A study of the relaxation dynamics of local vibrational modes associated with hydrogen in diamond

Atomic-scale defects can control the exploitable optoelectronic performance of crystalline materials, and several point defects in diamond are emerging functional components for a range of quantum technologies. Nitrogen and hydrogen are common impurities incorporated into diamond, and there is a family of defects that includes both. The N3VH0 defect is a lattice vacancy where three nearest neighbor carbon atoms are replaced with nitrogen atoms and a hydrogen is bonded to the remaining carbon. It is regularly observed in natural and high-temperature annealed synthetic diamond and gives rise to prominent absorption features in the mid-infrared, the strongest of these being its C-H stretch mode at 3107 cm-1. Often, it is observed alongside another feature at 3237 cm-1. This feature is presently unidentified, but speculated to belong to an N-H stretch. Here, we combine time- and spectrally resolved infrared absorption spectroscopy to yield unprecedented insight into the vibrational dynamics of both of these defects, following both infrared and ultraviolet excitation of the C-H stretch. In doing so, we gain fundamental information about the energies of quantized vibrational states and corroborate our results with theory. We map out, for the first time, energy relaxation pathways, which include multiphonon relaxation processes and, in the case of N3VH0, anharmonic coupling to the bend modes. These advances provide a new route to probe and quantify atomic-scale defects in diamond.