Temperature dependence of the electron spin resonance spectrum of the ClO3 radical trapped in γ-irradiated barium perchlorate

The e.s.r. parameters of the ClO3 radical trapped in γ-irradiated Ba(ClO4)2.3H2O crystals at 298 K are presented. The quadrupole coupling is too small to be determined precisely from the positions of the strongly allowed transitions: the parallel component is < 10 MHz. The e.s.r. parameters are temperature-dependent and have been studied throughout the range 11 to 313 K. The data cannot be interpreted satisfactorily using 'isolated-molecule' models, and it is suggested that the temperature dependence reflects the way in which the environment of the radical in the crystal constrains its vibrational potential. (author)