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排序方式: 共有117条查询结果,搜索用时 15 毫秒
91.
H. P. Dixon
H. D. B. Jenkins
T. C. Waddington
《Chemical physics letters》1971,10(5):600-604The calculations reported here assign a charge qN = −0.52 electron units to the terminal nitrogen atoms in the azide ion and a value of 141.9 kJ mole−1 to the enthalpy of formation of the gaseous azide ion, ΔHf0(N3−(g)). The total lattice potential energies are found to be: Epot(NaN3) = 725.1 kJ mole−1; Epot(KN3) = 650.7 kJ mole−1 and Epot(RbN3) = 632.1 kJ mole−1. 相似文献
92.
Th. Andersson D. Rudolph C. Baktash J. Eberth C. Fahlander D. Haslip D.R. LaFosse S.D. Paul D.G. Sarantites C.E. Svensson H.G. Thomas J.C. Waddington W. Weintraub J.N. Wilson B.A. Brown 《The European Physical Journal A - Hadrons and Nuclei》1999,6(1):5-8
High-spin states of the mass A= 39 mirror pair 39K and 39Ca were investigated via the fusion-evaporation reaction 28Si +16O at 125 MeV beam energy. The Gammasphere array in conjunction with the 4π charged-particle detector array Microball and neutron detectors was used to detect γ rays in coincidence with evaporated light particles. The results of the first
high-spin study of the T
z=−1/2 nucleus 39Ca are discussed in terms of mirror symmetry and compared to spherical shell-model calculations in the 1d
3/2–; 1f
7/2 configuration space.
Received: 18 August 1999 相似文献
93.
2-Propyl radicals have been generated from the photolysis of solutions of 2,2-azopropane and 2,4-dimethyl-3-pentanone in decane in a glass and a metal cell. The time course of their reactions in the presence and absence of oxygen has been monitored between 323 and 373 K. The primary process involves the formation of solvent-caged radical pairs, two 2-propyl radicals and a 2-propyl and a 2-methylpropanoyl radical from the azo and ketone precursors, respectively. Subsequently these radicals are partitioned between cage escape and dimerization and disproportionation within the cage. In oxygenated solution the free 2-propyl radicals are effectively trapped as 2-propylperoxyl radicals. However, oxygen does not react with the solvent-caged radicals. This leads to a major difference in the hydrocarbon products from the two precursors. 2,2′-Azopropane gives propane, propene, and 2,3-dimethylbutane from the start of the reaction whereas the ketone only gives propene. Following the depletion of oxygen or in the absence of oxygen, both precursors behave analogously and give all three hydrocarbons. The 2-propylperoxyl radicals undergo self-reaction and hydrogen abstraction from the solvent to give 2-propanol, propanone, and 2-propyl hydroperoxide and, under conditions of low oxygen concentration, by reaction with 2-propyl radicals they give 2,2′-dipropylperoxide. Although the two cells lead to different overall rates of reaction, the relative rates and product distributions are unaffected by the cell design. A unified mechanism is described and the known and best estimates of rate constants for the individual steps are used to simulate the time dependence of the product yields from the photolysis of both precursors. © 1996 John Wiley & Sons, Inc. 相似文献
94.
A rate constant for the epoxidation of acrolein by acetylperoxyl radicals has been determined to be k4 = (1.3 ± 0.9) × 104 dm3mol−1s−1 at 383 K, which is anomalously fast in comparison with the epoxidation of alkenes. Abstraction of the acyl hydrogen atom from acrolein by acetylperoxyl radicals at 393 K was found to be at least 60 times slower than from acetaldehyde and at least three orders of magnitude slower than abstraction of the acyl hydrogen atom of the epoxide of acrolein. The fast rate for epoxidation of acrolein and the slow rate for hydrogen abstraction provide an explanation for the anomalously slow rate for the autoxidation of acrolein and suggests that acrolein formed during the autoxidation of alkene will react further to give its epoxide, and not exclusively by abstraction of the acyl hydrogen atom as was previously accepted. © 1999 John Wiley & Sons, Inc., Int J Chem Kinet 31: 277–282, 1999 相似文献
95.
96.
A. Dabrowska R. Hołyński A. Olszewski M. Szarska A. Trzupek B. Wilczyńska H. Wilczyński W. Wolter B. Wosiek K. Woźniak K. Zalewski M. L. Cherry W. V. Jones K. Sengupta J. P. Wefel P. S. Freier C. J. Waddington 《Zeitschrift fur Physik C Particles and Fields》1993,59(3):399-403
The degree of excitation of the emulsion target nuclei due to nuclear interactions of oxygen and sulfur projectiles at 200 GeV/nucleon incident energy has been investigated. Using the plausible assumption that the numberN b of slow particles emitted from the struck target nucleus can be interpreted as a measure of the temperatureT of the residual nucleus, we have found that there exists a critical temperatureT c of the excited target nucleus. For Ag and Br target nuclei this temperature corresponds to <N b>≌12 and it is attained when the impact parameters are less than about 4 fm. 相似文献
97.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献
98.
A. Dąbrowska P. S. Freier R. Holyński W. V. Jones A. Jurak D. Kudzia A. Olszewski M. Szarska A. Trzupek C. J. Waddington J. P. Wefel B. Wilczyński H. Wilczyński W. Wolter B. Wosiek K. Woźniak 《Zeitschrift fur Physik C Particles and Fields》1995,68(1):65-71
The fluctuations of produced particles are investigated in central collisions of proton, oxygen and sulphur projectiles with (Ag,Br) target nuclei at 200 GeV per nucleon. The analysis is carried out in terms of factorial moments and correlation integrals in different pseudorapidity regions. Evidence is found for nonstatistical fluctuations. These fluctuations depend weakly on the phase space, although a slightly stronger effect is seen in the forward pseudorapidity region. The dependence of the observed effect on the mass of the projectile particle disagrees with the expectations of superposition models. The results of this analysis indicate that a self-similar cascade process is the origin of the fluctuations, even though the association of the observed effect with the occurence of a second order phase transition cannot be definitely ruled out. 相似文献
99.
Park HS Blewitt G Cortez BG Foster GW Gajewski W Haines TJ Kielczewska D LoSecco JM Bionta RM Bratton CB Casper D Chrysicopoulou P Claus R Errede S Ganezer KS Goldhaber M Jones TW Kropp WR Learned JG Lehmann E Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak LR Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(1):22-25
100.