[Show abstract][Hide abstract] ABSTRACT: Formation of superheavy nuclei is greatly hindered by the inner barrier and strong dissipation on the way from the contact point of two colliding nuclei to the compound nucleus configuration. One of the dissipation mechanisms is related to the exchange of particles across the window between two nuclei in relative motion, which is the "window" term in the "wall-plus-window" formula. By means of the dynamic analysis for the symmetric systems Xe132 + Xe132 and Xe136 + Xe136, we have shown that the window component of friction tensor retards the elongation of the fusing composite nucleus, decreases the height of the inner barrier, and hence increases the fusion probability. Therefore, the friction associated with "window" term enhances the formation cross sections of superheavy nuclei. Besides, we have shown the mass difference (in units of the temperature) of the fission and neutron emission saddle points as a function of mass number of the hassium isotopes, which may provide a useful reference for synthesis and study of the nuclei adjacent to the doubly magic nucleus Hs270.
Physical Review C 02/2014; 89(3). DOI:10.1103/PhysRevC.89.034627 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nucleon flow in the process of evolution from dinucleus to mononucleus is studied by means of the coupled Langevin equations in the three-dimensional collective space of the radial, neck, and asymmetry degrees of freedom for the systems 48Ca+238U and 58Fe+248Cm. For a comparison, the dynamic evolution of the neck is also investigated with the Langevin equations in the two-dimensional collective space of the radial and neck for these two reaction systems. The results show that nucleon flow is strongly damped in the stage of the dinuclear system due to the large dissipation associated with the mass asymmetry degree of freedom. The evaporation residue (ER) cross sections for the 48Ca+238U and 58Fe+248Cm reactions are evaluated by means of the modified fusion-by-diffusion (FBD) model, in which the injection distance distributions in the asymmetric fission valley obtained from the dynamic calculations are integrated. The theoretical excitation functions of the 48Ca+238U reaction are in good agreement with the experimental data. For the 58Fe+248Cm reaction, the maximum ER cross sections in 3n- and 4n-evaporation channels calculated with the three-dimensional Langevin equations are, respectively, 0.008 and 0.020 fb. We have demonstrated that the effect of drift and diffusion towards a more symmetric configuration on the ER cross sections is counterbalanced by that of diffusion towards a more asymmetric one. The ER excitation functions calculated with the two approaches are similar, which means that the impact of the nucleon flow during the process of neck evolution on the formation probability of superheavy nuclei is small in the framework of the dynamic model. In this sense, the frozen approximation of mass asymmetry in the FBD model should be reasonable in the hot fusion reactions.
Physical Review C 04/2013; 87(4). DOI:10.1103/PhysRevC.87.047602 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The evolution of neck for the asymmetric system 58Fe + 244Pu at E
c.m. = 260 MeV has been studied with the coupled Langevin equations in two-dimensional collective space and the results compared to those obtained with a one-dimensional approach under the frozen assumption. It is found that the coupling between the radial and neck degrees of freedom reduces the drift velocity of neck growth and delays the transition from dinucleus to mononucleus. Besides, the coupling brings the system into a somehow elongated shape when the injection into the asymmetric fission valley takes place, hence, the fusion probability and the relevant evaporation residue (ER) cross-sections decrease. For the system 58Fe + 244Pu , the ER cross-sections decrease by about 30% as compared to those obtained under the frozen approximation. Therefore, we may arrive at the conclusion that for the heavy asymmetric systems such as 58Fe + 244Pu the coupling between different degrees of freedom has important effects on the evolution from dinucleus to mononucleus and the frozen approximation is basically not satisfied as far as the neck dynamics is concerned. However, as compared to the symmetric reactions, the influence of the neck dynamics on the fusion hindrance factor of heavy systems is much weaker for the asymmetric reactions.
European Physical Journal A 10/2012; 48(10). DOI:10.1140/epja/i2012-12133-3 · 2.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Synthesis of element 120 in the 58Fe+244Pu hot fusion reaction has been evaluated by means of a modified “fusion by diffusion” (FBD) model. In the model, dynamic evolution from dinucleus to mononucleus is taken into account with the two-dimensional coupled Langenvin equations. The calculated maximum evaporation residue cross sections in 3n- and 4n-evaporation channels of 58Fe+244Pu reaction are 0.005 and 0.016 pb, which are far below the present experimental sensitivity for the detection of one decay. The fusion probability calculated with the modified FBD model clearly shows that fusion of the heavy system 58Fe+244Pu is severely hindered.
Physical Review C 09/2012; 86(3). DOI:10.1103/PhysRevC.86.037602 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper makes some qualitative and quantitative analyses about halo formation rules of some mirror nuclei with the relativistic mean-field (RMF) theory and the Woods-Saxon mean-field model. By analysing two opposite effects of Coulomb interaction on the proton halo formation, it finds that the energy level shift has a larger contribution than that of the Coulomb barrier when the mass number A is small, the hindrance of the Coulomb barrier becomes more obvious with the increase of the mass number A, and the overall effect of the Coulomb interaction almost disappears when A approx 39 as its two effects counteract with each other.
Chinese Physics B 01/2009; 18(12):5267-5271. · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The halo structures in some light nuclei are investigated systemically with the nuclear asymptotic normalization coefficient (ANC) method and the relativistic mean-field (RMF) theory. Some important results about the halo structures in mirror nuclei are obtained, and some qualitative analyses are made to explore the role of Coulomb effects on the formation of proton halo nuclei.
International Journal of Modern Physics E 10/2008; 17(09):1729-1738. DOI:10.1142/S0218301308010738 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The exotic structures in the 2s_{1/2} states of five pairs of mirror nuclei ^{17}O-^{17}F, ^{26}Na-^{26}P, ^{27}Mg-^{27}P, ^{28}Al-^{28}P and ^{29}Si-^{29}P are investigated with the relativistic mean-field (RMF) theory and the single-particle model (SPM) to explore the role of the Coulomb effects on the proton halo formation. The present RMF calculations show that the exotic structure of the valence proton is more obvious than that of the valence neutron of its mirror nucleus, the difference of exotic size between each mirror nuclei becomes smaller with the increase of mass number A of the mirror nuclei and the ratios of the valence proton and valence neutron root-mean-square (RMS) radius to the matter radius in each pair of mirror nuclei all decrease linearly with the increase of A. In order to interpret these results, we analyze two opposite effects of Coulomb interaction on the exotic structure formation with SPM and find that the contribution of the energy level shift is more important than that of the Coulomb barrier for light nuclei. However, the hindrance of the Coulomb barrier becomes more obvious with the increase of A. When A is larger than 34, Coulomb effects on the exotic structure formation will almost become zero because its two effects counteract with each other. Comment: 9 pages, 6 figures. One column
[Show abstract][Hide abstract] ABSTRACT: We present a scheme for multiparty quantum secret sharing of a private key with pure entangled states and decoy photons. The boss, say Alice uses the decoy photons, which are randomly in one of the four nonorthogonal single-photon states, to prevent a potentially dishonest agent from eavesdropping freely. This scheme requires the parties of communication to have neither an ideal single-photon quantum source nor a maximally entangled one, which makes this scheme more convenient than others in a practical application. Moreover, it has the advantage of having high intrinsic efficiency for qubits and exchanging less classical information in principle.
Physica A: Statistical Mechanics and its Applications 07/2007; 381(1-381):164-169. DOI:10.1016/j.physa.2007.04.018 · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An efficient quantum cryptography network protocol is proposed with d-dimension polarized photons, without resorting to entanglement and quantum memory. A server on the network, say Alice, provides the service for preparing and measuring single photons whose initial state are |0>. The users code the information on the single photons with some unitary operations. For preventing the untrustworthy server Alice from eavesdropping the quantum lines, a nonorthogonal-coding technique (decoy-photon technique) is used in the process that the quantum signal is transmitted between the users. This protocol does not require the servers and the users to store the quantum state and almost all of the single photons can be used for carrying the information, which makes it more convenient for application than others with present technology. We also discuss the case with a faint laser pulse.
Chinese Physics Letters 06/2007; 23(11). DOI:10.1088/0256-307X/23/11/004 · 0.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present two schemes for multiparty quantum remote secret conference in
which each legitimate conferee can read out securely the secret message
announced by another one, but a vicious eavesdropper can get nothing about it.
The first one is based on the same key shared efficiently and securely by all
the parties with Greenberger-Horne-Zeilinger (GHZ) states, and each conferee
sends his secret message to the others with one-time pad crypto-system. The
other one is based on quantum encryption with a quantum key, a sequence of GHZ
states shared among all the conferees and used repeatedly after confirming
their security. Both these schemes are optimal as their intrinsic efficiency
for qubits approaches the maximal value.
Chinese Physics Letters 01/2007; 24(1). DOI:10.1088/0256-307X/24/1/007 · 0.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two deterministic secure quantum communication schemes are proposed, one based on pure entangled states and the other on $d$-dimensional single-photon states. In these two schemes, only single-photon measurements are required for the two authorized users, which makes the schemes more convenient than others in practical applications. Although each qubit can be read out after a transmission of additional classical bit, it is unnecessary for the users to transmit qubits double the distance between the sender and the receiver, which will increase their bit rate and their security. The parties use decoy photons to check eavesdropping efficiently. The obvious advantage in the first scheme is that the pure entangled source is feasible with present techniques.
Journal- Korean Physical Society 07/2006; 49(4). · 0.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A multiparty quantum secret report scheme is proposed with quantum encryption. The boss Alice and her $M$ agents first share a sequence of ($M$+1)-particle Greenberger--Horne--Zeilinger (GHZ) states that only Alice knows which state each ($M$+1)-particle quantum system is in. Each agent exploits a controlled-not (CNot) gate to encrypt the travelling particle by using the particle in the GHZ state as the control qubit. The boss Alice decrypts the travelling particle with a CNot gate after performing a $\sigma_x$ operation on her particle in the GHZ state or not. After the GHZ states (the quantum key) are used up, the parties check whether there is a vicious eavesdropper, say Eve, monitoring the quantum line, by picking out some samples from the GHZ states shared and measure them with two measuring bases. After confirming the security of the quantum key, they use the GHZ states remained repeatedly for next round of quantum communication. This scheme has the advantage of high intrinsic efficiency for qubits and the total efficiency. Comment: 4 pages, no figures
Chinese Physics Letters 06/2006; 23(7). DOI:10.1088/0256-307X/23/7/006 · 0.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a scheme for quantum secure direct communication with quantum encryption. The two authorized users use repeatedly a sequence of the pure entangled pairs (quantum key) shared for encrypting and decrypting the secret message carried by the traveling photons directly. For checking eavesdropping, the two parties perform the single-photon measurements on some decoy particles before each round. This scheme has the advantage that the pure entangled quantum signal source is feasible at present and any eavesdropper cannot steal the message.
Chinese Physics 01/2006; 16(8). DOI:10.1088/1009-1963/16/8/001 · 1.34 Impact Factor