Transition Probabilities and Collisional Cross Sections for Ultraviolet Lines.

Abstract

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Transition Probabilities and Collisional Cross Sections for Ultraviolet Lines. Varsavsky, Carlos M. Abstract With the advent of rocket-born and satellite-born spectrographo it is becoming possible to study celestial objects in the hitherto inaccessible ultraviolet. The spectroscopic analysis will require the knowledge of the basic atomic parameters of the lines observed. To satisfy this need, a program for the computation of these parameters has been started at the University of Colorado. The nuclear-charge expansion method of Layzer and Varsavsky has been applied to the computation of the electric dipole matrix elements for many lines of interest. The method is particularly suitable for the treatment of a particular transition along an isoelectronic sequence. In a forthcoming publication we shall present the numerical results obtained for typical allowed transitions in the isoelectronic sequences from helium through chlorine (except neon), together with a detailed account of the mechanics of the method that will enable other investigators to calculate the matrix elements for any other transition of interest. The matrix elements for electric dipole transitions are easily related to optical transition probabilities and total excitation cross sections by electronic impact. In the first case we must make some assumptions about the coupling of the angular momenta. Our tables are based on the L-S coupling scheme. In the case of total cross sections, a simple relationship is obtained if we can make use of the Born approximation, and if the transition is optically allowed; these restrictions reduce, of course, the scope of the tables but allow the treatment of many transitions of interest in the solar corona. An attempt is made to evaluate our method by comparison with the available experimental and theoretical data. In the few cases where such data exist the agreement is satisfactory. Publication: The Astronomical Journal Pub Date: March 1960 DOI: 10.1086/108190 Bibcode: 1960AJ.....65...58V full text sources ADS |