15min:

EIZI HIROTA, The Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan; KENTAROU KAWAGUCHI, Department of Chemistry, Okayama University, Tsushima-naka 3-1-1, Okayama 700-8530, Japan; TAKASHI ISHIWATA, Department of Information Machines and Interfaces, Faculty of Information Sciences, Hiroshima City University, Ozukahigashi, Asaminami, Hiroshima 731-3194, Japan; IKUZO TANAKA, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro, Tokyo 152-8550, Japan.

We have previously analyzed a band of the NO₃ radical observed at 1492cm^-1 and have established that the band was of E type, thus being assigned to the degenerate N-O stretching, b 3 . We have explained several anomalies noticed in the band in terms of a vibronic interaction model . Stanton recently proposed an alternative assignment b 1 + b 4 for this band, primarily based on an ab ~initio calculated potential. In order to establish the vibrational assignment of the band, we applied the vibronic interaction modelc to the ¹⁴NO₃-¹⁵NO₃ isotope shift and calculated it to be 16 cm^-1 in reasonable agreement with the observed value of 20 cm^-1 when the band is b 3, whereas we obtained a very small value (about 1 cm^-1 or less) for Stanton's assignment, at variance with the observed data. We have also scanned the region from 700 up to 1400 cm^-1 to detect the b 3 band predicted by Stanton at 994 cm^-1 , by using a Fourier transform spectrometer. Although some part of this region was covered by strong absorption of the precursor HNO₃, we confirmed that there were no bands observed between 925 and 1277 cm^-1 that were more than 1/10 as intense as the 1492 cm^-1 band.