1,063 research outputs found
Statistical features of the thermal neutron capture cross sections
We discuss the existence of huge thermal neutron capture cross sections in
several nuclei. The values of the cross sections are several orders of
magnitude bigger than expected at these very low energies. We lend support to
the idea that this phenomenon is random in nature and is similar to what we
have learned from the study of parity violation in the actinide region. The
idea of statistical doorways is advanced as a unified concept in the
delineation of large numbers in the nuclear world. The average number of maxima
per unit mass, in the capture cross section is calculated and related
to the underlying cross section correlation function and found to be , where is a characteristic mass
correlation width which designates the degree of remnant coherence in the
system. We trace this coherence to nucleosynthesis which produced the nuclei
whose neutron capture cross sections are considered here.Comment: 7 pages, 6 figures. To appear in Acta Physica Polonica B as a
Contribution to the proceedings of:Jagiellonian Symposium of Fundamental and
Applied Subatomic Physics, June 7- 12, 2015 Krakow, Polan
Production and state-selective detection of ultracold, ground state RbCs molecules
Using resonance-enhanced two-photon ionization, we detect ultracold,
ground-state RbCs molecules formed via photoassociation in a laser-cooled
mixture of 85Rb and 133Cs atoms. We obtain extensive bound-bound excitation
spectra of these molecules, which provide detailed information about their
vibrational distribution, as well as spectroscopic data on the RbCs ground
a^3\Sigma^+ and excited (2)^3\Sigma^+, (1)^1\Pi states. Analysis of this data
allows us to predict strong transitions from observed excited levels to the
absolute vibronic ground state of RbCs, potentially allowing the production of
stable, ultracold polar molecules at rates as large as 10^7 s^{-1}
Loading of a surface-electrode ion trap from a remote, precooled source
We demonstrate loading of ions into a surface-electrode trap (SET) from a
remote, laser-cooled source of neutral atoms. We first cool and load
neutral Sr atoms into a magneto-optical trap from an oven that
has no line of sight with the SET. The cold atoms are then pushed with a
resonant laser into the trap region where they are subsequently photoionized
and trapped in an SET operated at a cryogenic temperature of 4.6 K. We present
studies of the loading process and show that our technique achieves ion loading
into a shallow (15 meV depth) trap at rates as high as 125 ions/s while
drastically reducing the amount of metal deposition on the trap surface as
compared with direct loading from a hot vapor. Furthermore, we note that due to
multiple stages of isotopic filtering in our loading process, this technique
has the potential for enhanced isotopic selectivity over other loading methods.
Rapid loading from a clean, isotopically pure, and precooled source may enable
scalable quantum information processing with trapped ions in large, low-depth
surface trap arrays that are not amenable to loading from a hot atomic beam
A Complex Chemical Potential: Signature of Decay in a Bose-Einstein Condensate
We explore the zero-temperature statics of an atomic Bose-Einstein condensate
in which a Feshbach resonance creates a coupling to a second condensate
component of quasi-bound molecules. Using a variational procedure to find the
equation of state, the appearance of this binding is manifest in a collapsing
ground state, where only the molecular condensate is present up to some
critical density. Further, an excited state is seen to reproduce the usual
low-density atomic condensate behavior in this system, but the molecular
component is found to produce an underlying decay, quantified by the imaginary
part of the chemical potential. Most importantly, the unique decay rate
dependencies on density () and on scattering length () can be measured in experimental tests of this theory.Comment: 4 pages, 1 figur
Fine Structure Discussion of Parity-Nonconserving Neutron Scattering at Epithermal Energies
The large magnitude and the sign correlation effect in the parity
non-conserving resonant scattering of epithermal neutrons from Th is
discussed in terms of a non-collective local doorway model. General
conclusions are drawn as to the probability of finding large parity violation
effects in other regions of the periodic table.Comment: 6 pages, Tex. CTP# 2296, to appear in Z. Phys.
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