Temperature dependence of the quadrupole interaction of67Ge and67Zn ins-p metals

The temperature dependence of the electric quadrupole interaction was measured on the 9/2⁺ isomeric state of⁶⁷Ge in metallic Zn, Cd, In, and Sn and on the 9/2⁺ isomeric state of⁶⁷Zn in Cd metal. For all investigated systems, the temperature dependence reproduces very well aT ^1.5-relation. The analysis shows that the strength of the temperature dependence in the pure metals is correlated to 1/(M _D ² ) ( _D =Debye-temperature). This favours lattice vibrations as the main component of the temperature dependence of the electric field gradient. The strength of the temperature dependence measured on an impurity atom generally differs from the value of the pure host. Possible explanations for this effect are discussed.     

Temperature dependence of the nuclear quadrupole interaction and the Knight shift in rhenium metal

The temperature dependences of the static nuclear quadrupole interaction and the Knight shift in rhenium metal were investigated for 2K ≦ T ≦150 K by the method of Nuclear Acoustic Resonance (NAR). For the quadrupole interaction ¦e²qQ/h¦ an increase occurs from 255.2(5) MHz at 2 K to 257.2(8) MHz at 150 K in¹⁸⁷Re [269.5(7) to 271.5(10) in¹⁸⁵Re] whereas for the Knight shift a slight decrease from 1.14(4)% at 2K to 1.10(8)% at 150 K [1.16(6) to 1.12(10)] is found.     

Temperature dependence of the radius of electron-hole drops in Ge

The temperature dependence of the radius of electron-hole drops in Ge is determined from measurements of the number of particles in the drops using the p-n junction technique. The drop radius is found to increase from 5.5μ at 1.7 K to 10μ at 3.2 K for an excitation intensity of 160 mWatt/mm². As a function of excitation level at 1.8 K the drop radius is found to increase from 2.9μ at 8 mWatt/mm² to 6.5μ at 300 mWatt/mm². Our data are compared to results available in this field.     

Nuclear quadrupole alignment in Zn,Lu, and Re and the quadrupole moments of69m Zn and177m Lu

We report low-temperature nuclear quadrupole alignment of^69m Zn,^{177m, g} Lu and^{186, 188}Re in the corresponding metal single crystal hosts. A comparison with data on these systems from other laboratories is given, and sources of systematic error discussed. In the Lu system, measurements on in situ irradiated and implanted samples are found to be in agreement. From the measured quadrupole frequencies, we derive the following quadrupole moments: Q(^69m Zn, 13.86 h, 9/2⁺)=?0.45(7)b,Q(^177m Lu, 161 d, 23/2^?) =4.23(67)b,Q(¹⁸⁶Re, 90h, 1^?)=0.57(9)b, andQ(¹⁸⁸Re, 16.7h, 1^?)=0.38(17)b.     

Temperature dependence of the quadrupole interaction of69GeTl and113SnSn

The quadrupole interaction constants of⁶⁹GeT1 and¹¹³SnSn were measured by means of the perturbed angular distribution technique as a function of temperature in the range of 80KT508 K and 80KT480 K, respectively. Isomeric states in⁶⁹Ge and¹¹³Sn were populated by the heavy ion reactions⁵⁶Fe(¹⁶O, 2p n) and¹⁰⁰Mo(¹⁶O, 3n) and recoil implanted into polycrystalline Tl- and single crystalline Sn-backings. In the case of¹¹³SnSn, where the quadrupole coupling is weak, a special single crystal geometry was employed to enhance the sensitivity of the measurement. Within the limits of the errors the temperature dependence for both systems follows the empirical T^1.5-dependence. While a strong temperature dependence comparable to InIn is observed for⁶⁹GeT1, that for¹¹³SnSn is weaker than expected. The strength of the temperature dependence for¹¹³SnSn does not agree with the predictions of a lattice vibration model proposed recently for the temperature dependence of the quadrupole interaction.Supported in part by NSFAssociate of the Graduate Faculty of Rutgers University     

Temperature dependence of nuclear magnetization and relaxation

The temperature dependences of nuclear magnetization and relaxation rates are reviewed theoretically and experimentally in order to quantify the effects of temperature on NMR signals acquired by common imaging techniques. Using common sequences, the temperature dependences of the equilibrium nuclear magnetization and relaxation times must each be considered to fully understand the effects of temperature on NMR images. The temperature dependence of the equilibrium nuclear magnetization is negative because of Boltzmann's distribution for all substances at all temperatures, but the combined temperature dependences of the equilibrium magnetization and relaxation can be negative, weak or positive depending on the temperature (T), echo time (T(E)), repetition time (T(R)), and the temperature dependences of the relaxation times T(1)(T) and T(2)(T) in a pulse sequence. As a result, the magnitude of the NMR signal from a given substance can decrease, increase or stay somewhat constant with increasing temperature. Nuclear thermal coefficients are defined and predictions for spin echo and other simple sequences are verified experimentally using a number of substances representing various thermal and NMR properties.     

Temperature dependence of nuclear surface properties

Thermal properties of nuclear surface are investigated in a semi-infinite medium. Explicit analytical expressions are given for the temperature dependence of surface thickness, surface energy and surface free energy. In this model the temperature effects depend critically on the nuclear incompressibility and on the shape of the effective mass at the surface. To illustrate the relevance of these effects we made an estimate of the temperature dependence of the fission barrier height.     

67Zn Mössbauer study of Zn metal and Cu−Zn alloys at high pressure

A high pressure Mössbauer spectrometer for the 93.3keV resonance in⁶⁷Zn has been used to investigate Zn metal and two Cu?Zn alloys with Zn concentrations of 41.9at% and 48.0at% at 4.2K and pressures up to ～58kbar. For Zn metal the c/a-ratio plays an important role to describe the change of the Mössbauer parameters with pressure. Most striking is the increase of the recoil-free fraction by a factor of ～3. In the brass alloys a new phase is observed at 4.2K and high pressures which we tentatively identify with a martensitic α₁-phase.     

Temperature dependence of the interband absorption edge of copper

The optical absorption spectra of bulk copper measured by Pells and Shiga have been fitted by means of a model calculation in the interband edge region. The optical gap and the dipole matrix element of the L₃-L'₂(E_F) transition have been determined as a function of the temperature and a comparison with similar results obtained for silver and gold is presented.     

Temperature dependence of oxidation rate in clean Ge(111)

The temperature dependence of the sticking coefficient of oxygen on a clean Ge(111) surface has been investigated over a wide temperature range from 300 to 1100 °K using three methods. In the interval 300–600 °K a flash technique was used, the desorbed germanium oxide being detected by the time of flight mass-spectrometer. In the range from 500 to 1000 °K the sticking coefficient was measured from the pumping speed of oxygen by the sample surface, and in the range from 800 to 1100 °K the temperature dependence of the etching speed by oxygen was determined.The measured temperature dependence of the sticking coefficient is complex. It increases between 300 and 400 °K, remaining virtually constant from 400 to 500 °K with a new increase in the range from 500 to 1000 °K. A rapid fall in the sticking coefficient was observed at temperatures above 1000 °K.The dependence of the adsorption coverage on exposure has also been obtained for sample temperatures of 300, 350, 400 and 500 and 600 °K. The form of the adsorption curves differs considerably from a theoretical one based on a decrease in the sticking coefficient with coverage given by s = s₀(1 ? θ)². At 600 °K the sticking coefficient decreases more slowly than predicted by this equation. On the contrary, at 300 °K it begins to decrease rapidly at low coverages less than 0.1 of a monolayer.To explain the results it is assumed that oxygen molecules adsorb on the surface structural defects. At 300 °K such defects may be in the form of steps or other morphological disturbances on the surface, and above 500 °K they are probably equilibrium thermal defects, for example, surface vacancies.     

The sign of the electric field gradient at the nuclear site of Zn in Zn metal

By use of low temperature nuclear quadrupole orientation the quadrupole coupling constant of^69mZn in a Zn single crystal has been determined asv _Q=eQV _zz/h=–28(3) MHz.A positive sign forV _zzat the nuclear site of Zn in Zn is deduced. The half-life of^69mZn has been remeasured asT _1/2=13.756 (18)h.     

Temperature dependence of quadrupole interaction of99Ru in Zn

The quadrupole interaction (QI) of⁹⁹Ru as a dilute impurity in Zn, Cd and Sn lattices was studied by using time differential perturbed angular correlation technique. The electric field gradients calculated from the measured quadrupole interaction frequencies at room temperature are 5.14 × 10¹⁷ volts/cm² for⁹⁹RuZn, 4.58 × 10¹⁷ volts/cm² for⁹⁹RuCd and 2.87 × 10⁹⁹ volts/cm² for⁹⁹RuSn. The temperature dependence of the QI studied in the case⁹⁹RuZn is similar to that of¹¹⁷InZn.     

Temperature dependence of the electric field gradient in Er metal

The method of perturbed angular distributions was used to measure the temperature dependence of the electric field gradient in Er single crystal for 98 KT156 K. The I=11^– isomer in Er¹⁵⁴) was used as a probe. ₀ increases monotonically for 98 KT259 K and then decreases. A possible cause for this effect may be short range interactions between the f electrons above the Neel point.Visitor from the Weizmann Institute, Rehovoth, Israel.