Measurements of the Singly Ionized Oxygen Auroral Doublet Lines λλ7320, 7330 Using High‐Resolution Sky Spectra

Abstract

The wavelengths of the individual [O ii] 2s 2 2p 3 2 D o 5=2-2s 2 2p 3 2 P o 1=2;3=2 k7320 and [O ii] 2s 2 2p 3 2 D o 3=2-2s 2 2p 3 2 P o 1=2; 3=2 k7330 auroral doublet component lines have been measured directly in the nightglow for the first time, from high-resolution spectra obtained with the High Resolution Echelle Spectrophotometer (HIRES) spectrograph on the Keck I telescope at the W. M. Keck Observatory. Specifically, we find doublet splittings of 1.077 AE 0.003 8 and 1.080 AE 0.003 8 at k7320 and k7330, respectively, with the former significantly larger than the often quoted and utilized value of 0.8 8 from Moore and in line with the National Institute of Standards and Technology (NIST) (1.07 8) as well as more recent astrophysical observations of the lines in planetary nebulae, including 1.07 8 from De Robertis, Osterbrock, & McKee and 1.09 8 from Barnett & McKeith. Our results suggest, however, that adjustments of +0.124 8 and +0.131 8 should be made to current NIST wavelengths for the blue and red components of the k7320 doublet respectively, while our wavelengths of the k7330 doublet components are little changed from current NIST values. The observed intensity ratio of k7320/k7330 from these measurements agrees with the theoretical value calculated under conditions of thermally populated 2 P o levels.