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Liquid-vapor phase transition in nuclei or compound nucleus decay?  [PDF]
L. G. Moretto,J. B. Elliott,L. Phair,G. J. Wozniak
Physics , 2002,
Abstract: Recent analyses of multifragmentation in terms of Fisher's model and the related construction of a phase diagram brings forth the problem of the true existence of the vapor phase and the meaning of its associated pressure. Our analysis shows that a thermal emission picture is equivalent to a Fisher-like equilibrium description which avoids the problem of the vapor and explains the recently observed Boltzmann-like distribution of the emission times. In this picture a simple Fermi gas thermometric relation is naturally justified. Low energy compound nucleus emission of intermediate mass fragments is shown to scale according to Fisher's formula and can be simultaneously fit with the much higher energy ISiS multifragmentation data.
Nuclear matter phase diagram from compound nucleus decay  [cached]
Moretto L.G.,Elliott J.B.,Lake P.T.,Phair L.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122108009
Abstract: The finite size of nuclei and the Coulomb interaction make it difficult to describe systems interacting through the strong force into thermodynamic terms. Our task is to extract the phase diagram of the theoretical infinite symmetrical uncharged nuclear matter from experiments of nuclear collisions where the systems are neither infinite, symmetrical, nor uncharged. Decay yields from such experiments are translated into coexistence densities and pressures by use of Fisher's droplet model. This method is tested on model systems such as the Ising model and a system of particles interacting via the Lennard-Jones potential. The specific problems inherent to nuclear reactions are considered. These include finite size effects, Coulomb repulsion, and the lack of a physical vapor in contact with a decaying system. Experimental data of compound nucleus experiments are studied within this framework, which is also shown to extend to higher energy reactions. Finally, the phase diagram of nuclear matter is extracted.
Cascade Gamma-Decay of the 193Os Compound Nucleus and some Aspects of Dynamics of Change in Nuclear Properties below Bn  [PDF]
V. A. Bondarenko,J. Honzatko,V. A. Khitrov,A. M. Sukhovoj,I. Tomandl
Physics , 2001,
Abstract: Two-step cascades from the 192Os(n th,gamma)193Os reaction were studied in gamma-gamma coincidence measurement. The decay scheme of 193Os was established up to the excitation energy ~3 MeV. The excitation spectrum of intermediate levels of most intense cascades was found to be practically harmonic.
Nuclear effects in proton decay  [PDF]
Dorota Stefan,Artur M. Ankowski
Physics , 2008,
Abstract: An experimental observation of proton decay would be a spectacular proof of grand unification. Currently, the best constraint on the proton lifetime for the p->e+ pi0 decay channel, coming from the Super-Kamiokande experiment, reaches 8*10^33 years. To improve the measurement, much bigger detectors should be constructed. Moreover, a better description of the bound-nucleon states and of the propagation of the proton-decay products through nuclear matter have to be developed. In this article special attention is paid to the argon nucleus because a liquid argon detector is a promising candidate for the future large apparatus.
Classical picture of post-exponential decay  [PDF]
E. Torrontegui,J. G. Muga,J. Martorell,D. W. L. Sprung
Physics , 2010, DOI: 10.1103/PhysRevA.81.042714
Abstract: Post-exponential decay of the probability density of a quantum particle leaving a trap can be reproduced accurately, except for interference oscillations at the transition to the post-exponential regime, by means of an ensemble of classical particles emitted with constant probability per unit time and the same half-life as the quantum system. The energy distribution of the ensemble is chosen to be identical to the quantum distribution, and the classical point source is located at the scattering length of the corresponding quantum system. A 1D example is provided to illustrate the general argument.
Uniqueness of Fisher plots and their inferred (nuclear) liquid-vapor phase diagrams  [PDF]
J. B. Elliott,L. G. Moretto,L. Phair
Physics , 2004,
Abstract: A detailed study of the lattice gas (Ising) model shows that the correct definition of cluster concentration in the vapor at coexistence with the liquid leads to Fisher plots that are unique, independent of fixed particle number density $\rho_{\text{fixed}}$, and completely reliable for the characterization of the liquid-vapor phase diagram of any van der Waals systems including nuclear matter.
Delta Decay in the Nuclear Medium  [PDF]
Hungchong Kim,S. Schramm,Su Houng Lee
Physics , 1996, DOI: 10.1103/PhysRevC.56.1582
Abstract: The $\Delta$ decay in the nuclear medium is calculated in the relativistic meson-nucleon model. The delta spreading width is calculated and compared with the Pauli-blocked $\pi$N decay width. The influence of relativistic mean fields is also studied. We stress the importance of understanding the delta spreading width in interpreting experiments involving delta resonances.
On a translationally invariant nuclear single particle picture  [PDF]
W. Gloeckle,H. Kamada,J. Golak
Physics , 2011,
Abstract: If one assumes a translationally invariant motion of the nucleons relative to the c. m. position in single particle mean fields a correlated single particle picture of the nuclear wave function emerges. A single particle product ansatz leads for that Hamiltonian to nonlinear equations for the single particle wave functions. In contrast to a standard not translationally invariant shell model picture those single particle s-, p- etc states are coupled. The strength of the resulting coupling is an open question. The Schroedinger equation for that Hamiltonian can be solved by few- and many -body techniques, which will allow to check the validity or non-validity of a single particle product ansatz. Realistic nuclear wave functions exhibit repulsive 2-body short range correlations. Therefore a translationally invariant single particle picture -- if useful at all -- can only be expected beyond those ranges. Since exact A = 3 and 4 nucleon ground state wave functions and beyond based on modern nuclear forces are available, the translationally invariant shell model picture can be optimized by an adjustment to the exact wave function and its validity or non-validity decided.
Atomic Radiation in Nuclear Decay  [cached]
Lee B.Q.,Kibédi T.,Stuchbery A.E.,Robertson K.A.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20123504003
Abstract: Auger electrons emitted in nuclear decay offer a unique tool to kill cancer cells at the scale of a DNA molecule. Over the last forty years many aspects of this promising therapeutic tool have been explored, however it is still not in the phase of large scale clinical trials. In this paper we review the physical processes of Auger emission in nuclear decay and present a new model being developed to evaluate the energy spectrum of Auger electrons, and hence overcome the limitations of existing computations.
Signature of nonexponential nuclear decay  [PDF]
A Ray,A K Sikdar,A De
Physics , 2015,
Abstract: Precision tests of decay law of radioactive nuclei have not so far found any deviation from the exponential decay law at early time, as predicted by quantum mechanics. In this paper, we show that the quantum decoherence time (i.e. the timescale of nonexponential decay) of the quasifission or fission process should be of the order of attosecond considering the atom of the fissioning nucleus as a quantum detector. Hence, the observed decay timescale of the quasifission or fission process of even highly excited (EX greater than 50 MeV) transuranium and uraniumlike complexes should be rather long (of the order of attosecond) in spite of their very fast exponential decay timescale (of the order of zeptosecond) as measured by the nuclear techniques. Recent controversy regarding the observation of very long (of the order of attosecond ) and very short (of the order of zeptosecond ) quasifission or fission timescales for similar systems at similar excitation energies as obtained by direct techniques (crystal blocking, X ray fission fragment) and nuclear techniques could be interpreted as evidence for nonexponential decays in nuclear systems
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