An Ultrafast Shakedown Reveals the Energy Landscape, Relaxation Dynamics, and Concentration of the N₃VH⁰ Defect 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. Here, we combine time- and spectrally resolved infrared absorption spectroscopy to yield unprecedented insight into the N₃VH⁰ defect’s vibrational dynamics following infrared 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 anharmonic coupling to the C–H bend mode. These advances provide new routes to quantify and probe atomic-scale defects.