The vibrational spectra of molecular ions isolated in solid neon. IV. NO+, NO−, ONNO+, and ONNO−

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Abstract
When a Ne:NO sample is codeposited at approximately 5 K with a beam of neon atoms that has been excited in a microwave discharge, photoionization and Penning ionization of the NO lead to the stabilization of both monomer and dimer ions. The most prominent infrared absorption, at 1619.2 cm−1, results from the reaction of NO− with NO or of an electron with (NO)2 to form the charge‐delocalized trans‐ONNO− species. The position of the totally symmetric NO‐stretching absorption of trans ONNO− can be inferred from observation of a combination band. The infrared absorption of NO+ has been detected very close to the gas‐phase band center. Other infrared absorptions have been tentatively assigned to NO−, cis ONNO−, trans ONNO, and the lowest energy isomer of ONNO+. Comparison of the gas‐phase vibrational frequencies observed for the weakly bound species cis ONNO and N2O3 with the corresponding frequencies observed in this neon‐matrix study suggests that the matrix shifts for the dimer ion absorptions in the mid‐infrared probably amount to less than 1%.