| Abstract |
Our group is interested in characterizing the diffusion of chemical impurities in quantum solids such as solid parahydrogen (pH 2 ).In this work we report FTIR studies of the 193 nm photodissociation of diborane (B 2 H 6 ) isolated in solid pH 2 in the 1.5 K to 4.3 K temperature range.In the gas phase, diborane photodissociation at 193 nm has been shown to produce BH 3 with a quantum yield of 2.00(25).a In our studies, we deposit B 2 H 6 in solid pH 2 and fully resolve vibrational peaks for the 11 B 2 H 6 , 11 B 10 BH 6 , and10 B 2 H 6 isotopologs of diborane in natural abundance.We then photolyze the B 2 H 6 /pH 2 sample for a short period of time (30 min, 100 mW/cm 2 ) and observe the B 2 H 6 peaks decrease in intensity as new peaks grow in.We suspect that we are producing BH 3 upon photolysis which forms a complex with the pH 2 host to form BH 3 -pH 2 .What we found surprising is that after we stop the 193 nm laser, we observe regrowth of the diborane peaks indicating that the photoproducts can readily diffuse through solid pH 2 even at the lowest temperatures studied (T = 1.52 K).We can track the regrowth in the concentration of each diborane isotopolog separately, which means we can extract rate constants for the kinetics of recombination for each isotopolog.Assuming the recombination process is diffusioncontrolled, we can use the fitted rate constants to look for kinetic isotope effects in the recombination reaction.We use these measurements to distinguish between two potential diffusion mechanisms, activated thermal hopping and quantum tunneling.This project is still ongoing, and the most recent results and analysis will be presented. |
, Minh Ngoc Nguyen 
