H. Hohenstein

Electric hyperfine interaction in solid CF4 at the fluorine site

Using the time differential perturbed angular distribution method (TDPAD), the quadrupole coupling constant for CF4 has been measured to be νQ = 59.7(3) MHz. This value is discussed in connection with measurements of the other carbon tetrahalides and can be well understood in the framework of the Townes and Dailey theory.

Temperature dependence of the electric field gradient in CdSe and HfO2

The time differential perturbed angular correlation technique was applied to study the electric field gradient in the semiconductor CdSe and the insulator HfO2 at different temperatures. Whereas the semiconductor CdSe shows an increasing quadrupole coupling constant with increasing temperature, the insulator HfO2 exhibits no temperature dependence of the electric field gradient over the whole temperature range investigated.

A simple interpretation of the electric field gradient in some fluorides

Abstract With the time-differential perturbed-angular-distribution method (TDPAD) using the second excited level in 19 F we measured the efgs at the 19 F site in different fluorine compounds. The data can be interpreted quite sufficiently by the model of Townes and Dailey and the bond switching model of Das and Hahn.

Charge carrier governed temperature dependence of the electric field gradient for111Cd in tellurium

Using the TDPAC-method with the proble nucleus111Cd the electric quadrupole interaction (QI) in the trigonal semiconductor Te has been investigated in the temperature range 77 K≦T≦655 K. In contrast to most metals the quadrupole frequencyvQ increases with increasing temperature. This is a consequence of the fact that in metals the charge carrier density is temperature independent, whereas in semiconductors it strongly increases with temperature. A comparison between the temperature variation of the quadrupole coupling constantvQ and that of the charge carrier density leads to the conclusion that the QI in Te is governed by changes in the free electron density.

Concentration and temperature dependence of the electric quadrupole interaction for 111Cd in the system Sb1−xInx

Abstract The time differential perturbed angular correlation method (TDPAC) was applied to investigate the influence of impurities on the electric field gradient (efg) in semimetals. The system under study, Sb1−xInx, shows an unexpected temperature dependence of the efg for low In-concentrations x, which continuously approaches a T 3 2 -dependence with increasing impurity content, a well-known relation from investigations in metals.

The electric hyperfine interaction in solid fluorine

Abstract The quadrupole coupling constant of F 2 in the solid phase has been investigated at a temperature of 17.5 K by means of the time differential perturbed angular distribution technique. For the coupling constant a value of ν Q = 127.2(1.0) MHz results. The data are discussed in comparison with NQR-studies in the molecules I 2 , Br 2 and Cl 2 , and in terms of the Townes and Dailey theory. A small fraction of the 19 F nuclei was exposed to an electric field gradient of 85(5) MHz. Possible explanations are proposed.

Temperature dependence of the electric field gradient for111Cd in antimony

For the temperature dependence of the electric field gradient of111Cd in the semimetal antimony the well knownT3/2 relationship is valid over a wide temperature range. The slope parameterB differs from that for121, 123Sb in antimony by a factor of about 2.3.

THE ELECTRIC QUADRUPOLE INTERACTION IN THE DI- AND TRIFLUORIDES OF THE TRANSITION METALS AND IN THE TRIFLUORIDES OF THE RARE EARTH ELEMENTS

Using the time differential perturbed angular distribution (TDPAD) the electric quadrupole interaction at the 19F site for the di- and trifluorides of the transition metals and the trifluorides of the rare earths was investigated. The measurements show a dependence of ~Q on the 3d-electrons in the first mentioned targets, whereas there is no dependence of ~Q on the 4f-electrons in the rare earth trifluerides.

The temperature dependence of quadrupole interactions at cadmium impurities in Arsenic metal

We have performed time differential perturbed angular correlation measurements over a temperature range from 77 K to 763 K to investigate the static electric quadrupole interaction of111Cd in rhombohedral Arsenic metal. The observed quadrupole interaction frequency decreases with increasing temperature and is consistent with the well knownT3/2 relation, valid for metals.

Investigation of the electric field gradient in semimetals using the probe nucleus111Cd

Abstract With the time-differential-perturbed-angular-correlation method (TDPAC) we measured the efg for the probe nucleus 111 Cd in the system 111 Cd Sb with small amounts of inactive In-metal. For the quadrupole frequency we observed a relatively strong dependence of the In-concentration. The temperature dependence of the quadrupole interaction follows for In-concentrations larger than 0.1 % of weight a well-known T 3 2 relation. For smaller concentrations we got strong deviations. For the concentration of 0.5 % In we also did an isochronous annealing measurement. The resulting curve is in analogy to that one for radiation induced lattice defects in cubic lattices.