On the precise measurement of the frequency transition 1S–2S of the hydrogen atom

An experiment is suggested for the precise measurement of the frequency transition 1S–2S of the hydrogen atom with a relative precision of 10^-12 based on the use of a narrow resonance of two-photon absorption in a standing wave field. The relative width of the absorption line is determined by the second-order Doppler effect and has the same order as the relative width of Mössbauer transitions with absorption of γ-quanta. The results of this experiment can be included in the system of fundamental constants. A possibility for creating a new standard of the atomic time unit with a reproducibility of ～ 10^-15 has been examined.     

Deformed dispersion relation constraint with hydrogen atom 1S-2S transition

We use the latest results of the ultra-high accuracy 1S-2S transition experiments in the hydrogen atom to constrain the forms of the deformed dispersion relation in the non-relativistic limit.For the leading correction of the non-relativistic limit,the experiment sets a limit at an order of magnitude for the desired Planck-scale level,thereby providing another example of the Planck-scale sensitivity in the study of the dispersion relation in controlled laboratory experiments.For the next-to-leading term,the bound is two orders of magnitude away from the Planck scale,however it still amounts to the best limit,in contrast to the previously obtained bound in the non-relativistic limit from the cold-atom-recoil experiments.     

Measurement of the hydrogen 1S- 2S transition frequency by phase coherent comparison with a microwave cesium fountain clock

We report on an absolute frequency measurement of the hydrogen 1S-2S two-photon transition in a cold atomic beam with an accuracy of 1.8 parts in 10(14). Our experimental result of 2 466 061 413 187 103(46) Hz has been obtained by phase coherent comparison of the hydrogen transition frequency with an atomic cesium fountain clock. Both frequencies are linked with a comb of laser frequencies emitted by a mode locked laser.     

Magic Wavelengths for the 1S-2S and 1S-3S Transitions in Hydrogen Atoms

The dynamic dipole polarizabilities for 1S,2S and 3S states of the hydrogen atom are calculated using the finite B-spline basis set method,and the magic wavelengths for 1S-2S and 1S-3S transitions are identified.In comparison of the solutions from the Schrodinger and Dirac equations,the relativistic corrections on the magic wavelengths are of the order of 10~(-2) nm.The laser intensities for a 300-E_r-deep optical trap and the heating rates at 514 and 1371 nm are estimated.The reliable prediction of the magic wavelengths would be helpful for the experimental design on the optical trapping of the hydrogen atoms,and in turn,it would be helpful to improve the accuracy of the measurements of the hydrogen 1S-2S and 1S-3S transitions.     

Low phase noise diode laser oscillator for 1S-2S spectroscopy in atomic hydrogen

We report on a low-noise diode laser oscillator at 972?nm actively stabilized to an ultrastable vibrationally and thermally compensated reference cavity. To increase the fraction of laser power in the carrier we designed a 20?cm long external cavity diode laser with an intracavity electro-optical modulator. The fractional power in the carrier reaches 99.9%, which corresponds to an rms phase noise of φ(rms)2=1?mrad2 in 10?MHz bandwidth. Using this oscillator, we recorded 1S-2S spectra in atomic hydrogen and have not observed any significant loss of the excitation efficiency due to phase noise multiplication in the three consecutive two-photon processes.     

Absolute frequency measurement of rubidium 5S-7S two-photon transitions with a femtosecond laser comb

The absolute frequencies of rubidium 5S-7S two-photon transitions at 760 nm are measured to an accuracy of 20 kHz with an optical frequency comb based on a mode-locked femtosecond Ti:sapphire laser. The rubidium 5S-7S two-photon transitions are potential candidates for frequency standards and serve as important optical frequency standards for telecommunication applications. The accuracy of the hyperfine constant of the 7S1/2 state is improved by a factor of 5 in comparison with previous results.     

Precision measurement of the double quantum transition 32S12−32D52 in hydrogen

By observing the $\text{3}{}^2\text{S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(F =0) – 3}{}^2\text{D}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{(F = 2)}$ double quantum transition in a fast beam of atomic hydrogen, we have found for the $\text{3}{}^2\text{S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{– 3}{}^2\text{D}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ interval the value 4013.152± 0.098 MHz, in satisfactory agreement with QED theory.     

Improved measurement of the 1s2s 1S0-1s2p 3P1 interval in heliumlike silicon

Using colinear fast-beam laser spectroscopy with copropagating and counter-propagating beams we have measured the 1s2s 1S0-1s2p 3P1 intercombination interval in 28Si12+ with the result 7230.585(6) cm{-1}. The experiment made use of a dual-wavelength, high-finesse, power build-up cavity excited by single-frequency lasers at 1319 and 1450 nm. The result will provide a precision test of ab initio relativistic many-body atomic theory at moderate Z.     

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.     

On the 2S1/2–1S1/2 photon-plasmon transition in hydrogenous atoms

The probabilities of the two-quantum induced (according to the number of plasmons) photon-plasmon transitions 2S_1/2–1S_1/2 are calculated for hydrogenous atoms. In a turbulent plasma medium this process may be more effective than conventional two-photon radiation and collisions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 15, No. 2, pp. 305–307, February, 1972.The authors thank L. A. Vainshtein and Yu. P. Nikitin for discussing the work and for their valuable comments.