4,160 research outputs found
Enhancement of the electric dipole moment of the electron in PbO
The a(1) state of PbO can be used to measure the electric dipole moment of
the electron d_e. We discuss a semiempirical model for this state, which yields
an estimate of the effective electric field on the valence electrons in PbO.
Our final result is an upper limit on the measurable energy shift, which is
significantly larger than was anticipated earlier: .Comment: 4 pages, revtex4, no figures, submitted to PR
Electric dipole moment of the electron in YbF molecule
Ab initio calculation of the hyperfine, P-odd, and P,T-odd constants for the
YbF molecule was performed with the help of the recently developed technique,
which allows to take into account correlations and polarization in the
outercore region. The ground state electronic wave function of the YbF molecule
is found with the help of the Relativistic Effective Core Potential method
followed by the restoration of molecular four-component spinors in the core
region of ytterbium in the framework of a non-variational procedure. Core
polarization effects are included with the help of the atomic Many Body
Perturbation Theory for Yb atom. For the isotropic hyperfine constant A,
accuracy of our calculation is about 3% as compared to the experimental datum.
The dipole constant Ad (which is much smaller in magnitude), though better than
in all previous calculations, is still underestimated by almost 23%. Being
corrected within a semiempirical approach for a perturbation of 4f-shell in the
core of Yb due to the bond making, this error is reduced to 8%. Our value for
the effective electric field on the unpaired electron is 4.9 a.u.=2.5E+10 V/cm.Comment: 7 pages, REVTE
The Bose-Einstein correlation function from a Quantum Field Theory point of view
We show that a recently proposed derivation of Bose-Einstein correlations
(BEC) by means of a specific version of thermal Quantum Field Theory (QFT),
supplemented by operator-field evolution of the Langevin type, allows for a
deeper understanding of the possible coherent behaviour of the emitting source
and a clear identification of the origin of the observed shape of the BEC
function . Previous conjectures in this matter obtained by other
approaches are confirmed and have received complementary explanation.Comment: Some misprints corrected. To be publishe in Phys. Rev.
ESR evidence for disordered magnetic phase from ultra-small carbon nanotubes embedded in zeolite nanochannels
A multi-frequency electron spin resonance (ESR) study provides evidence for
the occurrence of low temperature ferromagnetic/spin-glass behavior in aligned
arrays of sub-nanometer single walled carbon nanotubes confined in zeolite
nano-channels, owing to sp2-type non-bonding carbon associated localized states
with density of ~3 x 1019 /g. Features related to the much anticipated
conduction ESR are not detected. In the paramagnetic phase, the ESR linewidth
is found to be weakly dependent on microwave frequency.Comment: Accepted to be published in EuroPhysics Letter
Using Molecules to Measure Nuclear Spin-Dependent Parity Violation
Nuclear spin-dependent parity violation arises from weak interactions between
electrons and nucleons, and from nuclear anapole moments. We outline a method
to measure such effects, using a Stark-interference technique to determine the
mixing between opposite-parity rotational/hyperfine levels of ground-state
molecules. The technique is applicable to nuclei over a wide range of atomic
number, in diatomic species that are theoretically tractable for
interpretation. This should provide data on anapole moments of many nuclei, and
on previously unmeasured neutral weak couplings
A search for varying fundamental constants using Hz-level frequency measurements of cold CH molecules
Many modern theories predict that the fundamental constants depend on time,
position, or the local density of matter. We develop a spectroscopic method for
pulsed beams of cold molecules, and use it to measure the frequencies of
microwave transitions in CH with accuracy down to 3 Hz. By comparing these
frequencies with those measured from sources of CH in the Milky Way, we test
the hypothesis that fundamental constants may differ between the high and low
density environments of the Earth and the interstellar medium. For the fine
structure constant we find \Delta\alpha/\alpha = (0.3 +/- 1.1)*10^{-7}, the
strongest limit to date on such a variation of \alpha. For the
electron-to-proton mass ratio we find \Delta\mu/\mu = (-0.7 +/- 2.2) * 10^{-7}.
We suggest how dedicated astrophysical measurements can improve these
constraints further and can also constrain temporal variation of the constants.Comment: 8 pages, 3 figure
Dynamical Susceptibility in KH2PO4-type Crystals above and below Tc
The time dependent cluster approximation called the path probability method
(PPM) is applied to a pseudo-spin Ising Hamiltonian of the Slater-Takagi model
for KH2PO4-type hydrogen-bonded ferroelectrics in order to calculate the
homogeneous dynamical susceptibility above and below the ferroelectric
transition temperature. Above the transition temperature all the calculations
are carried out analytically in the cactus approximation of the PPM. Below the
transition temperature the dynamical susceptibility is also calculated
accurately since the analytical solution of spontaneous polarization in the
ferroelectric phase can be utilized. When the temperature is approached from
both sides of the transition temperature, only one of relaxation times shows a
critical slowing down and makes a main contribution to the dynamical
susceptibility. The discrepancy from Slater model (ice-rule limit) is discussed
in comparison with some experimental data.Comment: 8 pages, 10 figure
Highly anisotropic energy gap in superconducting Ba(FeCo)As from optical conductivity measurements
We have measured the complex dynamical conductivity, , of superconducting Ba(FeCo)As ( K) at terahertz frequencies and temperatures 2 - 30 K. In the frequency
dependence of below , we observe clear signatures of the
superconducting energy gap opening. The temperature dependence of
demonstrates a pronounced coherence peak at frequencies below 15 cm (1.8
meV). The temperature dependence of the penetration depth, calculated from
, shows power-law behavior at the lowest temperatures. Analysis of
the conductivity data with a two-gap model, gives the smaller isotropic s-wave
gap of meV, while the larger gap is highly anisotropic with
possible nodes and its rms amplitude is meV. Overall, our
results are consistent with a two-band superconductor with an gap
symmetry.Comment: 6 pages, 4 figures, discussion on pair-barking scattering and
possible lifting of the nodes is adde
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