EPR Study of Gamma Irradiated Arsanilic Acid Single Crystal

Abstract

EPR spectra of gamma irradiated arsanilic acid single crystal shows rarely observed and unstable arsenate centred [(OH)<inf>2</inf>As=O]. radical. There are two magnetically distinct sites in monoclinic lattice. The principal hyperfine and g values of both sites are determined from spectra taking the large hyperfine effects into account. The principal hyperfine values are found to be A(x)=602, A(y)=437 and A(z)=428 Gauss for one site and A(x)=602, A(y)=438 and A(z)=429 Gauss for the other site. The g values of both sites are the same with the values g(x)=2.048, g(y)=2.001 and g=2.000. The radical is in slightly distorted C(3v) symmetry. The unpaired electron is mainly localised on s orbitals of O atoms and partly on p orbital of central As atom. Calculations of EPR parameters for large hyperfine values are discussed and some easily applicable numerical techniques are utilised.; EPR spectra of gamma irradiated arsanilic acid single crystal shows rarely observed and unstable arsenate centred [(OH)<inf>2</inf>As = O] radical. There are two magnetically distinct sites in monoclinic lattice. The principal hyperfine and g values of both sites are determined from spectra taking the large hyperfine effects into account. The principal hyperfine values are found to be A<inf>x</inf> = 602, A<inf>y</inf> = 437 and A<inf>z</inf> = 428 Gauss for one site and A<inf>x</inf> = 602, A<inf>y</inf> = 438 and A<inf>z</inf> = 429 Gauss for the other site. The g values of both sites are the same with the values g<inf>x</inf> = 2.048, g<inf>y</inf> = 2.001 and g = 2.000. The radical is in slightly distorted C<inf>3v</inf> symmetry. The unpaired electron is mainly localized on s orbitals of O atoms and partly on p orbital of central As atom. Calculations of EPR parameters for large hyperfine values are discussed and some easily applicable numerical techniques are utilized.