Knowledge Bank

The absorption spectrum of NO has been investigated with a 6.65-m vacuum spectrograph using the helium continuum as a background source. Previously studied $\gamma -$, and $\beta$-Rydberg $series1,2$ have been reinvestigated. In the $\gamma$-series two series limits at 147 811.1 (m = 30) and 147 689.1 $cm-1$ (m = 26) were obtained. The series going to the latter limit has not been reported previously and is relatively weak; it disappears when the gas is cooled with liquid nitrogen. The two series originate from the $X2\Pi 12$ and $X2\Pi 3/2$ states, respectively. The limit of the $\beta$-series obtained from this work is 133 565.3 $cm-1$ (m = 29). Additional series which seem to be associated with the $\beta$-series will be discussed.