States Of Cesium Research Articles

Empirical Determination of the Bohr-Weisskopf Effect in Cesium and Improved Tests of Precision Atomic Theory in Searches for New Physics.

The finite distribution of the nuclear magnetic moment across the nucleus gives a contribution to the hyperfine structure known as the Bohr-Weisskopf (BW) effect. We have obtained an empirical value of -0.24(18)% for this effect in the ground and excited s states of atomic ^{133}Cs. This value is found from historical muonic-atom measurements in combination with our muonic-atom and atomic many-body calculations. The effect differs by 0.5% in the hyperfine structure from the value found using the uniform magnetization distribution, which has been commonly employed in the precision heavy-atom community over the last several decades. We also deduce accurate values for the BW effect in other isotopes and states of cesium. These results enable cesium atomic wave functions to be tested in the nuclear region at an unprecedented 0.2% level, and are needed for the development of precision atomic many-body methods. This is important for increasing the discovery potential of precision atomic searches for new physics, in particular for atomic parity violation in cesium.

Measurement of the hyperfine coupling constants and absolute energies of the 8p P1/22 and 8p P3/22 levels in atomic cesium

We report measurements of the hyperfine coupling constant for the $8p \ ^2P_{1/2}$ level of atomic cesium, $^{133}$Cs, with a relative uncertainty of $\sim$0.019\%. Our result is $A = 42.933 \: (8)$ MHz, in good agreement with recent theoretical results. We also examine the hyperfine structure of the $8p \ ^2P_{3/2}$ state, and derive new values for the state energies of the $8p \ ^2P_{1/2}$ and $8p \ ^2P_{3/2}$ states of cesium.

Measurement of the hyperfine coupling constants and absolute energies of the 12s 2S1/2, 13s 2S1/2 , and 11d 2DJ levels in atomic cesium

We report measurements of the absolute energies of the hyperfine components of the $12s{\phantom{\rule{0.16em}{0ex}}}^{2}{S}_{1/2}$ and $13s{\phantom{\rule{0.16em}{0ex}}}^{2}{S}_{1/2}$ levels of atomic cesium, $^{133}\mathrm{Cs}$. Using the frequency difference between these components, we determine the hyperfine coupling constants for these states, and report these values with a relative uncertainty of $\ensuremath{\sim}0.06$%. We also examine the hyperfine structure of the $11d{\phantom{\rule{0.16em}{0ex}}}^{2}{D}_{J}$ ($J=3/2,5/2$) states, and resolve the sign ambiguity of the hyperfine coupling constants from previous measurements of these states. We also derive new, high precision values for the state energies of the $12s{\phantom{\rule{0.16em}{0ex}}}^{2}{S}_{1/2}, 13s{\phantom{\rule{0.16em}{0ex}}}^{2}{S}_{1/2}$, and $11d{\phantom{\rule{0.16em}{0ex}}}^{2}{D}_{J}$ states of cesium.

Large-Scale Bose-Einstein Condensation in an Atomic Gas by Applying an Electric Field

Large-scale Bose-Einstein condensation (BEC) of cesium atoms has been observed (T=343K). The technical bottleneck of BEC is very small trapping volume (10-8cm3), which made the number of condensed atoms still stagnant (less than 107), much smaller than normal condensation (more than 1013), large-scale BEC has never been observed. In BEC experiment, scientists have applied magnetic field (used to trap atoms) and laser (used to cool atoms), but never considered applying electric field, because they think that all kinds of atoms are non-polar atoms. The breakthrough of the bottleneck lies in the application of electric field. In theory, despite 6s and 6p states of cesium are not degenerate, but Cs may be polar atom doesn't conflict with quantum mechanics because it is hydrogen-like atom. When an electric field was applied, Cs atoms become dipoles, therefore large-scale BEC can be observed. BEC experiment of cesium has been redone. From the entropy S=0, critical voltage Vc=78V. When V 0; when V > Vc, S Vc, almost all Cs atoms (bosons) are in exactly the same state，according to Feynman, “the quantum physics is the same thing as the classical physics”, so our classical theory can explain BEC experiment satisfactorily. Ultra-low temperature is to make Bose gas phase transition, we used critical voltage to achieve phase transition, ultra-low temperature is no longer necessary. Five innovative formulas were first reported in the history of physics, the publication of this article marking mankind will enter a new era of polar atoms.

Time-resolved fine structure mixing of cesium induced by helium and argon

The rates for fine structure mixing and quenching of the moderately excited and states of cesium under collision with argon and the more impulsive helium have been measured, using two-photon pulsed excitation and time-resolved fluorescence techniques. The pressure dependence of the eigenvalues of the rate matrix yields very rapid rate coefficients of for He and for Ar, about two–three times faster than for the Cs relaxation. The quenching rates are also rapid, and for He and Ar respectively. The rapid fine structure rates are explained by the highly impulsive nature of the collisions, and the large average distance of the valence electron from the nucleus. Quenching rates (intra-multiplet transfer) are likely enhanced by the closely spaced, levels. The observed rates are compared with the predictions from time-dependent perturbation theory.

Cascade coherence transfer and magneto-optical resonances at 455 nm excitation of cesium

We present an experimental and theoretical study of nonlinear magneto-optical resonances observed in the fluorescence to the ground state from the 7 P 3/2 state of cesium, which was populated directly by laser radiation at 455 nm, and from the 6 P 1/2 and 6 P 3/2 states, which were populated via cascade transitions that started from the 7 P 3/2 state and passed through various intermediate states. The laser-induced fluorescence (LIF) was observed as the magnetic field was scanned through zero. Signals were recorded for the two orthogonal, linearly polarized components of the LIF. We compared the measured signals with the results of calculations from a model that was based on the optical Bloch equations and averaged over the Doppler profile. The calculations agree quite well with the measurements, especially when taking into account the fact that some experimental parameters were only estimated in the model.

Blue and infrared stimulated emission from alkali vapors pumped through two-photon absorption

The 5 2D3/2, 5 2D5/2, and 7 2S1/2 states of rubidium and the 7 2D3/2, 7 2D5/2, and 9 2S1/2 states of cesium were populated at low pressure by two photon excitation using a pulsed dye laser. Blue beams from the Rb 6 2P3/2, 1/2–5 2S1/2 and Cs 7 2P3/2, 1/2–6 2S1/2 transitions were observed. In addition, infrared beams were observed arising directly from the pumped 2D states, establishing a collisionless cascade mechanism. Threshold is modest at about 0.3 mJ/pulse or 2×105 W/cm2. Slope efficiencies increase dramatically with alkali concentration and peak at 0.4%, with considerable opportunity for improvement. This versatile system might find applications in both underwater communications and for infrared counter measures.

Correlation potential and ladder diagrams

The all-order correlation potential method of accurate atomic structure calculations for atoms with one external electron is extended to include one more class of correlation diagrams to all orders. These are the so-called ladder diagrams, which describe residual Coulomb interaction between an external electron and atomic core. This is in addition to the screening of Coulomb interaction by core electrons and the hole-particle interaction in the core polarization operator, which are also included in all orders. Calculations of the energies of the lowest $s$, $p$, and $d$ states of cesium and thallium show that inclusion of the ladder diagrams leads to significant improvement of the accuracy of the calculations. The discrepancy between theoretical and experimental energies is reduced to a small fraction of 1% in all cases. This widens the range of atoms and atomic states for which the correlation potential method can produce very accurate results.

Measurement of atomic lifetimes with a mode-locked laser.

We present a new technique for measuring atomic lifetimes with a mode-locked laser. A single laser pulse excites the atoms and a subsequent frequency-doubled pulse ionizes the excited-state atoms. The ions are collected and counted. The measurement is repeated using excitation and detection pulses with different time separations, which determines the excited-state decay rate. We demonstrated this technique for the 6P(3/2) state of cesium. The measured lifetime was 30.5 ns and had a statistical uncertainty of 0.1 ns. Systematic effects limited the overall experimental uncertainty to approximately 0.6 ns in this initial experiment.

Describing the observed vertical transport of radiocesium in specific soils with three time-dependent models

In this paper three transport models are applied to describe the vertical migration process of 137 Cs in undisturbed soil. The same experimental data set is used for the calibration of each model. These data were obtained from areas in northeast Italy, where the 137 Cs deposition following the Chernobyl accident ranged from 20 to 40 kBq m −2. A diffusion model (called DSF) is presented, which takes into account three states of cesium in the soil matrix: mobile, sorbed and bound. It is shown that this model provides a reasonably good description of the temporal evolution of the radiocesium profile in soil. In addition, a new version of the RABES model (called RABES I) is proposed, with only two free parameters: the rate of change of the vertical profile and the diffusion length in the equilibrium. This paper includes a critical evaluation among the DSF, RABES and RABES I models, considering, mainly, their predictive aspect about the temporal change of the radiocesium profile in soil.

Precision measurement of parity nonconservation in cesium

The measurement of parity nonconservation (PNC) in atomic cesium is discussed in detail. With a spin-polarized atomic beam, this experiment achieves a fractional uncertainty of 0.35% in the measurement of the PNC amplitude for the transition between the 6S and 7S states of cesium, the lowest uncertainty of atomic PNC to date. By comparing the PNC amplitude on two hyperfine transitions, we measure for the first time the nuclear-spin-dependent contribution that arises from the nuclear anapole moment. A major portion of this paper describes the characterization and elimination of systematic errors.PACS Nos.: 32.80.Ys, 11.30.Er, 12.15.Ji, 32.10.Dk

Solid-State NMR Investigation of Promoted Silver Catalysts

The effects of cesium promoters on silver catalysts, supported by γ-alumina, were studied by adsorbing mono- or dilabeled [13C]ethylene onto the catalysts and performing low-temperature (70 K) solid-state13C NMR measurements on the ethylene. Selective isotopic enrichment was used to investigate the electronic environment present in and around the ethylene molecule as a function of promoter concentration. Changes in the spectroscopic parameters describing the ethylene lineshapes were extracted using a nonlinear least-squares procedure. These parameters were then used to determine the structure of the ethylene molecule on the surface and to probe the changes induced by adding cesium promoters. Similarly, the state of cesium in the catalyst system was investigated by spin-echo double-resonance spectroscopy and scanning electron microscopy X-ray fluorescence methods. The results imply that the form of cesium is not that of an oxide but, in all probability, reflect those of a cation–anion pair.

Measurement of the photoionization cross section of the6P3/2state of cesium

We report the measurement of the absolute photoionization cross section for the ${6P}_{3/2}$ state of cesium. Cross sections were determined by measuring the photoionization rate of cesium atoms confined in a magneto-optical trap. The photoionization rate was measured by monitoring the decay of trap fluorescence during exposure to ionizing laser radiation. The measurements were made in the wavelength range 457.9 to 501.7 nm using several lines from an Ar-ion laser. Our results are compared to other experimental measurements as well as to existing theories.

Circular-dichroism effects on photoelectron angular distributions for the 7P and 8P states of cesium.

Circular dichroism in the photoelectron angular distribution (CDAD) of the 7${\mathit{P}}_{\mathit{J}}$ and 8${\mathit{P}}_{\mathit{J}}$ states of cesium have been measured using plane-polarized light to excite and align the atoms and alternately right- and left-circularly polarized light to ionize them. The experiments are compared with the results of theory, calculated using the Hartree-Fock wave functions with many electron correlations included in the random-phase approximation with exchange. A comparison of theory and experiment allows information on the alignment of the resonant state to be extracted from the experimental data. No CDAD effect is observed for the ${\mathit{nP}}_{1/2}$ states that cannot be aligned, whereas CDAD is observed for the 7${\mathit{P}}_{3/2}$ and 8${\mathit{P}}_{3/2}$ states. The CDAD signal is significantly larger for the 8${\mathit{P}}_{3/2}$ state than for the 7${\mathit{P}}_{3/2}$ state, indicating a greater retention of the optical alignment of the 8${\mathit{P}}_{3/2}$ state within the time sampled by the ionizing laser pulse. The differences in the retention of alignment for the two states are attributed to effects of hyperfine depolarization, caused by coupling of the electronic angular momentum to the nuclear spin. \textcopyright{} 1996 The American Physical Society.

Excitation of vacuum UV transitions of alkali-metal atoms by charge-exchange reactions

We investigate the vacuum UV radiation spectra of atoms and ions of Rb, Cs, He, Ne, and Ar in a discharge plasma of their mixtures at different concentration of metal vapors in rare gases. The reactions leading to population and deactivation of resonant states of rare-gas atoms were studied. The observation of lines 109.1, 119.6, and 124.7 nm, corresponding to the radiation transitions from the 5p55d6s4P5/2 quasi-metastable autoionizing level of cesium, allowed us to estimate experimentally the cross section σ=(9±3) · 10−15 cm2 of the charge-exchange reaction of the metastable cesium ion on the cesium atom, giving as a result the above-mentioned quasi-metastable state of cesium.

Polarizabilities of cesium S, P, D, and F states

The scalar and tensor polarizabilities of over sixty S, P, D, and F states of cesium are evaluated using a Coulomb approximation. The expected scaling of polarizabilities as n ∗7, where n ∗ is the effective principal quantum number, was found to hold well for the higher excited states. The computed results agree closely with experimental measurements which are reviewed.

Raman study of pressure-induced structural transitions in CsIO 4 to 12 GPa

High pressure Raman scattering studies have been carried out on cesium periodate (CsIO 4) using the diamond anvil cell. Three pressure-induced phase transitions occur in the range 0.1–12 GPa as indicated by abrupt changes in the Raman spectra, and pressure dependence of the phonon frequencies. The transitions are observed at 1.5, 4.5 and 6.2 GPa in the increasing pressure cycle. A large hysteresis is noticed for the reverse transition when releasing the pressure. The high pressure phase is nearly quenchable to ambient pressure. The nature of the pressure-induced transitions are discussed in terms of the sequence of pressure-induced transitions expected for scheelite-pseudoscheelite structure ABO 4 compounds from crystal chemical considerations. For the softening of the two high frequency internal modes, a pressure-induced electronic change involving the 5 d states of cesium and 5 p states of iodine is invoked.

Rydberg states of cesium in the flux from surfaces at high temperatures

Diffusion of cesium through an Ir foil at high temperature is used to give a flux of desorbing atoms and/or ions, which is not in equilibrium at the surface temperature. The desorbing flux is studied with electrostatic fields in a grid-collector combination, to determine the charge states and the interaction of the different states with an electric field and with a surface. At low Cs flux densities to the back of the foil, the desorbed flux contains positive ions and ordinary neutrals. At large flux densities from the source, however, both neutral Rydberg states and negative ions in the form of multiply-excited states of cesium are found in the flux. The negative ion states do not dissociate (detach) readily in such weak external electric fields where the neutral Rydberg state atoms ionize. Instead, they can emit two of their outer electrons in contact with the collector surface, thus giving positive collector currents when the field accelerates the electrons away from the collector. The large flux of such states indicates that the electron affinity is large for Rydberg state atoms. The origin of the excited states leaving the hot Ir surface is discussed. It appears to be related to the close coincidence of the desorbing ionic state and the Rydberg state at low work function.

Rydberg states of cesium in the flux from surfaces at high temperatures

Rydberg states of cesium in the flux from surfaces at high temperatures

Collisional ionisation of high-Rydberg atoms. Diffusive mechanism

The ionisation of highly excited Rydberg atoms in collisions with ground-state atoms is considered. The stationary diffusion-like mechanism of the ionisation is presented. The investigation is based on the Fokker-Planck equation. Analytical expressions for the probabilities of stationary diffusive ionisation are obtained and applied for the explanation of experimental results on the ionisation of highly excited Rydberg states of caesium in collisions with ground-state Cs atoms. It is concluded that the diffusive mechanism is the main mechanism for collisional ionisation of Rydberg atoms with n>or approximately=25-30.