Coupled-states model calculations of L-subshell ionisation probabilities for Ne on Yb, Pt collisions

Sarkadi, L.; Mukoyama, Takeshi

doi:10.1088/0022-3700/20/17/004

Cited by 22 publications

(7 citation statements)

References 16 publications

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“…Interestingly enough, this is not only true for the CSA but also for the more sophisticated continuum coupled-channel calculations of Mehler et ai (SofT 1987). On the other hand, our results significantly improve upon the simplified CSA calculations recently reported by Sarkadi and Mukoyama (1987). In conclusion, the simple CSA scheme reproduces results of more complex continuum coupled-channel calculations quite well, and improves significantly upon the SCA for predicting relative L-subshell cross sections.…”

Section: L103supporting

confidence: 83%

“…Kocbach (1984), reporting on a model calculation with three bound and one continuum states, has suggested the name 'generalised distortion approximation' for this kind of approach. Subsequently, Sarkadi (1986b) (see also Sarkadi and Mukoyama 1987) has performed calculations of the L-vacancy production probability with non-relativistic wavefunctions, but with the bound-continuum matrix elements approximated by their Ef = 0 values, E; being the 6-electron kinetic energy, restricted to multipole components with 1=0 and 1 in the final state. Berinde et a1 (1985) have reported a close-coupling calcu!ation of Azo using a UA basis; however, the ionisation was assumed to take place suddenly at the turning point of the classical trajectory, providing the starting amplitudes for the coupled-channel calculations.…”

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confidence: 99%

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Coupled-subshell approximation for L-shell ionisation

Amundsen

Jakubaßa-Amundsen

1988

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. The ionisation probability for target L subshells by light ion impact is calculated in the semiclassical approximation, including the couplings between the subshells during the collision. The inclusion of these couplings is found to modify the subshell occupation numbers only slightly for proton and alpha particle impact on heavy target atoms, but a marked effect is found for heavier projectiles. Numerical results for the systems H e + Pt, Ne+ Pt and N e + % are presented.There is in general quiie satisfactory agreement between perturbation theory and experiments for inner-shell ionisation in very asymmetric ion-atom collisions (see e.g. the contributions in Paul 1982). However, when one considers L-subshell ionisation, some significant discrepancies have persisted since the first cross section measurements were reported, in particular at very low collision energies (Daiz er a1 1974, Chang et a1 1975). Introducing a relativistic electron description, using united-atom ( C A ) binding energies a n d wavefunctions and corrections for projectile Coulomb deflection only marginally improves the situation (Amundsen 1977, Aashamar andAmundsen 1982). It was unclear, however, for a long time to what extent these discrepancies are spurious, in the sense that they arise from errors in the values of the fluorescence yields and Coster-Kronig ratios used t o convert measured x-ray intensities into subshell ionisation cross sections. Recent accurate measurements of the radiative and radiationless yields for Au (Jitschin et a1 1985) have indeed given results significantly different from those recommended by Krause (1979), but, as these authors note, it does not explain all the differences between theory and experiment for ionisation. Such discrepancies also appear in some o f the recent measurements of impact-parameter-dependent ionisation probabilities, P ( b ) (Dexheimer et a1 1986, Zehender et a1 1986).A widely accepted explanation for the disagreements between theory and experiment is that perturbation theory is inadequate even in rather asymmetric collisions. This effect was first studied quantitatively by Sarkadi and Mukoyama (1981) for systems like C + A u in a simple two-step model, treating ionisation and subshell couplings as independent processes. This two-step model has subsequently been refined (Fink et ai 1983, Sarkadi a n d Mukoyama 1984, Sarkadi 1986a

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Section: L103supporting

confidence: 83%

mentioning

confidence: 99%

Coupled-subshell approximation for L-shell ionisation

Amundsen

Jakubaßa-Amundsen

1988

J. Phys. B: At. Mol. Opt. Phys.

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“…A disagreement observed between the experimental and calculated x-ray production cross sections (see figure 2), particularly for the low energies, suggests the necessity to include the subshell coupling effects in the theoretical treatment. In fact, similar effects, which were observed earlier for the decay of L 2 -vacancies, were discussed in terms of the intra-shell transitions and coupling effects for the L-shell [5][6][7][8][9][10]. We would like to note here that a contribution of other possible mechanisms of the L-shell vacancy production, such as electron capture to the projectile or the target atom recoil, were found to be practically negligible for the studied energies.…”

Section: Figuresupporting

confidence: 83%

“…The ionization of higher shell electrons by heavy ion impact becomes more complicated, mainly due to much stronger perturbation of target electrons by the increased Coulomb field of the projectile. In this case three important phenomena have to be considered: (i) modification of initial electronic wavefunction induced by the projectile (bindingpolarization effects [3]); (ii) simultaneous ionization of several electrons known as multiple ionization [4]; and (iii) projectile-induced intra-shell transitions, or more generally, the subshell coupling effects [5][6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…These works were focused on the description of the L-shell intra-shell transitions, since this effect was recognized to be responsible for observed strong enhancement of ionization cross sections for the L 2 -subshell at low relative velocities v 1 /v 2 1, with v 1 and v 2 being the projectile and electron velocities, respectively. Several theoretical approaches were developed to account for the L-subshell coupling effects: from the first simple 'two-step model' [5,6], through the simplified 'coupled-subshell model' (CSM) [7][8][9][10] and the 'coupled-state approximation' [11], to full coupled-channel calculations [12,13]. Although all these models confirm the importance of the vacancy-sharing processes, in particular for the L 2 -subshell, the absolute agreement of experimental data with theoretical predictions remains unsatisfactory for individual L-subshells.…”

Section: Introductionmentioning

confidence: 99%

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The role of multiple ionization and subshell coupling effects in L-shell ionization of Au by oxygen ions

Banaś

Braziewicz

Pajek

et al. 2002

J. Phys. B: At. Mol. Opt. Phys.

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The ionization of L-subshell electrons in gold by the impact of 0.4-2.2 MeV amu-1 O ions was studied by observing excited Lγ(L-N, O) x-rays. We demonstrate that both the multiple ionization in outer M- and N-shells as well as the coupling effects in the L-shell play an important role in understanding the measured L-subshell ionization cross sections. The multiple ionization was found to be important in two aspects: first, the analysis of x-ray energy shifts and line broadening was crucial for proper interpretation of measured x-ray spectra; second, the additional vacancies in the M- and N-shells substantially influenced the L1-subshell fluorescence and Coster-Kronig (CK) yields, mainly by closing strong L1-L3M4,5 CK transitions. The data are compared with the simplified coupled-channels calculations using the `coupled-subshell model' (CSM) based on the semiclassical approximation (SCA), which describes both direct Coulomb ionization as well as the L-subshell couplings within the same theoretical approach. A good agreement of the present data with the theoretical predictions based on the discussed SCA-CSM approach is observed. Present findings partly explain the long-standing problem of inadequate theoretical description of L-shell ionization by heavy ion impact.

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Inner-shell ionization in near-central collisions of 6.7 MeV/amu4He ions with mid-Z atoms

Carlen

Dousse

Gasser

et al. 1992

Z Phys D - Atoms, Molecules and Clusters

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Abstract. The K[3 spectra of molybdenum, palladium and lanthanum bombarded by 6.7 MeV/amu 4He ions were measured with a transmission curved crystal spectrometer. L and M satellite lines were observed and resolved. Experimental energies are compared with those calculated with a MCDF program. M-shell ionization probabilities are deduced from the measured satellite intensity ratios and compared with theoretical (SCA) predictions.The experimental values are found to be higher than the calculated ones (by a factor of 2 for La and a factor of about 4 for Mo and Pd). The influence of coupling effects, electron wave functions, electron capture, electron correlation and target activation is discussed.

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Coupled-states model calculations of L-subshell ionisation probabilities for Ne on Yb, Pt collisions

Cited by 22 publications

References 16 publications

Coupled-subshell approximation for L-shell ionisation

Coupled-subshell approximation for L-shell ionisation

The role of multiple ionization and subshell coupling effects in L-shell ionization of Au by oxygen ions

Inner-shell ionization in near-central collisions of 6.7 MeV/amu4He ions with mid-Z atoms

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