Rotation–Torsion Analysis of the High-Resolution ν6 and ν8 Fundamentals of 70Ge2H6

Abstract

The ν6 (A4s) and ν8 (E1d) Coriolis coupled fundamental bands of 70Ge2H6, occurring between 730 and 950 cm−1, have been rotationally analyzed under high resolution. The interactions of ν8 with the nearby lying ν2 + ν4 (A4s), 2ν3 + ν9 (E1d), and ν∓19 + ν∓112 (E) have also been accounted for in the analysis. We determined rotational constants of the ground state, vibrational and rotational parameters of ν6 and ν8, interaction parameters, and a few leading parameters of the other three mentioned perturbers of ν8. The torsional barrier height is estimated about 285 cm−1, leading to the prediction of a tunneling splitting of about 0.049 cm−1 in the ground torsional state. No torsional splitting was observed in the ν6 band, showing that the splittings in the v6 = 1 vibrational state are the same as in the ground state. The ν8 band shows almost constant splittings of about 0.047 cm−1. This result and the assignments of the split torsional components in all the observed subbranches of ν8 show that the torsional splittings in the v8 = 1 state are quite small, and the observed splittings are almost completely due to the ground state. We have proved by numerical calculation that the lowering of the torsional splitting found in the v8 = 1 state can be explained by the vibration–torsion (γ-Coriolis) coupling mechanism of the degenerate vibrational states.