ELECTRON-IMPACT EXCITATION OF Cr II: A THEORETICAL CALCULATION OF EFFECTIVE COLLISION STRENGTHS FOR OPTICALLY ALLOWED TRANSITIONS

Journal Article · Sat Oct 01 04:00:00 EDT 2011 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1088/0067-0049/196/2/24· OSTI ID:21562419

Wasson, I R; Ramsbottom, C A

In this paper, we present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for the complicated iron-peak ion Cr II. We consider specifically the allowed lines for transitions from the 3d {sup 5} and 3d {sup 4}4s even parity configuration states to the 3d {sup 4}4p odd parity configuration levels. The parallel suite of R-Matrix packages, RMATRX II, which have recently been extended to allow for the inclusion of relativistic effects, were used to compute the collision cross sections. A total of 108 LS{pi}/280 J{pi} levels from the basis configurations 3d {sup 5}, 3d {sup 4}4s, and 3d {sup 4}4p were included in the wavefunction representation of the target including all doublet, quartet, and sextet terms. Configuration interaction and correlation effects were carefully considered by the inclusion of seven more configurations and a pseudo-corrector 4d-bar type orbital. The 10 configurations incorporated into the Cr II model thus listed are 3d {sup 5}, 3d {sup 4}4s, 3d {sup 4}4p, 3d {sup 3}4s {sup 2}, 3d {sup 3}4p {sup 2}, 3d {sup 3}4s4p, 3d{sup 4}4d-bar, 3d{sup 3}4s4d-bar, 3d{sup 3}4p4d-bar, and 3d{sup 3}4d-bar{sup 2}, constituting the largest Cr II target model considered to date in a scattering calculation. The Maxwellian averaged effective collision strengths are computed for a wide range of electron temperatures 2000-100,000 K which are astrophysically significant. Care has been taken to ensure that the partial wave contributions to the collision strengths for these allowed lines have converged with 'top-up' from the Burgess-Tully sum rule incorporated. Comparisons are made with the results of Bautista et al. and significant differences are found for some of the optically allowed lines considered.

• OSTI ID: 21562419
• Journal Information: Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 2 Vol. 196; ISSN 0067-0049; ISSN APJSA2
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
COLLISIONS
CORRELATIONS
CROSS SECTIONS
ELECTRONS
ELEMENTARY PARTICLES
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
FERMIONS
FUNCTIONS
LEPTONS
MATRICES
R MATRIX
STRENGTH FUNCTIONS
WAVE FUNCTIONS