Measurements of the singly ionized oxygen auroral doublet lines λλ7320,7330Å using high resolution sky spectra

The wavelengths of the individual [O II] 2s2p Do5/2 – 2s 2p Po1/2,3/2 λ7320Å and [O II] 2s2p D3/2 – 2s 2p P1/2,3/2 λ7330Å auroral doublet component lines have been measured directly in the nightglow for the first time, from high resolution spectra obtained with the HIRES spectrograph on the Keck I telescope at the W.M. Keck Observatory. Specifically, we find 7320Å and 7330Å doublet splittings of 1.077±0.003Å and 1.080±0.003Å respectively, with the former significantly larger than the often quoted and utilized value of 0.8Å from Moore (1949, Atomic Energy Levels, Vol 1), and in line with NIST (1.07Å) as well as more recent astrophysical observations of the lines in planetary nebulae including 1.07Å from DeRobertis, Osterbrock, & McKee (1985,ApJ,293,459) and 1.09Å from Barnett & McKeith (1988,MNRAS,234,241). Our results suggest, however, that adjustments of +0.124Å and +0.131Å should be made to current NIST wavelengths for the blue and red components of the 7320Å doublet respectively, while the wavelengths of the 7330Å doublet components are little changed from current NIST values. The observed intensity ratio of 7320Å/7330Å from these measurements agrees with the theoretical value calculated under conditions of thermally populated P levels. Subject headings: atomic data – methods:data analysis – techniques:spectroscopic