engleski

ENDOR STUDY OF JAHN-TELLER EFECT IN GAMMA-IRRADIATED L-ALANINE CRYSTAL PROBED BY SECOND STABLE RADICAL

L-alanine has been widely studied as basic biological molecular systems as well as due to the application in dosimetry. Until now extensive investigations of L-alanine crystal have been undertaken, pointing out very interesting physical properties. Despite the fact that x-ray and neutron single-crystal diffraction measurements support the same crystal structure at low (20 K) and at room temperature, there are several other experimental evidences for lattice instability at around 220 K such as birefringence and light depolarization measurements and 1H NMR measurements around the same temperature. In this study dynamical properties of the second stable L-alanine radical, R2, induced by gamma-irradiation have been investigated by the electron nuclear double resonance technique (ENDOR). The study focuses on the properties of three amino protons of R2 radical in the temperature range from 120-300 K. The motional dynamics of the amino group is important due to its involvement in intermolecular interactions through the hydrogen bond network in the crystal lattice. The results of the temperature dependence of the ENDOR line widths show phase transition around 220 K for all three amino protons and additionally confirm the strong dynamic Jahn-Teller effect in the L-alanine lattice and support evidence for properties related to lattice instability at around 220 K.

ENDOR; L-alanine; Jahn-Teller effect; radical

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