A reinvestigation of the NO3 1492 cm−1 band

Abstract

Ishiwata et al. [J. Chem. Phys. 82, 2196(1985] have recently observed an infrared diode laser spectrum of N0 3 in the 1492 cm -I region and have assigned it to the V3 band in the X 2 A i state. However, some of the derived constants such as the Coriolis coupling and spin-rotation constants did not conform well with expected values. In the present study, the observation was extended so as to take combination differences, which led us to revise the previous assignment slightly and to remove all the anomalies in the lower (i.e., ground) state. A most important result of the present study is that a spin-orbit interaction constant a eff I (L z ) I = 0.17 cm -I is indispensable to explain the spin splitting observed for the upper state. The first-order Coriolis coupling constant of the upper state (; = 0.19) remains essentially the same as in the previous study and differs considerably from the value calculated for the V3 state (; = 0.7). Possible explanations of these data are discussed in some detail to obtain more information on the molecular structure of the N0 3 radical.

On the vibrational assignment in the ground electronic state of NO3

“…The reason was not clear at that time. Although we noticed an effect of vibronic interaction appeared in the spin-orbit interaction constant in 1990 [2], we could not relate the effect of the vibronic mixing to the cancellation of the m 3 fundamental band intensity.…”

The infrared spectroscopy and photochemistry of NO3 trapped in solid neon

“…30,39 The presence of NO 2 led to the appearance of absorptions of NO 2 − and NO 3 − . 35 A very sharp, unstructured absorption at 762.9 cm −1 lies very close to the 762.33 cm −1 gas-phase band center determined by Friedl and Sander 17 for the 2 fundamental of NO 3 , and a prominent absorption at 1491.4 cm −1 with a weaker companion at 1492.7 cm −1 lies close to the gas-phase band center of the absorption heretofore assigned [16][17][18] to the 3 fundamental of NO 3 . Absorptions of all but the weakest of the higher frequency absorptions attributed to overtones and combination bands of NO 3 in earlier studies appeared within 2.5 cm −1 of their gas-phase positions.…”

“…3, which also shows an absorption of NO 3 at 1412.5 cm −1 , together with its 15 NO 3 counterpart. The effects of 18 O enrichment were also explored. Because a sample of 14 N 18 O was not available, it was not possible to obtain spectra in which 14 An alternate strategy was used to obtain the infrared spectrum of 14 Table II, and the positions of all of the observed NO 3 absorptions between 1100 and 3200 cm −1 are summarized in Table E-2. 36 Almost all of the NO 3 absorptions appear in pairs, with a weaker absorption about 1 -3 cm −1 higher in frequency than the main absorption.…”

“…A later high-resolution Fourier-transform infrared study of NO 3 by Friedl and Sander 17 confirmed the contribution of the 1492 cm −1 band by NO 3 3 ͑eЈ͒ and assigned the 2 ͑a 2 Љ͒ fundamental as well. Continuing studies in the laboratory of Hirota and co-workers 18,19 suggested that the anomalies associated with the 1492 cm −1 band 16 resulted from vibronic interaction between 3 ͑eЈ͒ and excited electronic states of EЈ symmetry. They also reported high-resolution spectra of several NO 3 absorption bands between approximately 1900 and 2600 cm −1 , all originating in the ground state of the molecule, for which definitive assignments were not possible.…”

Conflicting Observations Resolved by a Far IR and UV/Vis Study of the NO3 Radical

“…The prominent infrared absorption at 1492 cm À1 was thoroughly investigated by highresolution gas phase spectroscopy almost 25 years ago. [13,19] Although this band was assigned to the degenerate stretching fundamental, n 3 , [12,13,16] recent calculations [11] have challenged that assignment. The absorptions above 1100 cm À1 seem to be almost entirely binary or higher combinations of the three fundamentals n 1 (1053 cm À1 ), [9] n 3 (between 900-1100 cm…”