Polarization spectroscopy of Rb and Cs

Theoretical calculation of ⁸⁵Rb and ¹³³Cs D₁ signals in polarization spectroscopy is presented by using the method of velocity-selective optical pumping in a four-level system. Since good agreement between theory and experiment has been found in Na D₁ polarized signals, the theoretical calculation can be also applied to Rb and Cs D₁ lines. Rb and Cs atoms have higher total angular momentum F in the hyperfine structures than Na atom and then the calculation is more complicated. The relative signal intensities in polarization spectroscopy are compared with those in saturation spectroscopy.     

Selective reflection spectroscopy at the interface between a calcium fluoride window and Cs vapour

A special vapour cell has been built, that allows the measurement of the atom–surface van der Waals interaction exerted by a CaF₂ window at the interface with Cs vapour. Mechanical and thermal fragility of fluoride windows make common designs of vapour cells impractical, so that we have developed an all-sapphire sealed cell with an internal CaF₂ window. Although some impurities have remained when filling up the prototype cell, leading to line broadening and a shift, the selective reflection spectrum of the Cs D₁ line (894 nm) makes apparent the weak van der Waals surface interaction. The uncertainties introduced by the effects of these impurities in the van der Waals measurement are nearly eliminated when comparing the selective reflection signal at the CaF₂ interface of interest and at a sapphire window of the same cell. The ratio of the interactions respectively exerted by a sapphire interface and a CaF₂ interface is found to be 0.55±0.25, in good agreement with the theoretical evaluation of ∼0.67. PACS 34.35.+a; 42.62.Fi; 42.70.Km     

Selective reflection of resonance radiation from excited media

According to quantum electrodynamics, the cross section for resonant scattering of radiation on an aggregate of excited atoms can be written as a sum of positive definite terms. This type of structure is not consistent with the Fresnel formulas for the reflection coefficient of radiation from thermally excited media. The difference shows up on a macroscopic level and indicates that semiclassical radiation theory cannot be used. A study of the correlation between elastic scattering and stimulated emission processes clarifies the reason for the discrepancies. The resulting singularities require summing of Feynman diagrams which appear beginning in the sixth order of perturbation theory. A lower bound estimate for the reflection coefficient from a plane layer is given, including processes which violate the statistics of radiation. The contribution of stimulated emission processes caused by the initially scattered photon are examined specifically. An experiment is proposed which would settle the choice of theories. Zh. éksp. Teor. Fiz. 113, 521–538 (February 1998)     

Selective reflection from Rb vapor in half- and quarter-wave cells: Features and possible applications

The features of the effect of selective reflection from rubidium vapor in a nanocell with the thickness L ≈ λ/2 and L ≈ λ/4, where λ = 795 nm is the wavelength of laser radiation resonant with the Rb D₁ line, are studied. It is shown that, because of the behavior of the nanocell as a low-Q-factor Fabry–Pérot etalon, the sign of the derivative of the selective reflection spectra changes near L ≈ λ/2 from negative at L > λ/2 to positive at L < λ/2. The simplicity of the experimental implementation, large amplitude, and sub-Doppler width (40MHz) of a detected signal at an atomic transition frequency are appropriate for applications in metrology and magnetometry. In particular, selective reflection from the nanocell is a convenient frequency marker of atomic transitions; in this case, the amplitudes of peaks are proportional to the transition probabilities. The remote optical monitoring of a magnetic field with a spatial resolution L = λ/4 ≈ 199 of nm is possible on the basis of the splitting of selective reflection peaks in a strong magnetic field (up to 3 kG). A theoretical model describes well the experimental results.     

Selective reflection by atomic vapor: experiments and self-consistent theory

Selective reflection of laser radiation from the interface between atomic vapor and a dielectric is studied for a wide range of vapor density. A self-consistent model is developed, some analytical results are obtained, as well as a number of curves are computed that are in good agreement with experimental spectra measured in cesium and rubidium vapor cells.     

Accurate determination of the atomic number density in dense Cs vapors by absorption measurements of Cs2 triplet bands

The spectra of Cs metal vapor have been experimentally investigated by spatially resolved absorption in overheated cesium vapor generated in a heat pipe oven. The reduced absorption coefficients of the triplet satellite bands at 875.5 nm and the diffuse band between 705 nm and 720 nm were found to be independent of temperature in the range between 600 K and 1000 K. The absorption data of these molecular features can be successfully used for very simple and accurate Cs number density determination in the range from about 5×10¹⁷ cm^-3 to 5×10¹⁸ cm^-3. PACS 33.20.Ea; 33.20Kf; 33.70.Fd     

Selective reflection of a laser beam from a dilute rubidium vapor

We study the selective reflection of the laser beam from rubidium atomic vapor at the D₂ line (wavelength λ = 780 nm) at different atomic densities. We use a tunable free-running diode laser. We observed a measurable signal at a low atomic density N when the mean distance between resonance atoms reached two wavelengths. In our experiment, the dimensionless parameter N ^1/3 λ varied from 0.5 to 2.8. The reflectivity increased with density monotonically. It is interesting to perform experiments when the parameter N ^1/3 λ ≪ 1.     

Shape of the signal of double radio-optical resonance in 85Rb atomic vapors in strong fields

A transmission peak has been experimentally observed in the center of the signal of double radio-optical resonance in rubidium atomic vapors at the hyperfine splitting frequency of the ground state. It has been shown that this structure appears due to the Doppler detuning of the optical field and the corresponding optical shift of the microwave field. An analytical expression has been obtained for the shape of this resonance and the effect has been qualitatively explained.     

Efficiency of raman conversion of XeCl laser radiation in metal vapors

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 1, pp. 80–83, July, 1991.     

Dynamics of resonant fluorescence from atomic Cs vapor at scanning the frequency of laser radiation in the presence of a constant magnetic field

The dynamics of interaction of laser radiation resonant with the transitions of D₂ line in atomic Cs¹³³ in the presence of an external magnetic field is studied. Populations of levels and dynamics of resonant fluorescence at scanning frequency of the laser radiation with linear and circular polarizations are considered.     

X-ray laser gain from Bragg reflection in relativistic electronbeam channel radiation systems

The application of distributed feedback by Bragg reflections in electron-beam channeling X-ray lasers is investigated. Expressions for low-threshold gain are derived for this cavity mirror structure in single crystals and are shown to have possible application in reducing beam high-current requirements by many orders of magnitude     

Nuclear spins of76Rb and119Cs byβ radiation detected optical pumping

An optical pumping apparatus has been attached to the reconstructed ISOLDE on-line mass separator at CERN in order to obtain nuclear data of isotopes far fromβ stability. As first results the spins of⁷⁶Rb (T _1/2=36.8 s) and¹¹⁹Cs (T _1/2=37.7 s) have been determined byβ radiation detected optical pumping (β-RADOP) to beI=1 andI=9/2 respectively.     

Experimental investigation of non-linear selective reflection at the interface of Cs atomic vapor and quartz

We present an experimental study of non-linear selective reflection (SR) at a quartz–Cs-vapor interface in a V-type three-level scheme. The non-linear selective reflection at the Cs D₂ resonance line (⁶ S _1/2F=4→⁶ P _3/2) is monitored with and without pumping. The sub-Doppler reflection spectrum is observed and the effect of pumping on the signal of the selective reflection is investigated. The experimental result is in agreement with the theoretical calculation. Received: 16 April 2002 / Revised version: 12 June 2002 / Published online: 25 September 2002 RID="*" ID="*"Corresponding author. Fax: +86-351/701-1500, E-mail: zhaojm@sxu.edu.cn     

Collimation and decollimation of atomic beams by laser radiation

Efficient collimation and decollimation of an atomic beam by spontaneous radiation pressure acting on the atoms in axially symmtric light fields has been accomplished. The on-axic atomic-beam intensity was changed by 800 times. The entire effect of collimation and decollimation takes place in a laser-frequency variation about the natural line width.     

On-line production of Rb and Cs isotopes from uranium carbide targets

A series of on-line mass separation experiments have been performed at the IRIS facility to measure the yield and release of Rb and Cs neutron-rich isotopes produced by fission reaction of ²³⁸U. A 1 GeV proton beam was used to bombard uranium carbide targets with the densities of 11 g/cm³ and 1.5 g/cm³ held at temperatures in the range (2000-2230) ^°C. The release curves of Rb and Cs long-lived isotopes were measured from both kinds of targets. The overall production efficiency was determined making use of experimentally measured cross-sections of that isotope production. Comparison of the experimental yields of Rb and Cs isotopes with the calculated ones after corrections for losses due to finite release times suggests that the diffusion is the dominating process reducing the efficiency for short-lived isotopes. When normalized to the same thickness, an enhancement for the high-density rod target of the measured isotope yields is observed when going far from stability. This is possibly explained by the reactions induced by secondary neutrons. A significant odd-even effect with higher yields of Cs even neutron isotopes has been observed, confirming a similar effect obtained in earlier experiments.     

Dark resonances in 87Rb atomic vapors interacting with the field of copropagated linearly polarized waves of various frequencies

The results of theoretical and numerical analysis of resonances of coherent population trapping in ⁸⁷Rb atomic vapors, obtained using copropagated linearly polarized waves, are presented. Various schemes for exciting dark resonance are compared with a view to obtaining a new-generation small-size quantum frequency standard.     

Amplification of radiation in atomic vapor induced by a linearly polarized laser radiation

We present the results of spectroscopic and polarization studies of dilute rubidium vapor exposed to a single-frequency linearly polarized diode laser radiation in a spectral range of atomic D₂ line. We report the origin of a circularly polarized radiation on V-type transitions of ⁸⁷Rb F _g = 2 → F _e = 3 and ⁸⁵Rb F _g = 3 → F _e = 4, and amplification of this radiation in backward direction caused by a partial population inversion among magnetic sublevels of the ground and excited levels. This is confirmed experimentally by high directivity of backward radiation, absence in its spectrum of ⁸⁵Rb F _g = 2 → F _e = 1 (Λ-type) radiation, as well as by different nature of intensity dependences of backward and fluorescence radiations.