High-Resolution Photoelectron Spectroscopy of NO 3 – Vibrationally Excited Along Its ν 3 Mode

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 129; no. 6; p. 1634
• Main Authors: Lau, Jascha A., DeWitt, Martin, Franke, Peter R., Stanton, John F., Neumark, Daniel M.
• Format: Journal Article
• Language: English
• Published: United States 13.02.2025
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/acs.jpca.4c07682

The nitrate (NO ) radical has long been the subject of both experimental and theoretical studies due to its complex electronic structure resulting from vibronic interactions between its and states. In particular, the definite assignment of the fundamental of its degenerate stretching vibration (ν ) is still under debate. Here, we report high-resolution photoelectron spectra of vibrationally pre-excited NO using the recently developed IR-cryo-SEVI technique. The anions are excited through infrared (IR) excitation near 1350 cm , accessing the ν and 2ν ( ') vibrational levels with band centers at 1350.5 and ∼2700 cm , respectively. The IR-cryo-SEVI spectrum for 2ν pre-excitation shows clear evidence for an intense 3 transition. From the position of this feature (30031 cm ), the electron affinity of NO also determined in this work (31680 cm ), and the IR excitation energy, we obtain a fundamental frequency of 1051 cm for the ν fundamental of the NO radical. This assignment and other features in the IR-cryo-SEVI spectra are supported by spectral simulations based on a vibronic Köppel-Domcke-Cederbaum Hamiltonian. The simulations also show that nearly all features in the IR-cryo-SEVI spectra arise because of pseudo-Jahn-Teller coupling between the and states of NO . The results and analysis presented here settle a long-standing controversy regarding the ν frequency of NO .