Measurements of thef‐Values of the Resonance Transitions of Niiiat 1317.217 and 1370.132 A

We have retrieved high-resolution UV spectra of 69 hot stars from the HSTarchive and determined the strengths of the interstellar Ni II absorptionfeatures at 1317.217A. We then compared them to absorptions from either thetransitions at 1741.553A (covered in the spectra of 21 of the stars) or the oneat 1370.132A (seen for the remaining 48 stars). All spectra were recorded bythe either the E140M, E140H, or E230H gratings of STIS. By comparing thestrengths of the two lines in each spectrum and evaluating a weighted averageof all such comparisons, we have found that the f-value of the 1317A line is1.34 +/-0.019 times the one at 1741A and 0.971 +/-0.014 times that of the oneat 1370A. We adopt as a comparison standard an experimentally determinedf-value for the 1741A line (known to 10% accuracy), so that f(1317A) = 0.0571+/-0.006. It follows from this f-value and our measured line-strength ratiosthat f(1370A) = 0.0588 +/-0.006. As an exercise to validate our methodology, wecompared the 1317A transition to another Ni II line at 1454.842A and arrived atan f-value for the latter that is consistent with a previously measuredexperimental value to within the expected error.Comment: 14 pages, 4 figures, accepted for publication in the Astrophysical Journa