VIBRATIONAL ISOTOPE SHIFTS OF ABSORPTION BANDS OF N2 IN THE SPECTRAL REGION 720–830 Å

Abstract

Using a normal-incidence vacuum spectrograph with a 3-meter concave grating, the absorption spectra of 14N2 and 15N2 in the 720–830 Å region have been investigated. From the vibrational isotope shifts, it has been confirmed that the previous assignment given by Ogawa and Tanaka for the Rydberg series converging to the A2Πu state of N2+ was correct. The observed series limits converging to the [Formula: see text] state of 15N2+ are 134735(0,0), 136540(1,0), 138320(2,0), and 140070(3,0) cm−1. The observed vibrational isotope shifts at the series limits in both Rydberg series converging to the A2Πu and the X2Σg+ states of N2+ agree with those values calculated from the known vibrational constants of the A2Πu, and the X2Σg+ states of 14N2+ and the X1Σg+ state of 14N2. In addition to the Rydberg series, four new progressions have been identified tentatively. The observed vibrational quanta of the upper states of these progressions are almost the same, and are, moreover, almost the same as those of the A2Πu state of N2+.