Temperature Determination by EPR at 275 GHz and the Detection of Temperature Jumps in Aqueous Samples.

Second-moment analysis along two dimensions of continuous-wave EPR spectra of nitroxides enables EPR thermometry in a broad temperature range. Simulations show that the temperature can be derived in both the slow-motion and the fast-motion regime, which is experimentally verified at 275 GHz for H2O/glycerol (50/50% by volume) and pure water. We demonstrate that this tool allows the calibration of temperature jumps induced by infrared laser irradiation of a submicroliter sample in the single-mode cavity of a 275 GHz spectrometer, which prepares for kinetic studies of processes involving paramagnetic species.