共查询到20条相似文献,搜索用时 437 毫秒
1.
Incomplete-Fusion-Fragmentation Model is used to analyze the multifragmentation of the projectile remnant in 600MeV/u Au+Au reaction.The theoretical resultsof the mass number,the excitation energy and the thermodynamical temperature of the projectile remnant agree well with experimental data.The backbending structure in the curve of temperature as a function of the excitation energy per nucleon,i.e. the evidence of liquid-gas phase transition,is reproduced and reasonably related to the decay modes phase transformation from dominance of the multifragmentation mode to the vaporization mode. 相似文献
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利用核物质理论研究气–液相变结果表明,气–液相变中临界温度Tc随系统质量的增加而增加,但随碰撞系统同位旋的增加而减小.利用改进的同位旋相关的量子分子动力学模型,研究了中能重离子碰撞过程中同位旋分馏强度随碰撞系统的同位旋和系统质量的变化,结果表明,同位旋分馏强度与气–液相变临界温度Tc有对应的关系,特别是气–液相变和同位旋分馏都发生在正常核密度以下低密度的spinodal不稳定区.这表明气–液相变和同位旋分馏具有相类似的动力学行为和内在联系,也预示着可以通过对同位旋分馏强度的研究和测量来揭示中能重离子碰撞过程中气–液相变的动力学特征 相似文献
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Bimodal distributions of some chosen variables measured in nuclear collisions were recently proposed as a non-ambiguous signature
of a first-order phase transition in nuclei. This section presents a compilation of both theoretical and experimental studies
on bimodalities performed so far, in relation with the liquid-gas phase transition in nuclear matter. 相似文献
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V. A. Karnaukhov H. Oeschler A. Budzanowski S. P. Avdeyev A. S. Botvina E. A. Cherepanov W. Karcz V. V. Kirakosyan P. A. Rukoyatkin I. Skwirczyńska E. Norbeck 《Physics of Atomic Nuclei》2008,71(12):2067-2073
Critical temperature T
c
for the nuclear liquid-gas phase transition is estimated from both the multifragmentation and fission data. In the first
case, the critical temperature is obtained by analysis of the intermediate-mass-fragment yields in p(8.1 GeV) + Au collisions within the statistical model of multifragmentation. In the second case, the experimental fission
probability for excited 188Os is compared with the calculated one with T
c
as a free parameter. It is concluded for both cases that the critical temperature is higher than 15 MeV.
The text was submitted by the authors in English. 相似文献
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U. Katscher J. A. Maruhn W. Greiner I. N. Mishustin 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(3):251-252
We present the excitation function of the reaction Au+Au in the frame work of the recently developed (2+1)-fluid model. In the (2+1)-fluid model, it is assumed that two baryonic fluids formed by the projectile and target nucleons produce a third hadronic fluid via inelastic nucleon-nucleon collisions. For this third fluid we use the equation of state of an interacting hadron gas obtained within the relativistic mean field model, including a first order phase transition. The dependence of the pion mean transverse momentum is investigated to observe the predicted plateau in the region of the phase transition of the hadronic matter to the quark-gluon plasma. 相似文献
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H. Stein C. Porthun G. Röpke 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):393-398
For fermionic model systems with a separable interaction the BCS equations are solved self-consistently. In addition, the
possibility of a liquid-gas phase transition is considered by inspecting thermodynamic stability. Different examples of temperature-density
phase diagrams are given depending on the parameters of a model interaction. In particular, a liquid-gas binodal anomaly is
found due to the superposition of the superfluid and the liquid-gas phase transition.
Received: 14 October 1997 / Accepted: 2 December 1997 相似文献
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我们在HIRFL提供的46.7MeV/u的~(12)C离子轰击~(58)Ni、~(115)In和~(197)Au靶所引起的核反应中研究了弹核碎裂与转移反应的竞争,分别提取了对应于弹核碎裂和转移反应的类弹碎片的约化动量宽度,从粒子发射不稳定态的相对布居得到了不同反应系统的核温度参数。 The projectile fragmentation and its competition with the transfer reactions have beenstudied in the reactions induced by 46.7 MeV/u ~(12)C ion on the ~(58)Ni, ~(115)In and ~(197)Au targets. Thereduced momentum distribution widths of the projectile-like fragments for projectile fragmentationand transfer reactions were extracted from the experimental data respectively. The nuclear temperatureperameters were obtained from the relative populations of the unstable particle emission ... 相似文献
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The isentropic expansion of a blob of nuclear matter towards the two-phase instability region is studied by considering two extreme conditions: the instantaneous development of the phase transition and the spinodal decomposition. We show that the experimentally observed entropy values of light clusters give evidence for the onset of a liquid-gas phase transition in heavy ion and proton induced reactions, but to be more conclusive the disassembly of relatively cold nuclear systems has experimentally to be investigated in more detail. 相似文献
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Manfred Requardt 《Journal of statistical physics》1982,29(1):117-127
We introduce a method to prove poor decay of certain cross-correlation functions which are closely related to the phase transition. The methods apply both to equal and nonequal times, which gives access to the dynamical regime. We establish a criterion which displays openly what happens when the Goldstone picture breaks down. Since no rudiments of translation invariance are needed the treatment covers phases in coexistence like, e.g., liquid-gas interfaces and completely inhomogeneous systems. Furthermore a perhaps surprising connection with the breaking of time reflection invariance of the equilibrium state is established. 相似文献
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V. A. Karnaukhov S. P. Avdeyev E. V. Duginova L. A. Petrov V. K. Rodionov H. Oeschler A. Budzanowski W. Karcz M. Janicki O. V. Bochkarev E. A. Kuzmin L. V. Chulkov E. Norbeck A. S. Botvina 《Physics of Atomic Nuclei》2003,66(7):1242-1251
Multiple emission of intermediate-mass fragments (IMF) in the collisions of protons (up to 8.1 GeV), 4He (4 and 14.6 GeV), and 12C (22.4 GeV) on Au has been studied with the 4π setup FASA. In all the cases, thermal multifragmentation of the hot and diluted target spectator takes place. The fragment multiplicity and charge distributions are well described by the combined model including the modified intranuclear cascade followed by the statistical multibody decay of the hot system. IMF-IMF-correlation study supports this picture, giving a very short time scale of the process (≤70 fm/c). This decay process can be interpreted as the first-order nuclear “liquid-fog” phase transition inside the spinodal region. The evolution of the mechanism of thermal multifragmentation with increasing projectile mass was investigated. The onset of the radial collective flow was observed for heavier projectiles. The analysis reveals information on the fragment space distribution inside the breakup volume: heavier IMFs are formed predominantly in the interior of the fragmenting nucleus possibly due to the density gradient. 相似文献
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V. A. Karnaukhov 《Physics of Atomic Nuclei》2014,77(1):117-125
Nuclear multifragmentation is the main channel of decay of hot nuclei at temperatures of 5 to 6 MeV. Investigation of this process permits experimentally determining the critical temperature for the liquid-gas nuclear phase transition. It was found that T c = 17±2 MeV. Characteristic times of the process are measured by analyzing correlation functions for fragment pairs. The mean fragment-emission time was found to be 1 to 2 × 10?22 s. 相似文献
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I. N. Mishustin 《The European Physical Journal A - Hadrons and Nuclei》2006,30(1):311-316
It is commonly accepted that strongly interacting matter has several phase transitions in different domains of temperature
and baryon density. In this contribution I discuss two most popular phase transitions which, in principle, can be accessed
in nuclear collisions. One of them, the liquid-gas phase transition, is well established theoretically and studied experimentally
in nuclear multifragmentation reactions at intermediate energies. The other one, the deconfinement-hadronization phase transition,
is at the focus of present and future experimental studies with relativistic heavy-ion beams at SPS, RHIC and LHC. Possible
links between these two phase transitions are identified from the viewpoint of their manifestation in violent nuclear collisions. 相似文献
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The premartensitic tweed in Au–Cu–Al alloys, contrary to previous thought that resort to defects, is confirmed to be associated with the coherent embryos of an intermediate phase (I phase) embedded in parent phase. The parent?→?I phase transformation temperature was measured by differential scanning calorimeter and dynamic mechanical analysers, which shifts from 82.3 to 557.6?°C depending on the alloy composition. X-ray diffraction and transmission electron microscopes (TEM) results show that the parent?→?I phase transformation is a charge density wave transition that cannot be suppressed even by melt-spun method, which shows obvious compositional inhomogeneity between I phase and parent. The results imply that the parent?→?I phase transition is a fast displacive transformation coupled with diffusion. Moreover, accompanying the parent?→?I phase transformation, alloys demonstrate diversified microstructure revealed by TEM observation, from tweed to chessboard nanowires or twins. These findings provide the experimental evidence for that parent?→?I phase transformation in Au–Cu–Al alloys is originated from pseudospinodal decomposition as theoretically predicted. 相似文献
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W. Terlau M. Bürgel A. Budzanowski H. Fuchs H. Homeyer G. Röschert J. Uckert R. Vogel 《Zeitschrift für Physik A Hadrons and Nuclei》1988,330(3):303-310
Correlations between emission angles and energies of coincidentα-particle projectile-fragment pairs have been measured for the20Ne+197Au system at 390 MeV beam energy. Theα-particles observed close to the direction of the projectile-like fragment were found to result essentially from sequential projectile decay. Starting from the close-geometry data, the contribution of sequentially emittedα-particles was calculated by Monte Carlo simulations for the entire angular range. For deep inelastic events, the measured angular correlations exhibit a spectacular excess over the calculated correlation. This excess is centred close to the beam direction but on the opposite side of it with respect to the detected projectile-like fragment. The correspondingα-particles have velocities around 85% of the projectile velocity indicating emission in an early reaction phase. 相似文献