Highly excited vibrational states of the KCN molecule

Abstract

Vibrational (J= 0) states for the KCN molecule are calculated in Jacobi coordinates, employing a discrete variable representation (DVR) for the angular internal coordinate. The power of the DVR method is once again illustrated in that some 800 vibrational (J= 0) states are converged for a two-dimensional potential-energy surface. The energy region studied is that where the classical dynamics of the system are known to be chaotic. Most of the states are found to be irregular, although there are classes which appear to be regular and can be assigned effective quantum numbers corresponding to excitation in particular ‘separable’ modes of the system. Phenomenological aspects of the wavefunctions are discovered via graphical analysis, in particular many linearly localised states are identified where the potential-energy surface actually has a saddle point. The statistical behaviour of the level spacings is also investigated. Comparison with a similar study on LiCN (J. R. Henderson and J. Tennyson, Mol. Phys., 1990, 69, 639) is made.