1,229 research outputs found
Complete hyperfine Paschen-Back regime at relatively small magnetic fields realized in Potassium nano-cell
A one-dimensional nano-metric-thin cell (NC) filled with potassium metal has
been built and used to study optical atomic transitions in external magnetic
fields. These studies benefit from the remarkable features of the NC allowing
one to use - and -methods for effective investigations of
individual transitions of the K D_1 line. The methods are based on strong
narrowing of the absorption spectrum of the atomic column of thickness L equal
to and to (with \lambda = 770\un{nm} being the resonant
laser radiation wavelength). In particular, for a -polarized radiation
excitation the -method allows us to resolve eight atomic transitions
(in two groups of four atomic transitions) and to reveal two remarkable
transitions that we call Guiding Transitions (GT). The probabilities of all
other transitions inside the group (as well as the frequency slope versus
magnetic field) tend to the probability and to the slope of GT. Note that for
circular polarization there is one group of four transitions and GT do not
exist. Among eight transitions there are also two transitions (forbidden for
= 0) with the probabilities undergoing strong modification under the
influence of magnetic fields. Practically the complete hyperfine Paschen-Back
regime is observed at relatively low (\sim 1\un{kG}) magnetic fields. Note
that for K line GT are absent. Theoretical models describe the experiment
very well.Comment: 6 page
Measurement of the parity violating 6S-7S transition amplitude in cesium achieved within 2 \times 10^{-13} atomic-unit accuracy by stimulated-emission detection
We exploit the process of asymmetry amplification by stimulated emission
which provides an original method for parity violation (PV) measurements in a
highly forbidden atomic transition. The method involves measurements of a
chiral, transient, optical gain of a cesium vapor on the 7S-6P_{3/2}
transition, probed after it is excited by an intense, linearly polarized,
collinear laser, tuned to resonance for one hyperfine line of the forbidden
6S-7S transition in a longitudinal electric field. We report here a 3.5 fold
increase, of the one-second-measurement sensitivity, and subsequent reduction
by a factor of 3.5 of the statistical accuracy compared with our previous
result [J. Gu\'ena et al., Phys. Rev. Lett. 90, 143001 (2003)]. Decisive
improvements to the set-up include an increased repetition rate, better
extinction of the probe beam at the end of the probe pulse and, for the first
time to our knowledge, the following: a polarization-tilt magnifier,
quasi-suppression of beam reflections at the cell windows, and a Cs cell with
electrically conductive windows. We also present real-time tests of systematic
effects, consistency checks on the data, as well as a 1% accurate measurement
of the electric field seen by the atoms, from atomic signals. PV measurements
performed in seven different vapor cells agree within the statistical error.
Our present result is compatible with the more precise Boulder result within
our present relative statistical accuracy of 2.6%, corresponding to a 2 \times
10^{-13} atomic-unit uncertainty in E_1^{pv}. Theoretical motivations for
further measurements are emphasized and we give a brief overview of a recent
proposal that would allow the uncertainty to be reduced to the 0.1% level by
creating conditions where asymmetry amplification is much greater.Comment: Article 21 pages, 6 figures, 3 tables Typos, addition of few comments
and little more data (1 week) leading to a slight reduction of the error bar
Accepted for publication in Phys.Rev.
High contrast D line electromagnetically induced transparency in nanometric-thin rubidium vapor cell
Electromagnetically induced transparency (EIT) on atomic D line of
rubidium is studied using a nanometric-thin cell with atomic vapor column
length in the range of L= 400 - 800 nm. It is shown that the reduction of the
cell thickness by 4 orders as compared with an ordinary cm-size cell still
allows to form an EIT resonance for ( nm) with the
contrast of up to 40%. Remarkable distinctions of EIT formation in
nanometric-thin and ordinary cells are demonstrated. Despite the Dicke effect
of strong spectral narrowing and increase of the absorption for , EIT resonance is observed both in the absorption and the fluorescence
spectra for relatively low intensity of the coupling laser. Well resolved
splitting of the EIT resonance in moderate magnetic field for
can be used for magnetometry with nanometric spatial resolution. The presented
theoretical model well describes the observed results.Comment: Submitted to Applied Physics B: Lasers and Optics, 9 pages, 10
figure
A new Manifestation of Atomic Parity Violation in Cesium: a Chiral Optical Gain induced by linearly polarized 6S-7S Excitation
We have detected, by using stimulated emission, an Atomic Parity Violation
(APV) in the form of a chiral optical gain of a cesium vapor on the 7S -
6P transition,consecutive to linearly polarized 6S-7S excitation. We
demonstrate the validity of this detection method of APV, by presenting a 9%
accurate measurement of expected sign and magnitude. We underline several
advantages of this entirely new approach in which the cylindrical symmetry of
the set-up can be fully exploited. Future measurements at the percent level
will provide an important cross-check of an existing more precise result
obtained by a different method.Comment: 4 pages, 2 figure
Giant modification of atomic transitions probabilities induced by magnetic field: forbidden transitions become predominant
Magnetic field-induced giant modification of probabilities for seven
components of 6S1/2 (Fg=3) - 6P3/2 (Fe=5) transition of Cs D2 line forbidden by
selection rules is observed experimentally for the first time. For the case of
excitation with circularly-polarized laser radiation, the probability of
Fg=3,mF=-3 - Fe=5,mF=-2 transition becomes the largest among 25 transitions of
Fg=3 - Fe=2,3,4,5 group in a wide range of magnetic field 200 - 3200 G.
Moreover, the modification is the largest among D2 lines of alkali metals. A
half-wave-thick cell (length along the beam propagation axis L=426 nm) filled
with Cs has been used in order to achieve sub-Doppler resolution which allows
for separating the large number of atomic transitions that appear in the
absorption spectrum when an external magnetic field is applied. For B > 3 kG
the group of seven transitions Fg=3 - Fe=5 is completely resolved and is
located at the high frequency wing of Fg=3 - Fe=2,3,4 transitions. The applied
theoretical model very well describes the experimental curves.Comment: 7 pages, 8 figure
Saturation effects in the sub-Doppler spectroscopy of Cesium vapor confined in an Extremely Thin Cell
Saturation effects affecting absorption and fluorescence spectra of an atomic
vapor confined in an Extremely Thin Cell (cell thickness ) are
investigated experimentally and theoretically. The study is performed on the
line ( of and concentrates on the two
situations and , the most contrasted ones with
respect to the length dependence of the coherent Dicke narrowing. For , the Dicke-narrowed absorption profile simply broadens and
saturates in amplitude when increasing the light intensity, while for , sub-Doppler dips of reduced absorption at line-center appear on the
broad absorption profile. For a fluorescence detection at ,
saturation induces narrow dips, but only for hyperfine components undergoing a
population loss through optical pumping. These experimental results are
interpreted with the help of the various existing models, and are compared with
numerical calculations based upon a two-level modelling that considers both a
closed and an open system.Comment: 11 pages, 12 figure
- …