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

Abstract

By codeposition of NO/Ne and O(2)/Ne mixtures at 6 K, weakly bound complexes between O(2) and NO are formed. They exhibit a strong, structured charge transfer UV band at lambda(max)=275 nm. The UV band disappears during UV irradiation of the neon matrix, while the visible spectrum of the NO(3) radical appears. Simultaneously, the fundamental nu(4) of the NO(3) radical in the X (2)A(2)' ground state is observed in infrared absorption for the first time at 365.6 cm(-1). Its (14/15)N and (16/18)O isotopic shifts reveal strong couplings between the two e'-type modes of NO(3), which are both active in a pseudo-Jahn-Teller interaction with the excited B (2)E' electronic state. The dispute on the vibrational fundamentals of the NO(3) radical is now concluded by the unambiguous assignment of combination bands associated with the fundamental nu(4). Taking into account the observed isotopic shifts and estimated anharmonicities for nu(4) and the most intense IR band of NO(3) at 1492 cm(-1) (nu(3)+nu(4)), the frequency of the so far not observed fundamental nu(3) is estimated to be 1100+/-10 cm(-1). A tentative assignment of the vibronic levels in the IR spectrum in the range from 1000 to 3000 cm(-1) is given.

On Walking in the Footprints of Giants

“…Real-time comparison between the results of our experiments and his new calculations was exciting, and the agreement was remarkably good. Using the new synthetic procedure, Helmut Beckers and Helge Willner, of the University of Wuppertal, measured the far-infrared ν 4 absorption for five isotopologues of NO 3 trapped in solid neon (87). The position and isotopic shifts agree closely with those predicted by Stanton.…”

Communication: MULTIMODE calculations of low-lying vibrational states of NO3 using an adiabatic potential energy surface

“…It has been the focus of a large body of spectroscopic work due to its complexity and difficulty in making state assignments. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Theoretically, numerous papers have appeared dealing with various aspects of the electronic structure and vibrational analysis [15][16][17][18][19][20][21] and we refer the reader to those papers for details. We note that theoretical work on vibrational assignments done by Stanton has used a model vibronic Hamiltonian, developed by Köppel−Domcke−Cederbaum, 22 with high-level ab initio input and some empirical scaling of the diabatic coupling to obtain good agreement with experiment.…”

Intermediates Involved in the Oxidation of Nitrogen Monoxide: Photochemistry of the cis‐N2O2⋅O2 complex and of sym‐N2O4 in Solid Ne Matrices

“…(1)] provided the earliest known, and perhaps the most frequently cited example of a trimolecular reaction, [33] but its mechanism is still under discussion. [37,38] This controversy initiated some recent computational studies on its mechanism and of the N 2 O 4 potential-energy surface (PES).…”

“…[1] During these experiments we noticed the formation of various N 2 O 4 species by either thermal or photochemical reactions. Because such binary nitrogen oxides are of considerable significance in tropospheric air pollution, [2] physiological systems, [3,4] and industrial processes, [5] we decided to explore in more detail the formation of these N 2 O 4 species by photochemical isomerisation of sym-N 2 O 4 (D 2h ) and from NO and molecular O 2 isolated in solid Ne.…”

“…[1,53] As shown in Figure 4, the ON·O 2 complex produced under these conditions displays a prominent and slightly split N=O stretching band at 1871.9 cm À1 that strongly increases with the relative amount of O 2 in the deposit. This band also corresponds to both a weak O=O stretching-band doublet located at 1540.0 and 1531.1 cm…”