Slow Atomic Beam Research Articles

Focusing of an Atomic Beam for the Efficient Loading of an Atom Chip

A method has been proposed to increase the rate of loading of atoms in a U-magneto-optical trap near an atom chip. The method is based on the focusing of a slow atomic beam into the localization region of the atom chip. The overdamped focusing regime has been considered. In this case, the focal length is independent of the initial transverse velocity of atoms. It has been shown that the focusing of the atomic beam makes it possible to increase the loading rate in the localization region 250 μm in diameter by a factor of 160.

Zeeman slowing of a group-III atom

We realize the first Zeeman slower of an atom in the Main Group III of the periodic table, otherwise known as the "triel elements". Despite that our atom of choice (namely indium) does not have a ground state cycling transition suitable for laser cooling, slowing is achieved by driving the transition $\lvert 5P_{3/2},F=6 \rangle \rightarrow \lvert 5D_{5/2},F=7 \rangle$, where the lower-energy state is metastable. Using a slower based on permanent magnets in a transverse-field configuration, we observe a bright slowed atomic beam at our design goal velocity of 70 m/s. The techniques presented here can straightforwardly extend to other triel atoms such as thallium, aluminum, and gallium. Furthermore, this work opens the possibility of cooling Group III atoms to ultracold temperatures.

Characterising a tunable, pulsed atomic beam using matter-wave interferometry

We describe the creation and characterisation of a velocity tunable, spin-polarized beam of slow metastable argon atoms. We show that the beam velocity can be determined with a precision below 1% using matter-wave interferometry. The profile of the interference pattern was also used to determine the velocity spread of the beam, as well as the Van der Waals (VdW) co-efficient for the interaction between the metastable atoms and the multi-slit silicon nitride grating. The VdW co-efficient was determined to be C 3 = 1.84 ± 0.17 a.u., in good agreement with values derived from spectroscopic data. Finally, the spin polarization of the beam produced during acceleration of the beam was also measured, demonstrating a spatially uniform spin polarization of 96% in the m = +2 state.

A slow and clean fluorine atom beam source based on ultraviolet laser photolysis

A slow and clean fluorine atom beam source is one of the essential components for the low-collision energy scattering experiment involving fluorine atom. In this work, we describe a simple but effective photolysis fluorine atom beam source based on ultraviolet laser photolysis, the performance of which was demonstrated by high-resolution time-of-flight spectra from the reactive scattering of F+HD. This beam source paved the way for studies of low energy collisions with fluorine atoms.

A bright and stable beam of slow metastable helium atoms

A stable high-intensity atomic beam source plays a key role in many precision measurements. The precision spectroscopy of slow metastable (<inline-formula><tex-math id="M6">\begin{document}$2^3{\rm S}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M6.png"/></alternatives></inline-formula>) helium atoms is of great interest in testing quantum electrodynamics and determining the fine structure constant. By improving the source cavity structure and using laser cooling method, the beam flux is greatly enhanced. The added Zeeman slower reduces the longitudinal velocity of atoms, and at the same time increases the beam brightness of atoms at one single speed. Near the back end of Zeeman slower, a two-dimensional magneto-optical trap is added to collimate and focus the atomic beam. In addition, A beam stabilizing system is developed by using feedback control method. By changing the frequency of transverse cooling laser to change the cooling efficiency, the fluctuation of atomic beam intensity can be compensated in real time, and then the beam intensity can be stabilized at the target number. Experiments show that the continuous beam of metastable helium atoms at a velocity of <inline-formula><tex-math id="M7">\begin{document}$(100\pm 3.6)$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M7.png"/></alternatives></inline-formula> m/s has an intensity of <inline-formula><tex-math id="M8">\begin{document}$5.8\times10^{12}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M8.png"/></alternatives></inline-formula> atoms/s/sr and a relative stability of 0.021%. In the experiment of precise spectral measurement based on atomic beam, the narrow longitudinal velocity distribution reduces the lateral Doppler broadening effect, and the lower longitudinal velocity also reasonably reduces the systematic error caused by the first-order Doppler effect. The atomic beam with such high intensity and stability in a single momentum and quantum state obviously improves the signal-to-noise ratio of the spectrum, and further reduces the statistical error of the results in the same detection time. Using this atomic beam, we demonstrated spectroscopy of the <inline-formula><tex-math id="M9">\begin{document}$2^3{\rm S}-2^3{\rm P}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M9.png"/></alternatives></inline-formula> transition of <inline-formula><tex-math id="M10">\begin{document}$^4{\rm{He}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20201833_M10.png"/></alternatives></inline-formula> under the condition of only 0.1% of the saturated intensity. At this time, the full width at half maximum of the spectral peak is almost close to the natural line width, but the spectral signal-to-noise ratio is still better than 400 and the frequency shift caused by the detection laser power can be less than 1 kHz. This kind of spectral detection at low power can effectively reduce the power-dependent frequency shift, thus obtaining more reliable detection results. This metastable helium atom beam experimental system can also be used as a reference for similar precision measurement experiments.

Three-Dimensional Cooling of an Atom-Beam Source for High-Contrast Atom Interferometry

We present a compact, two-stage atomic beam source that produces a continuous, narrow, collimated and high-flux beam of rubidium atoms with sub-Doppler temperatures in three dimensions, which features very low emission of near-resonance fluorescence along the atomic trajectory. The atom beam source originates in a pushed two-dimensional magneto-optical trap (2D$^+$ MOT) feeding a slightly off-axis three-dimensional moving optical molasses stage that continuously cools and redirects the atom beam. The capture velocity of the moving optical molasses is deliberately chosen to be low, $\sim 3$ m/s, to reduce fluorescence, and the cooling light is detuned by several atomic linewidths from resonance to reduce the absorption cross-section of cooling-induced fluorescence. Near-resonance light from the 2D$^+$ MOT and the push beam does not propagate to the output atomic trajectory due to a 10 degree bend in the atomic trajectory. The atomic beam emitted from the two-stage source has a flux up to $1.6(3)\times 10^9\;\textrm{atoms/s}$, with an optimized temperature of $15.0(2)\;\mu$K. We employ continuous Raman-Ramsey interference measurements at the atom beam output to study the sources of decoherence in the presence of continuous cooling, and demonstrate that the atom beam source effectively preserves high fringe contrast even during cooling. This cold-atom beam source is appropriate for use in atom interferometers and clocks, where continuous operation eliminates dead time, the slow atom beam velocity (6 - 16 m/s) improves sensitivity, the narrow 3D velocity distribution improves fringe contrast, and the low reabsorption of scattered light mitigates decoherence caused by the continuous cooling process.

Formation of a beam of cold atoms by laser frequency tuning

We report the possibility of producing a beam of slow atoms with a characteristic velocity of by the ‘chirp’ method, namely, cooling by variable-frequency radiation. Method modifications are considered, which substantially reduce dimensions of the slower, the width of the longitudinal velocity distribution of the atomic beam, and the area of its cross section. The modified method of laser radiation frequency tuning for cooling rubidium atoms is mathematically simulated.

An adaptable dual species effusive source and Zeeman slower design demonstrated with Rb and Li.

We present a dual-species effusive source and Zeeman slower designed to produce slow atomic beams of two elements with a large mass difference and with very different oven temperature requirements. We demonstrate this design for the case of (6)Li and (85)Rb and achieve magneto-optical trap (MOT) loading rates equivalent to that reported in prior work on dual species (Rb+Li) Zeeman slowers operating at the same oven temperatures. Key design choices, including thermally separating the effusive sources and using a segmented coil design to enable computer control of the magnetic field profile, ensure that the apparatus can be easily modified to slow other atomic species. By performing the final slowing using the quadrupole magnetic field of the MOT, we are able to shorten our Zeeman slower length making for a more compact system without compromising performance. We outline the construction and analyze the emission properties of our effusive sources. We also verify the performance of the source and slower, and we observe sequential loading rates of 12 × 10(8) atoms/s for a Rb oven temperature of 140 °C and 1.1 × 10(8) atoms/s for a Li reservoir at 460 °C, corresponding to reservoir lifetimes for continuous operation of 10 and 4 years, respectively.

Particularities of optical pumping effects in cold and ultra-slow beams of Na and Cs in the case of cyclic transitions

The time-dependent population dynamics of hyperfine (HF) levels of n 2 p 3/2 states is examined for cyclic transitions in alkali atoms. We study a slow and cold atomic beam of Na (n = 3) and Cs (n = 6), taking into account the long interaction time of light with atoms (~200 μs) inside the resonant laser beam. Simple analytical expressions for the populations of the excited states and for the intensities of the absorption lines are derived for a three-level system model. We show that at moderate pump laser power the mixing of HF levels is sufficient to form a flow of population from a cyclic transition to partially open transitions. We discuss various phenomena associated with the evolution of optical pumping that cannot be explained by general analysis of two-level system model.

Experimental apparatus for generating quantum degenerate gases of ytterbium atoms

We describe our experimental apparatus for generating quantum degenerate gases of bosonic 174Yb and fermionic 173Yb atoms. We use a Zeeman slower to generate a slow atomic beam and collect atoms in a magneto-optical trap formed by 556-nm laser beams without frequency modulations. Laser-cooled ytterbium atoms are transferred to a crossed optical dipole trap and evaporatively cooled to quantum degeneracy. Our system generates a Bose-Einstein condensate containing over 6 × 104174Yb atoms or a degenerate Fermi gas of about 7 × 104173Yb atoms at T/TF=0.8(1), where TF is the Fermi temperature of the gas. We highlight the high performance of the Zeeman slower and the home-made frequency-doubling systems for 399-nm and 556-nm lasers.

Nonlinear effects in optical pumping of a cold and slow atomic beam

By photoionizing hyperfine (HF) levels of the Cs state $6{\phantom{\rule{0.16em}{0ex}}}^{2}{P}_{3/2}$ in a slow and cold atom beam, we find how their population depends on the excitation laser power. The long time (around $180\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s})$ spent by the slow atoms inside the resonant laser beam is large enough to enable exploration of a unique atom-light interaction regime heavily affected by time-dependent optical pumping. We demonstrate that, under such conditions, the onset of nonlinear effects in the population dynamics and optical pumping occurs at excitation laser intensities much smaller than the conventional respective saturation values. The evolution of population within the HF structure is calculated by numerical integration of the multilevel optical Bloch equations. The agreement between numerical results and experiment outcomes is excellent. All main features in the experimental findings are explained by the occurrence of ``dark'' and ``bright'' resonances leading to power-dependent branching coefficients.

Radiative lifetimes and transition probabilities of neutral lanthanum

The radiative lifetimes of 72 odd-parity levels of neutral lanthanum are measured to ±5% accuracy using time-resolved laser-induced fluorescence on a slow atomic beam. The levels range in energy from 15031 to 32140 cm−1. Branching fraction measurements using Fourier-transform spectroscopy are attempted and completed for all of the 72 levels. The branching fractions, when combined with the radiative lifetimes, yield new transition probabilities for 315 lines of the first spectrum of lanthanum (La i ). This study is part of a larger body of work on the radiative properties of rare earth neutral atoms, and is motivated by research needs in lighting science and astrophysics.

Fe I OSCILLATOR STRENGTHS FOR TRANSITIONS FROM HIGH-LYING EVEN-PARITY LEVELS

New radiative lifetimes, measured to $\pm$ 5 % accuracy, are reported for 31 even-parity levels of Fe I ranging from 45061 cm$^{-1}$ to 56842 cm$^{-1}$. These lifetimes have been measured using single-step and two-step time-resolved laser-induced fluorescence on a slow atomic beam of iron atoms. Branching fractions have been attempted for all of these levels, and completed for 20 levels. This set of levels represents an extension of the collaborative work reported in Ruffoni et al. (2014). The radiative lifetimes combined with the branching fractions yields new oscillator strengths for 203 lines of Fe I. Utilizing a 1D-LTE model of the solar photosphere, spectral syntheses for a subset of these lines which are unblended in the solar spectrum yields a mean iron abundance of <log[{\epsilon}(Fe)]> = 7.45 $\pm$ 0.06.

A proposed method of efficient laser trapping of neutral radium atoms

We report theoretical studies of an efficient accumulation of 225Ra atoms in a magneto-optical trap (MOT) from an atomic beam. The number of atoms in the trap is limited due to the large leakage into metastable D states from the cooling transition and the loss mechanism from collisions with the background gases and with other elements in the atomic beam. We propose a setup consisting of an efficient Zeeman slower, an optical atomic beam deflector, and an Egg-MOT, which provides a large capture velocity, e.g. the Zeeman slower capture velocity of 581 ms−1 and the MOT capture velocity of 46 ms−1. Furthermore, the pure slow atomic beam produced by the optical atomic beam deflector can maximize the number of trapped atoms and their lifetime in a ultra high vacuum chamber by minimizing the collisional loss. Our proposed setup allows for the search for a permanent electric dipole moment based on laser-cooled and trapped radium atoms with improved sensitivity.

Cold beam of isotopically pure Yb atoms by deflection using 1D-optical molasses

We demonstrate generation of an isotopically pure beam of laser-cooled Yb atoms by deflection using 1D-optical molasses. Atoms in a collimated thermal beam are first slowed using a Zeeman Slower. They are then subjected to a pair of molasses beams inclined at $45^\circ$ with respect to the slowed atomic beam. The slowed atoms are deflected and probed at a distance of 160 mm. We demonstrate selective deflection of the bosonic isotope $^{174}$Yb, and the fermionic isotope $^{171}$Yb. Using a transient measurement after the molasses beams are turned on, we find a longitudinal temperature of 41 mK.

Guided and focused slow atomic beam from a 2 dimensional magneto optical trap

We report experimental results which demonstrate how a single laser can be used to both accelerate and guide caesium atoms initially trapped in a two dimensional magneto-optical trap (2D-MOT). The atomic beam size and velocity can be modified using both the laser power and detuning as parameters. In particular, using a 750 mW laser detuned 10 GHz from resonance, we demonstrate that it is possible to focus an atomic beam to a size of 0.4 mm as far as 60 cm from the output of the 2D-MOT with a flux on the order of 3 × 109 atoms/s.

Radiative lifetimes of neutral samarium

Radiative lifetimes of 120 odd-parity levels of neutral samarium, ranging in energy from 17 190 to 33 507 cm−1, are measured using the technique of time-resolved laser-induced fluorescence on a slow atomic beam. This work is part of an ongoing study of radiative properties of rare earth neutral atoms, and is motivated by research needs in astrophysics and lighting technology. This set of Sm i lifetimes substantially increases the available published lifetime data, with 49 of the 120 level lifetimes measured for the first time. These data, most of which are accurate to ±5%, will be combined with branching fractions determined from Fourier transform spectroscopy to produce a large set of measured Sm i transition probabilities.

Measurement of the hyperfine structure of antihydrogen in a beam

A measurement of the hyperfine structure of antihydrogen promises one of the best tests of CPT symmetry. We describe an experiment planned at the Antiproton Decelerator of CERN to measure this quantity in a beam of slow antihydrogen atoms.

Radiative lifetimes of neutral neodymium

This work is part of an on-going study of radiative properties of rare earth neutral atoms. This work is motivated by research needs in several disparate fields including astrophysics and lighting technology. Radiative lifetimes of 100 levels of neutral neodymium are measured using the technique of time-resolved laser-induced fluorescence on a slow atomic beam. Of the 100 levels, 3 are even parity ranging in energy from 25 746 to 26 835 cm−1, and the remaining 97 are odd parity ranging from 17 787 to 27 786 cm−1. This set of Nd i lifetimes represents a significant extension to the available published data, with 51 of the 100 level lifetimes measured for the first time. These data, which are accurate to ±5%, provide the absolute normalization for a large set of measured Nd i transition probabilities.

A Zeeman slower design with permanent magnets in a Halbach configuration

We describe a simple Zeeman slower design using permanent magnets. Contrary to common wire-wound setups, no electric power and water cooling are required. In addition, the whole system can be assembled and disassembled at will. The magnetic field is however transverse to the atomic motion and an extra repumper laser is necessary. A Halbach configuration of the magnets produces a high quality magnetic field and no further adjustment is needed. After optimization of the laser parameters, the apparatus produces an intense beam of slow and cold (87)Rb atoms. With typical fluxes of (1-5) × 10(10) atoms/s at 30 m s(-1), our apparatus efficiently loads a large magneto-optical trap with more than 10(10) atoms in 1 s, which is an ideal starting point for degenerate quantum gas experiments.