Matrix infrared spectra and anharmonic force field of NCO−

Abstract

Cyanate ions enriched in ¹⁵N, ¹³C, and ¹⁸O have been prepared by direct oxidation reactions and introduced into KCl and KBr single crystals to a maximum concentration of $\text{≈ 5}\mathrm{wt}\%$ . The infrared absorption spectra of the resultant cyanate ion isotopic species observed between 550 and 5000 cm⁻¹ from 320 to 77°K have added more than 50 new vibrational features to those previously reported. 2v₃ has been observed for ¹⁴N‐¹²C¹⁶O⁻ and ¹⁵N¹²C¹⁶O⁻ in both KBr and KCl matrices, thus permitting an unambiguous determination of x₃₃. The observed energy levels reported here have been combined with those previously reported and have been used to determine the anharmonic force field including cubic and quartic force constants in KBr, KCl, and KI matrices.