calculations are reported of the nonlinear screening of a proton in an electron gas of densities corresponding to rs=1-6. Results for charge densities and total energies are presented from self-consistent Kohn-Sham ground-state calculations. The results differ markedly from the case of linear screening, particularly at low densities. The occurrence of a bound state around the proton for rs>1.9 indicates that hydrogen in jellium is in the form of a screened H- ion. It is also found that at metallic densities the induced polarization around the proton is insensitive to rs, and the screening length is almost constant (0.65) for 2
|
|
| 3. |
- Almbladh, Carl-Olof, et al.
(författare)
-
The spherical-solid model: An application to x-ray edges in Li, Na, and Al
- 1976
-
Ingår i: Physical Review B. - 1550-235X. ; 13:8, s. 3307-3319
-
Tidskriftsartikel (refereegranskat)abstract
- In order to treat highly localized excitations in a solid a simple spherical model has been developed. The Coulomb potential from the nucleus at the site of the excitation is treated exactly, while the potentials from the surrounding sites are turned into pseudoion pontentials. Only the spherical average of these potentials is retained and separate self-consistent calculations for the ground state and for the excited state are made. These states are mistreated by the model but the difference accurately describes the large effects of polarization involved. The positions of the x-ray edges are obtained with an accuracy of 0.5 eV for singly ionized levels and 1 eV for doubly ionized levels. The phase shifts relevant to the Nozières-De Dominicis theory of x-ray absorption and emission edges and x-ray photoemission line shapes are also calculated. We obtain a noticeable many-body enhancement of the L2,3 edge in Na while the many-body effect in Li and Al is negligible. Our exponents agree with those extracted from recent x-ray photoemission experiments, but they do not agree with those extracted from x-ray emission or absorption spectra. We argue that the exponents taken from the photoemission experiment are more reliable but no definite conclusion concerning the validity of the present many-body theory should be drawn until the experimental situation has become more clear.
|
|
