4,121 research outputs found
Resonances in three-body systems with short and long-range interactions
The complex scaling method permits calculations of few-body resonances with
the correct asymptotic behaviour using a simple box boundary condition at a
sufficiently large distance. This is also valid for systems involving more than
one charged particle. We first apply the method on two-body systems. Three-body
systems are then investigated by use of the (complex scaled) hyperspheric
adiabatic expansion method. The case of the 2 resonance in Be and
Li is considered. Radial wave functions are obtained showing the correct
asymptotic behaviour at intermediate values of the hyperradii, where wave
functions can be computed fully numerically.Comment: invited talk at the 18th International Conference on Few-Body
Problems in Physics, Santos-S.Paulo, August 21-26, 200
Measurement of the neutron electric dipole moment by crystal diffraction
An experiment using a prototype setup to search for the neutron electric
dipole moment by measuring spin-rotation in a non-centrosymmetric crystal
(quartz) was carried out to investigate statistical sensitivity and systematic
effects of the method. It has been demonstrated that the concept of the method
works. The preliminary result of the experiment is ecm. The experiment showed that an accuracy of ecm can be obtained in 100 days data taking, using available
quartz crystals and neutron beams.Comment: 13 pages, 4 figure
Photon noise in a random laser amplifier with fluctuating properties
We study fluctuations of the number of photocounts measured by an ideal
photodetector illuminated by light scattered in an amplifying disordered
medium, below the threshold for random lasing. We show that the variance of
fluctuations and their correlation function carry information about fluctuating
properties of the medium. A direct link is established between the fluctuations
of the number of photocounts due to the amplified spontaneous emission (ASE)
and the dimensionless conductance g of the medium. Our results suggest a
possibility of probing amplifying disordered media by analyzing statistics of
their ASE, without illuminating them from outside by a probe beam.Comment: 14 pages, 9 figure
Anatomy of three-body decay III. Energy distributions
We address the problem of calculating momentum distributions of particles
emerging from the three-body decay of a many-body resonance. We show that these
distributions are determined by the asymptotics of the coordinate-space
complex-energy wave-function of the resonance. We use the hyperspherical
adiabatic expansion method where all lengths are proportional to the
hyperradius. The structures of the resonances are related to different decay
mechanisms. For direct decay all inter-particle distances increase proportional
to the hyperradius at intermediate and large distances. Sequential three-body
decay proceeds via spatially confined quasi-stationary two-body configurations.
Then two particles remain close while the third moves away. The wave function
may contain mixtures which produce coherence effects at small distances, but
the energy distributions can still be added incoherently. Two-neutron halos are
discussed in details and illustrated by the resonance in He. The
dynamic evolution of the decay process is discussed.Comment: 30 pages, 8 figures, to be published in Nuclear Physics
Anatomy of three-body decay I. Schematic models
Sequential three-body decay proceeds via spatially confined quasi-stationary
two-body configurations. Direct three-body decay populates the three-body
continuum without intermediate steps. The relative importance of these decay
modes is discussed in a schematic model employing only Coulomb or centrifugal
barrier potentials. Decisive dimensionless charge, mass and energy ratios are
derived. Sequential decay is usually favored for charged particles. Small
charge and small mass of high energy is preferably emitted first. Without
Coulomb potential the sequential decay is favored except when both resonance
energy and intermediate two-body energy are large.Comment: To be published in Nuclear Physics
Two-color interference stabilization of atoms
The effect of interference stabilization is shown to exist in a system of two
atomic levels coupled by a strong two-color laser field, the two frequencies of
which are close to a two-photon Raman-type resonance between the chosen levels,
with open channels of one-photon ionization from both of them. We suggest an
experiment, in which a rather significant (up to 90%) suppression of ionization
can take place and which demonstrates explicitly the interference origin of
stabilization. Specific calculations are made for H and He atoms and optimal
parameters of a two-color field are found. The physics of the effect and its
relation with such well-known phenomena as LICS and population trapping in a
three-level system are discussed.Comment: the paper includes 1 TeX file and 16 picture
- …