Interaction of 4p⁵4d^N+1and 4p⁶4d^N−14f configurations and its influence on the photoexcitation and emission spectra in the isoelectronic and isonuclear sequences

Abstract

The strong interaction of 4p54dN+1 + 4p64dN−14f configurations and its influence on the photoexcitation and emission spectra corresponding to the excitations from the ground level of 4p64dN have been considered. The results are presented for the isoelectronic sequences from the ionization degree q = 5 up to q = 29–37 as well as for the isonuclear sequences of Snq+ and Wq+. It is shown that depending on the number of 4d electrons, the variation of spectra in the isoelectronic sequences corresponds to three different types. At N = 4 and N = 6–9, the strong concentration of lines takes place in the whole isoelectronic sequence, except for small ionization degrees. At N ⩽ 3, the width of photoexcitation and emission spectra also obtains a relatively larger value at small ionization degrees, decreases with ionization degree rising, but tends to increase again at large ionization degrees. In the whole isoelectronic sequence, a very narrow group of a few intense lines is obtained for N = 5. The transitions from the excited levels mainly proceed to the lowest level of the ground configuration; it is the reason for the similarity of photoexcitation and emission spectra. The quenching of many lines and the concentration of line strengths in a few transitions indicate the existence of some wavefunction basis with strict selection rules for dipole transitions.

Tungsten spectra recorded at the LHD and comparison with calculations

“…In preparing these plots the results for each stage were seen to be very similar to the theoretical spectra shown in the works of Jonsaukas et al and Kucas et al [30,31]. Any differences could be attributed to the different atomic structure codes used.…”

“…Recently a detailed theoretical study of both EBIT and ASDEX-Upgrade spectra have been made which show that the emission spectra of the various open 4d-subshell ions, calculated by taking into account excitation from the ground state only, agree quite well with the results obtained with the CR model [30,31]. The calculations were made using the relativistic Dirac Fock approximation [32].…”

“…From earlier data it should be possible to associate the mean peak lying between 4.9 and 5.5 nm with transitions from open 4d subshell ions, i.e. W XXIX-W XXXVIII [28][29][30][31]. Interestingly, the 4p-4d and 4d-4f lines of Rb-like W 37+ , expected to be strong because of the 4p 6 4d ground configuration, are clearly present in the 3 keV spectrum but essentially absent in the lower temperature one.…”

“…In order to obtain further information and to simulate the emission from the contributing ions, calculations were performed with the Hartree-Fock with CI suite of codes written by Cowan [43]. For transitions from stages with an open 4d subshell, CI effects have already been shown to be very important [25][26][27][28][29][30][31] because of the proximity of the 4p-4d and 4d-4f excitation energies. Thus in the calculations for W XXX-W XXXVIII excited state CI of the form 4p 5 4d m+1 +4p 6 4d m−1 4f (1 m 9) was included.…”

“…Thus the emission is essentially dominated by excitation rates from the ground level and the gA distribution of the excited ones. The influence of CI on these rates as a function of the number of 4d electrons in the lower level was explored in detail [31]. The authors also succeeded in identifying the origin of a weak unexplained feature observed in the EBIT spectra of W XXX-W XXXV as originating from the 4p-5s satellite transitions [30].…”