DIPOLE-MOMENT OF THE LOWEST PI-BENDING STATE OF (HCN)(2)

The dipole moment of the lowest Pi bending state of (HCN)(2) has been determined by tunable far-infrared Stark spectroscopy to be 6.023(31) D. This represents a reduction in dipole moment of 0.54(5) D relative to the ground state, which is over five times too large for simple har monic oscillations of uncoupled rods. Although qualitative comparison with related systems suggests the possibility of a secondary minimum n ear the T-shaped configuration, electrostatic modeling does not suppor t the existence of such a feature. (C) 1995 Academic Press, Inc.