By codeposition of NO/Ne and O2/Ne mixtures at 6 K, weakly bound complexes between O2 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 NO3 radical appears. Simultaneously, the fundamental v4 of the NO3 radical in the X 2A2' 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 NO3, which are both active in a pseudo-Jahn-Teller interaction with the excited B 2E' electronic state. The dispute on the vibrational fundamentals of the NO3 radical is now concluded by the unambiguous assignment of combination bands associated with the fundamental v4. Taking into account the observed isotopic shifts and estimated anharmonicities for v4 and the most intense IR band of NO3 at 1492 cm-1 (v3 + v4), the frequency of the so far not observed fundamental v3 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.
Pub Type: Journals
charge transfer, electronic spectrum, neon matrix, NO3, (O2)(NO) complex