TOTAL DIELECTRONIC RECOMBINATION RATE COEFFICIENT FOR AR-LIKE TUNGSTEN

Ab initio calculations of the total dielectronic recombination (DR) ra te coefficient for Ar-like tungsten (W56+) are performed using the rel ativistic HULLAC code package based on the parametric potential method . The high efficiency of HULLAC compared to other codes enables us to perform extensive DR calculations for highly complex atomic systems su ch as Ar-like tungsten. The present work provides a general procedure for computing the DR rate coefficients for multielectron high-Z ions. This procedure is applicable to DR computations for other Ar-like ions , as well as for ions in neighboring isoelectronic sequences. In the p resent work level-by-level calculations are performed for evaluating t he contributions to DR through all the relevant K-like autoionizing in ner-shell excited configuration complexes: 3p(5)4ln'l' (4 less than or equal to n'less than or equal to 17), 3s3p(6)4ln'l' (4 less than or e qual to n'less than or equal to 12), 3p(5)3dn'l' (8 less than or equal to n'less than or equal to 18), 3s3p(6)3dn'l' (7 less than or equal t o n'less than or equal to 18), 2p(5)3s(2)3p(6)3dn'l', II (3 less than or equal to n'less than or equal to 8), 2s2p(6)3s(2)3p(6)3dn'l' (3 les s than or equal to n'less than or equal to 5), and 3p(5)5l5l'. in addi tion, extrapolation methods are developed to calculate the contributio ns of even higher n' complexes along each complex series. In the case of 3p(5)3dn'l', the usual complex-by-complex extrapolation method base d on the n'(-3) scaling law is found to be inaccurate; thus, a more de tailed level-by-level procedure is discussed. All calculations are car ried out assuming no electron collisions occur after the initial elect ron capture. Although the dominant DR contributions come from 3p(5)4ln 'l' and 3p(5)3dn'l', the contributions of the other complex series can not be neglected. A comparison between the present results and the Bur gess-Merts (BM) approximation shows that at low electron temperatures the BM approximation greatly underestimates the DR rate coefficients, whereas at high electron temperatures this approximation is fairly goo d.