Savely G. Karshenboim

Limit on the present temporal variation of the fine structure constant

The comparison of different atomic transition frequencies over time can be used to determine the present value of the temporal derivative of the fine structure constant alpha in a model-independent way without assumptions on constancy or variability of other parameters, allowing tests of the consequences of unification theories. We have measured an optical transition frequency at 688 THz in 171Yb+ with a cesium atomic clock at 2 times separated by 2.8 yr and find a value for the fractional variation of the frequency ratio f(Yb)/f(Cs) of (-1.2+/-4.4)x10(-15) yr(-1), consistent with zero. Combined with recently published values for the constancy of other transition frequencies this measurement sets an upper limit on the present variability of alpha at the level of 2.0x10(-15) yr(-1) (1sigma), corresponding so far to the most stringent limit from laboratory experiments.

Precision physics of simple atoms: QED tests, nuclear structure and fundamental constants

Abstract Quantum electrodynamics (QED) is the first successful and still the most successful quantum field theory. Simple atoms, being essentially QED systems, allow highly accurate theoretical predictions. Because of their simple spectra, such atoms have also been efficiently studied experimentally frequently offering the most precisely measured quantities. Our review is devoted to comparison of theory and experiment in the field of precision physics of light simple atoms. In particular, we consider the Lamb shift in the hydrogen atom, the hyperfine structure in hydrogen, deuterium, helium-3 ion, muonium and positronium, as well as a number of other transitions in positronium. Additionally to a spectrum of unperturbed atoms, we consider annihilation decay of positronium and the g factor of bound particles in various two-body atoms. Special attention is paid to the uncertainty of the QED calculations due to the uncalculated higher-order corrections and effects of the nuclear structure. We also discuss applications of simple atoms to determination of several fundamental constants.

NUCLEAR STRUCTURE-DEPENDENT RADIATIVE CORRECTIONS TO THE HYDROGEN HYPERFINE SPLITTING

Abstract Radiative corrections to the Zemach contribution of the hydrogen hyperfine splitting are calculated. Their contributions amount to −0.63(3) ppm to the HFS. The radiative-recoil corrections are estimated to be 0.09(3) ppm and the heavy particle vacuum polarization shifts the HFS by 0.10(2) ppm. The status of the nuclear-dependent contributions is considered. From the comparison of theory and experiment a proton polarizability contribution of 3.5(9) ppm is found. The large shift from an earlier result (0.48(56) ppm) is due to using a more recent proton radius for the Zemach term calculation. The nuclear structure-dependent corrections to the difference v HFS (1s) − n 3 v HFS ( ns ) are also obtained.

Precision study of positronium: Testing bound state QED theory

As an unstable light pure leptonic system, positronium is a very specific probe atom to test bound state QED. In contrast to ordinary QED for free leptons, the bound state QED theory is not so well understood and bound state approaches deserve highly accurate tests. We present a brief overview of precision studies of positronium paying special attention to uncertainties of theory as well as comparison of theory and experiment. We also consider in detail advantages and disadvantages of positronium tests compared to other QED experiments.

Fundamental physical constants: Looking from different angles

We consider fundamental physical constants that are among a few of the most important pieces of information we have learned about Nature after intensive centuries-long study. We discuss their multifunctional role in modern physics including problems related to the art of measurement, natural and practical units, the origin of the constants, their possible calculability and variability, etc.PACS Nos.: 06.02.Jr, 06.02.Fn

High-precision optical measurement of the 2S hyperfine interval in atomic hydrogen.

We have applied an optical method to the measurement of the 2S hyperfine interval in atomic hydrogen. The interval has been measured by means of two-photon spectroscopy of the 1S-2S transition on a hydrogen atomic beam shielded from external magnetic fields. The measured value of the 2S hyperfine interval is equal to 177 556 860(16) Hz and represents the most precise measurement of this interval to date. The theoretical evaluation of the specific combination of 1S and 2S hyperfine intervals D21 is in fair agreement (within 1.4 sigma) with the value for D21 deduced from our measurement.

Hyperfine structure in hydrogen and helium ion

Abstract QED theory of the hyperfine splitting of the 1 s and 2 s state in hydrogen isotopes and helium-3 ion is considered. We develop an accurate theory of a specific difference 8 E HFS (2 s )− E HFS (1 s ). We take into account higher-order QED and nuclear structure effects. In particular, we found the vacuum polarization contribution in order α ( Zα ) 3 E F and examined the recoil contribution in order ( Zα ) 3 m / M and thus completed a calculation of the fourth order QED corrections. The higher-order nuclear structure contributions were also analysed. The theoretical predictions reported here are now of a higher accuracy than the experiment. The study of the difference provides the most accurate test (at a level of a part in 10 8 ) of the QED theory of ns HFS up to date. The theory agrees with most of the experimental data.

Non-relativistic calculations of the g-factor of a bound electron

Abstract We study the g -factor of a bound electron in hydrogen-like ions within a non-relativistic approach. The one-loop and two-loop vacuum polarization contributions are found in a closed analytic form as well as the finite-nuclear-size correction. We present numerical results for low and moderate values of the nuclear charge Z ≤30.

Contribution of light-by-light scattering to energy levels of light muonic atoms

The complete contribution of diagrams with the light-by-light scattering to the Lamb shift is found for muonic hydrogen, deuterium and helium ion. The results are obtained in the static-muon approximation and a part of the paper is devoted to the verification of this approximation and analysis of its uncertainty.

The Lamb shift of excited s levels in hydrogen and deuterium atoms

A specific combination of s-state Lamb shift ΔEL(1s1/2)-n3ΔEL(ns1/2) is considered. Its value is calculated both in the hydrogen and deuterium atoms for n up to 12. The result includes all correction which can contribute more than 1 kHz, particularly the one-loop corrections for both the self energy and the vacuum polarization, and the two-loop contribution. Nuclear finite-size corrections for the isotopic difference of the combination are also evaluated.