ELECTRON-PARAMAGNETIC-RESONANCE OF GAMMA-IRRADIATED SINGLE-CRYSTALS OF 2 ISOBUTYRIC ACID-DERIVATIVES

The electron paramagnetic resonance spectra of gamma-irradiated alpha- hydroxy isobutyric acid, (CH3)(2)C(OH)COOH and alpha-amino isobutyric acid hydrochloride, (CH3)(2) C(NH2)COOH . HCl, single crystals and pow ders were investigated at 300 K and 113 K. The radiation damage center s in both compounds were attributed to the (CH3)(2)COOH radical. The h yperfine coupling constants of the six hydrogens of the two methyl gro ups were found to be equivalent, isotropic and 22.2 G at room temperat ure. However, at 113 K the hyperfine coupling constants of the methyl groups displayed a slightly anisotropic behavior. The g values were fo und to be isotropic and g = 2.0028 and g = 2.0032 respectively for the alpha-hydroxy isobutyric acid and alpha-amino isobutyric acid hydroch loride between 300 and 113 K. (C) 1997 Elsevier Science Ltd.