排序方式: 共有62条查询结果,搜索用时 15 毫秒
1.
2.
3.
Radioactive129mTe was implanted in 6 different transition metals (V, Fe, W, Au, Pt, Pb) and internal conversion electron spectra as well as Mössbauer spectra of the daughter nucleus129I were measured. A value (r
2)=+1.8(4)×10–2 fm2 (corresponding to R/R=+4.1(10)×10–4) was derived for the change of the mean square charge radius during the 27.8 keV transition in129I. The consequences of this measurement on the calibration constants of the Mössbauer isomer shifts of other isotopes of the 5sp elements are discussed. 相似文献
4.
B. Kastelein van der Marel J. Andriessen H. Postma F. Pleiter 《Hyperfine Interactions》1992,73(3-4):357-369
The nuclear electric quadrupole interaction of111In ion-implanted in hightly oriented pyrolytic graphite has been observed by means of low-temperature nuclear orientation
and by means of perturbed angular correlations. From the first kind of experiment, it is concluded that a relatively large
number of indium nuclei experience a well-defined macroscopic orientation, which is partly lost after the radioactive decay
to cadmium. Indeed, the second kind of experiment revealed a broad distribution of electrid field gradients interacting with
the 245 keV Cd excited state, as well as a small faction experiencing a unique electric field gradient. The experimental results
are compared with theoretical calculations of the electric field gradient at various lattice positions, in which carbon and
indium electronic wavefunctions are allowed to hybridize. Lattice positions of the covalent indium atom between the graphite
layers can explain the measured electric field gradient ofV
22=+1.47(11)·1022 V/m2, directed parallel to the graphitec-axis. 相似文献
5.
6.
7.
Göckeler M Horsley R Pleiter D Rakow PE Schäfer A Schierholz G Schroers W;QCDSF Collaboration 《Physical review letters》2004,92(4):042002
We perform a quenched lattice calculation of the first moment of twist-two generalized parton distribution functions of the proton, and assess the total quark (spin and orbital angular momentum) contribution to the spin of the proton. 相似文献
8.
The DPAC technique was applied to measure the quadrupole moments of the 300 ps, 5/2− states in75,77As. The isotopes were implanted in α-Ga. The following results were obtained: Q(5/2−)=30(10) fm2 for75As, and Q(5/2−)<75 fm2 for77As. 相似文献
9.
Göckeler M Hägler P Horsley R Nakamura Y Pleiter D Rakow PE Schäfer A Schierholz G Stüben H Zanotti JM;QCDSF;UKQCD 《Physical review letters》2007,98(22):222001
We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72, 094020 (2005)], we predict that the Boer-Mulders function h(1/1), describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks. 相似文献
10.
The hydrogen-vacancy interaction in W and Mo was investigated by applying the perturbed angular correlation technique, using the isotope111In as a probe. Hydrogen trapping at InV2 manifests itself as a change of the vacancy-induced quadrupole frequency. We have observed trapping of up to two H atoms. The binding energies for the first H atom are 1.07(2) eV in Mo and 1.16(2) eV in W. These results are close to the values calculated with the effective-medium theory. The frequency shifts are both negative and amount to a few Mrad/s per trapped H atom. Contrary to the theoretical predictions, the binding energies for the second H atom differ strongly: 0.44(3) eV in Mo and 0.99(2) eV in W. The corresponding frequency shifts have opposite signs. Therefore, the lattice positions of the first H atom in Mo and W are similar, while those of the second H atom must be completely different. 相似文献