engleski

Relaxation mechanism in gamma-ray-irradiated L-alanine studied by transfer saturation EPR and pulse EPR

Stable paramagnetic centers in gamma-ray-irradiated L-alanine dosimeters exhibit a maximum in relaxation rate in the vicinity of 190 K. The mechanism of this relaxation rate has been investigated on the first stable alanine radical center, SARI, by employing continuous-wave transfer saturation electron paramagnetic resonance and pulse electron paramagnetic resonance techniques. The detected in-phase and out-of-phase spectra as well as phase memory times, T-M, indicate that besides the well-known tau(p) of the CH3 group of SARI an additional correlation time, tau(1) (DeltaE/k = 2689+/-50 K and tau(10) = 0.15+/-0.03 ps), is involved in the transverse relaxation process and effects the SARI center. For the SAR1 center this mechanism originates from the hindered motion of undamaged CH3 and NH3+ groups in the lattice. The motion of these groups additionally effects the spectrum of the SARI center through averaging out of the anisotropic splitting.

electron-spin-resonance; endor spectroscopy; dosimetry; crystal; time

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