arXiv subjects

M. Lintz

Publications and source records attributed to M. Lintz.

5 recordsLinked to original sources

arXiv2005

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. Guéna 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.

physics.atom-ph↗

arXiv2004

Proposal for high-precision Atomic Parity Violation measurements using amplification of the asymmetry by stimulated emission in a transverse E and B field pump-probe experiment

Amplification by stimulated emission of radiation provides an intriguing means for increasing the sensitivity of Atomic Parity Violation (APV) measurements in a pump-probe configuration well adapted to the 6S-7S cesium transition. It takes advantage of the large number of atoms excited along the path of the pump beam. In the longitudinal E-field configuration currently exploited in an ongoing APV measurement, this number is limited only by the total voltage sustainable by the Cs vapor. In order to overcome this limit, we consider, both theoretically and experimentally, the possibility of performing the measurements in a transverse E-field configuration requiring a much lower voltage. We discuss the necessarily different nature of the observable and the magnetoelectric optical effects entering into play. They condition modifications of the experimental configuration with, in particular, the application of a transverse magnetic field. We suggest the possibility of rotating the transverse direction of the fields so as to suppress systematic effects. With a long interaction length, a precision reaching 0.1 percent in a quantum noise limited measurement can be expected, now limited only by the necessity of operating below the threshold of spontaneous superradiant emission of the excited medium. If we approached this limit, however, we could greatly amplify the asymmetry using triggered superradiance.

physics.atom-ph↗

arXiv2003

Cylindrical Symmetry Discrimination of Magnetoelectric Optical Systematic Effects in a Pump-probe Atomic Parity Violation Experiment

A pump-probe atomic parity violation (APV) experiment performed in a longitudinal electric field, provides a signal breaking mirror symmetry while preserving the cylindrical symmetry of the set-up. The excited vapor acts on the probe beam as a linear dichroic amplifier, imprinting a very specific signature on the detected signal. Our differential polarimeter is oriented to yield a null result unless the excited atoms are endowed with a chirality of some kind. Ideally, only the APV (E-odd) and the calibration (E-even) signals contribute to a chiral atomic response, a situation highly favourable to the detection of a tiny effect. In the present work we give a thorough analysis of possible unwanted defects like stray transverse fields or misalignments which would spoil the ideal set-up and lead to chiral systematics. A possible way to suppress such effects is to perform global rotations of the experiment by incremental steps of 45 degrees, leaving both stray fields and misalignments unaltered. The conspiration of at least two defects is necessary to affect the E-odd polarimeter signal. The transverse nature of the defects manifests itself by an azimuthal cosine square modulation. The harmful systematics are those which survive the averaging over four successive configurations. They require the presence of a stray transverse electric field, which can be determined and eventually minimized by auxiliary measurements of the systematic effects, amplified by applying a known external magnetic field. Transverse stray magnetic fields must be compensated by a similar procedure. We also propose statistical correlation tests as diagnoses of the aforementioned systematic effects.

physics.atom-ph↗

arXiv2003

Prospects for Forbidden-Transition Spectroscopy and Parity Violation Measurements using a Beam of Cold Stable or Radioactive Atoms

Laser cooling and trapping offers the possibility of confining a sample of radioactive atoms in free space. Here, we address the question of how best to take advantage of cold atom properties to perform the observation of as highly forbidden a line as the 6S-7S Cs transition for achieving, in the longer term, Atomic Parity Violation measurements in radioactive alkali isotopes. Another point at issue is whether one might do better with stable, cold atoms than with thermal atoms. To compensate for the large drawback of the small number of atoms available in a trap, one must take advantage of their low velocity. To lengthen the time of interaction with the excitation laser, we suggest choosing a geometry where the laser beam exciting the transition is colinear to a slow, cold atomic beam, either extracted from a trap or prepared by Zeeman slowing. We also suggest a new observable physical quantity manifesting APV, which presents several advantages:specificity, efficiency of detection, possibility of direct calibration by a parity conserving quantity of a similar nature. It is well adapted to a configuration where the cold atomic beam passes through two regions of transverse, crossed electric fields, leading both to differential measurements and to strong reduction of the contributions from the M_1-Stark interference signals, potential sources of systematics in APV measurements. Our evaluation of signal to noise ratios shows that with available techniques, measurements of transition amplitudes, important as required tests of Atomic Theory should be possible in cesium 133 with a statistical precision of 1/1000 and probably also in Fr isotopes for production rates of 10^6 Fr atoms/s.

physics.atom-ph↗

arXiv2002

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$_{3/2}$ 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.

physics.atom-ph↗