**56**, 157-166 (2010)

https://doi.org/10.1140/epjd/e2009-00285-3

## Dielectronic recombination rate coefficients for the Ni isoelectronic sequence

^{1}
Shanghai EBIT Lab, Modern Physics Institute, Fudan
University, Shanghai , P.R. China

^{2}
Key Lab of Applied Ion
Beam Physics, Ministry of Education, P.R. China

Corresponding author: chychen@fudan.edu.cn

Received:
20
March
2009

Revised:
20
September
2009

Published online:
17
November
2009

Ab initio calculations of the total dielectronic
recombination (DR) rate coefficients for thirteen ions along the NiI
isoelectronic sequence in the ground state (Kr^{8+}, Mo^{14+},
Ag^{19+}, Sn^{22+}, Xe^{26+}, Nd^{32+}, Gd^{36+},
Yb^{42+}, W^{46+}, Au^{51+}, Pb^{54+}, At^{57+}, and
U^{64+}) have been performed using the flexible atomic code. The
level-by-level calculations are performed for evaluating the DR
contributions through the relevant Cu-like autoionizing inner-shell
excited 3l^{17}4l^{′}n^{′′}l^{′′} and 3l^{17}5l^{′}n^{′′}l^{′′} configuration complexes with n^{′′}
≤15, which are associated with Δn=1 and Δn=2
core-excitations, respectively. The usual (n^{′′})^{-3} scaling
law is found to be invalid for low-*Z* ions. A level-by-level
extrapolation procedure is employed to obtain the contributions
through higher n^{′′} complexes. The decays to autoionizing
levels followed possibly by radiative cascades could enlarge the
rates at relatively high temperature by a factor up to about 23%.
For the whole isoelectronic ions the contributions from
3s^{2}3p^{6}3d^{9} 4l^{′}n^{′′}l^{′′} dominate the total DR
rates while the contributions from the 3s^{2}3p^{6}3d^{9} 5l^{′}n^{′′}l^{′′} configuration complexes are about 10-20% at
relatively high temperature. On the basis of the calculated results,
a general analytic formula for the total DR rate coefficients of all
the ions with 36≤Z ≤92 along the NiI isoelectronic
sequence is constructed. The comparisons of the rates obtained from
the general formula with those from the detailed calculations show
that the formula is of high precision, generally better than 3%
accuracy for electron temperatures kT≥0.1E_{I}, where E_{I} is
the ionization energy of the Cu-like ion. The present DR rates at
temperature above 1.0E_{I} are larger than the previously published
data by a factor above 30%. The commonly used semiempirical formula
proposed by Burgess and modified by Merts may overestimate the rates
at high temperature by a factor of about 2 for low-Z ions.

PACS: 34.80.Lx – Recombination, attachment, and positronium formation

*© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009*