Infrared diode laser spectroscopy of the Ne-D2O van der Waals complex: Strong Coriolis and angular-radial coupling

Abstract

Four internal-rotationvibration bands of the Ne-D2O complex have been measured in the v2 bend region of D2O using a tunable infrared diode laser spectrometer to probe a slit supersonic expansion. Three ortho bands are excited from the ground state ∑(000) to the ∑ and Π(111, ν2 = 1) internal rotor states and the n = 1, ∑(000, ν2 = 1) stretching-internal rotor combination state. Strong perturbations between the excited vibrational states are evident. The observed spectra are analyzed separately with a three-state J-dependent Coriolis plus J-independent angular-radial coupling model M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 106, 3078 (1997) and a three-state Coriolis coupling model R. C. Cohen and R. J. Saykally, J. Chem. Phys. 95, 7891 (1991). The former model works more successfully than the latter. Molecular constants for the ground and excited vibrational states of ortho 20Ne-D2O isotopomer as well as the Coriolis and angular-radial coupling constants are determined accurately. The van der Waals stretching frequency is estimated to be νs 24.85 cm-1 in the ground state and decreases to about 20.8 cm-1 upon vibrational excitation of the D2O bend. © 2011 American Institute of Physics.