The weakly-bound nitrous oxide–acetylene complex: Fundamental and torsional combination bands of N2O–C2H2 and N2O–C2D2 in the N2O ν1 region

Spectra of the weakly-bound N2O–C2H2 and N2O–C2D2 complexes in the region of the N2O ν1 fundamental band (∼2224 cm−1) are observed in a pulsed supersonic slit jet expansion probed with a tunable diode laser. Two bands are analyzed for each complex: the fundamental (N–N stretch), and a combination involving the intermolecular torsional (out-of-plane bend) vibration. The resulting torsional frequencies are 44.37 and 40.01 cm−1 for the C2H2 and C2D2 complexes, respectively. This represents the first observation of the N2O–C2D2 isotopomer, and the first direct determination of an intermolecular frequency for nitrous oxide–acetylene.