Knowledge Bank

We have previously analyzed a band of the NO$3$ radical observed at 1492\wn and have established that the band was of $E$ type, thus being assigned to the degenerate N-O stretching, \nub {3} }. We have explained several anomalies noticed in the band in terms of a vibronic interaction model }. Stanton } recently proposed an alternative assignment \nub {1} + \nub {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 $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$NO$3$-$\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$NO$3$ isotope shift and calculated it to be 16 \wn in reasonable agreement with the observed value of 20 \wn } when the band is \nub {3}, whereas we obtained a very small value (about 1 \wn or less) for Stanton's assignment, at variance with the observed data. We have also scanned the region from 700 up to 1400 \wn to detect the \nub {3} band predicted by Stanton at 994 \wn }, by using a Fourier transform spectrometer. Although some part of this region was covered by strong absorption of the precursor HNO$3$, we confirmed that there were no bands observed between 925 and 1277 \wn that were more than 1/10 as intense as the 1492 \wn band.