摘要:

A review of recent measurements of parity violation in atoms is given. In the past few years several experiments that measure atomic parity violation by optical rotation have achieved fractional accuracies between one and a few percent. A recent measurement in atomic cesium using the Stark interference technique has achieved 0.35&percent;. This experiment also provided the first measurement of a nuclear spin dependence to atomic parity violation. This dependence provides the first measurement of a nuclear anapole moment. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59371

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

There are two sources of parity nonconservation (PNC) in atoms: the electron-nucleus weak interaction and the magnetic interaction of electrons with the nuclear anapole moment. A nuclear anapole moment has recently been observed. This is the first discovery of an electromagnetic moment violating fundamental symmetries—the anapole moment violates parity and charge-conjugation invariance. We describe the anapole moment and how it can be produced. The anapole moment creates a circular magnetic field inside the nucleus. The interesting point is that measurements of the anapole allow one to study parity violation inside thenucleusthrough atomic experiments. We use the experimental result for the nuclear anapole moment of133Csto find the strengths of the parity violating proton-nucleus and meson-nucleon forces. Measurements of the weak charge characterizing the strength of the electron-nucleon weak interaction provide tests of the Standard Model and a way of searching for new physics beyond the Standard Model. Atomic experiments give limits on the extraZ-boson, leptoquarks, composite fermions, and radiative corrections produced by particles that are predicted by new theories. The weak charge and nuclear anapole moment can be measured in the same experiment. The weak charge gives the mean value of the PNC effect while the anapole gives the difference of the PNC effects for the different hyperfine components of an electromagnetic transition. The interaction between atomic electrons and the nuclear anapole moment may be called the “PNC hyperfine interaction.” ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59353

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Microwave spectroscopy using trapped and cooled ions can achieve precision and accuracy comparable to the best cesium frequency standards. We discuss standards based on199Hg+ions trapped in linear Paul traps: the Jet Propulsion Laboratory (JPL) standard, which uses up to107atoms confined near the trap axis, and the recently evaluated NIST standard, which uses approximately ten ions laser cooled and crystalized on the trap axis. We consider future directions in trapped ion frequency standard work, including the use of entangled states for achieving higher precision, and progress on trapped ion optical frequency standards. Finally, we discuss scientific and technical applications of extremely stable frequency standards. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59372

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

High-precision laser spectroscopy of helium is a powerful tool for testing QED calculations and for an accurate determination of the fine-structure constant &agr;. Here, we report a new measurement of the fine-structure intervals of the23Plevel of helium with an accuracy of kHz. They are measured from the frequency difference between23S1→23PJoptical transitions observed with fluorescence-saturation spectroscopy in an atomic beam, in the absence of magnetic fields. A discussion of the systematic effects in the measurements is given, describing for the first time in helium the shift induced by mechanical effects of the light. Finally, a comparison with previously reported measurements is discussed. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59368

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Bose-Einstein condensation (BEC) of atoms with attractive interactions is profoundly different from BEC of atoms with repulsive interactions, in several respects. We describe experiments with Bose condensates of7Liatoms, which are weakly attracting at ultralow temperature. We measure the distribution of condensate occupation numbers occurring in the gas, which shows that the number is limited and demonstrates the dynamics of condensate growth and collapse. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59369

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

This lecture describes recent work in our group on gapless mean-field theories for trapped Bose-Einstein condensates. We discuss the physical basis for these theories and compare them to the better known approaches. The proposed theories are based on suitable inclusion of the anomalous average of the Bose field operator. This leads to an effective interaction between two atoms which is both temperature and density dependent, as opposed to the widely used HFB-Popov approach for which it is constant. The predictions of these theories differ from the corresponding HFB-Popov ones by at most a few per cent for the lower-temperature gases studied in the laboratory at present. For systems that may well be studied in the next few years the effects can be much more profound. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59370

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Laser-cooled ions in a trap can be strongly coupled and form crystalline states. We describe experimental studies that measure the spatial correlations of the ion crystals formed in Penning traps. Both Bragg scattering of the cooling-laser light and spatial imaging of the laser-induced ion fluorescence are used to measure these correlations. In spherical plasmas with more than2×105ions, body-centered-cubic (bcc) crystals, the predicted bulk structure, are the only type of crystals observed. We are able to phase-lock the orientation of the ion crystals to a rotating electric-field perturbation. With this “rotating wall” technique and stroboscopic detection, images of individual ions in a Penning trap are obtained. The rotating-wall technique also provides a precise control of the time-dilation shift due to the plasma rotation, which is important for Penning trap frequency standards. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59373

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We discuss our recent experimental demonstrations of three novel atom traps which are all based on the optical dipole force in far-detuned laser light. In the gravito-optical surface trap (GOST), Cs atoms are trapped and cooled by means of an evanescent-wave mirror very closely above a dielectric surface. This trap allows for optical cooling at very high densities and provides good starting conditions for evaporative cooling to quantum degeneracy and the realization of a 2D quantum gas. The conical atom trap (CAT) uses a hollow blue-detuned laser beam in combination with gravity to trap atoms in a dark spatial region. This trap is experimentally simple and provides high loading efficiency, tight confinement, efficient sub-Doppler cooling, and strong suppression of collisional losses. The standing-wave red-detuned (STAR) trap allows one to confine atoms in a shallow optical potential at a very low photon scattering rate, and is thus an interesting tool for studies of the atomic ground-state dynamics in external electro-magnetic fields. We have studied atomic spin polarization in this trap. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59350

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We are experimenting with individual neutral cesium atoms stored in a magneto-optical trap. The atoms are detected by their resonance fluorescence, and fluorescence fluctuations contain signatures of the atomic internal and external degrees of freedom. This noninvasive probe provides a rich source of information about atomic dynamics at all relevant time scales. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59374

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

With the advent of evaporative cooling methods, atomic collisions can be studied at microkelvin and even sub-microkelvin temperatures. At these energies, resonance and threshold phenomena become very pronounced. Near zero-energy resonances lead to large variations in collision cross sections with energy. Magnetically tunable Feshbach resonances have been observed, which allow elastic collision cross sections and scattering lengths to be tuned over large ranges with small changes in an applied magnetic field. These resonance effects are extremely sensitive to small variations in atomic interaction parameters, including scattering lengths. The combined results of ultracold atomic collision and photoassociation spectroscopy experiments is leading to a complete and consistent picture of collisions of ultracold alkali atoms. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59351

出版商:AIP    

年代:1999

数据来源: AIP