FOURIER TRANSFORM INFRARED EMISSION SPECTROSCOPY AND AB INITIO CALCULATIONS OF RuN

Abstract

The emission spectrum of RuN has been observed in the near infrared using a Fourier transform spectrometer. RuN molecules were excited in a hollow cathode lamp operated with neon gas and a trace of nitrogen. Two bands with 0-0 Q heads near 7354 and $8079 cm^{-1}$ and a common lower state have been assigned as $^{2}\Pi_{1/2}- {^{2}}\Sigma^{+}$ and ${^{2}}\Pi_{3/2-} {^{2}}\Sigma^{+}$ subbands, respectively, of a $A {^{2}}\Pi -X^{2}\Sigma^{+}$ transition. A rotational analysis of these bands has been performed and molecular constants have been extracted. The principal molecular constants for the ground $X^{2}\Sigma^{+}$ state of the most abundant $^{102}RuN$ isotopomer are: $B_{0}=0.5527738(99)cm^{-1}, D_{0}= 5.511(19)\times 10^{***}cm^{-1}, \gamma_{0}= -0.044401(30 cm^{-1})$ and $r_{0}=1.573882(14)${\AA}. The excited $A^{2}\Pi$ state has the following molecular constants: $T_{\infty}= 7714.34082(66)cm^{-1}, A_{0}= 725.8031(13)cm^{-1}, B_{0}= 0.516818(11) cm^{-1}, D_{0}=5.664(67)\times 10^{-2} cm^{-1}, p_{0}= 5.446(46) \times 10^{***} cm^{-1}$ and $r_{0}= 1.627710(17)${\AA}. Ab initio calculations have been carried out on RuN to assertain the nature of the experimentally observed states and predict the spectroscopic properties of the low-lying electronic states. Our electronic assignment is supported by these calculations and is also consistent with the observations for the isoelectronic RhC molecule [Kaving and Scullman, J. Mol. Spectrosc. 32, 475-500 (1969)]. The valence electron configuration $1 \sigma^{2}2\sigma^{2}1 \pi^{4}1\delta^{4}3\sigma^{1}$ is proposed for the $X^{2}\Sigma^{+}$ ground state of RuN and the configurations for the excited states have been discussed. There is no previous experimental or theoretical work on RuN.