Evidence for a phase-transition-induced change in the surface spin-flip probability of conduction electrons from CESR on n-irradiated, LIF; its application as an intensity reference

In view of its application as an intensity marker in electron spin resonance, the conduction electron spin resonance signal of Li particles in neutron-irradiated LiF has been analysed regarding its lineshape, linewidth, intensity and spectral composition in the temperature range 4.2<or=T<or=300 K at the X and K bands. While the lineshape is Lorentzian at 300 K, apparently, strong deviations from this shape develop at lower temperatures, without any noticeable change in the g-value or the peak-to-peak linewidth Delta B pp approximately=0.065 mT; the linewidth, as expected, is found to be dominated by electron-surface scattering. Double numerical integration of the absorption-derivative dP mu a /dB spectra shows the number of spins to be T-independent, as expected from a Pauli-paramagnetic behaviour. Data analysis reveals that, as T decreases, the single Lorentzian line observed at 300 K gradually evolves more and more to a sum of Lorentz lines (likely 2) of all identical g but of different widths 0.065