AbstractMeasurements of the conduction electron spin resonance linewidths of Li particles in neutron‐irradiated LiF are presented as a function of temperature and at a frequency of 9.27 GHz. A temperature range of 20 to 500°K was covered, and a genuine reversible temperature dependence of the linewidths was observed. The results are interpreted in terms of a temperature dependent surface relaxation mechanism and a temperature dependent intrinsic one. The latter has a room temperature value of 45 mG which compares favourably with the theoretical prediction of Overhauser. It is shown that the assumptions made for the analysis are compatible with the results of other workers.