EFFECTIVE COLLISION STRENGTHS FOR ELECTRON-IMPACT EXCITATION OF TRIPLY IONIZED ARGON

✍ Scribed by C.A. Ramsbottom; K.L. Bell

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 797 KB
• Volume: 66
• Category: Article
• ISSN: 0092-640X
• DOI: 10.1006/adnd.1997.0741

✦ Synopsis

A comprehensive tabulation of the effective collision strengths for electron-impact excitation of Ar IV is presented in this paper for use by the astrophysics and plasma physics communities. The collision strengths are calculated in the close-coupling approximation using the multichannel R-matrix method and sophisticated configuration-interaction wave functions are utilized to represent the target states. Thirteen LS target eigenstates of Ar IV, arising from the 3s 2 3p 3 , 3s3p 4 , and 3s 2 3p 2 3d configurations, are included in the expansion of the total wave function. These 13 ionic states correspond to 30 fine-structure levels, leading to a total of 435 possible independent transitions (including all forbidden, semi-forbidden, and allowed). All 435 fine-structure transitions are considered in this paper, making it the most comprehensive tabulation of effective collision strengths for the Ar IV ion. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities for electron temperatures ranging from 2,000 to 100,000 K. The present results indicate that the effective collision strengths for many of the forbidden lines are greatly enhanced by the presence of autoionizing resonances converging to the target state thresholds.