H atom H-2 molecule van der Waals complexes in solid argon matrix by high-resolution ESR spectroscopy

Van der Waals addition complexes of a hydrogen atom with a hydrogen molecul e, H-H-2, H-HD, H-D-2, and D-D-2, generated in Ar matrixes have been studie d by high-resolution ESR spectroscopy. The complexes were formed by hydroge n atoms migrating in Ar matrices to encounter the hydrogen molecules trappe d in the substitutional site. The decay rates of the thermally activated co mplexes were experimentally determined, and a potential energy of 3.5 kJ mo l(-1) to stabilize H-H-2 complexes was evaluated in the temperature region 24.4-29.3 K. Additionally, the mean distance between the H atom and H-2 mol ecule in the complex was refined to be 0.245 nm by the help of ab-initio MO calculations at the QCISD/aug-cc-pvqz level. (C) 1999 Elsevier Science B.V . All rights reserved.