FTIR SPECTROSCOPY OF NO$_3$ : OBSERVATION AND ANALYSIS OF THE 1127 cm$^{-1}$ BAND

Abstract

We report the infrared spectrum of NO$_3$ studied with a Bruker 120 HR. In the present experiment, the NO$_3$ production was monitored by using He-Ne laser absorption at 633 nm. The multi-path cell was also improved to attain 48 m effective path length, and a new HgCdTe detector was introduced. In the 1000-1900 cm$^{-1}$ region, the following 7 bands were observed at 1127, 1137, 1173, 1413, 1492, 1550, 1927 cm$^{-1}$. The 1127, 1137 and 1550 bands were not reported by matrix isolation, and these are thought to be due to hot bands from the $\nu_4$ state. The analysis of the 1127 band was carried out by fixing the upper state parameters to those of the 1492 band, and major molecular constants are determined as follows, B=0.459339(12), C=0.228848(20), C$\zeta$$_4$=-0.044279(29), $\nu_4$=365.4887(13) cm$^{-1}$. The two A-E type bands are also assigned in the 1133 and 1137 cm$^{-1}$ regions in addition to E-E type, indicating that the 1492 band is assignable to $\nu_3$ + $\nu_4$, in contrast to the previous $\nu_3$ assignment.