Electron spin relaxation rates T[sub 1][sup −1] and T[sub 2][sup −1] in diluted solid N@C[sub 60]

Abstract

We report on pulsed electron-spin-resonance (ESR) investigations of endohedral N@C60. The measurements were performed in X band (9.5 GHz) and W band (94 GHz). Applying a two-pulse sequence with a variable flip angle of the second pulse, we could not only separate the contributions of the central and the satellite transitions, but also monitor the phase transition in C60 at T≈250 K. Analysing the temperature dependence of the longitudinal relaxation rate T1−1, the hyperfine relaxation, which is caused by the damped quantum oscillator of the nitrogen atom inside C60, was found to play the most important role. From a comparison of the experimental data with our relaxation model, the oscillator energy was determined to be Eosc≈11(2) meV.