An adiabatic-hindered-rotor treatment allows para-H2 to be treated as if it were spherical

In para-H-2-{molecule} interactions, the common assumption that para-H-2 may be treated as a spherical particle is often substantially in error. For example, quantum mechanical eigenvalues on a full four-dimensional (4D) potential energy surface for para H-2-{linear molecule} species often differ substantially from those calculated from the corresponding two-dimensional (2D) surface obtained by performing a simple spherical average over the relative orientations of the H-2 moiety. However, use of an adiabatic-hindered-rotor approximation can yield an effective 2D surface whose spectroscopic properties are an order of magnitude closer to those yielded by a full 4D treatment. (c) 2010 American Institute of Physics. [doi:10.106311.3476465]