Model 19180 4 wire rtd probe

EPR spectra were collected by using a Bruker E500 ElexSys EPR spectrometer equipped with a Bruker ER4123 SHQE cavity. Instrumentation and methods for measurements of the substrate radical decay kinetics by EPR have been described in detail.^{8 (link)} Briefly, EPR samples were held at a staging temperature of 160–180 K in the ER4131VT cryostat system in the spectrometer, and temperature was step-increased to the decay measurement values. The time from initiation of the temperature step to the start of acquisition of the first spectrum was 30–60 s. Continuous acquisition of EPR spectra proceeded for the duration of the decay (24 s sweep time; 2.56 ms time constant; sampling interval, 5–60 s, depending on T). Temperature at the sample was determined by using an Oxford Instruments ITC503 temperature controller with a calibrated model 19180 4-wire RTD probe, which has ±0.3 K accuracy over the range of decay measurements. The ER4131VT cryostat/controller system provided a temperature stability of ±0.5 K over the length of the EPR sample cavity. The temperature was therefore stable to ±0.5 K during each run.

EPR spectra were collected by using a Bruker E500 ElexSys EPR spectrometer equipped with a Bruker ER4123 SHQE cavity. Instrumentation and methods for measurements of the substrate radical decay kinetics by EPR have been described in detail.^{28 (link)} Briefly, EPR samples were held at a staging temperature of 160–180 K in the ER4131VT cryostat system in the spectrometer, and temperature was step-increased to decay measurement values of 203–230 K. The time from initiation of the temperature step to the start of acquisition of the first spectrum was 30–60 s. Repetitive acquisition of EPR spectra (24 s sweep time; 2.56 ms time constant) proceeded for the duration of the decay. The temperature at the sample was determined by using an Oxford Instruments ITC503 temperature controller with a calibrated model 19180 4-wire RTD probe, which has ±0.3 K accuracy over the range of decay measurements. The ER4131VT cryostat/controller system provided a temperature stability of ±0.5 K over the length of the EPR sample cavity. The temperature was therefore stable to ±0.5 K during each run.