Higher triplet state of fullerene C70 revealed by electron spin relaxation

Abstract

Spin-lattice relaxation times T1 of photoexcited triplets (3)C70 in glassy decalin were obtained from electron spin echo inversion recovery dependences. In the range 30-100 K, the temperature dependence of T1 was fitted by the Arrhenius law with an activation energy of 172 cm(-1). This indicates that the dominant relaxation process of (3)C70 is described by an Orbach-Aminov mechanism involving the higher triplet state t2 which lies 172 cm(-1) above the lowest triplet state t1. Chemical modification of C70 fullerene not only decreases the intrinsic triplet lifetime by about ten times but also increases T1 by several orders of magnitude. The reason for this is the presence of a low-lying excited triplet state in (3)C70 and its absence in triplet C70 derivatives. The presence of the higher triplet state in C70 is in good agreement with the previous results from phosphorescence spectroscopy.

Photoexcited Triplet State Kinetics Studied by Electron Paramagnetic Resonance Spectroscopy

“…Very recently, Uvarov et al . reinvestigated the temperature dependent SLR behavior of 3 C 70 using ESE inversion recovery.…”

“…Very recently,U varov et al [87] reinvestigated the temperature dependentS LR behavior of 3 C 70 using ESE inversion recovery. Whereas the time constants of ESE inversion recovery were similar to the rate of spectral change observedb yT erazima et al [85] their interpretationa sS LR time is at variancew ith the spectrald iffusion model.T he SLR rates observed by Uvarov et al obeyed an Arrhenius behavior with an activation energy of ca.…”

Spin Relaxation of the Neutral Germanium‐Vacancy Center in Diamond

“…Using the selective pulse sequence we can measure relaxation times only for defects which axes are perpendicular to the magnetic field. It is interesting to note, that in the paper the spin‐lattice relaxation is described by the biexponential law (that was expected for the paramagnetic center in triplet state), and the difference between T 1a and T 1b times reaches the maximum when B is perpendicular to defects axes.…”