Knowledge Bank

An iterative procedure for obtaining the eigenvalues of the vibrational problem utilizing an expansion of the secular determinant through sixth-order has been developed. This method, in conjunction with an extension of the transformations given by Kuchitsu and $Morino,1$ has been used to obtain valence force constants for water from $H2O$, $D2O$, and HDO vibrational data using least squares procedures. The present approach provides significantly improved results by taking into account accidental resonances with greater precision than previous methods. Values for rotational constants in the Watson representation through fourth-order for a number of vibrational states are compared with the experimental values based on these new force constants.