Ortho/Para Hydrogen Converter for Rapid Deposition Matrix Isolation Spectroscopy.

摘要

We describe the construction and operation of a catalyst-bed type device for precooling and equilibrating the ortho/para composition of a hydrogen gas flow. We use this device to vapor deposit millimeters thick cryogenic parahydrogen (pH2) solids which are remarkably transparent M.E. Fajardo and S. Tam, J. Chem. Phys. 108, 4237 (1998). Infrared absorption spectra of solids deposited at pH2 flow rates up to 290 mmol/hour (solid thickness growth rates up to 75 um/min) indicate a residual orthohydrogen (oH2) content of less than 0. 01%. Gas phase thermal conductivity measurements indicate a residual oH2 content of 0(+5/-0)% for flow rates up to 1.9 mol/hour. These pH2 solids can be doped readily by simple co-deposition of various impurities produced by any of the numerous dopant sources developed in previous matrix isolation spectroscopy (MIS) studies. The long achievable pathlengths, and the desirable properties of pH2 as a matrix host, will enable revolutionary new fundamental and practical applications for MIS.