Intermolecular potentials from crossed beam differential elastic scattering measurements. VII. para-H2 + para-H2

The differential elastic scattering cross section for para-H2+para-H2 has been measured at a collision energy of 2.71×10−14 erg. Oscillations due to nuclear symmetry were observed in the angular distribution. The data were fit to a spherically symmetric multiparameter potential form giving a well depth ε /k= 34.8°K, rm= 3.49 Å. This potential is closer to those obtained from the total elastic scattering cross section by Gengenbach and Toennies and from differential cross sections by Dondi, Valbusa, and Scoles than to those derived from bulk properties and early valence bond calculations. The position of the bound vibrational level has been computed and is found 2.0 cm−1 below the continuum.