Eur. Phys. J. D (2013) 67: 255
https://doi.org/10.1140/epjd/e2013-40255-6

Regular Article

Collision strengths for transitions of Ni XXI

¹ Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, P.R. China
² Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, P.R. China

^a e-mail: gjiang@scu.edu.cn

Received: 22 April 2013
Received in final form: 24 August 2013
Published online: 10 December 2013

Abstract

In this paper, we use Dirac R-matrix theory to calculate the collision strengths for electron impact excitation of Ni XXI with the Dirac atomic R-matrix code (DARC), which includes contributions of resonances, channel coupling, and relativity. A DARC calculation has been performed for transitions among 86 levels of (1s²) 2s²2p⁴, 2s2p⁵, 2p⁶ and 2s²2p³3l (l = 0, 1, 2) configurations of Ni XXI. The GRASP code has been adopted for the description of target. A comparison is made with the results of Bhatia et al. for the collision strengths of five incident energies, 85, 170, 255, 340, and 425 Ryd, which use distorted wave calculations that do not include channel coupling. Effective collision strengths are calculated by averaging collision strengths over a Maxwellian velocity distribution. The accuracy of our calculations is assessed.