Infrared spectroscopy of chemically doped solid parahydrogen

Abstract

This review article presents an overview of recent infrared spectroscopic studies of chemical species trapped in solid parahydrogen at liquid helium temperatures. An overriding theme that emerges from this work is that, even at liquid helium temperatures, chemically doped solid parahydrogen is dynamic with a variety of quantum mechanical and energy transfer processes that occur, such as orthohydrogen quantum diffusion, hydrogen nuclear spin conversion, and, in radical doped parahydrogen solids, chemical reactions can occur. To illustrate these dynamical phenomena we examine (1) clustering of orthohydrogen to dopant molecules, (2) solid parahydrogen infrared absorptions induced or perturbed by the presence of the dopant, and (3) chemical reactions initiated by infrared absorptions of the parahydrogen solid. Contents PAGE 1. Introduction 470 2. Experimental method 472 3. Weakly bound clusters in solid pH2 473 3.1. Forming weakly bound clusters 473 3.2. Intracluster nuclear spin conversion 479 4. Dopant-induced IR activity 482 4.1. Rg atom-induced Q1(0) vibron band 483 4.2. Rg atom-perturbed S1(0) transitions 484 5. Infrared-induced chemical reactions 486 6. Concluding remarks 494 Acknowledgments 494 References 494