GRID REPRESENTATION OF ROTATING TRIATOMICS

A grid formulation is presented for the body-fixed (BF) motion of a rotating triatomic molecule. The BF component of the wave function, described in terms of Jacobi coordinates, is discretized on a {R(i) x r(j) x theta-alpha} grid. By use of the generalized discrete variable representation (DVR) of Light, Hamilton, and Lill [J. Chem. Phys. 82, 1400 (1985)] one can employ the same theta grid for the different OMEGA components of the wave function, OMEGA corresponding to the projection of the total angular momentum J onto the z BF axis. Such a unique grid definition allows one to define adiabatic status, with respect to the theta coordinate, independent of the OMEGA value considered. These states have been directly computed by means of a distributed 2D DVR, sampling only the relevant points in configuration space. Further reduction of the rovibrational basis set was achieved by defining new adiabatic states, with respect to the OMEGA component. This formation is applied to the calculation of bound rovibrational states of the HCN molecule for the J = 2 value.