A high-resolution infrared study of the bending pentad of (GeH2D2)-Ge-70 in the region 500-1000 cm(-1)

The gas phase IR spectra of the v(4) (A(1), 620.38 cm(-1)), v(7) (B-1, 658. 88 cm(-1)), v(9) (B-2, 771.56 cm(-1)), and v(3) (A(1), 882.91 cm(-1)) bands of monoisotopic (GeH2D2)-Ge-70 have been studied at a resolution of about 0.0030 cm(-1). Together with the inactive v(5) band near 806.34 cm(-1) thes e bands form an isolated pentad which is coupled by a-, b-, and c-Coriolis resonances. The a-Coriolis interactions within the pairs (v(4), v(7)) and ( v(9), v(5)) are particularly strong. A ground state combination difference analysis yields the following ground state rotational constants of the mole cule: A(0) = 2.174757291(25) cm(-1), B-0 = 1.802371905(23) cm(-1) and C-0 = 1.549145635(23) cm(-1). A simultaneous upper state analysis of the four IR active bands belonging to the pentad based on the Watson asymmetric rotor Hamiltonian for each of the five states and taking into account Coriolis in teractions up to the fourth order has been performed. A set of spectroscopi c parameters including sextic centrifugal distortion constants for the four IR active bands, and the band center, A and (B + C)/2 for the inactive v(5 ) band, have been obtained using fixed first order Coriolis resonance param eters. In addition, a number of higher order Coriolis interaction constants have been determined. (C) 2000 Elsevier Science B.V. All rights reserved.