Long nuclear spin coherence times for molecules trapped in high-purity solid parahydrogen

We measure the ensemble transverse relaxation time (T2*) and spin-echo coherence time (T2) of the proton spin of HD molecules trapped in solid parahydrogen. By using high-purity parahydrogen matrices, we are able to measure significantly longer T2 and T2* times than seen in prior work. We also measure the longitudinal spin relaxation time T1. We examine how these parameters scale with the matrix purity and find limits on the coherence time from the parahydrogen matrix itself.