摘要:

If there is either T or P symmetry, there can be no electric dipole moment for particles whose orientations are fully specified by the orientations of their spin angular momenta. As a result, there have been extensive searches for electric dipole moments as tests of these symmetries. CP non‐conservation has been observed, which implies non‐conservation of T if CPT is conserved, but it has only been seen in the decay of the artificially producedK0L. The history of the searches for neutron and atomic electric dipole moments is summarized. The earliest experiments utilized a neutron beam magnetic resonance apparatus, but the present neutron experiments study ultra cold neutrons trapped in bottles whose walls totally reflect the neutrons. Recent atomic and molecular searches are sensitive both to particle electric dipole moments and to other related T non‐conserving quantities. The various neutron, atomic and molecular experiments are described. The results of these searches are compared with the predictions of theories that account for the known CP non‐conservation in the decay of theK0L. The experiments directly set limits to T‐odd, P‐odd interaction terms, but through eleectroweak radiative corrections they also set limits to T‐odd, P‐even interactions.

ISSN:0094-243X    

DOI:10.1063/1.2946019

出版商:AIP    

年代:1994

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.2946005

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The advent of heavy‐ion cooler rings has created a completely new scope for the application of laser spectroscopy on accelerator beams. The unique potential opened for laser spectroscopic applications by the exotic properties of the stored ions can be exploited to address fundamental problems of physics.The high, but very well controlled velocity of the ions has been used as a test ground for the theory of special relativity. The availability of highly‐charged ions beyond all previous possibilities has been exploited for precision laser spectroscopy of the ground state hyperfine splitting of heavy hydrogen‐like ions. This represents a novel opportunity to study QED corrections in the previously unexplored combination of strong magnetic and electric fields.

ISSN:0094-243X    

DOI:10.1063/1.2946013

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Atomic structure is discussed in the context of expansion parameters. For simple atoms, an expansion in the fine structure con‐ stant allows the most precise tests of Quantum Electrodynamics. For more complicated atoms such an expansion is not generally available. In the special case of highly charged ions, however, an expansion in 1/Zagain allows precision tests of QED. It is argued that neutral systems require a different kind of expansion, and applications to the properties of cesium are discussed. Throughout, the role of nuclear structure as a limit of precision QED tests is stressed.

ISSN:0094-243X    

DOI:10.1063/1.2946024

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The simple hydrogen atom permits unique confrontations between spectroscopic experiment and fundamental theory. The experimental resolution and measurement accuracy continue to improve exponentially. Recent advances include a new measurement of the Lamb shift of the 1S ground state which provides now the most stringent test of QED for an atom and reveals unexpectedly large two‐loop binding corrections. The H‐D isotope shift of the extremely narrow 1S–2S two‐photon resonance is yielding a new value for the structure radius of the deuteron, in agreement with nuclear theory. The Rydberg constant as determined within 3 parts in 1011by two independent groups has become the most accurately known of any fundamental constant. Advances in the art of absolute optical frequency measurements will permit still more precise experiments in the near future.

ISSN:0094-243X    

DOI:10.1063/1.2946026

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Recent progress in high resolution laser spectroscopy of Helium is reviewed. The direct determination of the frequency of the 23S1→ 33PJtransition in the near ultraviolet at 389 nm is illustrated. The novel scheme uses the heterodyne with a laser diode locked to 5S→5D two‐photon transition in Rubidium which serves as optical frequency reference in the near infrared at 778 nm. A precise value for the 23S1level Lamb shift is extracted, more than two orders of magnitude more accurate than theoretical calculations. Measurements include3He‐4He isotope shift and3He hyperfine structure. Results for the 23S1→ 33PJtransition are analyzed in conjunction with those for the 23S1→ 23PJtransition for a precise test of QED corrections. Perspectives for a helium atom determination of the fine structure &agr; are also discussed.

ISSN:0094-243X    

DOI:10.1063/1.2946027

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Simple exotic atomic systems render the possibility of studying fundamental interactions and testing basic symmetries in physics and of determining precise values for fundamental constants. Of particular interest in this connection are hydrogen‐like systems. Examples for systems, where some progress has been made recently, are among others pionic hydrogen, antiprotonic helium, muonic helium, positronium, and muonium.

ISSN:0094-243X    

DOI:10.1063/1.2946000

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An overview is given of the current experimental effort to investigate the level structure of highly charged ions with the Livermore electron beam ion trap (EBIT) facility. The facility allows the production and study of virtually any ionization state of any element up to bare U92+. Precision spectroscopic measurements have been performed for a range of&Dgr;n = 0and&Dgr;n = 1transitions. Examples involving 3–4 and 2–3 as well as 3‐3 and 2‐2 transitions in uranium ions are discussed that illustrated some of the measurement and analysis techniques employed. The measurements have allowed tests of calculations of the the quantum electrodynamical contributions to the transitions energies at the 0.4% level in a regime where(Z&agr;) ≈ 1.

ISSN:0094-243X    

DOI:10.1063/1.2946001

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Precision measurements of excited‐state lifetimes play important roles in many areas of physics. Measurements of atomic lifetimes are used to determine fundamental interaction parameters, test atomic and molecular theory, and place constraints on models of stellar evolution and big‐bang nucleosynthesis. A variety of techniques for measuring atomic and molecular lifetimes are presented along with a discussion of associated systematic effects. A comparison is made between experimental and theoretical results for a variety of alkali and alkali‐like systems. Lifetime measurements in cesium are used to test atomic‐structure calculations necessary for the interpretation of parity nonconservation experiments.

ISSN:0094-243X    

DOI:10.1063/1.2946002

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We report measurements of mass ratios of 20 pairs of molecular ions with a single ion Penning trap mass spectrometer having an accuracy exceeding one part in 1010. The dominant source of error is random magnetic field fluctuations which cause a2.6×10−10rms scatter in measurements of the cyclotron frequency. Robust statistical analysis of the data ensures that nongaussian outliers are weighted less heavily in a smooth and consistent manner. Systematic errors are estimated to be2×10−11or below for doublet mass comparisons. The ratios form an overdetermined set, such that the atomic masses of nine isotopes can be derived from at least two independent groups of ion mass ratios, providing many consistency checks for systematic errors at the 10−10level. At this level of precision, certain mass measurements have important implications in fundamental metrology. Results presented here are essential for defining a practical atomic standard of mass, for calibrating &ggr;‐ray wavelengths, and for determining the molar Planck constant and the fine structure constant.

ISSN:0094-243X    

DOI:10.1063/1.2946003

出版商:AIP    

年代:1994

数据来源: AIP