Journal of Chemical Physics, Vol.107, No.20, 8432-8436, 1997
A grid representation for spherical angles: Decoupling of the angular momentum operator
The angular momentum operator which is a function of the orientational angle theta and the azimuthal angle phi may be split into the phi-dependent and phi-independent parts so that the split exponential operator method can be exactly implemented (with orthogonal transformations) in a direct product discrete variable representation of theta and phi. Although one loses the exact representation of the angular momentum in the spherical harmonic basis, the direct product representations have been proved to converge and to be stable and efficient. An advantage is that computational time for a wave-packet propagation (for a matrix-vector product) is reduced for split exponential propagators since a direct product representation is preserved for all the angles. (C) 1997 American Institute of Physics. [S0021-9606(97)01644-9].