Spectroscopy and dynamics of hydride radical van der Waals complexes

Abstract

Spectroscopic and theoretical studies of hydride radical–rare gas atom complexes (Rg–HX) are reviewed. This family of van der Waals molecules is of interest as they can be used to explore the characteristics of the long-range forces associated with open-shell species. Orbitally degenerate states of HX radicals have an electronic anisotropy that results in van der Waals interactions that are qualitatively different from those exhibited by the corresponding closed-shell systems. Rg–HX complexes, where X is a first- or second-row p-block element, reveal systematic trends where the anisotropic components of the physical interactions are determined by the electronic orbital configuration. Radicals in Σ, Π and Δ states with singlet, doublet and triplet spin multiplicities have been examined. When Rg = He, Ne or Ar the interaction potential energy surfaces can be predicted using high-level ab initio methods. Theoretical studies have established the methods and basis sets that are capable of providing an accurate description of the long-range forces for open-shell molecules. Clusters consisting of an HX molecule with multiple rare gas atoms are model systems for studies of solvated radicals. Potential energy surfaces derived from the binary clusters are being used to construct approximate potentials for Rg n –HX clusters. The equilibrium structures and vibrational dynamics predicted for these systems show that solvated radicals exhibit unique properties. Contents PAGE 1. Introduction 376 2. Experimental methods 377 3. Theoretical considerations 378 4. Binary complexes 384 4.1. BH–Ar and AlH–Ar 384 4.2. CH–Rg complexes (Rg = He, Ne and Ar) 386 4.3. NH–Rg complexes (Rg = He, Ne and Ar) 397 4.4. OH–Rg and SH–Rg complexes 407 5. Complexes of HX radicals with multiple Rg atoms 413 6. Conclusions and future directions 417 Acknowledgements 418 References 418