Vibrational-Excitation-Induced and Spontaneous Conformational Changes in Solid Para-H2—Diminished Matrix Effects

Both vibrational-excitation-induced (by (N)IR laser) and spontaneous (by H atom tunneling) conformational changes are often investigated by matrix-isolation spectroscopy. It is well known that rigid hosts, such as solid noble gases, N2, or normal-H2, can largely affect both the quantum efficiency of the (N)IR photon-induced process and the tunneling rate. In the present study, the conformational changes of formic and acetic acids, as well as glycine, were investigated in a soft quantum host, solid para-H2. It is shown that the tunneling rates in para-H2 are orders of magnitude larger than those in rigid hosts. Furthermore, our results also suggest that the quantum efficiencies of some (N)IR-light-induced conformational changes are larger than in rigid matrices. These results can open a door for the applications of para-H2 host in conformational and tunneling studies and can help understand the details of these complex processes.