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11.
G. M. Gurevich S. V. Topalov A. L. Erzinkyan V. P. Parfenova M. Finger V. N. Pavlov J. Slovák R. Drevenak M. Trhlík 《Hyperfine Interactions》1993,78(1-4):497-500
The low-temperature nuclear orientation technique has been used to study the magnetic behaviour of60Co and54Mn impurity atoms in the reentrant spin glass Au0.82Fe0.18. The results obtained for60Co indicate that Co moments follow the distribution of Fe directions. In contrast, Mn moments show a spread directional distribution. These results are the consequence of the different character of Mn-Fe andFe-Fe interactions at short distances. 相似文献
12.
13.
J. Dupák M. Finger M. FingerJr. A. Janata R. V. Jolos T. I. Kracíková M. Slunecka 《Czechoslovak Journal of Physics》2001,51(1):A47-A58
Two complementary facilities for nuclear orientation of radioactive nuclei, based on hyperfine interactions at low temperatures obtained with top loading 3He?4He dilution refrigerators, have been developed at JINR Dubna and Charles University in Prague. These facilities are well suited for nuclear orientation studies practically of any nuclei of physical interest, which can be produced on JINR YASNAPP and DRIBs complexes. Wide variety of precise nuclear spectroscopy experiments with oriented nuclei is carried out with this technique-SPIN program at JINR. The physics potential of nuclear orientation experiments and the information, which can be obtained from the study of directional distribution of gamma radiation from oriented nuclei, are summarized. As the result of such nuclear orientation experiments extensive tests of different symmetry and supersymmetry schemes relevant to nuclear physics can be performed. Some examples of such symmetry and supersymmetry schemes in nuclei, which can be tested in the framework of SPIN program, are indicated. 相似文献
14.
M. Finger 《Physics of Particles and Nuclei》2008,39(3):348-381
A survey of available experimental data on the measurement of spin observables in neutron-proton (np) elastic scattering in the neutron energy range 200–600 MeV is presented. Sixteen spin observables (the polarization of recoil particles P 0n00, the analyzing power A 00n0, the spin correlation parameters A 00nn , A 00ss , A 00sk , and A 00kk , the spin transfer parameters K 0nn0, K 0ss0, and K 0sk0, the depolarization parameters D 0n0n , D 0s0s , and D 0s0k , and the three-spin parameters N 0nkk , N 0skn , N 0ssn , and N 0sns for energies of 200–590 MeV and scattering angles in the center of mass system of 60°–164°) were studied in experiments using polarized neutron beams and polarized proton targets at the Paul Scherrer Institute. The results of these investigations present a complete set of precision data on np elastic scattering which, along with the complete set of data for proton-proton (pp) elastic scattering obtained earlier, provides a basis for unambiguous determination of the amplitudes of the scattering matrix for nucleon-nucleon (NN) elastic scattering for the channel with the isotopic spin I = 0 and makes it possible to describe NN interaction in a model-independent way. 相似文献
15.
Susann Paul W. Bernd Schweizer Graham Rugg Hans Martin Senn Ryan Gilmour 《Tetrahedron》2013,69(27-28):5647-5659
Herein, we report the synthesis and X-ray structural analysis of a collection of fluorinated metal N-heterocyclic carbenes (Ag, Au, Pd, Rh, Ir) and their precursor salts. The common structural feature of these species is a flanking fluoroethyl group, which is either freely rotating or embedded within a bicyclic framework. Solid state analysis confirmed a gauche conformational preference in all cases with the fluorine adopting a syn clinal arrangement (?[NCCF]~60°) with respect to the triazolium nitrogen at the vicinal position of the NHC. A density functional theory analysis was employed to quantify these effects and evaluate the influence of electronic modulation of the carbenic carbon [(CN+); neutral carbene (C:); metal-bound carbene (CM)], on the relative gauche/anti preference, thus highlighting the potential of this conformational phenomenon as a useful molecular design strategy for controlling the topology of organometallic complexes. 相似文献
16.
17.
E. Šimečková P. Čižek M. Finger J. John P. Malinský V. N. Pavlov 《Hyperfine Interactions》1990,59(1-4):185-188
The angular distribution of γ-radiation from the decay of239Np oriented at low temperatures in gadolinium host was investigated. The orientation parameters B2 and B4 were determined.
The attenuation factors for two long-living states in239Pu at 391.5 keV and 285.4 keV were calculated. From the anisotropies measured the multipole mixing ratios for 11 gamma-transitions
in239Pu were deduced. The results obtained support the assignment of spins of the levels at 492.2 keV and 391.6 keV as 3/2− and 7/2−, respectively. 相似文献
18.
J. Říkovská A. Machová W. D. Hamilton J. Dupák Chan Chen Mo M. Finger N. A. Lebedev B. S. Neganov V. N. Pavlov A. F. Shchus 《Czechoslovak Journal of Physics》1979,29(6):620-639
The anisotropy of the angular distribution of gamma-rays from the decay of156Tb, oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction in the range of temperatures from 14·6 to 68·4 mK. The temperature dependence of anisotropy was measured for the first time. The parameters of hyperfine magnetic dipole and electric quadrupole splittings have been determined and the values of the magnetic dipole moment ¦Μ156¦=(9·6±1·3)×10?27 J/T and the electric quadrupole momentQ 156=(2·9±0·9)×10?28 m2 of the156Tb ground state have been calculated. Multipole mixing ratios andB(E2) branching ratios of many gamma-ray transitions occurring in156Gd have been found and the results have been discussed in terms of the rotational-vibration and pairing-plus-quadrupole models. 相似文献
19.
J. Behrends A. Schnegg C. Boehme S. Haas H. Stiebig F. Finger B. Rech K. Lips 《Journal of Non》2008,354(19-25):2411-2415
An analysis of spin-dependent processes in microcrystalline silicon (μc-Si:H) pin solar cells is presented using pulsed electrically detected magnetic resonance (pEDMR). In this first study it is shown that by modulating the morphology of the n-type contact layer from amorphous to microcrystalline, pronounced changes in the pEDMR spectra may be observed. Due to the fact that pEDMR allows a deconvolution of the spin-dependent signals in time as well as in magnetic field domain, we were able to significantly reduce the complexity of the spectra compared to conventional EDMR. In the samples containing amorphous n-type contact layers we found signals from shallow localized conduction band tail states and phosphorous donor states. Upon replacement of this layer by its microcrystalline counterpart both signals disappeared. Possible spin-dependent transport mechanisms involving paramagnetic states in the various layers are discussed in view of sign and time evolution of the associated pEDMR signals. 相似文献
20.
Nathanaëlle Schneider Dr. Markus Finger Dr. Christian Haferkemper Stéphane Bellemin‐Laponnaz Dr. Peter Hofmann Prof. Dr. Lutz H. Gade Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11515-11529
A detailed density functional theory (DFT) computational study (using the BP86/SV(P) and B3LYP/TZVP//BP86/SV(P) level of theory) of the rhodium‐catalyzed hydrosilylation of ketones has shown three mechanistic pathways to be viable. They all involve the generation of a cationic complex [LnRhI]+ stabilized by the coordination of two ketone molecules and the subsequent oxidative addition of the silane, which results in the Rh–silyl intermediates [LnRhIII(H)SiHMe2]+. However, they differ in the following reaction steps: in two of them, insertion of the ketone into the Rh? Si bond occurs, as previously proposed by Ojima et al., or into the Si? H bond, as proposed by Chan et al. for dihydrosilanes. The latter in particular is characterized by a very high activation barrier associated with the insertion of the ketone into the Si? H bond, thereby making a new, third mechanistic pathway that involves the formation of a silylene intermediate more likely. This “silylene mechanism” was found to have the lowest activation barrier for the rate‐determining step, the migration of a rhodium‐bonded hydride to the ketone that is coordinated to the silylene ligand. This explains the previously reported rate enhancement for R2SiH2 compared to R3SiH as well as the inverse kinetic isotope effect (KIE) observed experimentally for the overall catalytic cycle because deuterium prefers to be located in the stronger bond, that is, C? D versus M? D. 相似文献