Electron-impact excitation of Cr II A theoretical calculation of collision and effective collision strengths for forbidden transitions

被引:10
作者
Wasson, I. R. [1 ]
Ramsbottom, C. A. [1 ]
Norrington, P. H. [1 ]
机构
[1] Queens Univ Belfast, Dept Appl Math & Theoret Phys, Belfast BT7 1NN, Antrim, North Ireland
关键词
atomic data; atomic processes; methods: numerical; scattering; plasmas; STAR;
D O I
10.1051/0004-6361/201015200
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Context. Absorption or emission lines of Cr II are observed in a wide variety of astrophysical spectra and accurate atomic data are urgently needed to interpret these lines. Many of these data are impossible to measure experimentally and a full theoretical treatment is the only means by which these data can be obtained. Aims. In this paper, we present collision strengths and effective collision strengths for electron-impact excitation of Cr II for forbidden transitions among the lowest-lying 74 fine-structure levels. Effective collision strengths have been computed for 18 individual electron temperatures of astrophysical importance, ranging from 2000-100 000 K. Methods. The parallel suite of R-matrix packages, RMATRX II, which has recently been extended to allow for the inclusion of relativistic effects, has been used in the present work to compute the collision strengths and effective collision strengths for electron-impact excitation of Cr II. We concentrate in this publication on low-lying forbidden lines among the lowest 74 jj fine-structure levels with configurations 3d(5) and 3d(4)4s, although atomic data has been evaluated for all 39 060 transitions among the 280 jj levels of configurations 3d(5), 3d(4)4s and 3d(4)4p. This work constitutes the largest evaluation ever performed for this ion involving 1932 coupled channels. Results. Collision and effective collision strengths are presented for all transitions among the lowest 74 J pi states of Cr II and comparisons made with the work of Bautista et al. (2009). While the effective collision strengths agree well for some transitions, significant discrepancies exist for others. We believe that the present atomic data represents the most accurate, most sophisticated and most complete data set for electron-impact excitation of Cr II and we would recommend them to astrophysicists and plasma physicists in their application work. We would expect that the effective collision strengths presented for the important low-lying forbidden lines are accurate to within 15%.
引用
收藏
页数:6
相关论文
共 18 条
[1]  
BABEL J, 1992, ASTRON ASTROPHYS, V263, P232
[2]   Electron-impact excitation of neon: a pseudo-state convergence study [J].
Ballance, CP ;
Griffin, DC .
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 2004, 37 (14) :2943-2957
[3]  
Bautista MA, 2009, MON NOT R ASTRON SOC, V393, P1503, DOI [10.1111/j.1365-2966.2008.14246.x, 10.1111/J.1365-2966.2008.14246.x]
[4]   Atomic data from the iron project - LV. Electron impact excitation of NiII [J].
Bautista, MA .
ASTRONOMY & ASTROPHYSICS, 2004, 420 (02) :763-768
[5]   ELECTRON-IMPACT EXCITATION OF COMPLEX ATOMS AND IONS [J].
BURKE, PG ;
BURKE, VM ;
DUNSEATH, KM .
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 1994, 27 (21) :5341-5373
[6]   Electron-impact excitation of Ni II Collision strengths and effective collision strengths for low-lying fine-structure forbidden transitions [J].
Cassidy, C. M. ;
Ramsbottom, C. A. ;
Scott, M. P. ;
Burke, P. G. .
ASTRONOMY & ASTROPHYSICS, 2010, 513
[7]   A refined analysis of the remarkable Bp star HR 6000 [J].
Castelli, F. ;
Hubrig, S. .
ASTRONOMY & ASTROPHYSICS, 2007, 475 (03) :1041-U93
[8]  
CLEMENTI E, 1974, ATOM DATA NUCL DATA, V14, P3
[9]  
Dimitrijevic M. S., 2007, M A A, V469, P681
[10]   CIV3 - GENERAL PROGRAM TO CALCULATE CONFIGURATION INTERACTION WAVE-FUNCTIONS AND ELECTRIC-DIPOLE OSCILLATOR-STRENGTHS [J].
HIBBERT, A .
COMPUTER PHYSICS COMMUNICATIONS, 1975, 9 (03) :141-172