Initially, a temperature optimization in the range of 30 K to 70 K was performed by generating a temperature-dependent RIDME sensitivity profile (Figure , Tables ). An optimum temperature of 40 K was determined for CuNTA-SLIM RIDME measurements, in agreement with a recent study. Thus, compared to the CuNTA-nitroxide RIDME measured at 30 K, here the unfavourable change in thermal polarisation resulting from a 10 K increase in temperature was outweighed by faster repetition rate with higher temperature. With the SRT of the trityl (at 40 K, this study) and of the nitroxide (at 30 K) being very similar, an overall increase in sensitivity of the CuNTA-SLIM RIDME measurement will therefore be due to the excitation of the full spectral width of the trityl. Assuming that only approximately one quarter to one third of the nitroxide spectrum have been excited in previous CuNTA-nitroxide RIDME studies, we hypothesised that an increase in sensitivity by a factor of 3 to 4 could be expected in an ideal case.