254 research outputs found
Excited states of beryllium atom from explicitly correlated wave functions
A study of the first excited states of beryllium atom starting from
explicitly correlated wave functions is carried out. Several properties are
obtained and discussed focusing on the analysis of the Hund's rules in terms of
the single--particle and electron pair intracule and extracule densities. A
systematic study of the differences on the electronic distributions of the
singlet and triplet states is carried out. The trial wave function used to
describe the different bound states consists of a generalized Jastrow-type
correlation factor times a configuration interaction model wave function. This
model wave function has been fixed by using a generalization of the optimized
effective potential method to deal with multiconfiguration wave functions. The
optimization of the wave function and the calculation of the different
quantities is carried out by means of the Variational Monte Carlo method.Comment: 28 pages, 6 figure
Quadratic diffusion Monte Carlo and pure estimators for atoms
The implementation and reliability of a quadratic diffusion Monte Carlo
method for the study of ground-state properties of atoms are discussed. We show
in the simple yet non-trivial calculation of the binding energy of the Li atom
that the method presented is effectively second-order in the time step. The
fulfilment of the expected quadratic behavior relies on some basic requirements
of the trial wave function used for importance sampling, in the context of the
fixed-node approximation. Expectation values of radial operators are calculated
by means of a pure estimation based on the forward walking methodology. It is
shown that accurate results without extrapolation errors can be obtained with a
pure algorithm that can be easily implemented in any previous diffusion Monte
Carlo program.Comment: RevTex, 20 pages, 3 figures, accepted in J. Chem. Phy
Density functional study of two-dimensional He-4 clusters
Binding energies and density profiles of two-dimensional systems of liquid
He-4 with different geometries are studied by means of a zero-range density
functional adjusted to reproduce the line tension obtained in a previous
diffusion Monte Carlo calculation (lambda_{DMC}=0.121 K/A). It is shown that
this density functional provides accurate results for the binding energy of
large clusters with a reasonable computational effort.Comment: RevTeX4, 11 pages + 2 tables + 6 figure
Quantum defect asymptotics at the critical charge: A study of the integrality conjecture
A single (n, ℓ) electron outside an (N −1)-electron atomic core is bound as long as Z > Zc = N − 1. A conjecture is examined, according to which the quantum defect of the outermost electron satisfies limZ!Zc δn,ℓ(Z) = Nℓ, where Nℓ is the number of occupied or partially occupied orbitals with angular momentum quantum number ℓ within the (N − 1)-electron core. Specifically, the 3s quantum defect is inspected for the different occupancies of the n = 1 and n = 2 shells. The conjecture is found to hold in all the cases considered
Parameterized optimized effective potential for the ground state of the atoms He through Xe
Parameterized orbitals expressed in Slater-type basis obtained within the
optimized effective potential framework as well as the parameterization of the
potential are reported for the ground state of the atoms He through Xe. The
total, kinetic, exchange and single particle energies are given for each atom.Comment: 47 pages, 1 figur
Status and preliminary results of the ANAIS experiment at Canfranc
ANAIS (Annual Modulation with NaI's) is an experiment planned to investigate
seasonal modulation effects in the signal of galactic WIMPs using up to 107 kg
of NaI(Tl) in the Canfranc Underground Laboratory (Spain). A prototype using
one single crystal (10.7 kg) is being developed before the installation of the
complete experiment; the first results presented here show an average
background level of 1.2 counts/(keV kg day) from threshold (Ethr~4 keV) up to
10 keV.Comment: 3 pages, 2 figures, talk delivered at the 7th International Workshop
on Topics in Astroparticle and Underground Physics (TAUP 2001), September
2001, Laboratori Nazionali del Gran Sasso, Italy (to appear in the Conference
Proceedings, Nucl. Phys. B (Proc. Suppl.)
Sensitivity plots for WIMP direct detection using the annual modulation signature
Annual modulation due to the Earth's motion around the Sun is a well known
signature of the expected WIMP signal induced in a solid state underground
detector. In the present letter we discuss the prospects of this technique on
statistical grounds, introducing annual-modulation sensitivity plots for the
WIMP-nucleon scalar cross section for different materials and experimental
conditions. The highest sensitivity to modulation is found in the WIMP mass
interval 10 GeV< m_W < 130 GeV, the actual upper limit depending from the
choice of the astrophysical parameters, while the lowest values of the
explorable WIMP-nucleon elastic cross-sections fall in most cases within one
order of magnitude of the sensitivities of present direct detection WIMP
searches.Comment: 24 pages, ReVTeX, 9 figures, submitted to Astroparticle Physic
- …