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31.
32.
OK Yoon WG Hwang JC Choe MS Kim 《Rapid communications in mass spectrometry : RCM》1999,13(14):1515-1521
A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
33.
K. Wosińska J. Pluta F. Hanappe L. Stuttge J. C. Angelique B. Benoit E. de Goes Brennand G. Bizard J. Colin G. Costa P. Desesquelles O. Dorvaux D. Durand B. Erazmus S. Kuleshov R. Lednicky M. Marques Th. Materna K. Mikhailov G. Papatheofanous T. Pawlak A. Staranowicz A. Stavinskiy B. Tamain A. Vlasov L. Vorobyev 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):55-59
The measurement of the two-particle correlation function for different particle species allows to obtain information about
the development of the particle emission process: the space-time properties of emitting sources and the emission time sequence
of different particles. The single-particle characteristics and two-particle correlation functions for neutral and charged
particles registered in forward direction are used to determine that the heavy fragments (deuterons and tritons) are emitted
in the first stage of the reaction (pre-equilibrium source) while the majority of neutrons and protons originates from the
long-lived quasi-projectile. The emission time sequence of protons, neutrons and deuterons has been obtained from the analysis
of non-identical particle correlation functions. 相似文献
34.
We have searched for Coulomb fission induced by 84Kr ions on a 238U target at energies ranging from the interaction barrier down to 37 MeV below (408–458 MeV lab). No event attributed to Coulomb fission was detected; it was deduced that the cross section for this reaction is lower than 0.3 mb/sr near the interaction barrier. This value was compared to theoretical predictions. However, fission events originating from transfer reactions at the interaction barrier have been detected. 相似文献
35.
Jason T Miller John H Bartley Hereward JC Wimborne Aisha L Walker David C Hess William D Hill James E Carroll 《BMC neuroscience》2005,6(1):63
Background
Stromal cell-derived factor 1 (SDF-1 or CXCL12) is chemotaxic for CXCR4 expressing bone marrow-derived cells. It functions in brain embryonic development and in response to ischemic injury in helping guide neuroblast migration and vasculogenesis. In experimental adult stroke models SDF-1 is expressed perivascularly in the injured region up to 30 days after the injury, suggesting it could be a therapeutic target for tissue repair strategies. We hypothesized that SDF-1 would be expressed in similar temporal and spatial patterns following hypoxic-ischemic (HI) injury in neonatal brain. 相似文献36.
M. F. Rivet B. Gatty H. Guillemot B. Borderie R. Bimbot I. Forest J. Galin D. Gardes D. Guerreau M. Lefort X. Tarrago B. Tamain L. Novicki 《Zeitschrift für Physik A Hadrons and Nuclei》1982,307(4):365-373
rgy of light charged-particles has been measured in coincidence with one or two fission fragments in the reaction20Ne+197Au at a bombarding energy of 13 MeV/u. The fission cross section was found equal to 1,340±260 mb. Assuming that it represents the totality of the fusion cross section, the critical valuel c is deduced equal to 93±9?, higher thanl Bf=0=74 in the rotating liquid drop model. The main emission source for protons and alpha particles seems to be a thermally equilibrated composite system. The competition between fission and charged particle emission is unexpected in the frame of the statistical treatment. A high energy component is observed in the forward direction. These results correspond to the first step of a study programme on the evolution of nucleus-nucleus collisions between 10 and 100 MeV per nucleon. 相似文献
37.
B. Tamain R. Chechik H. Fuchs F. Hanappe M. Morjean C. Ngô J. Peter M. Dakowski B. Lucas C. Mazur M. Ribrag C. Signarbieux 《Nuclear Physics A》1979,330(1):253-268
We have detected in nine different positions of space the neutrons associated with the collision of 63Cu on 197Au at 400 MeV bombarding energy. The deep inelastic products were detected at two different angles: close to the grazing angle and 30° forwards of it. Their masses were measured using a time-of-flight technique. The neutrons were detected in coincidence with the fragments - the efficiency of the neutron detectors was measured relatively to a 252Cf source during beam time. The neutron threshold was set at 300 keV. Within an accuracy of 10% all the emitted neutrons are evaporated by the fully accellerated deep inelastic fragments. It is shown that the excitation energy is shared between the fragments in proportion to their masses and that the relaxation time for internal equilibration of the composite system is very short (~10?22 s). 相似文献
38.
57MeV/u 64Zn+27Al反应中集体流的研究 总被引:1,自引:0,他引:1
贺智勇 J.Peter J.C.Angelique G.Bizard R.Brou D.Cussol A.Kerambrun J.P.Patry R.Regimbart J.C.Steckmeyerr B.Tamain E.Vient G.Auger C.Cabot 《中国物理 C》1994,18(9):800-806
报道了利用4π带电粒子阵列测量的57MeV/u的64Zn轰击27Al反应中的集体物质流.各事件的碰撞参数分类采用平均平行速度方法,反应平面的确定采用横向动量分析方法.实验观察到在反应平面内的集体横向动量(边流参数)随着碰撞参数和粒子产物而变化. 相似文献
39.
B. Borderie M. Berlanger D. Gardès F. Hanappe L. Nowicki J. Péter B. Tamain S. Agarwal J. Girard C. Grégoire J. Matuszek C. Ngô 《Zeitschrift für Physik A Hadrons and Nuclei》1981,299(3):263-271
The influence of the orbital angular momentuml on the mass distribution of fission fragments is studied, both on previously available data on heavy ion induced fission and in new specifically planned experiments: systems40Ar+165Ho and24Mg+181Ta at bombarding energies ranging from 180 up to 391 MeV and leading to the same fissioning nucleus205At with differentl distributions. Whenl values corresponding to a vanished fission barrier are reached, the mass distribution broadens. This suggest the existence of a specific process, “fast fission”, atl-values intermediate betweenl-values leading to compound nucleus formation and deep inelastic collisions, respectively. This process and its conditions of occurence are discussed; of special interest are the correlated differences between the limitations to the fusion cross-section and the fission mass distributions broadenings, respectively, for the Ar+Ho and Mg+Ta systems. 相似文献
40.
α-Haloketones and -dibromides are converted to the corresponding ketones and alkenes respectively with nickel boride generated from sodium borohydride and nickel chloride. 相似文献