The nuclear quadrupole interaction at 111Cd and 181Ta sites in anatase and rutile TiO2: A TDPAC study

The nuclear quadrupole interaction of the I=5/2 state of the nuclear probes 111Cd and 181Ta in the anatase and rutile polymorphs of bulk TiO2 was studied using the time differential perturbed angular correlation (TDPAC) method. The fast-slow coincidence setup is based on CAMAC electronics. For anatase, the asymmetry parameter of the electric field gradient was η=0.22(1) and a quadrupole interaction frequency of ωQ=44.01(3) Mrad/s was obtained for 181Ta. For rutile, the respective values are η=0.56(1) and ωQ=130.07(9) Mrad/s. The values for rutile match closely with the literature values. In case of the 111Cd probe produced from the beta decay of 111Ag, the quadrupole interaction frequency for anatase was negligibly small as indicated by an unperturbed angular correlation in anatase. On the other hand for rutile the quadrupole frequency is ωQ=61.74(2) Mrad/s and the asymmetry parameter η=0.23(1) for the 111Cd probe. The results are interpreted in terms of the surrounding atom positions in the lattice and the charge state of the probe nucleus.