The structure of N2⋅SO2 from diode laser and molecular-beam electric resonance spectroscopy

Abstract

The b-type vibration–rotation band of N2⋅SO2 near the SO2 ν3 band origin was observed in a molecular-beam, diode laser direct absorption experiment. Rotational transitions and Stark effect data for this complex were additionally measured using molecular-beam electric resonance methods. The vibrational band origin was 1361.1440(2) cm−1, shifted by 0.9167(2) cm−1 from that of the SO2 monomer. Rotational constants were measured for the upper and lower vibrational states with A″=8875.3(22) MHz, B″=1620.3(22) MHz, C″=1426.1(24) MHz, A′=8832.4(26) MHz, B′=1617.3(28) MHz, and C′=1431.6(15) MHz. The electric dipole moment components were determined, with μa = 0.0441(16) D and μc = 1.5884(29) D. The c component of the nitrogen quadrupole coupling component was found to be eqccQ = 1.30(21) MHz. A structure analysis gave the separation between the centers of mass of the monomers as 3.8925(28) Å. The angles between the symmetry axes of the SO2 and N2 units and the line connecting these monomers were calculated as 61.35° and 24.54°, respectively. Additionally, the SO2 monomer a axis was found to lie along the b axis of the complex. The electric dipole moment data indicate that the equilibrium angle for the SO2 is much closer to 90° than the rms result. These structural results were compared to model calculations of the binding energy of the complex.