Transition In Cesium Research Articles

Calculations of the parity non-conserving 6s ? 7s transition in caesium

The electroweak interaction between electrons and nucleons destroys the mirror symmetry of an atom. The size of the effect depends on the weak interaction constants as well as on the atomic structure. Small-scale experiments studying atomic parity non-conservation can thus give a quantitative test of the standard model for the electro-weak interaction — provided the atomic structure is sufficiently well understood. The increasing experimental accuracy, in particular for Cs, raises new demands on atomic theory. The various contributions to the parity non-conserving electric dipole transition matrix element are discussed together with the methods used to calculate them. The uncertainty in the atomic calculation is estimated. A discussion of radiative corrections with emphasis on the role of the top quark mass is also given.

A semi-empirical ratio method for the calculation of parity non-conservation in caesium

The semi-empirical method proposed by Bouchiat et al (1986) for the calculation of the parity non-conserving E1 transition matrix element for the 6s1/2 to 7s1/2 transition in caesium is re-examined in terms of many body perturbation theory. A slightly modified formulation is derived and this is used to provide an improved value for the E1 amplitude. The value is E1PNC=0.904 (1+or-0.02)*10-11 (-iea0QW/N).

Cesium–photoionization laser with anti-Stokes Raman scheme

Laser oscillation has been observed at five ionic transitions in cesium, involving Stokes and anti-Stokes Raman schemes. The laser process starts from the metastable 5p56s levels in the cesium ion. These levels are populated by inner-shell photoionization of cesium atoms, using soft x rays of a laser-produced plasma. When suitable pump radiation is used, the metastable population is transferred into the 5p56p levels, resulting in laser radiation to 5p55d states with wavelengths in the range of 665–800 nm.

Correlation effects in the parity-nonconserving 6s-->7s transition in cesium.

The amplitude of the parity-nonconserving (PNC) electric-dipole transition 6s\ensuremath{\rightarrow}7s in cesium is calculated to third order in many-body perturbation theory. Inclusion of the corresponding corrections in calculations of parity-conserving transition amplitudes and atomic hyperfine constants leads to agreement with experiment at a level under 5%. We obtain a value of 0.951${\mathrm{iea}}_{0}$\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$${Q}_{W}$/-N with an estimated error of 5% for the PNC amplitude. A determination of the Weinberg angle is made by combining the present calculation with recent measurements of the PNC amplitude: the result is ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$=0.229 ${(24)}_{\mathrm{expt}}$ ${(16)}_{\mathrm{theor}}$. Issues involved in improving the accuracy of the calculations of atomic properties of cesium are discussed.

Influence of the Dirac-Hartree-Fock starting potential on the parity-nonconserving electric-dipole-transition amplitudes in cesium and thallium.

The parity-nonconserving electric-dipole-transition amplitudes for the 6${s}_{1/2}$\ensuremath{\rightarrow}7${s}_{1/2}$ transition in cesium and the 6${p}_{1/2}$\ensuremath{\rightarrow}7${p}_{1/2}$ transition in thallium have been calculated by the Dirac-Hartree-Fock method. The effects of using different Dirac-Hartree-Fock atomic core potentials are examined and the transition amplitudes for both the length and velocity gauges are given. It is found that the parity-nonconserving transition amplitudes exhibit a greater dependence on the starting potential for thallium than for cesium.

Improved determination of the scalar stark polarizability α for the 6s → 7s transition in cesium

Abstract Calculations of the scalar Stark polarizability α(6s, 7s) for the 6s → 7s transition in cesium are reported. These calculations lead to a value Δα (6 s , 7 s )=-3.4±0.8 a 3 0 , for the contributions from states other than 6p or 7p. Combining this value with experimental measurements leads to an improved semi-empirical value α(6s, 7s) = -269.2±2.8 a 3 0 .

Noble-gas broadening of the fine-structure transition in caesium (7P [formula omitted] - 7P [formula omitted]) using tri-level echoes

We report tri-level echo measurements of collision cross-sections and broadening constants for the electric-dipole-forbidden fine-structure transition in caesium (7p 1 2 - 7P 3 2 ) perturbed by low pressures (< 1 torr) of He, Ne, A, Kr, Xe. The hyperfine structures of the levels were not resolved. A brief description of the tri-level echo mechanism is given.

Atomic parity violation measurements in the highly forbidden 6S1/2-7S 1/2 caesium transition. II. Analysis and control of systematic effects

The parity-violating signal is discriminated by its specific behaviour when the handedness of the experiment is reversed. Yet conspiracy of experimental imperfections can generate false parity signals. We establish a model of systematic effects, whose parameters are the imperfections in the handedness reversals realized experimentally. We describe how their actual values are measured and minimized, mostly by continuous control of atomic signals during data acquisition. This allows estimation and reduction of possible systematic effects. These remain finally at or below a few percent of the PV effect. We estimate possible limitations in the real-time controls, or in the model itself (e.g. due to spatial correlations in the imperfections). These limitations, together with statistical uncertainties in the controls, will be included in the final systematic uncertainty (Part III) En vue d'etudier le signal de violation de parite par son comportement specifique dans une inversion de chiralite de l'experience, etablissement d'un modele d'effets systematiques dont les parametres sont les imperfections dans les renversements de chiralite. Description de la mesure de leurs valeurs reelles et de leur minimisation pour la plupart, au moyen de controles continus de signaux atomiques pendant l'acquisition des donnees

Atomic parity violation measurements in the highly forbidden 6S 1/2 - 7S1/2 caesium transition. - III. Data acquisition and processing. Results and implications

This paper completes the detailed presentation of our PV experiment on the 6S 1/2 -7S 1/2 transition in Cs. A detailed description of the data acquisition and processing is given. The results of two independent measurements made on ΔF=0 and ΔF=1 hfs components agree, providing an important cross-check. After a complete reanalysis of systematics and calibration, the precision is slightly improved, leading to the weighted average ImE pv 1 /β=−1.52±0.18 mV/cm. Later results from an independent group agree quite well. With the semi-empirical value β=(26.8±0.8) a 3 0 , our result yields E 1 pv =(−0.79±0.10)×10 −11 i|e|a 0 . Coupled with the atomic calculations, this implies that the weak nuclear charge of Cs is Q w =−68±9. This value agrees with the standard electroweak theory and leads to a weak interaction angle sin 2 θ w =0.21±0.04. The complementarity of these measurements with high energy experiments is illustrated Description detaillee de l'acquisition et du traitement des donnees. Test sur deux mesures independantes realisees sur deux composantes hyperfines ΔF=0 et ΔF=1. Nouvelle analyse complete des systematiques et de l'etalonnage. Deduction de la charge nucleaire «faible» de Cs et de l'auger d'interaction faible

Sound-wave velocities in liquid alkali metals studied at temperatures up to 150 degreesC and pressures up to 0.7 GPa.

We have measured compressional sound-wave velocities in liquid sodium, potassium, rubidium, and cesium at pressures up to 0.7 GPa and temperatures up to 150 \ifmmode^\circ\else\textdegree\fi{}C, by ultrasonic pulse transmission. The alkali metals are among the simplest of liquids and accurate data on the sound speeds allow the calculation of thermodynamic properties which may be used in the development of the theory of the liquid state. Most previous data are from P-V-T measurements, which are inherently less accurate than ultrasonic measurements.Comparison of the present data with previous room-pressure ultrasonic data shows very good agreement. The present data may also be compared, through calculation of equation-of-state parameters and compressions, with previous piezometric data, some of which extend to pressures higher than those reached in the present experiments. Again the agreement is quite good. The present data show the expected decrease in sound velocity with increasing temperature at all temperatures, with some suggestion that the temperature coefficient may decrease at higher pressures. The calculated values of the bulk modulus (either adiabatic or isothermal) at zero pressure decrease with increasing temperature, and decrease going from sodium to cesium, as expected.The pressure derivative of the bulk modulus at zero pressure (${K}_{0}^{\mathcal{'}}$) is close to 4 in all cases, and the isothermal value is greater than the adiabatic value, though not by much. More accurate data will be needed to determine whether ${K}_{0}^{\mathcal{'}}$ increases or decreases with increasing temperature. The values for the second pressure derivative of the bulk modulus (${K}_{0}^{2\mathrm{sprime}}$) are not well determined; only the data for the highest-pressure runs give any meaningful results. It appears that ${K}_{0}^{2\mathrm{sprime}}$ is negative and has a value around -0.01 to -0.03 ${\mathrm{GPa}}^{\mathrm{\ensuremath{-}}1}$.The value of ${K}_{0}^{2\mathrm{sprime}}$ for the highest-temperature run on cesium is the highest measured, at -0.044 ${\mathrm{GPa}}^{\mathrm{\ensuremath{-}}1}$. This value may indicate the onset of the electronic transition in cesium in the liquid state at pressures well below the transition pressure in the solid. Such a large negative value of ${K}_{0}^{2\mathrm{sprime}}$ will produce a marked curvature in the velocity-pressure curve at higher pressures, and possibly a reversal in the pressure derivative of the sound velocity.

Hartree-Fock-calculation of parity-violation in cesium

We present a relativistic Hartree-Fock calculation of the parity violatingE1-matrixelement of the 6s↔7s transition in cesium. Our resultE1= −8.4·10−12iea0 for sin2θw = 0.22 is in good agreement with the experimental value. We also give a general discussion of the consequences of a violation of discrete symmetries for the solutions of the Dirac equation.

Experimental equations of state for cesium and lithium metals to 20 kbar and the high-pressure behavior of the alkali metals.

Experimental equation-of-state results to 20 kbar and from 4 K to room temperature are given for cesium and lithium metals which are comparable with those published previously for sodium, potassium, and rubidium [Phys. Rev. B 28, 5395 (1983)]. The same generalization holds that the isothermal bulk modulus is a function of the volume only. Cesium and lithium each are slightly more compressible in a reduced sense than the other three alkali metals, and have Gr\uneisen parameters (1.14 and 0.878, respectively) which are smaller than the common value for the others, 1.25. Extrapolations of the present results for the alkali metals are compared with other data to 100 kbar, with these earlier results scattering about the extrapolation. It is suggested that the bcc-to-fcc transitions in potassium, rubidium, and cesium occur at common values of the ratio of the nearest-neighbor distance to the ionic or pseudopotential radius. No systematic trends are observed in these equation-of-state results which can be associated with an increase in s-d mixing effects with increasing ionic mass.

Atomic parity violation measurements in the highly forbidden 6S 1/2-7S1/2 caesium transition. - I. Theoretical analysis, procedure and apparatus

This paper is the first part of a detailed presentation of parity violation measurements performed in two hfs components of the highly forbidden 6S-7S transition of the Cs atom. Under excitation by a circularly polarized laser in a dc electric field, interference takes place between an electromagnetic amplitude induced by the field and the parity-violating amplitude induced by weak interactions. This interference gives rise in the electronic polarization of the 7S state to a contribution which behaves like a vector when the handedness of the experiment is reversed. In principle, only this contribution is observed in the chosen direction of observation. Detection proceeds through the circular polarization ratio of the 7S-6P 1/2 fluorescence. By Hanle effect in a magnetic field applied periodically, the parity-conserving contribution is observed in the same way and used to calibrate the experiment. The final result is the ratio Im E i pv /β of the parity-violating amplitude to the vector polarizability. Our value is (−1.56±0.17 (stat.)±0.12 (syst.)) mV/cm. In what follows, we give the formulae for all available atomic signals and describe the apparatus and procedures Lors de l'excitation par un faisceau laser polarise circulairement dans un champ electrique statique, l'interference entre une amplitude electromagnetique induite par le champ et l'amplitude induite par l'interaction faible engendre, dans la polarisation electronique de l'etat 7S, une contribution qui se comporte comme un vecteur polaire lorsqu'on inverse la chiralite de l'experience et que l'on observe par l'intermediaire du taux de polarisation circulaire de la fluorescence 7S-6P

Theoretical study of the correlation and relativistic effects in the shakeup in the photoelectron spectrum of cesium

Quasidegeneracy effects in the transitions in cesium are considered by relativistic and nonrelativistic CI calculations, and the interplay between correlation and relativistic effects is discussed. Dynamical correlation effects in the core shakeup are treated by nonrelativistic MCSCF calculations. Good agreement with experimental data is obtained and a revision of some features is suggested.

Collision cross sections for the noble-gas broadening of the Cs 6S-7P doublet using photon echoes

Collisional cross sections and broadening constants are presented for each of the fine-structure components of the second resonance transition in caesium (6S12/-7P32,1/2/, 4555 AA, 4593 AA) perturbed by the five noble gases He-Xe. The results were obtained at perturber pressures of less than 0.5 Torr using the photon echo technique. The cross sections correspond closely with those obtained from spectral line profile measurements, but there are some significant discrepancies.

Hanle effect detection of the [formula omitted] single-photon transition of cesium, without electric field

Although the oscillator strength of the 6S 1 2 −7S 1 2 transition is only 4.0×10 -15, by the Hanle effect in a zero electric field this transition gives rise to a very specific signal well above noise and background. From the hfs profile, we can test the magnetic dipole nature of the transition and obtain direct evidence for its perturbation by hyperfine mixing between the two S states. Our new values of M hf 1/ M 1 and M 1 and M 1/β agree with previous results, and the accuracy of M hf 1/ M 1 is improved.

Relativistic many-body calculation of parity-violating E1-amplitude for the 6S → 7S transition in atomic cesium

The parity violating E1-amplitude for the 6S–7S transition in cesium has been calculated from first principles: 〈7S|D z|6S〉 = (0.88 ± 0.03) × 10 −11 ( −Q W N )(−iea B) , where Q W is the weak nuclear charge, N is the number of neutrons, and a B is The Bohr radius. The experimental data from Bouchiat et al. make it possible to find Q W = −73.4 ± 8.1 ± 6 and the Weinberg angle sin 2 θ W = 0.237 ± 0.036 ± 0.03. To control the accuracy, the energy levels, the fine and hyperfine structure intervals and the oscillator strenghts in the S-P transitions in Cs have been calculated.

Photon echo relaxation in caesium perturbed by noble gases

The collisional relaxation of photon echoes generated on the 6S built1 2 - 7P built3 2 (455 nm) transition in caesium has been observed and measured as a function of perturber pressure. Values for the collision cross-sections have been obtained using helium, neon, argon and krypton as perturbers. There is good agreement between these results and those obtained from high resolution measurements of pressure-broadened line profiles. The echoes were observed using the polarization rotation technique and all the measurements were made at perturber pressures below 0.5 torr.

Generation of tunable picosecond pulses in the vibrational infrared by stimulated electronic Raman scattering of rhodamine-dye-laser pulses from the 6s–5d cesium transition

The first reported use of a rhodamine-dye laser to generate tunable high-power picosecond pulses in the vibrational infrared is described. By using stimulated electronic Raman scattering from the 6s-5d transition in a superheated cesium vapor, we have shifted I-psec pulses from an amplified rhodamine-dye laser (568-590nm) to 3040-2320 cm(-1) (3.3-4.3 microm). Somewhat longer pulses have been shifted to 1950 cm(-1) (5.1 microm). Peak infrared energies of 11 microJ, representing a quantum efficiency of 4.6%, were obtained at a 10-Hz repetition rate. Tuning to longer wavelengths with short pulses is limited by nonlinear processes but should be possible by further reductions of cesium dimer effects.

X-Ray Diffraction Study of Electronic Transitions in Cesium Under High Pressure.

The crystal structure of the high-pressure phase of cesium (IV) was determined to be a tetragonal lattice with $Z=4$. The space group is ${{D}_{4h}}^{19}\ensuremath{-}\frac{I{4}_{1}}{\mathrm{amd}}$ and the lattice parameters are $a=3.349$ \AA{} and $c=12.487$ \AA{} at 8.0 GPa. From the structure it is deduced that the atomic radius of cesium decreases dramatically at the III-IV transition, which suggests a discontinuous $s\ensuremath{-}d$ electronic transition.