排序方式: 共有21条查询结果,搜索用时 31 毫秒
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L.P. Ekström D.E.C. Scherpenzeel G.A.P. Engelbertink H.J.M. Aarts H.H. Eggenhuisen 《Nuclear Physics A》1978,295(3):525-531
The mean life of 22Ne(4+1) has been measured by means of the high-velocity coincidence DSA method with the 4He(19F, pγ)22Ne reaction. The 22Ne recoils are slowed down in Ti, Cu, Ag and Au and the γ-ray Doppler patterns are observed with a large Ge(Li) detector at 0° in coincidence with protons. Interpretation of the patterns with recent experimental stopping powers yields . The present result serves as a calibration measurement and helps to reduce uncertainties in calculated stopping powers for low-velocity DSA measurements. 相似文献
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Eggenhuisen TM den Breejen JP Verdoes D de Jongh PE de Jong KP 《Journal of the American Chemical Society》2010,132(51):18318-18325
We explored melt infiltration of mesoporous silica supports to prepare supported metal catalysts with high loadings and controllable particle sizes. Melting of Co(NO(3))(2)·6H(2)O in the presence of silica supports was studied in situ with differential scanning calorimetry. The melting point depression of the intraporous phase was used to quantify the degree of pore loading after infiltration. Maximum pore-fillings corresponded to 70-80% of filled pore volume, if the intraporous phase was considered to be crystalline Co(NO(3))(2)·6H(2)O. However, diffraction was absent in XRD both from the ordered mesopores at low scattering angles and from crystalline cobalt nitrate phases at high angles. Hence, an amorphous, lower density, intraporous Co(NO(3))(2)·6H(2)O phase was proposed to fill the pores completely. Equilibration at 60 °C in a closed vessel was essential for successful melt infiltration. In an open crucible, dehydration of the precursor prior to infiltration inhibited homogeneous filling of support particles. The dispersion and distribution of Co(3)O(4) after calcination could be controlled using the same toolbox as for preparation via solution impregnation: confinement and the calcination gas atmosphere. Using ordered mesoporous silica supports as well as an industrial silica gel support, catalysts with Co metal loadings in the range of 10-22 wt % were prepared. The Co(3)O(4) crystallite sizes ranged from 4 to 10 nm and scaled with the support pore diameters. By calcination in N(2), pluglike nanoparticles were obtained that formed aggregates over several pore widths, while calcination in 1% NO/N(2) led to the formation of smaller individual nanoparticles. After reduction, the Co/SiO(2) catalysts showed high activity for the Fischer-Tropsch synthesis, illustrating the applicability of melt infiltration for supported catalyst preparation. 相似文献
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H.H. Eggenhuisen L.P. Ekström G.A.P. Engelbertink H.J.M. Aarts J.A.J. Hermans 《Nuclear Physics A》1977,285(1):167-188
Yrast levels in 40K and 40Ar have been investigated with the 26Mg(16O, pnγ)40K and 26Mg(16O, 2pγ)40Ar reactions at a beam energy of 34 MeV. Gamma-ray angular distribution and γ-γ coincidence measurements have been performed with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. Gamma-ray linear polarizations have been measured with a three-crystal Ge(Li) Compton polarimeter. The 40K decay scheme involves new high-spin levels at Etx = 4365.6±0.3, 4875.6±0.4 and 6227.0±0.5 keV with lifetime limits of < 1, < 1 and < 2ps, respectively. Unambiguous spin-parity assignments of to the 40K levels at Ex = 0.89, 2.88, 4.37, 4.88 and 6.23 and of levels at Ex = 2.89 and 3.46 MeV, respectively, have been obtained. Branching ratios and multipole mixing ratios are reported. 相似文献
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J.A.J. Hermans G.A.P. Engelbertink D. Bucurescu M.A. Van Driel H.H. Eggenhuisen 《Physics letters. [Part B]》1974,50(3):337-339
The inverse reaction is used to measure the mean life of 33S(1). Coincident Dopplet broadened lineshapes measured for the slowing-down materials Mg, Al, Cu and Ag are analysed with experimental stopping powers. The results for the different materials agree with each other and lead to a mean life of τm=1.65±0.04 ps. 相似文献
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H.H. Eggenhuisen L.P. Ekström G.A.P. Engelbertink H.J.M. Aarts W.G.J. Langeveld 《Nuclear Physics A》1978,299(1):175-188
Yrast states of 41K and 41Ca have been investigated with the 26Mg(18O, p2nγ)41K and 26Mg(18O, 3nγ)41Ca reactions at a beam energy of 34 MeV. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization measurements were performed with a Ge(Li)-NaI(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of , , , , and to the 41K levels at Ex = 1.68, 2.53, 2.76, 2.77, 4.27 and 4.98 MeV and of to the 41Ca levels at Ex = 3.20, 3.37 and 3.83 MeV, respectively, have been obtained. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The main features of the 41K and 41Ca level and decay schemes are reproduced in a 2p-1h and 3p-2h shell-model calculation. 相似文献
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H.J.M. Aarts G.A.P. Engelbertink H.H. Eggenhuisen L.P. Ekström 《Nuclear Physics A》1979,321(2):515-532
High-spin states of 38Ar have been studied with the 35Cl(α, pγ)38Ar reaction at Eα = 18 MeV and with the 24Mg(16O, 2pγ)38Ar reaction at . The 38Ar level scheme is obtained with the former reaction from a proton-γ coincidence measurement. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization experiments have been performed with a Ge(Li)-Na(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of to the 38Ar levels at Ex = 7.51, 8.08, 8.57, 8.97, 10.17 and 11.61 MeV, respectively, are obtained. The 8.57 MeV, 8+ level has a mean life below 0.8 ps. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The experimental results are compared with shell-model calculations. 相似文献