ACCURATE OSCILLATOR-STRENGTHS FOR INTERSTELLAR ULTRAVIOLET LINES OF CL-1

Analyses on the abundance of interstellar chlorine rely on accurate oscillator strengths for ultraviolet transitions. Beam-foil spectroscopy was used to obtain f-values for the astrophysically important lines of Cl I at 1088, 1097, and 1347 angstrom. In addition, the line at 1363 angstrom was studied. Our f-values for lambdalambda1088, 1097 represent the first laboratory measurements for these lines; the values are f (1088) = 0.081 +/- 0.007 (1 sigma) and f(1097) = 0.0088 +/- 0.0013 (1 sigma). These results resolve the issue regarding the relative strengths for lambdalambda1088, 1097 in favor of those suggested by astronomical measurements. For the other lines, our results of f(1347) = 0.153 +/- 0.011 (1 sigma) and f (1363) = 0.055 +/- 0.004 (1 sigma) are the most precisely measured values available. The f-values are somewhat greater than previous experimental and theoretical determinations.