Excited-state lifetime of the N V- infrared transition in diamond

The negatively charged nitrogen vacancy (NV-) defect in diamond serves as a popular platform for manipulating and exploiting long-lived coherent spin dynamics at room temperature combined with optical readout. The required spin polarization of the spin triplet A23 electronic ground state occurs through a cycle of repetitious optical photoexcitation events to the E3 electronic excited state that is accompanied by a series of electronic transitions to a A11 and a E1 electronic state, and back to the A23 state. The timescales of these transitions are largely known, yet for the relaxation time of the A11→E1 infrared transition, which predominantly occurs via nonradiative recombination, only an upper limit of 1 ns could be determined so far. Here, we employ ultrafast transient absorption spectroscopy to probe the dynamics of the nonradiative relaxation from the A11 to the E1 state after photoexcitation of the E3 state and find a relaxation time of 100 ps at a temperature of 78 K.