HFCN open-shell isomers in solid argon. I. Spectroscopy of the ground and excited states of HFC=N radical

Abstract

Fluoromethylene amidogen radicals, HFC=N•, were generated in solid argon by solid-state chemical reactions of mobile F atoms with hydrogen cyanide. Highly resolved infrared and electroparamagnetic resonance spectra of HFC=N• were obtained in the temperature range 15–30 K. All six vibrational frequencies and the complete set of isotropic hyperfine coupling constants on magnetic nuclei H1, F19, and N14 were determined experimentally. Calculated spectroscopic characteristics are in excellent agreement with experiments, showing that HFC=N• radical has a planar structure in the ground state. Two electronic absorption transitions were observed in the near-ultraviolet and visible spectral region. The first excited A″2 state of HFC=N• radical is calculated to have a planar structure very similar to the ground state, and lies 20 726 cm−1 above the ground state [at the CCSD(T)/cc-pVTZ level of theory], in good agreement with the experimental value, 20 430 cm−1. The observed Franck–Condon envelope in the laser-induced fluorescence spectra provides strong evidence for the similarity of the structures of the ground and first excited states. An intense absorption band centered at 355 nm is attributed to electronic transition between the ground and second excited states.