Selective detection of minor isotope lines in saturated absorption spectra by absorption filtering of major isotope lines

We demonstrate a simple method that can be used to detect minor isotope lines in a saturated absorption spectrum by the absorption filtering of major isotope lines. We investigate this method for use in the spectroscopy of the ¹S₀-¹P₁ transition in Yb at 399 nm by controlling the density of Yb atoms by varying the discharge current of a hollow cathode lamp. The performance of an extended-cavity laser diode using a high-power ultraviolet diode chip is also analyzed.     

Theoretical study on isotope separation of an ytterbium atomic beam by laser deflection

Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted onedimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes like172Yb,173Yb, and174Yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are studied, and the optimal parameters for the isotope separation are also investigated. Furthermore, the isotope separation efficiency and purity are estimated. Finally a new scheme for the efficient isotope separation is proposed. These findings will give a guideline for simply obtaining pure isotopes of various elements.     

Loading of a cold atomic beam into a magnetic guide

We demonstrate experimentally the continuous and pulsed loading of a slow and cold atomic beam into a magnetic guide. The slow beam is produced using a vapor loaded laser trap, which ensures two-dimensional magneto-optical trapping, as well as cooling by a moving molasses along the third direction. It provides a continuous flux larger than 10⁹ atoms/s with an adjustable mean velocity ranging from 0.3 to 3 m/s, and with longitudinal and transverse temperatures smaller than 100 μK. Up to 3×10⁸ atoms/s are injected into the magnetic guide and subsequently guided over a distance of 40 cm. Received 19 February 2002 Published online 28 June 2002     

A cold 87Rb atomic beam

We demonstrate an experimental setup for the production of a beam source of cold ⁸⁷Rb atoms. The atoms are extracted from a trapped cold atomic cloud in an unbalanced three-dimensional magneto-optical trap. Via a radiation pressure difference generated by a specially designed leak tunnel along one trapping laser beam, the atoms are pushed out continuously with low velocities and a high flux. The most-probable velocity in the beam is varied from 9 m/s to 19 m/s by varying the detuning of the trapping laser beams in the magneto-optical trap and the flux can be tuned up to 4×10⁹ s^-1 by increasing the intensity of the trapping beams. We also present a simple model for describing the dependence of the beam performance on the magneto-optical trap trapping laser intensity and the detuning.     

Laser cooling and trapping of Yb from a thermal source

We have successfully loaded a magneto-optic trap for Yb atoms from a thermal source without the use of a Zeeman slower. The source is placed close to the trapping region so that it provides a large flux of atoms that can be cooled and captured. The atoms are cooled on the transition at 398.9 nm. We have loaded all seven stable isotopes of Yb into the trap including the rarest isotope, ¹⁶⁸Yb. For the most abundant isotope (¹⁷⁴Yb), we load more than 10⁸ atoms into the trap within 1 s. We have characterized the source by studying the loading rate and the loss rate for different isotopes and at different trapping powers. We extract values for the loss rate due to collisions and due to branching into low-lying metastable levels. At the highest trap densities, we find evidence of additional loss due to intra-trap collisions.Received: 15 February 2004, Published online: 23 March 2004PACS: 32.80.Pj Optical cooling of atoms; trapping - 42.50.Vk Mechanical effects of light on atoms, molecules, electrons, and ions     

Magneto-Optical Trapping of Ytterbium Atoms with a 398.9nm Laser

We report the realization of ytterbium magneto-optical trap （MOT） operating on the dipole-allowed ^1S0 - ^1P1 transition at 398.9nm. The MOT is loaded by a slowed atomic beam produced by a Zeeman slower. All seven stable isotopes of Yb atoms could be trapped separately at different laser detuning values. Over 10^7 174 Yb atoms are collected in the MOT, whereas the atom number of fermionic isotope ^171Yb is roughly 2.3 × 10^6 due to a lower abundance. Without the Zeeman slower the trapped atom numbers are one order of magnitude lower. Both the even and odd isotopes are recognized as excellent candidates of optical clock transition, so the cooling and trapping of ytterbium atoms by the blue MOT is an important step for building an optical clock.     

Simultaneous magneto-optical trapping of lithium and ytterbium atoms towards production of ultracold polar molecules

We have successfully implemented the first simultaneous magneto-optical trapping (MOT) of lithium (⁶Li) and ytterbium (¹⁷⁴Yb) atoms towards production of ultracold polar molecules of LiYb. For this purpose, we developed the dual atomic oven which contains both atomic species as an atom source and successfully observed the spectra of the Li and Yb atoms in the atomic beams from the dual atomic oven. We constructed the vacuum chamber including the glass cell with the windows made of zinc selenium (ZnSe) for the CO₂ lasers, which are the useful light sources of optical trapping for evaporative and sympathetic cooling. Typical atom numbers and temperatures in the compressed MOT are 7×10³ atoms, 640 μK for ⁶Li, 7×10⁴ atoms, and 60 μK for ¹⁷⁴Yb, respectively.     

26 Al beam production by a solid state laser ion source at TRIUMF

Many experiments carried out at radioactive beam facilities require the production of intense, isotopically clean and isobar free beams of a particular isotope. At TRIUMF the addition of a resonant ionization laser ion source (TRILIS) enables a multitude of new beams and therefore new experiments to be carried out. ²⁶Al was one of the first radioactive ion beams delivered to an experiment using TRILIS. This paper outlines the development of the ²⁶Al ion beam for nuclear astrophysics.      

One — dimensional laser beam steering using frequency detuning in two — wave mixing with a BaTiO3 crystal

We demonstrate a method of one-dimensional laser beam deflection using frequency detuning in two-wave mixing. Energy exchange between the interfering beams in a photo-refractive BaTiO₃ crystal has been used for deflection of a pump beam into predetermined probe beam directions. A one-dimensional array of several beams is generated from a single probe beam, employing a piezo-mirror and beam splitter combination. Probe beams so produced are detuned by exciting the piezo-mirror with a periodic near-saw-tooth voltage so as to produce running fringes. However, stable holographic gratings are recorded by matching the frequency of the probe beam with that of a pump beam reflected from another vibrating piezo-mirror, thereby controlling the direction of beam deflection.     

Quadrupole oscillations in a quantum degenerate Bose–Fermi mixture

We study the collective dynamics in a degenerate Bose–Fermi mixture of ¹⁷⁴Yb and ¹⁷³Yb atoms. We excite collective oscillations by a sudden reduction of the trapping confinement and observe low m=0 quadrupole oscillations of condensates in ¹⁷⁴Yb. First the oscillations in ¹⁷⁴Yb atoms alone are investigated, and they are well described by the time-dependent Gross–Pitaevskii equation in the Thomas–Fermi approximation. Using the same procedure the quadrupole oscillations are excited for a ¹⁷⁴Yb–¹⁷³Yb Bose–Fermi mixture. In comparing data taken with and without fermionic ¹⁷³Yb atoms, the oscillation frequency of the quadrupole mode in the condensate decreases with the presence of ¹⁷³Yb atoms.     

Development of an apparatus for cooling <Superscript>6</Superscript>Li-<Superscript>87</Superscript>Rb Fermi-Bose mixtures in a light-assisted magnetic trap

We describe an experimental setup designed to produce ultracold trapped gas clouds of fermionic ⁶Li and bosonic ⁸⁷Rb. This combination of alkali metals has the potential to reach deeper Fermi degeneracy with respect to other mixtures since it allows for improved heat capacity matching which optimizes sympathetic cooling efficiency. Atomic beams of the two species are independently produced and then decelerated by Zeeman slowers. The slowed atoms are collected into a magneto-optical trap and then transferred into a quadrupole magnetic trap. An ultracold Fermi gas with temperature in the 10^?3 T _F range should be attainable through selective confinement of the two species via a properly detuned laser beam focused in the center of the magnetic trap.     

Highly selective multistep ionization of atoms by laser radiation

The possibility of dramatic selectivity increase during the stepwise ionization of atoms due to selective excitation at every step has been examined. Evaluations have been made to estimate the selectivity of excitation and ionization by laser radiation of some atoms, their isotopic shifts of absorption lines being observed at several excitation steps, for instance those of U, Yb, Gd. During three-step ionization of Yb atoms in atomic beam one may obtain an excitation selectivity equal to 4.4 × 10¹⁶ cm².     

Experiments with intense secondary beams of radioactive ions

Electromagnetic mass separation applied on-line to accelerators and nuclear reactors is now a standard technique for producing preselected isotopic beams (A, Z selection) of nuclear reaction products. The development, performance and anatomy of a large on-line isotope separator facility, the CERN-ISOLDE, is discussed. As a result of recent technical developments it is now possible to study individual nuclei of about 40 elements, in many cases out to where the limits of nucleon binding are approached and half-lives become as short as 10 ms. It is shown that the nuclear reaction processes induced with the high-intensity several hundred MeV proton beam can provide secondary radioactive beams in almost all regions of the nuclidic chart with intensities which are not matched by any other method. The intense beams of 10⁸–10¹¹ atoms/s have opened up a number of new experimental possibilities like laser spectroscopy on radioactive atoms, radioactive targets for nuclear reaction spectroscopy, and precision X-ray shift measurements.     

Quantum-degenerate gases of Ytterbium atoms

Evaporative cooling of ultracold Yb atoms near the quantum-degenerate regime was experimentally studied. Three bosons of ¹⁷⁰Yb, ¹⁷²Yb, ¹⁷⁶Yb and two fermions of ¹⁷¹Yb and ¹⁷³Yb were evaporatively cooled in a crossed far-off resonant trap (FORT). We observed that ¹⁷⁰Yb and ¹⁷²Yb were not concentrated into the crossed region. We found that, in the cases of ¹⁷⁶Yb atoms, atoms were concentrated well into the crossed region. The following evaporative cooling in the crossed region, however, did not work well. We performed the simultaneous trapping and sympathetic cooling in the crossed FORT by use of ¹⁷²Yb-174Yb, ¹⁷⁴Yb-¹⁷⁶Yb, ¹⁷²Yb-¹⁷⁶Yb, and ¹⁷¹Yb-¹⁷⁴Yb pairs. We observed that evaporative cooling worked well. This result shows that we succeeded in the enhancement of the atom collision rate. Especially, by use of ¹⁷⁴Yb-¹⁷⁶Yb mixture, we obtained cold ¹⁷⁶Yb whose phase space density was 0.02. We observed a large atom loss, which limited the further sympathetic evaporative cooling. We also evaporatively cooled ¹⁷⁴Yb in a 1D optical lattice. Evaporative cooling worked very well because the atoms were initially trapped at a high density. After evaporative cooling, we obtained very cold atoms, and T/T _F was estimated to be 1.2.     

Detection of very rare isotopes by laser collinear resonant ionization of fast atoms

Results are presented of the work on the development of a method for detecting ultra rare isotopes, based on the collinear isotope-selective laser ionization of atoms in a fast bearn. The rare isotope³He was detected at a selectivity of 10⁹ and isotope-selective ionization of krypton atoms was demonstrated. A scheme is suggested for detecting the rare radioactive isotopes⁸⁵Kr and⁸¹Kr. The technique has been exploited for the measurement of hyperfine structures and isotope shifts of unstable Yb isotopes.     

激光冷却获得高亮度的亚稳态惰性气体原子束和原子阱

高强度的亚稳态惰性原子束流在原子分子物理实验研究中具有广泛的应用.使用射频电离方法和激光横向冷却技术制备了高强度的亚稳态氪原子束流,并使用数值模拟方法对横向冷却激光场中的原子径迹进行了分析.通过激光诱导荧光光谱方法测量原子束的束流特性,结果显示,横向冷却后在束流源下游230 cm处的原子束流强度达1.6atoms/(s*sr),束流强度提高了两个量级.利用这种高强度原子束流,我们成功囚禁了1.3×10¹⁰个亚稳态⁸⁴Kr原子,同时冷原子装载速率达到了3.0×10¹¹atoms/s;并利用该装置成功地实现了高亮度的亚稳态氩原子束和原子阱. 关键词： 横向冷却 原子束 原子阱 惰性气体     

Two-wave mixing and energy transfer in BaTiO3 application to laser beamsteering

Energy transfer between the two recording beams in a BaTiO₃ photorefractive crystal is analyzed as a function of the following parameters: incident beams ratio, spatial frequency, pump beam intensity. Exponential gain coefficients Γ ≈ 20 cm^-1 are reached for optimized holographic recording conditions. Application of the energy transfer to a new method of laser beam deflection is proposed.     

Experimental evaluation of the gas-phase collision cross-section of effusive Au beam with noble gases: The effect of size and flux

We find that the effusive atomic beam of Au atoms is deflected away by collision with noble gas atoms crossing in a perpendicular geometry with a beam flux of >1 × 10¹⁶/cm²s. The ratio of defected Au atoms is found to increase proportional to the flux of noble gases. In addition, the effective cross-section for the collision between Au and noble gases (Ne, Ar, Xe) is measured to increase in an order of Ne < Ar < Xe. As a result of the increased collision probability, the deflection ratio of Au beam in the noble gases is measured to be enhanced for the Au flux in the range of 1 × 10¹¹–10¹³ Au/cm²s. Our results show that the gas-phase collision can be reliably determined by measuring the deflection ratio. The experimentally determined collision cross-section also explains the variation in the deflection ratio among various noble gases and the importance of a long-range van der Waals interaction between Au and noble gases in the deflection efficiency.     

An intense, slow and cold beam of metastable Ne(3s) 3 P 2 atoms

We employ laser cooling to intensify and cool an atomic beam of metastable Ne(3 s) atoms. Using several collimators, a slower and a compressor we achieve a ²⁰Ne^* flux of 6×10 ¹⁰ atoms/s in an 0.7 mm diameter beam traveling at 100 m/s, and having longitudinal and transverse temperatures of 25 mK and 300μK, respectively. This constitutes the highest flux in a concentrated beam achieved to date with metastable rare gas atoms. We characterize the action of the various cooling stages in terms of their influence on the flux, diameter and divergence of the atomic beam. The brightness and brilliance achieved are 2.1 ×10 ²¹ s^-1m^-2sr^-1 and 5.0 ×10 ²² s^-1m^-2sr^-1, respectively, comparable to the highest values reported for alkali-metal beams. Bright beams of the ²¹Ne and ²²Ne isotopes have also been created. Received 22 June 2001     

A high-resolution time-of-flight mass spectrometer for the detection of ultracold molecules

We have realized a high-resolution time-of-flight mass spectrometer combined with a magneto-optical trap. The spectrometer enables excellent optical access to the trapped atomic cloud using specifically devised acceleration and deflection electrodes. The ions are extracted along a laser beam axis and deflected onto an off-axis detector. The setup is applied to detect atoms and molecules photoassociated from ultracold atoms. The detection is based on resonance-enhanced multi-photon ionization. Mass resolution up to m/Δm_rms=1000 at the mass of ¹³³Cs is achieved. The performance of this spectrometer is demonstrated in the detection of photoassociated ultracold ⁷Li¹³³Cs molecules near a large signal of ¹³³Cs ions. PACS 07.75.+h; 32.80.Rm; 37.10.Gh