6,637 research outputs found
Production of heavy isotopes in transfer reactions by collisions of U+U
The dynamics of transfer reactions in collisions of two very heavy nuclei
U+U is studied within the dinuclear system (DNS) model.
Collisions of two actinide nuclei form a super heavy composite system during a
very short time, in which a large number of charge and mass transfers may take
place. Such reactions have been investigated experimentally as an alternative
way for the production of heavy and superheavy nuclei. The role of collision
orientation in the production cross sections of heavy nuclides is analyzed
systematically. Calculations show that the cross sections decrease drastically
with increasing the charged numbers of heavy fragments. The transfer mechanism
is favorable to synthesize heavy neutron-rich isotopes, such as nuclei around
the subclosure at N=162 from No (Z=102) to Db (Z=105).Comment: 4 pages, 4 figure
Formation of superheavy nuclei in cold fusion reactions
Within the concept of the dinuclear system (DNS), a dynamical model is
proposed for describing the formation of superheavy nuclei in complete fusion
reactions by incorporating the coupling of the relative motion to the nucleon
transfer process. The capture of two heavy colliding nuclei, the formation of
the compound nucleus and the de-excitation process are calculated by using an
empirical coupled channel model, solving a master equation numerically and
applying statistical theory, respectively. Evaporation residue excitation
functions in cold fusion reactions are investigated systematically and compared
with available experimental data. Maximal production cross sections of
superheavy nuclei in cold fusion reactions with stable neutron-rich projectiles
are obtained. Isotopic trends in the production of the superheavy elements
Z=110, 112, 114, 116, 118 and 120 are analyzed systematically. Optimal
combinations and the corresponding excitation energies are proposed.Comment: 18 pages, 8 figure
Revisit the spin-FET: Multiple reflections, inelastic scattering, and lateral size effects
We revisit the spin-injected field effect transistor (spin-FET) by simulating
a lattice model based on recursive lattice Green's function approach. In the
one-dimensional case and coherent regime, the simulated results reveal
noticeable differences from the celebrated Datta-Das model, which motivate thus
an improved treatment and lead to analytic and generalized result. The
simulation also allows us to address inelastic scattering (using B\"uttiker's
fictitious reservoir approach) and lateral confinement effects on the control
of spins which are important issues in the spin-FET device.Comment: 9 pages, 4 figure
Transverse emission of isospin ratios as a probe of high-density symmetry energy in isotopic nuclear reactions
Transverse emission of preequilibrium nucleons, light clusters (complex
particles) and charged pions from the isotopic Sn+Sn
reactions at a beam energy of 400\emph{A} MeV, to extract the high-density
behavior of nuclear symmetry energy, are investigated within an isospin and
momentum dependent transport model. Specifically, the double ratios of
neutron/proton, triton/helium-3 and in the squeeze-out domain
are analyzed systematically, which have the advantage of reducing the influence
of the Coulomb force and less systematic errors. It is found that the
transverse momentum distribution of isospin ratios strongly depend on the
stiffness of nuclear symmetry energy, which would be a nice observable to
extract the high-density symmetry energy. The collision centrality and the mass
splitting of neutron and proton in nuclear medium play a significant role on
the distribution structure of the ratios, but does not change the influence of
symmetry energy on the spectrum.Comment: 5 figures, 13 page
Isospin effect on nuclear stopping in intermediate energy Heavy Ion Collisions
By using the Isospin Dependent Quantum Molecular Dynamics Model (IQMD), we
study the dependence of nuclear stopping Q_{ZZ}/A and R in intermediate energy
heavy ion collisions on system size, initial N/Z, isospin symmetry potential
and the medium correction of two-body cross sections. We find the effect of
initial N/Z ratio, isospin symmetry potential on stopping is weak. The
excitation function of Q_{ZZ}/A and R depends on the form of medium correction
of two-body cross sections, the equation of state of nuclear matter (EOS). Our
results show the behavior of the excitation function of Q_{ZZ}/A and R can
provide clearer information of the isospin dependence of the medium correction
of two-body cross sections.Comment: 3 pages including 4 figure
Supernova Constraints on Models of Neutrino Dark Energy
In this paper we use the recently released Type Ia Supernova (SNIa) data to
constrain the interactions between the neutrinos and the dark energy scalar
fields. In the analysis we take the dark energy scalars to be either
Quintessence-like or Phantom-like. Our results show the data mildly favor a
model where the neutrinos couple to a phantom-like dark energy scalar, which
implies the equation of state of the coupled system behaves like Quintom
scenario in the sense of parameter degeneracy. We find future observations like
SNAP are potentially promising to measure the couplings between neutrino and
dark energy.Comment: Typos fixed and references updated. Version pressed in PR
Continuous-variable controlled-Z gate using an atomic ensemble
The continuous-variable controlled-Z gate is a canonical two-mode gate for
universal continuous-variable quantum computation. It is considered as one of
the most fundamental continuous-variable quantum gates. Here we present a
scheme for realizing continuous-variable controlled-Z gate between two optical
beams using an atomic ensemble. The gate is performed by simply sending the two
beams propagating in two orthogonal directions twice through a spin-squeezed
atomic medium. Its fidelity can run up to one if the input atomic state is
infinitely squeezed. Considering the noise effects due to atomic decoherence
and light losses, we show that the observed fidelities of the scheme are still
quite high within presently available techniques.Comment: 7 pages, 3 figures, to appear in Physical Review
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