THE ABSORPTION SPECTRUM OF NO IN THE VUV REGION; RYDBERG BANDS,

$^{1}$ O. Edgvist et al., Arkiv Fysik 40, 439 (1969).Author Institution: Air Force, Cambridge Research Laboratories3sc $\leftarrow 1\Pi$ The absorption spectrum of NO has been photographed in the 600 - 1000 {\AA} region with a 6.65 m VUV spectrograph in the second order. Vibrational isotope shifts $(N^{14}O$, $N^{15}O)$ indicate that the four bands at 829.38, 820.73, 812.65, and 304.80 {\AA} belong to a single $v^{\prime}$ progression with $v^{\prime} = 1, 2, 3$, and 4, respectively. The upper electronic state should be the lowest member of the Rydberg series $\eta \leftarrow \ln^{1}$, with $\eta = 3$, converging to the $W^{1}\Delta$ state of $NO^{+}$. The (3,0) band is well resolved and a rotational analysis yields $B_{3} = 1.27 cm^{-1} (r_{3} = 1.33 {\AA})$, which is consistent with the suggested excitation of a bonding 1n electron from the ground state