ESR study of paramagnetic centers in irradiated Ba(ClO<inf>3</inf>) <inf>2</inf> · H<inf>2</inf>O · and Ba(ClO<inf>3</inf>) <inf>2</inf> · D<inf>2</inf>O single crystals

ESR study of γ-irradiated Ba(ClO3)2 · H2O revealed three main centers which are identified as O 3- ClO2 and (ClO2-H2O) radicals, trapped at two distinct sites. The parameters of the spin Hamiltonian have been determined from single crystal and powdered samples. The principal values for O3- and ClO2 centers agree with those reported in other systems. The chlorine center having " superhyperfine" interaction with the two protons of water of crystallization has been identified as a (ClO2-H2O) radical. The principal values of the g tensor are gxx = 2.0023, gyy = 2.0065, and gzz = 2.0150; those of the A tensor are axx = 102.11, ayy = 53.22, and azz = 7.79 G. The parameters of the hyperfine coupling of 35Cl with the first proton are axx = 8.6, ayy = 5.0, and azz = 5.0 G, with aiso = 6.2 G, and those for the second proton are a xx = 2.5, ayy = 1.2, and azz = 1.2 G. The (ClO2-H2O) center is found to be bleached at temperatures (above 120°C), where the crystal loses its water of hydration. On exposing the irradiated crystal to uv light, the two chlorine centers ClO2 and (ClO2-H2O) are fully bleached, followed by an increase in the concentration of the O3- center. Copyright © 1974 American Institute of Physics.