Matrix-Isolation Study of the Interaction of Electrons and Alkali Metal Atoms with Various Nitrogen Oxides. Infrared Spectra of the Species NO−, NO2−, and N2O2−

The infrared spectra which result when samples of NO₂ are codeposited with the various alkali metals in an argon matrix at 4 or at 14°K are consistent with the occurrence of strong charge‐transfer interaction. In addition to isolated ${\mathrm{NO}}_2^{-}$ , previously identified in this system, ion pairs of general formula ${\mathrm{M}}_{\mathrm{x}}^{+}{\mathrm{NO}}_2^{-}$ are stabilized. When NO is substituted for NO₂, the infrared spectrum of the initial deposit shows an absorption between 1350 and 1375 cm⁻¹ which can be assigned to the ${\mathrm{NO}}^{-}$ stretching fundamental of ${\mathrm{M}}_{\mathrm{x}}^{+}{\mathrm{NO}}^{-}$ ion pairs, in good agreement with the vibrational spacing recently reported for ground‐state ${\mathrm{NO}}^{-}$ in the gas phase. Weak charge‐transfer interaction occurs between alkali‐metal atoms and N₂O in an argon matrix environment. Results of the present experiments can be explained by postulating that the upper, predominantly ionic state of the charge‐transfer complex decomposes producing ${\mathrm{O}}^{-}$ , which may diffuse through the matrix. A new absorption which appears at 1205 cm⁻¹ has tentatively been assigned to ν₄(b₁) of a planar ${\mathrm{O}}_2\mathrm{N}={\mathrm{N}}^{-}$ anion. In studies of the interaction of sodium atoms with Ar:NO:N₂O mixtures, mercury‐arc irradiation of the sample leads to the appearance not only of the ${\mathrm{N}}_2{\mathrm{O}}_2^{-}$ absorption, but also of absorptions due to isolated ${\mathrm{NO}}_2^{-}$ and to ${\mathrm{Na}}_{\mathrm{x}}^{+}{\mathrm{NO}}_2^{-}$ .