Vibrational-rotational energies of all H2 isotopomers using Monte Carlo methods

Using variational Monte Carlo techniques, we have computed several of the lowest rotational-vibrational energies of all the hydrogen molecule isotopomers (H-2, HD, HT, D-2, DT, and T-2). These calculations do not require the excited states to be explicitly orthogonalized. We have examined both the usual Gaussian wave function form as well as a rapidly convergent Pade form. The high-quality potential energy surfaces used in these calculations are taken from our earlier work and include the Born-Oppenheimer energy, the diagonal correction to the Born-Oppenheimer approximation, and the lowest-order relativistic corrections at 24 internuclear points. Our energies are in good agreement with those determined by other methods. (c) 2006 Wiley Periodicals, Inc.