Cesium Nuclei Research Articles

Determination of the Scalar and Vector Polarizabilities of the Cesium 6s^{2}S_{1/2}→7s^{2}S_{1/2} Transition and Implications for Atomic Parity Nonconservation.

Using recent high-precision measurements of electric dipole matrix elements of atomic cesium, we make an improved determination of the scalar (α) and vector (β) polarizabilities of the cesium 6s^{2}S_{1/2}→7s^{2}S_{1/2} transition calculated through a sum-over-states method. We report values of α=-268.82(30)a_{0}^{3} and β=27.139(42)a_{0}^{3} with the highest precision to date. We find a discrepancy between our value of β and the past preferred value, resulting in a significant shift in the value of the weak charge Q_{w} of the cesium nucleus. Future work to resolve the differences in the polarizability will be critical for interpretation of parity nonconservation measurements in cesium, which have implications for physics beyond the standard model.

A facility for production and laser cooling of cesium isotopes and isomers

We report on the design, installation, and test of an experimental facility for the production of ultra-cold atomic isotopes and isomers of cesium. The setup covers a broad span of mass numbers and nuclear isomers, allowing one to directly compare chains of isotopes and isotope/isomer pairs. Cesium nuclei are produced by fission or fusion-evaporation reactions using primary proton beams from a 130 MeV cyclotron impinging upon a suitable target. The species of interest is ejected from the target in ionic form, electrostatically accelerated, mass separated, and routed to a science chamber. Here, ions are neutralized by implantation in a thin foil, and extracted by thermal diffusion. A neutral vapor at room temperature is thus formed and trapped in a magneto-optical trap. Real-time fluorescence imaging and destructive absorption imaging provide information on the number of trapped atoms, their density, and their temperature. Tests with a dedicated beam of 133Cs+ ions at 30 KeV energy confirm neutralization, evaporation, and laser cooling to 150 μK, with an average atomic density of 1010 cm−3. Availability of cold and dense atomic samples of Cs isotopes and isomers opens new avenues for high-precision measurements of isotopic and isomeric shifts thereby gaining deeper insight into the nuclear structure, as well as for sensitive measurements of isotopes’ concentration ratios in trace quantities. The facility also constitutes the core for future experiments of many-body physics with nuclear isomers.

Large-scale shell-model calculations of elastic and inelastic scattering rates of lightest supersymmetric particles (LSP) onI127,Xe129,Xe131, andCs133nuclei

We discuss the dark-matter detection rates for the elastic and inelastic scattering of the lightest supersymmetric particle (LSP) off nuclei. For this we use an easily accessible formalism where the underlying nuclear physics is condensed in structure coefficients multiplying the key parameters of supersymmetric theories. In this work we compute these coefficients for the stable iodine, xenon, and cesium nuclei by application of the nuclear shell model in a model space involving the 2s, 1d, 0g 7/2 , and 0h 11/2 single-particle orbitals. As an interaction we use the renormalized Bonn-CD G matrix. By using fitted nuclear gyromagnetic factors we have successfully reproduced the relevant spectroscopic data on magnetic moments and M 1 decays in the discussed nuclei.

51V and 133Cs MAS NMR Investigation of Crystalline Trivanadate and Hexavanadate Phases.

AbstractA complete solid state NMR characterization of the vanadium oxides Cs[V3O8] and Cs2[V6O16].0.7H2O is proposed. We used 51V and 133Cs MAS NMR to investigate the local environment of cesium and vanadium nuclei and 2D 1H- 133Cs CP MAS HETCOR experiments to explore the connectivities between cesium ions and water molecules in the interlamellar space.

ATOMIC PARITY VIOLATION: PRINCIPLES, RECENT RESULTS, PRESENT MOTIVATIONS

We review the progress made in the determination of the weak charge, QW, of the cesium nucleus which raises the status of Atomic Parity Violation measurements to that of a precision electroweak test. Not only is it necessary to have a precision measurement of the electroweak asymmetry in the highly forbidden 6S–7S transition, but one also needs a precise calibration procedure. The 1999 precision measurement by the Boulder group implied a 2.5 σ deviation of QW from the theoretical prediction. This triggered many particle physicist suggestions as well as examination by atomic theoretical physicists of several sources of corrections. After about three years, the disagreement was removed without appealing to "New Physics". Concurrently, an original experimental approach was developed in our group for more than a decade. It is based on detection by stimulated emission with amplification of the left–right asymmetry. We present our decisive, recent progress together with our latest results. We emphasize the important impact for electroweak theory, of future measurements in cesium possibly pushed to the 0.1% level. Other possible approaches are currently explored in several atoms.

Nuclear magnetic resonance and transferred hyperfine interaction study of the crystallographically inequivalent Cs(I) and Cs(II) in a Cs 2CuCl 4 single crystal

133Cs (I=7/2) nuclear magnetic resonance in a Cs 2CuCl 4 single crystal grown by using the slow evaporation method was measured in its three mutually perpendicular crystal planes. The 133Cs resonances of two different groups with two crystallographically inequivalent cesium nuclei, Cs(I) and Cs(II), in the unit cell were recorded. The transferred hyperfine fields for Cs(I) and Cs(II) calculated from the paramagnetic shift and the molecular susceptibility measurements could be expressed by the linear equation H hf= AT+ B. The angular dependence of the 133Cs nuclear magnetic resonance spectra showed that the Cs(I) and the Cs(II) nuclei had different values for the quadrupole coupling constant. The electric field gradient tensors of Cs(I) and Cs(II) were symmetric, and the orientations of their principal axes did not coincide. The Cs(I) ion surrounded by 11 chlorine ions had a small quadrupole parameter, a smaller charge distribution, and a small value for the transferred hyperfine field. However, the Cs(II) ion surrounded by nine chlorine ions had a larger quadrupole parameter, a larger charge distribution, and a larger value for the transferred hyperfine field.

Single Crystal133Cs NMR Study of Cs+(15-Crown-5)2I-

Cesium-133 NMR spectra of a single crystal of tetragonal <TEX>$Cs^+ (15-crown-5)_2I^-$</TEX> were obtained as a function of crystal orientation in an applied magnetic field of 9.40T and analyzed to provide the magnitudes and orientations of the <TEX>$^{133}Cs$</TEX> chemical shift and quadrupolar tensors for two magnetically nonequivalent and symmetry related sites. Chemical shift tensor components and parameters of quadrupolar interactions are obtained as <TEX>${\delta}_{11}=46(1),\;{\delta}_{22}=60(1),\;{\delta}_{33}=-30(1)$</TEX> ppm, quadrupole coupling constant QCC = 581(1) kHz, and asymmetry parameter <TEX>${\eta}$</TEX> = 0.481(1), respectively. The nonaxially symmetric NMR parameters imply that the local environment of the cesium nuclei is nonaxially symmetric. The DANTE experiment burned holes in the <TEX>$^{133}Cs$</TEX> NMR line of the title compound. The hole burning of the single crystal and powder <TEX>$^{133}Cs$</TEX> NMR lines showed that the NMR lines are not homogeneously broadened.

Probing supersymmetry with parity-violating electron scattering

We compute the one-loop supersymmetric (SUSY) contributions to the weak charges of the electron ${(Q}_{W}^{e}),$ proton ${(Q}_{W}^{p}),$ and cesium nucleus ${(Q}_{W}^{\mathrm{Cs}})$ in the minimal supersymmetric standard model (MSSM). Such contributions can generate several percent corrections to the corresponding standard model values. The magnitudes of the SUSY loop corrections to ${Q}_{W}^{e}$ and ${Q}_{W}^{p}$ are correlated over nearly all of the MSSM parameter space and result in an increase in the magnitudes of these weak charges. In contrast, the effects on ${Q}_{W}^{\mathrm{Cs}}$ are considerably smaller and are equally likely to increase or decrease its magnitude. Allowing for R-parity violation can lead to opposite sign relative shifts in ${Q}_{W}^{e}$ and ${Q}_{W}^{p},$ normalized to the corresponding standard model values. A comparison of ${Q}_{W}^{p}$ and ${Q}_{W}^{e}$ measurements could help distinguish between different SUSY scenarios.

Observation of the nuclear magnetic octupole moment of 133Cs.

We describe our high-resolution measurements of the 133Cs 6p (2)P(3/2) state hyperfine structure. An optically narrowed diode laser excites perpendicularly a highly collimated atomic beam. The spectra are calibrated with a stable reference diode laser using a rf locking scheme allowing us to determine the splittings with an accuracy of < or =2 kHz, an order of magnitude better than previous results. The magnetic dipole a, electric quadrupole b, and magnetic octupole c hyperfine coupling constants are determined. The values we obtained are a=50.288 27(23) MHz, b=-0.4934(17) MHz, and c=0.56(7) kHz. This work represents the first observation of the magnetic octupole moment of the cesium nucleus. We carry out atomic-structure calculations and determine the nuclear electric quadrupole moment Q= -3.55(4) mb and nuclear magnetic octupole moment Omega=0.82(10) b x mu(N).

Nuclear Magnetic Resonance Study of the Crystallographically Inequivalent Cs(I) and Cs(II) in a Cs2CoCl4Single Crystal

133 Cs ( I =7/2) nuclear magnetic resonance in a Cs 2 CoCl 4 single crystal grown by using the slow evaporation method was measured in the two mutually perpendicular crystal planes. The 133 Cs resonances of two different groups, respectively, with two crystallographically inequivalent cesium nuclei, Cs(I) and Cs(II) in the unit cell, were recorded. From their angular dependences, the Cs(I) and the Cs(II) nuclei have different values for the quadrupole coupling constant and the asymmetry parameter. The quadrupole coupling constant and the asymmetry parameter obtained for Cs(I) with a smaller separation were e 2 q Q / h =725 kHz and η=0.58. Those for Cs(II) with a larger separation were e 2 q Q / h =802 kHz and η=0.85. The electric field gradient (EFG) tensors of Cs(I) and Cs(II) are asymmetric, and the orientations of their principal axes do not coincide. The Cs(I) ion surrounded by 11 chlorine ions has a small quadrupole parameter and is high in symmetry. The Cs(II) ion surrounded by 9 chlorine ions has a larger quadrupole parameter and is lower in symmetry than the Cs(I) ion. In addition, the spin–lattice relaxation time for 133 Cs was decreased with increasing temperature in the temperature range from 180 to 400 K. The relaxation behavior of Cs(I) and Cs(II) can be explained by the direct process of scattering from a single phonon.

The hyperfine interactions in CsF

The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of CsF to determine the nuclear quadrupole interaction of the cesium nucleus. A total of 95 transitions in vibrational states v=0−5 and rotational states J=1−8 have been included in a fit to determine the cesium nuclear quadrupole and spin–rotation interactions, the fluorine spin–rotation interaction, and the tensor and scalar parts of the spin–spin interaction. Vibration and rotation dependencies of these constants have been determined, allowing correction for zero point vibration effects. This experimental Cs nuclear quadrupole coupling constant when combined with the electric field gradient calculated using a relativistic coupled cluster method yields a nuclear quadrupole moment of the Cs nucleus equal to eQ=−3.43098 mbarn. The vibrational dependence of the coupling constant is smaller than the theoretical estimate. The coupling constants we have determined are the following: eQCsqCs=1245.598(10)−14.322(25)(v+1/2)+0.080(14)(v+1/2)2+0.0040(22)(v+1/2)3−0.00209(59)J(J+1)+0.00048(40)(v+1/2)J(J+1), cCs=0.66177(14)−0.01509(28)(v+1/2)+0.000550(94)(v+1/2)2, cF=15.08163(84)−0.1744(14)(v+1/2)+0.00234(41)(v+1/2)2−0.000093(13)J(J+1), c3=0.92713(53)−0.00917(93)(v+1/2)+0.00097(29)(v+1/2)2, c4=0.62745(30)−0.00903(22)(v+1/2). All values are in kHz units, with one standard deviation uncertainty estimates in the last two digits shown in ( ).

Cesium-133 NMR Study of CsCd(SCN)3: Relative Orientation of the Chemical Shift and Electric Field Gradient Tensors

Single-crystal NMR was used to characterize the cesium-133 chemical shift and electric field gradient (EFG) tensors in CsCd(SCN)3. The principal axes of the two interaction tensors are not coincident, a reflection of the general positioning of cesium nuclei within the unit cell. Relative orientations of the chemical shift and EFG tensors have been determined, but assignment of the two magnetically distinct sites remains elusive. The span of the chemical shift, 94.4 ppm, is moderate in comparison with other cesium salts, and the magnitude of the nuclear quadrupole coupling constant, 148 kHz, is in the midrange of those reported for cesium compounds. Excellent agreement is observed between experimental 133Cs NMR spectra of a stationary powder sample and spectra calculated using NMR parameters from the single-crystal analysis. Moreover, simulations indicate that the static line shape is very sensitive to the relative orientation of the chemical shift and EFG tensors. Experimental 133Cs NMR spectra obtained w...

Pressure effects on electron charge densities and lattice dynamics in CsCl and CsI.

The effect of pressure on electron densities and lattice dynamics in CsCl and CsI has been investigated using the $^{133}\mathrm{Cs}$ high-pressure M\"ossbauer-effect technique. The analysis of the isomer-shift results and the corresponding s-electron density at the cesium nuclei allows one to evaluate the amount of 6s electrons residing on the cesium ion in both samples. The isomer-shift results reveal the important role played by the Cs 5p valence electron bands: the increasing overlap with the Cl 4p band and the I 5p band, respectively, accelerated by compression, causes a decrease in their shielding effect of the s electrons. This contribution is equivalent to 0.23 6s electrons at V/${\mathit{V}}_{0}$=0.85 for CsCl and to 0.24 at V/${\mathit{V}}_{0}$=0.78 for CsI. From the volume dependence of the recoilless fraction the behavior of the Gr\"uneisen coefficient was deduced. The results for CsI confirm the similarity between the lattice dynamical properties of CsI and solid xenon under pressure.

Spectral-moment constraints on electride-electron locations in the crystalline electride

The inverse-first moment and the first moment of the observed optical-absorption spectrum of the crystalline electride [Cs(18-crown-6${)}_{2}$] [where (18-crown-6) is (${\mathrm{CH}}_{2}$${\mathrm{CH}}_{2}$O${)}_{6}$] are used to determine rigorous upper and lower bounds for the absolute maximum of the single-particle probability density of a typical constituent electride electron. These bounds sufficiently bracket the contact densitites that are determined from magic-angle-spinning $^{133}\mathrm{NMR}$ spectra of the pure electride and of its mix-crystals with the isomorphous sodide, [Cs(18-crown-6${)}_{2}$Na], to indicate that the distribution of the electron most likely is located in the immediate vicinity of a cesium nucleus. Limitations on the number of $^{133}\mathrm{NMR}$ absorptions in sodide-electride mix-crystals are shown to support such a location.

Cs133spin-lattice relaxation study of phase transitions in CsPbCl3

Nuclear spin relaxation-time measurements of the cesium nuclei in the perovskite crystal CsPb${\mathrm{Cl}}_{3}$ are reported for the temperature range 300-430 K. The data exhibit the characterisitic anomaly which is expected to occur in the civinity of the structural phase transitions. Comparison of these data with corresponding data for the chlorine nuclei adds strong support to the earlier conjecture that Pb${\mathrm{Cl}}_{6}$ octahedral complexes in CsPb${\mathrm{Cl}}_{3}$ undergo hindered rotational motion in the hight-temperature cubic phase. The cesium relaxation-time minimum occurs at 315 K. This observation is explained on the basis of the fact that the energy of the ${T}^{2}$ phonon branch along the $[11\ensuremath{\xi}]$ direction is remarkably low at all temperatures.

Molecular Beam Measurement of the Hyperfine Structure of 133Cs19F

The magnitudes and signs of the hyperfine interaction constants for 133Cs19F in the J = 1, v = 0, 1, 2 states have been measured with a molecular beam electric resonance spectrometer. The results for v = 0 are: eQ1q1 = 1.2370(13) MHz, c1 = 0.70(7)kHz, c2 = 15.1(6)kHz, c3 = 0.92(12)kHz, c4 = 0.61(10)kHz. The numbers in parentheses are uncertainties in units of the last digit given. eQ1q1 is the quadrupole coupling constant for the cesium nucleus, c1 and c2 are the spin-rotation coupling constants for the cesium and fluorine nuclei, respectively, and c3 and c4 are the coupling constants for the tensor and scalar parts of the nuclear spin—spin interaction. These constants are obtained from the radio-frequency spectrum of CsF taken under veryweak-field conditions (Edc = 1.5 V/cm; H&amp;lt;0.05 Oe); some previously ignored contributions of the fluorine spin—rotation interaction and the spin—spin interaction are clearly evident. The observed variation in eQ1q1 with vibrational state shows only qualitative agreement with theory. An appendix gives compact expressions for the very-weak-field hfs energy levels of a 1Σ molecule in which only one nucleus has a quadrupole moment.

Low-lying energy levels of Cs 134

A study is made of the cascade γ-transitions following thermal neutron capture in cesium nuclei. Energy and quantum characteristics of low-lying excited states of Cs 134 with excitation energy up to 320 keV are determined.