9,785,145 research outputs found
Long-Range Correlations and the Momentum Distribution in Nuclei
The influence of correlations on the momentum distribution of nucleons in
nuclei is evaluated starting from a realistic nucleon-nucleon interaction. The
calculations are performed directly for the finite nucleus \,^{16}O making
use of the Green's function approach. The emphasis is focused on the
correlations induced by the excitation modes at low energies described within a
model-space of shell-model configurations including states up to the sdg shell.
Our analysis demonstrates that these long-range correlations do not produce any
significant enhancement of the momentum distribution at high missing momenta
and low missing energies. This is in agreement with high resolution
experiments for this nucleus. We also try to simulate the corresponding effects
in large nuclei by quenching the energy-spacing between single-particle orbits.
This yields a sizable enhancement of the spectral function at large momenta and
small energy. Such behavior could explain the deviation of the momentum
distribution from the mean field prediction, which has been observed in
experiments on heavy nuclei like Pb
Neutrino nucleus cross sections for low energy neutrinos at SNS facilities
We calculate the neutrino nucleus cross sections for charged lepton
production relevant for the experiments proposed with the stopped muon
neutrinos using neutron spallation source facility. The calculations are done
in local density approximation taking into account Pauli blocking, Fermi motion
effects and renormalization of weak transition strengths in the nuclear medium.
The effect of Coulomb distortion of the lepton produced in charge current
reactions is taken into account by using the Fermi function as well as in a
model where an effective momentum has been used for the lepton moving in the
local Coulomb field of the final nucleus. The numerical results for the
neutrino nucleus total cross sections averaged over Michel spectrum are
presented for various nuclei.Comment: 16pages, 9figures, Submitted to Nucl. Phys.
Spectroscopy of formaldehyde in the 30140-30790cm^-1 range
Room-temperature absorption spectroscopy of formaldehyde has been performed
in the 30140-30790cm^-1 range. Using tunable ultraviolet continuous-wave laser
light, individual rotational lines are well resolved in the Doppler-broadened
spectrum. Making use of genetic algorithms, the main features of the spectrum
are reproduced. Spectral data is made available as Supporting Information
Short-range correlations in finite nuclear systems
Recent results concerning the use of the Correlated Basis Function to
investigate the ground state properties of medium-heavy doubly magic nuclei
with microscopic interactions are presented. The calculations have been done by
considering a Short-Range Correlation between nucleons. The possibility of
identifying effects produced by Short-Range Correlations in electromagnetically
induced phenomena is discussed.Comment: 12 pages, 10 Postscript figures, Contribution to the International
Workshop on Nuclear Theory, Rila Mountains, Bulgaria 10 to June 15, 200
Random Phase Approximation and neutrino-nucleus cross sections
The Random Phase Approximation theory is used to calculate the total cross
sections of electron neutrinos on C nucleus. The role of the excitation
of the discrete spectrum is discussed. A comparison with electron scattering
and muon capture data is presented. The cross section of electron neutrinos
coming from muon decay at rest is calculated.Comment: 6 pages, 5 eps figures, Presented at the XX Max Born Symposium,
Wroclaw (Poland
Co
Different loading rates of photocatalysts Co3O4/C3N4 were prepared by calcination method. Their photocatalytic performances were evaluated by the degradation of methyl blue under visible light irradiation. The results show that the introduction of Co3O4 significantly improves the optical absorption properties of C3N4, which is beneficial to the separation of photogenerated electrons and holes on the surface of catalyst. The prepared Co3O4/C3N4 for visible photocatalytic degradation of methyl blue has higher catalytic efficiency than that of pure C3N4 or pure Co3O4. The best cobalt loading rate was 30% when the concentration of methylene blue was 40 mg/L. Recycling rate of 30% Co3O4/C3N4 composite catalyst was studied. After 4 cycles, the degradation rate was only slightly decreased from 86.8% to 82.8%, indicating the catalyst with good photostability and repeatability.nbs
Model calculations of doubly closed shell nuclei in CBF theory III. j-j coupling and isospin dependence
Correlated Basis Function theory and Fermi Hypernetted Chain technique are
extended to study medium-heavy, doubly closed shell nuclei in j-j coupling
scheme, with different single particle wave functions for protons and neutrons
and isospin dependent two-body correlations. Central semirealistic interactions
are used. Ground state energies, one-body densities, distribution functions and
momentum distributions are calculated for 12C, 16O, 40Ca, 48Ca and 208Pb
nuclei. The values of the ground state energies provided by isospin dependent
correlations are lower than those obtained with isospin independent
correlations. In finite nuclear systems, the two--body Euler equations provide
correlation functions variationally more effective than those obtained with the
same technique in infinite nuclear matter.Comment: 29 Latex pages plus 6 Postscript figure
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