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141.
Johann Wolfgang Hammer 《Zeitschrift für Physik A Hadrons and Nuclei》1968,216(4):355-371
The electron capture decay of Mn 54 and Zn 65 was investigated using Na I(Tl)-detectors. Spectroscopic-coincidence techniques were employed to examine theK-electron capture rates of Mn 54 and Zn 65, the branching ratio and positron rate of Zn 65. The experimental results are:P k ω k (Mn)=0.2492±0.0017,P k ω k (Zn)=0.3927±0.0026,EC * /EC 0(Zn)=53.2±1.0/46.8±1.0,γ/β +=35.1±1.7,K 0/β +=27.7±1.5. Thus electron capture to the excited state of Cu 65 occurs to the extent of 52.4±1.0% while electron capture and positron decay to the ground state were found to be associated with 46.1±1.0% and 1.49±0.05% of the disintegrations. These data partly disagree significantly from measurements of other authors. Using the fluorescence yieldsω k (Cr)=0.279 andω k (Cu)=0.4425, deduced from other measurements, values ofL+M/K of electron capture to the excited state could be derived:L+M/K(Mn 54)=0.120±0.015 andL+M/K(Zn 65)=0.127±0.015. These ratios agree with the calculations ofBahcall. The half-lives of Mn 54 and Zn 65 have been determined to beT 1/2(Mn 54)=312±5d,T 1/2(Zn 65)=243±4d The energy of the Zn 65-γ-rays was measured with a Ge(Li)-counter:E γ=1115.5±0.5 keV. 相似文献
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145.
Li WX Osterlund L Vestergaard EK Vang RT Matthiesen J Pedersen TM Laegsgaard E Hammer B Besenbacher F 《Physical review letters》2004,93(14):146104
Using scanning tunneling microscopy and temperature programmed desorption we investigate the Pt(110) surface under strongly oxidizing conditions involving either high-pressure O2 or atomic oxygen exposure. At low temperatures, only disordered Pt oxide structures are observed. After annealing ordered surface oxide islands are observed to coexist with a highly stable reconstructed (12x2)-O chemisorption structure. From density functional theory calculations a model for the surface oxide phase is revealed. The phase is found to be metastable, and its presence is explained in terms of stabilizing defects in the chemisorption layer and reduced Pt mobility. 相似文献
146.
Africh C Esch F Li WX Corso M Hammer B Rosei R Comelli G 《Physical review letters》2004,93(12):126104
By means of scanning tunneling microscopy and density functional theory calculations we demonstrate that on the Rh(110)-(10 x 2)-O surface, a prototypical multiphase surface of an oxidized transition metal model catalyst, water formation upon H2 exposure is a two-step reaction, with each step requiring special active sites. The 1st step initiates at (2 x 1)p2mg-O defect islands in the (10 x 2) structure and propagates across the surface as a reaction front, removing half of the adsorbed oxygen. The oxygen decorated Rh ridges of the (10 x 2) structure lose their tensile strain upon this reduction step, whereby nanoscale patches of clean Rh become exposed and act as special reaction sites in the 2nd reaction step, which therefore initiates homogeneously over the entire surface. 相似文献
147.
Jones OS Glenzer SH Suter LJ Turner RE Campbell KM Dewald EL Hammel BA Hammer JH Kauffman RL Landen OL Rosen MD Wallace RJ Weber FA 《Physical review letters》2004,93(6):065002
We present measurements of the absolute albedos of hohlraums made from gold or from high-Z mixtures. The measurements are performed over the range of radiation temperatures (70-100 eV) expected during the foot of an indirect-drive temporally shaped ignition laser pulse, where accurate knowledge of the wall albedo (i.e., soft x-ray wall reemission) is most critical for determining capsule radiation symmetry. We find that the gold albedo agrees well with calculations using the supertransition array opacity model, potentially providing additional margin for inertial confinement fusion ignition. 相似文献
148.
R.J. FurnstahlH.-W. Hammer 《Annals of Physics》2002,302(2):206-228
A system of fermions with short-range interactions at finite density is studied using the framework of effective field theory. The effective action formalism for fermions with auxiliary fields leads to a loop expansion in which particle-hole bubbles are resummed to all orders. For spin-independent interactions, the loop expansion is equivalent to a systematic expansion in 1/N, where N is the spin-isospin degeneracy g. Numerical results at next-to-leading order are presented and the connection to the Bose limit of this system is elucidated. 相似文献
149.
Cuneo ME Vesey RA Porter JL Bennett GR Hanson DL Ruggles LE Simpson WW Idzorek GC Stygar WA Hammer JH Seamen JJ Torres JA McGurn JS Green RM 《Physical review letters》2002,88(21):215004
A double Z pinch driving a cylindrical secondary hohlraum from each end has been developed which can indirectly drive intertial confinement fusion capsule implosions with time-averaged radiation fields uniform to 2%-4%. 2D time-dependent view factor and 2D radiation hydrodynamic simulations using the measured primary hohlraum temperatures show that capsule convergence ratios of at least 10 with average distortions from sphericity of /r200 MJ. 相似文献
150.
Kunz R Jaeger M Mayer A Hammer JW Staudt G Harissopulos S Paradellis T 《Physical review letters》2001,86(15):3244-3247
The angular distributions of gamma rays from the 12C(alpha,gamma)16O reaction have been measured at 20 energy points in the energy range E(cm) = 0.95 to 2.8 MeV. The sensitivity of the present experiment compared to previous direct investigations was raised by 1-2 orders of magnitude, by using an array of highly efficient ( 100%) Ge detectors shielded actively with BGOs, as well as high beam currents of up to 500 microA that were provided by the Stuttgart Dynamitron accelerator. The S(E1) and S(E2) factors deduced from the gamma angular distributions have been extrapolated to the range of helium burning temperatures applying the R-matrix method, which yielded S(300)(E1) = (76+/-20) keV b and S(300)(E2) = (85+/-30) keV b. 相似文献