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21.
Experimental -values are used to examine various theoretical treatments of analogue symmetry breaking in superallowed Fermi β-decay. None of the fits to experiment in more than barely acceptable and, contrary to a previous analysis, we find no clear preference for one type of treatment over another. 相似文献
22.
Effective charges are calculated for protons and neutrons in the region of mass 90. It is found that their magnitudes differ
appreciably depending on whether the proton p
1/2 shell is empty or full. The calculated values are compared with values deduced from nuclei with simple configurations, and
from a fit to N=50 data. The empirical values are used in shell-model calculations of quadrupole moments of N=50-58 nuclei.
Received: 16 February 1998 相似文献
23.
24.
Wolfgang Gärtner Henning Hopf William E. Hull Dieter Oesterhelt Dieter Scheutzow Paul Towner 《Tetrahedron letters》1980,21(4):347-350
All mono--isomers of 13-desmethyl-retinal have been prepared fro the alll--compound by photoisomerisation. The various isomers were separated by HPLC and identified by their 400 MHz-1NMR-spectra. 相似文献
25.
The organothiol 4-mercaptopyridine (pyS) has been used extensively as facilitator for the assessment of heterogeneous electron transfer reaction of cytochrome c (cyt c). Its efficiency, however, is strongly affected by the instability of the adlayer due to the C-S bond cleavage. The K(4)[Ru(CN)(5)(pyS)].3H(2)O complex was synthesized and characterized aiming its utilization as an inorganic self-assembled monolayer (SAM) that would enhance the gold adlayer stability. The SAM formed by this complex onto gold (RupySAu) was characterized by spectroscopic (FTIRRAS and SERS) and electrochemical (LSV) techniques. The ex situ vibrational SERS and FTIRRAS spectra data of this SAM formed onto gold suggest a sigma interaction between the gold and sulfur atoms of the complex, inducing a perpendicular arrangement in relation to the surface normal. Additionally, SERS and FTIRRAS spectra performed for freshly prepared RupySAu adlayer and for large immersion times in the precursor solution have not shown any significant change that would reflect the degradation of the adlayer. The LSV desorption curves of this SAM indicate an enhancement in the C-S bond strength of the pyS ligand when coordinated to the [Ru(CN)(5)](3-) moiety. Comparatively to the data obtained for the desorption process of the pyS monolayer, the reductive desorption potential, E(rd), of the RupySAu presents a shift of -17 mV. This bond strength intensification leads to an increase in the stability of the monolayer. The voltammetric curves of cyt c carried out with the RupySAu electrode showed electrochemical parameters consistent with those reported for the native protein, as well as the maintenance of the electrochemical kinetic data after repetitive cycles. The results all together suggest that the pi back-bonding effect from the [Ru(CN)(5)](3-) metal center plays an important role in the stability of the RupySAu adlayer, improving the assessment of the cyt c heterogeneous electron transfer reaction. 相似文献
26.
Bush CE Goldston RJ Scott SD Fredrickson ED McGuire K Schivell J Taylor G Barnes CW Bell MG Boivin RL Bretz N Budny RV Cavallo A Efthimion PC Grek B Hawryluk R Hill K Hulse RA Janos A Johnson DW Kilpatrick S Manos DM Mansfield DK Meade DM Park H Ramsey AT Stratton B Synakowski EJ Towner HH Wieland RM Zarnstorff MC Zweben S 《Physical review letters》1990,65(4):424-427
27.
Knecht A Hong R Zumwalt DW Delbridge BG García A Müller P Swanson HE Towner IS Utsuno S Williams W Wrede C 《Physical review letters》2012,108(12):122502
Studies of 6He beta decay along with tritium can play an important role in testing ab initio nuclear wave-function calculations and may allow for fixing low-energy constants in effective-field theories. Here, we present an improved determination of the 6He half-life to a relative precision of 3×10(-4). Our value of 806.89±0.11(stat)(-0.19syst)(+0.23) ms resolves a major discrepancy between previous measurements. Calculating the statistical rate function we determined the ft value to be 803.04(-0.23)(+0.26) s. The extracted Gamow-Teller matrix element agrees within a few percent with ab initio calculations. 相似文献
28.
J. L. Bradshaw N. P. Breznay J. D. Bruno J. M. Gomes J. T. Pham F. J. Towner D. E. Wortman R. L. Tober C. J. Monroy K. A. Olver 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):479
Type-II interband cascade lasers combine the advantage of an interband optical transition with interband tunneling to enable the cascading of type-II quantum well active regions as is done in type-I quantum cascade laser. The relatively high radiative efficiency resulting from interband optical transitions translates into very low-threshold current densities, and when combined with the high quantum efficiency of cascade lasers, this diode laser design has the potential to operate under cw conditions at room temperature with high output power. Experimental results have already demonstrated some of this potential including high differential external quantum efficiency (>600%), high peak output power (6 W/facet at 80 K), high cw power conversion efficiency (>17% at 80 K), and operation at 300 K under pulsed conditions. Recent work aimed at reducing device thermal resistance and increasing cw operating temperature is reviewed including the demonstration of significant reductions in thermal resistance (averaging 25 K/W or 40% for 1-mm-long devices), 80 K cw operation at 3.4 μm with high-power conversion efficiency (23%) and high differential external quantum efficiency (532%), and cw operation up to 214 K. 相似文献
29.
Muon-capture and β-decay rates for the transitions 16O(0+, ground) (a3) 16N(0?, 120 keV) are calculated to second order in perturbation theory. With a one-boson-exchange residual interaction, reasonable agreement to the decay rates Λμ and Λβ can be achieved, but only if meson-exchange corrections are incorporated in the transition operator. These corrections strongly influence the time-like part of the axial-vector current. 相似文献
30.
Ball GC Bishop S Behr JA Boisvert GC Bricault P Cerny J D'Auria JM Dombsky M Hardy JC Iacob V Leslie JR Lindner T Macdonald JA Mak HB Moltz DM Powell J Savard G Towner IS 《Physical review letters》2001,86(8):1454-1457
Presently, the world data for superallowed beta decay leads to a result in disagreement (at the 98% confidence level) with the predictions of the minimal standard model for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. Precise data for the superallowed 0(+)-->0(+) beta decay of (74)Rb would provide a critical test of the nucleus-dependent isospin symmetry-breaking corrections that must be calculated for these superallowed Fermi beta decays. The present work reports the first precise measurement of the half-life for (74)Rb ( t(1/2) = 64.761+/-0.031 ms). The data were obtained at the radioactive beam facility (ISAC) at TRIUMF using a beam of approximately 4000 (74)Rb ions s(-1). 相似文献