Dielectronic recombination measurements for highly charged ions were performed at the Stockholm refrigerated electron beam ion trap. We have obtained KLL DR resonance strengths for highly charged H- and He-like sulfur and silicon ions. The experimental results are compared with the theoretical data obtained from GRASP II code. Both the experimental and calculated results agree well within the experimental error bars. Moreover, the dielectronic recombination resonance strengths are used to obtain the new scaling parameters by incorporating our results with the previous measurements and to check the behaviour of scaling formula for H- and He-like isoelectronic sequences. 1. Introduction Dielectronic recombination (DR) process has been observed in high-temperature astrophysical and laboratory plasmas and thus affects the charge state distributions of the plasmas. It plays a crucial role in modelling and diagnosing of these plasmas [1]. For example, DR satellite lines from fusion plasma devices are often used to determine plasma temperature for diagnostics [2]. On the other hand, plasma modelling codes such as XSTAR [3], CLOUDY [4], and CHIANTI [5] crucially depend upon the input atomic data such as DR cross sections and rate coefficients to obtain ionization balance and physical conditions of the plasmas [6]. Highly charged sulfur and silicon ions are present in astrophysics and laboratory plasmas [7, 8]. Accurate atomic data for these ions is therefore needed for the identification of the emission lines and to derive ion abundances and plasma temperatures. Historically, DR process was first suggested as recombination mechanism by Sayers in 1939 [9]. Later, Massy and Bates [10] considered it theoretically to explain atomic processes related to O+ ions in the upper atmosphere. However, it was Burgess [11] who for the first time pointed that DR had a large recombination rate in high-temperature plasmas and dominates over the radiative recombination in the solar corona. DR is a resonant two-step electron-ion recombination process, in which a free electron is captured into a vacant shell of the ion, while one of the bound electrons is simultaneously excited producing a doubly excited state. The process is completed by stabilization through photon emission, reducing the ion energy below the ionization threshold. This process can be schematically represented as where is the charge state of ion , and subscripts , , and denote the initial, doubly excited, and final states, respectively. In this paper, we present the results for H- and He-like KLL DR resonances of
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