Rotation-torsion analysis of the high-resolution nu(6) and nu(8) fundamentals of (Ge2H6)-Ge-70

The v(6) (A(4s)) and v(8) (E-1d) Coriolis coupled fundamental bands of (Ge2 H6)-Ge-70, occurring between 730 and 950 cm(-1), have been rotationally ana lyzed under high resolution. The interactions of v(8) with the nearby lying v(2) + v(4) (A(4s)), 2v(3) + v(9) (E-1d), and v(9)(+/- 1) + v(12)(+/- 1) ( E) have also been accounted for in the analysis. We determined rotational c onstants of the ground state, vibrational and rotational parameters of v(6) and v(8), interaction parameters, and a few leading parameters of the othe r three mentioned perturbers of v(8). The torsional barrier height is estim ated about 285 cm(-1), leading to the prediction of a tunneling splitting o f about 0.049 cm(-1) in the ground torsional state. No torsional splitting was observed in the v(6) band, showing that the splittings in the v(6) = 1 vibrational state are the same as in the ground state. The v(8) band shows almost constant splittings of about 0.047 cm(-1). This result and the assig nments of the split torsional components in all the observed subbranches of v(8) show that the torsional splittings in the v(8) = 1 state are quite sm all, and the observed splittings are almost completely due to the ground st ate. We have proved by numerical calculation that the lowering of the torsi onal splitting found in the v(8) = 1 state can be explained by the vibratio n-torsion (gamma-Coriolis) coupling mechanism of the degenerate vibrational states, (C) 1999 Academic Press.