Atoms In Magneto-optical Trap Research Articles

Sensitivity of radio-frequency electric field sensor based on Rydberg Stark effect

Rydberg atoms hold special attraction in electric applications due to their large transition electric dipole moments and huge polarization, which leads to a strong response of atom to electric fields. In radio-frequency (RF) fields, the Rydberg levels are AC Stark shift and splitting, which can realize the study of high-sensitivity electric field sensor of Rydberg atoms. In this work, we use the simpler Shirley’s time-independent Floquet Hamiltonian model to calculate the AC Stark energy spectrum of Cs Rydberg atoms. This model can reduce the basic Hamiltonian into such a Hamiltonian that includes only those Rydberg states that have direct dipole-allowed transitions with the target state, thereby significantly improving the speed of computation. The accuracy of the calculation is proved by fitting with the calculated frequency shift of DC Stark energy levels in the weak fields, and the polarizability of 60D<sub>5/2</sub> and 70D<sub>5/2</sub> Rydberg atomic states are obtained by fitting with the measured ion spectra of DC Stark Cs ultra-cold Rydberg atoms in magneto-optical trap. In addition, we calculate the AC Stark shift of Cs Rydberg atom <inline-formula><tex-math id="M2">\begin{document}$ \left| {60{{\text{D}}_{5/2}},{m_j} = 1/2} \right\rangle $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M2.png"/></alternatives></inline-formula> state in electric fields with different frequencies with <i>ε</i> = 100 mV/m. Rydberg atoms provide a structured spectrum of sensitivity to electric fields due to strong resonant interaction and off-resonant interaction with many dipole-allowed transitions to nearby Rydberg states. This kind of the frequency response structure is of significance to a broadband sensor. And we calculate the sensitivity and the scaling of the signal-to-noise ratio (SNR), <i>β</i>, varying with detuning from the <inline-formula><tex-math id="M3">\begin{document}$ \left| {60{{\text{D}}_{5/2}}} \right\rangle \to \left| {61{{\text{P}}_{3/2}}} \right\rangle $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240162_M3.png"/></alternatives></inline-formula> transition. The value of <i>β</i> allows one to use the result for any Rydberg state sensor to determine the SNR for any <i>Ε</i> in a 1 s measurement. Therefrom, Rydberg sensor can preferentially detect many RF frequencies spreading across its carrier spectral range without modification while effectively rejecting large portions where the atom response is significantly weaker, and the signal depends primarily on the detuning of the RF field to the nearest resonance which does not convey the RF frequency directly.

Artificial magnetism for a harmonically trapped Fermi gas in a synthetic magnetic field

We have analytically explored the artificial magnetism for a 3D spin-polarized harmonically trapped ideal Fermi gas of electrically neutral particles exposed to a uniform synthetic magnetic field. Though polarization of the spin is necessary for trapping electrically neutral atoms in a magneto-optical trap, Pauli paramagnetism can not be studied for the spin-polarized Fermi system. However, it is possible to study Landau diamagnetism and de Haas-van Alphen effect for such a system. We have unified the artificial Landau diamagnetism and the artificial de Haas-van Alphen effect in a single framework for all temperatures as well as for all possible magnitudes of the synthetic magnetic field in the thermodynamic limit. Our prediction is testable in the present-day experimental setup for ultracold fermionic atoms in magneto-optical trap.

High-resolution collision energy control through ion position modulation in atom-ion hybrid systems.

We demonstrate an ion shuttling technique for high-resolution control of atom-ion collision energy by translating an ion held within a radio-frequency trap through a magneto-optical atom trap. The technique is demonstrated both experimentally and through numerical simulations, with the experimental results indicating control of ion kinetic energies from 0.05 to 1 K with a fractional resolution of ∼10 and the simulations demonstrating that kinetic energy control up to 120 K with a maximum predicted resolution of ∼100 is possible, offering order-of-magnitude improvements over most alternative techniques. Finally, we perform a proof-of-principle chemistry experiment using this technique and outline how the method may be refined in the future and applied to the study of molecular ion chemistry.

Measurements of quantum defect in Rydberg D-states for lithium atoms

We have developed an effective spectroscopic method for measure the energy spectra of highly excited ultracold atoms using the registration of resonance fluorescence of atoms in magneto-optical trap during two-step cw excitation of Rydberg states by uv laser. Using this method it was obtained the value of the quantum defect was determined for Rydberg states nD of lithium-7 atoms δ = 0.00192(17).

Background-free fluorescence detection of cold atoms in a two-color magneto-optical trap

A two-color magneto-optical trap (MOT) for trapping cesium (Cs) atoms is experimentally realized. This two-color MOT employs the radiation forces due to photon scattering from the Cs 6P(3/2) F' = 5 - 8S(1/2) F" = 4 excited-state transition, which replaced one pair of the three pairs of cooling/trapping laser beams operating on a single-photon red detuning to the Cs 6S(1/2) F = 4 - 6P(3/2) F' = 5 cycling transition in a standard six-beam Cs MOT, and can cool and trap atoms on both the red-detuning and blue-detuning sides of the two-photon resonance. Employing the two-color MOT, the background-free fluorescence detection of trapped atoms has been demonstrated. This technique will be useful for observation of weak fluorescence signal radiated from single atoms in MOT.

Determination of the rotational constant of the Cs_2 0_g ^- (6s + 6p_3/2) state by trap loss spectroscopy

we demonstrated a high sensitive trap-loss spectroscopy technique by modulating fluorescence of cold atoms in magneto-optical trap, which allow a direct spectroscopy detection of the rovibrational levels with a very weak transition probability. The low-lying vibrational spectroscopy of upsilon = 3 approximately 17 of Cs(2) 0g- pure long-range state have been observed with rotational structures, which are well resolved up to J = 8. The rotational constants are obtained by fitting experimental data to a nonrigid rotation model.

Low-Energy-Spread Ion Bunches from a Trapped Atomic Gas

We present time-of-flight measurements of the longitudinal energy spread of pulsed ultracold ion beams, produced by near-threshold ionization of rubidium atoms captured in a magneto-optical atom trap. Well-defined pulsed beams have been produced with energies of only 1 eV and a root-mean-square energy spread as low as 0.02 eV, 2 orders of magnitude lower than the state-of-the-art gallium liquid-metal ion source. The low energy spread is important for focused ion beam technology because it enables milling and ion-beam-induced deposition at sub-nm length scales with many ionic species, both light and heavy. In addition, we show that the slowly moving, low-energy-spread ion bunches are ideal for studying intricate space charge effects in pulsed beams. As an example, we present a detailed study of the transition from space charge dominated dynamics to ballistic motion.

Design and validation of an accelerator for an ultracold electron source

We describe here a specially designed accelerator structure and a pulsed power supply that are essential parts of a high brightness cold atoms-based electron source. The accelerator structure allows a magneto-optical atom trap to be operated inside of it, and also transmits subnanosecond electric field pulses. The power supply produces high voltage pulses up to 30 kV, with a rise time of up to 30 ns. The resulting electric field inside the structure is characterized with an electro-optic measurement and with an ion time-of-flight experiment. Simulations predict that 100 fC electron bunches, generated from trapped atoms inside the structure, reach an emittance of 0.04 mm mrad and a bunch length of 80 ps.

Semiclasical model of magneto-optical trap depth

We report the results of trap depth calculations based on the semiclassical theory of interaction of light field with atom in magneto-optical trap (MOT). In our model of magneto-optical trap we take into account Zeeman shift of ground and excited states in local magnetic field and only Doppler cooling force are considered. The calculated trap depth has been compared with value of trap depth estimated from experimental results for 7Li.

Measurement of the photoionization cross section of the(2p)(3p)5D33state of neon

We report a new measurement of the photoionization cross section for the $(2p)^{5}(3p)$ $^{3}D_{3}$ state of neon at the wavelengths of 351 and $364\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. These data were obtained by monitoring the decay of the fluorescence of atoms trapped in a magneto-optical atom trap under the presence of a photoionizing laser, a technique developed by Dinneen et al. [Opt. Lett. 17, 1706 (1992)]. We obtain absolute photoionization cross sections of $2.05\ifmmode\pm\else\textpm\fi{}0.25\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}$ at $\ensuremath{\lambda}=351\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ and $2.15\ifmmode\pm\else\textpm\fi{}0.25\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}$ at $\ensuremath{\lambda}=364\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, an improvement in accuracy of a factor of 4 over previously published values. These new values are not consistent with published theoretical data.

Enhancement in the number of trapped atoms in a cesium magneto-optical trap by a near-resonant control laser

We demonstrate enhancement in the number of trapped cesium atoms in a magneto-optical trap (MOT) using a control laser that illuminates only a small faction of the capture region of the trap without interacting with the cold cloud of atoms. The enhancement is maximized when the laser is slightly blue detuned with respect to the cooling transition. Trap loading curves point to approximately a twofold increase in the capture rate, which as a consequence results in the increase in the steady state number of trapped atoms. Enhanced loading is confirmed by MOT loading and decay curves taken under the modulation of the control laser beam. Optical pumping of the inaccessible Zeeman states into the stretched states is suggested as a possible mechanism.

Measurements of trap parameters of a magneto-optical trap by parametric resonance

We present a method to measure the trap frequency or the spring constant of a magneto-optical atom trap via the parametric resonance. When the intensity of the cooling laser is modulated at around twice its resonant trap frequency, the trapped atoms are parametrically excited and divided into two groups oscillating with the motional phase difference of $\ensuremath{\pi}$. We find that one can measure the natural trap frequency as the modulation amplitude is decreased down to its threshold value. The experimental results are in good agreement with the three-dimensional Doppler cooling theory based on the rate equation model.

Influence of the number of atoms in a ring-shaped magneto-optical trap: Observation of bifurcation

The spatial ring-shaped distribution of atoms in a magneto-optical trap, produced by misaligned Gaussian laser beams, is investigated with respect to the increase in the number of trapped atoms. Experimental observation of the bifurcation of a single ring into a double-ring structure is reported and explained using a model that includes radiation force due to reabsorption of photons together with the conventional radiative force.

Cold Atoms in a Hollow Mirror Trap

We present a novel and simple vapour-cell magneto-optical atom trap in a pyramidal and a conical hollow mirror cavity. A single laser beam having modulation sidebands at microwaves is used for cooling, trapping and repumping of rubidium atoms. When the laser is circularly polarized and sent into the hollow region, three pairs of counterpropagating beams are automatically produced therein, having the same polarization configuration as in the conventional six beam magneto-optical trap. The precooled atom sources thus produced may be used to obtain much colder and denser atoms for study of their quantum statistical properties.

Behavior of atoms in a compressed magneto-optical trap

We investigate the behavior of a cloud of atoms in a magneto-optical trap, which—after collection—is compressed when the field gradients of the trap magnetic field are increased. We measure sizes and shapes of the atom cloud as a function of laser detuning, magnetic field gradient, and number of trapped atoms. A transient density increase of more than an order of magnitude has been achieved. Moreover, reproducible Gaussian density distributions are observed at large detunings and intermediate magnetic-field gradients, permitting an accurate determination of density.