Dielectric Recombination of the Cd + Ion via 4 d 9 5 s 2 5 p Autoionizing States
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Journal of Applied Spectroscopy, Vol. 87, No. 5, November, 2020 (Russian Original Vol. 87, No. 5, September–October, 2020)
DIELECTRIC RECOMBINATION OF THE Cd+ ION VIA 4d 95s25p AUTOIONIZING STATES A. N. Gomonai,* A. I. Gomonai, Yu. I. Hutych, and V. V. Zvenigorodskij
UDC 539.186:546.48
Dielectronic recombination of the Cd+ (4d105s 2S1/2) ion via formation of the 4d 95s25p 3 D10 Cd atom autoionization state and its radiative decay to the 4d105p2 3PJ autoionization states were detected and studied in intersecting electron and ion beams using UV spectroscopy. The 4d 95s25p3 D10 → 4d105p2 3P0 radiative transition is found to be the strongest. The effective cross-section of the dielectronic recombination at the maximum equals (5.0 ± 2.0) × 10–17 cm2, which is comparable with those for electron excitation of the spectral lines (including resonance ones) of the investigated ion. Radiative decay of the 4d 95s25p3 D10 autoionization state has a high probability due to interconfigurational interaction (4d105s5p + 4d105p5d + 4d 95s25p + 4d 95p3). Keywords: electron, cadmium ion, autoionization state, dielectronic recombination, effective cross section. Introduction. Interactions between electrons and ions are responsible for the properties of most plasma systems. Inelastic electron–ion collisions play an important role in energy balance of plasmas. The electron-impact excitation cross sections of ions are needed to interpret spectroscopic measurements and plasma modeling using collisional-radiative models [1]. Dielectric recombination (DR) is an important aspect of plasma ionization balance. Therefore, errors in determining its characteristics can have substantial effects on the result [2]. The DR process plays an important role in establishing ionization equilibrium in astrophysical and laboratory plasmas, thereby leading to a serious problem with energy losses [3, 4]. DR is known to be a two-stage process [5]. The first stage (dielectron capture) involves capture of an incoming (free) electron into a bound state with simultaneous excitation of one of the ion′s electrons. An autoionization state (AIS) results that has two competing decay channels, i.e., autoionization related to loss of an electron and radiative decay into a bound atom state (itself the second stage of the DR process). It is noteworthy that DR is a resonance process that occurs only when the free-electron energy corresponds to the energy difference between the AIS and the initial ion state. The AIS participates in this process through interelectron interaction. Therefore, this interaction and other multi-electron effects can be studied during studies of DR. In this respect, studies of DR of complicated multi-electronic ions in which both correlation and relativistic effects play important roles are especially interesting. The applications of such research are important because heavy-metal elements are used to construct assemblies for studying thermonuclear synthesis and in astrophysical investigations. Seminal studies of DR were mainly theoretical because
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