Gamma-ray multiplicity studies for 40Ar and 86Kr induced reactions leading to Er compound nuclei at limiting angular momenta

The moments of the γ-ray multiplicity distributions as a function of evaporation residue and of E_γ have been determined from γ-multiplicity measurements for the ^{116, 120, 122, 124}Sn(⁴⁰Ar, xn) reactions at 161 ≦ E(Ar) ≦ 236 MeV and for the ⁷⁶Ge(⁸⁶Kr, xn) reaction at 314 ≦ E(Kr) ≦ 376 MeV. Even at the highest incident energies where l_gr ≈ 120 units, it is not possible to populate nuclei with l > 65 units, the limiting l predicted for a rotating liquid drop. For the lowest incident energies these data are in agreement with the decay of a compound system. At the highest incident energy, however, significant deviations are observed from the expected decay of an equilibrated system. Such deviations are indicative of pre-equilibrium particle decay. Statistical calculations utilizing the code GROG12 are used to substantiate these conclusions. No evidence for a lower l-cut in the population of the compound system is observed; however, these data would not be sensitive to an l_cut ? 10 units. The moments of inertia extracted from the edge of the “collective E2 bump” in the 〈M_γ〉 versus E_γ data are in agreement with those predicted for a rotating liquid drop. The average multiplicity of the noncompound processes is estimated to be 8–11 for l_gr ? 100 units and increasing to 21 for l_gr ? 120 units.     

The decomposition of formic acid vapor by infrared radiation from a pulsed HF-laser

The decomposition of formic acid vapor by 2.783 μm infrared radiation from a pulsed HF laser has been studied at pressures from 1.6 to 44 torr temper     

The heat of formation of the ethyl radical

An examination of the results of measurements of the forward and reverse rate constants for the reaction shows that agreement between the kinetics and the thermochemistry is achieved only through use of a value of ΔH_f(C₂H₅) = 28 kcal mol^?1. This system therefore provides further support for the recent measurement of this quantity.     

Mechanism of the bimolecular reactions of ethylene and propylene

Rate constants for the bimolecular reactions of ethylene and propylene to form radicals and to form cyclobutane or its derivatives have been calculated using thermodynamic and kinetic data. Comparison of these rates with the kinetics of the thermal reactions of ethylene and propylene show that cyclobutane and its derivatives are probably not important intermediates in the processes forming radicals.     

Unexpected behavior of heavy-ion fusion cross sections at extreme sub-barrier energies

The excitation function for fusion evaporation in the (60)Ni+ (89)Y system was measured over a range in cross section covering 6 orders of magnitude. The cross section exhibits an abrupt decrease at extreme sub-barrier energies. This behavior, which is also present in a few other systems found in the literature, cannot be reproduced with present models, including those based on a coupled-channels approach. Possible causes are discussed, including a dependence on the intrinsic structure of the participants.     

Charged-particle pseudorapidity density distributions from Au+Au collisions at sqrt[s(NN)]=130 GeV

The charged-particle pseudorapidity density dN(ch)/d eta has been measured for Au+Au collisions at sqrt[s(NN)] = 130 GeV at RHIC, using the PHOBOS apparatus. The total number of charged particles produced for the 3% most-central Au+Au collisions for /eta/相似文献   

Kinetic Studies of Metal Speciation Using Inductively-Coupled Plasma Mass Spectrometry

Abstract

Kinetic studies of uptake of metal ions by the Chelex batch technique were made to determine Cd, Cu and Pb speciation in model solutions, a snow sample and a river surface water sample. Inductively-coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS) were used for direct determination of these metals. ICP-MS with the solution nebulization technique minimized contamination and adsorption problems involved in the discrete sampling technique of GFAAS, and hence, gave more precise and accurate results. Also, ICP-MS allowed collection of many more data points than GFAAS and was able to resolve components with similar rates of dissociation, which could not always be resolved by GFAAS with its discrete sampling technique. ICP-MS was therefore preferable to GFAAS for kinetic studies of metal speciation. The kinetic data were analyzed by the iterative deconvolution method. The applicability of the Chelex batch technique to metal speciation was validated by analysis of model solutions containing these metal ions with or without EDTA, NTA and fulvic acid. Use of the Chelex batch technique for Cd, Cu and Pb speciation in snow and river surface water samples revealed a number of kinetically distinguishable components of these metals (as complexes) ranging from one to three, probably present as aquo ions or inorganic complexes in the snow sample, and bound to macromolecules/and or colloidal materials in the river surface water sample.