4,866 research outputs found
Entropy Distance: New Quantum Phenomena
We study a curve of Gibbsian families of complex 3x3-matrices and point out
new features, absent in commutative finite-dimensional algebras: a
discontinuous maximum-entropy inference, a discontinuous entropy distance and
non-exposed faces of the mean value set. We analyze these problems from various
aspects including convex geometry, topology and information geometry. This
research is motivated by a theory of info-max principles, where we contribute
by computing first order optimality conditions of the entropy distance.Comment: 34 pages, 5 figure
Reconciliation of experimental and theoretical electric tensor polarizabilities of the cesium ground state
We present a new theoretical analysis of the strongly suppressed F- and
M-dependent Stark shifts of the Cs ground state hyperfine structure. Our
treatment uses third order perturbation theory including off-diagonal hyperfine
interactions not considered in earlier treatments. A numerical evaluation of
the perturbation sum using bound states up to n=200 yields ground state tensor
polarizabilities which are in good agreement with experimental values, thereby
bridging the 40-year-old gap between experiments and theory. We have further
found that the tensor polarizabilities of the two ground state hyperfine
manifolds have opposite signs, in disagreement with an earlier derivation. This
sign error has a direct implication for the precise evaluation of the blackbody
radiation shift in primary frequency standards.Comment: 7 pages, 2 figures, accepted for publication in Europhysics Letter
Rb*He_n exciplexes in solid 4_He
We report the observation of emission spectra from Rb*He_n exciplexes in
solid 4He. Two different excitation channels were experimentally identified,
viz., exciplex formation via laser excitation to the atomic 5P3/2 and to the
5P1/2 levels. While the former channel was observed before in liquid helium, on
helium nanodroplets and in helium gas by different groups, the latter creation
mechanism occurs only in solid helium or in gaseous helium above 10 Kelvin. The
experimental results are compared to theoretical predictions based on the
extension of a model, used earlier by us for the description of Cs*He_n
exciplexes. We also report the first observation of fluorescence from atomic
rubidium in solid helium, and discuss striking differences between the
spectroscopic feature of Rb-He and Cs-He systems.Comment: 8 pages, 8 figure
A sound card based multi-channel frequency measurement system
For physical processes which express themselves as a frequency, for example
magnetic field measurements using optically-pumped alkali-vapor magnetometers,
the precise extraction of the frequency from the noisy signal is a classical
problem. We describe herein a frequency measurement system based on an
inexpensive commercially available computer sound card coupled with a software
single-tone estimator which reaches Cram\'er--Rao limited performance, a
feature which commercial frequency counters often lack. Characterization of the
system and examples of its successful application to magnetometry are
presented.Comment: 4 pages, 3 figures, 1 tabl
Spectroscopy of Rb dimers in solid He
We present experimental and theoretical studies of the absorption, emission
and photodissociation spectra of Rb molecules in solid helium. We have
identified 11 absorption bands of Rb. All laser-excited molecular states
are quenched by the interaction with the He matrix. The quenching results in
efficient population of a metastable (1) state, which emits
fluorescence at 1042 nm. In order to explain the fluorescence at the forbidden
transition and its time dependence we propose a new molecular exciplex
RbHe. We have also found evidence for the formation of
diatomic bubble states following photodissociation of Rb
Comparison of discharge lamp and laser pumped cesium magnetometers
We have performed a comparison of laser (LsOPM) and lamp (LpOPM) pumped cesium vapor magnetometers. Although the LsOPM operated 50% above its shot-noise limit we found an intrinsic sensitivity of 15 fT/√Hz and 25 fT/√Hz for the LsOPM and the LpOPM, respectively. Two modes of operation, viz. the phase-stabilized and the self-oscillating modes, were investigated and found to yield a similar performance. We have compared the performance of the LsOPM and the LpOPM directly by simultaneous measurements of field fluctuations of a 2-μT magnetic field inside a multilayer magnetic shield and have used one of the magnetometers for an active field stabilization. In the stabilized mode we found a gradient instability of 25 fT within an integration time of 100 s, which represents an upper limit of the long-term stability of the magnetometers. Our research is motivated by the need for an improved control of magnetic fields and gradients in a planned neutron electric dipole experimen
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