Bichromatic force on metastable argon for atom-trap trace analysis

Feng, Zhongyi; Ebser, Sven; Ringena, Lisa; Ritterbusch, Florian; Oberthaler, Markus K.

doi:10.1103/physreva.96.013424

Cited by 6 publications

(5 citation statements)

References 15 publications

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“…Two vertical red lines mark the region where the magnitude of the BCF exceeds purely radiative pressure. Sharp resonances around 0 and ±45 m/s represent Doppleron resonances and have been previously seen in BCF profiles for atoms [42]. Solid horizontal green line shows the average bichromatic force achieved in the experiment.…”

supporting

confidence: 52%

“…Using the measured optimal BCF deflections for SrOH we obtain F BCF = (3.7 ± 0.7) F rad , which is 35% lower compared to the predicted value. Experimental observations of BCF for atoms have seen significant reduction in the force magnitude under realistic experimental conditions [42]. In our experiment, some of possible explanations for discrepency are power imbalance between the two beat note trains, less than unity overlap efficiency between the laser and molecular beams, and a dependence of the two forces on irradiance which favors the radiative force in the wings of the Gaussian laser profile.…”

mentioning

confidence: 49%

“…For example, short-distance deceleration of Cs atomic beam with BCF was demonstrated, achieving a force ten times greater than radiative force [40]. Additionally, BCF has been used for He [41] and Ar [42] atomic beam collimation.…”

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confidence: 99%

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Coherent Bichromatic Force Deflection of Molecules

et al. 2018

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We demonstrate the coherent optical bichromatic force on a molecule, the polar free radical strontium monohydroxide (SrOH). A dual-frequency retro-reflected laser beam addressing theX 2 Σ + ↔Ã 2 Π 1/2 electronic transition coherently imparts momentum onto a cryogenic beam of SrOH. This directional photon exchange creates a bichromatic force that transversely deflects the molecules. By adjusting the relative phase between the forward and counter propagating laser beams we reverse the direction of the applied force. A momentum transfer of 70 k is achieved with minimal loss of molecules to dark states. Modeling of the bichromatic force is performed via direct numerical solution of the time-dependent density matrix and is compared with experimental observations. Our results open the door to further coherent manipulation of molecular motion, including the efficient optical deceleration of diatomic and polyatomic molecules with complex level structures.Laser manipulation of atomic motion has revolutionized atomic, molecular and optical (AMO) physics [1,2]. The widely-used techniques of laser cooling and trapping made possible the creation of ultracold degenerate quantum gases [3], simulation of important condensed matter models [4] and development of new quantum sensors [5,6] and clocks [7]. Laser deceleration and cooling of atomic beams -a necessary part of the trap loading process -typically requires scattering tens of thousands of photons in order to bring room (or oven) temperature atoms to velocities where they can be confined by electromagnetic traps for further studies [8]. While beam deceleration employing the spontaneous radiation pressure force has been a standard for atomic experiments, its application to slowing molecular beams has been limited by the small change in kinetic energy per scattered photon and the myriad of internal molecular states, which inhibits photon cycling. At the same time, there is extreme interest in creating ultracold molecules for new physics applications [9].Neutral diatomic molecules are predicted to play an important role in diverse research areas of modern physics such as quantum simulation [10] and computation [11], as well as searches for new particles and fields beyond the Standard Model [12]. Larger polyatomic molecules will provide additional opportunities in physics and chemistry [13][14][15]. For example, exploring the origin of biomolecular homochirality [16] and understanding primordial chemistry leading to the development of organic life requires the use of large molecules [17]. However, these molecules' complexity presents significant challenges for direct laser slowing and cooling. Yet these are the key ingredients that allow for optical trapping, which, in turn, realizes long moleculelaser coherence times and high levels of quantum state control. Previously, the external motion of gas-phase polyatomic molecules has been manipulated with off-resonant laser fields [18] as well as electric [19], magnetic [20], and mechanical techniques [21]. Inspired by the success of...

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confidence: 52%

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confidence: 49%

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Coherent Bichromatic Force Deflection of Molecules

et al. 2018

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“…In the present experiment the potential depth of each lattice site would be much too shallow to trap atoms at the observed temperatures and the gradient forces average to zero on a length scale larger than the optical wavelength. However, introducing a second frequency to the laser field can drastically change the situation resulting in bichromatic forces (for a recent example see [24]).…”

Section: Trapping Mechanismmentioning

confidence: 99%

All-optical atom trap as a target for MOTRIMS-like collision experiments

et al. 2018

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Momentum-resolved scattering experiments with laser-cooled atomic targets have been performed since almost two decades with MOTRIMS (Magneto-Optical Trap Recoil Ion Momentum Spectroscopy) setups. Compared to experiments with gas-jet targets, MOTRIMS features significantly lower target temperatures allowing for an excellent recoil ion momentum resolution. However, the coincident and momentum-resolved detection of electrons was long rendered impossible due to incompatible magnetic field requirements. Here we report on a novel experimental approach which is based on an all-optical 6 Li atom trap that -in contrast to magneto-optical traps -does not require magnetic field gradients in the trapping region. Atom temperatures of about 2 mK and number densities up to 10 9 cm −3 make this trap ideally suited for momentum-resolved electron-ion coincidence experiments. The overall configuration of the new trap is very similar to conventional magnetooptical traps. It mainly requires small modifications of laser beam geometries and polarization which makes it easily implementable in other existing MOTRIMS experiments.

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“…This makes BCF more applicable than the spontaneous force in manipulating diatomic and polyatomic molecules which lack near-cycling transitions due to poor vibrational overlap. BCF has been observed and studied in various atomic systems [18,[21][22][23][24][25][26]. Here we demonstrate the effectiveness of BCF in a molecular system via the transverse deflection of a beam of CaF, a polar diatomic molecule, as shown in Fig.…”

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confidence: 67%

Deflection of a molecular beam using the bichromatic stimulated force

et al. 2018

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We demonstrate that a bichromatic standing-wave laser field can exert a significantly larger force on a molecule than ordinary radiation pressure. Our experiment measures the deflection of a pulsed supersonic beam of CaF molecules by a two-frequency laser field detuned symmetrically about resonance with the nearly closed X(v = 0) → B(v ′ = 0) transition. The inferred force as a function of relative phase between the two counterpropagating beams is in reasonable agreement with numerical simulations of the bichromatic force in this multilevel system. The large magnitude of the force, coupled with the reduced rate of spontaneous emission, indicates its potential utility in the production and manipulation of ultracold molecules.Radiative forces on atoms have been the major tool enabling laser cooling and trapping [1] and the myriad of applications which have resulted, including precision spectroscopy, quantum degenerate gases, ultracold collisions, and quantum simulations. There are two general types of radiative force: spontaneous force, also known as radiation pressure, and stimulated force, also known as the dipole force. Radiation pressure is the result of absorption/spontaneous emission cycles, while the stimulated force arises from absorption followed by stimulated emission. The latter requires an intensity gradient and can be thought of as a coherent redistribution of photons between various propagation directions. Laser manipulation of atoms is a well-developed field, but recently, these techniques have been increasingly applied to molecules [2]. This extension is nontrivial due to the complicated internal structure of molecules caused by their vibrational and rotational degrees of freedom [3]. Radiation pressure has been used to slow, cool, and trap molecules that fortuitously have near-cycling transitions [4][5][6][7][8][9][10][11][12][13]. Stimulated forces have also been used to manipulate molecules [14-17], but on a more limited scale. Compared to radiation pressure, stimulated forces have two significant advantages for molecules: (1) radiation pressure is limited by the spontaneous emission rate, while stimulated forces can greatly exceed this saturated value; and (2) radiation pressure relies on spontaneous emission which can optically pump the molecules into "dark" states which no longer interact with the laser field.A specific type of stimulated force, the bichromatic force (BCF) [18,19], is particularly promising for manipulating molecules [20]. The BCF involves two frequencies which are tuned symmetrically above and below a resonant frequency ω by ±δ. The two frequencies are both present in oppositely-directed beams, which gives rise to counterpropagating trains of beat notes with a fixed relative phase, χ. In a simplified picture of BCF, if each beat is considered an effective π-pulse which inverts the population, a molecule can be excited by a beat from one direction and rapidly returned to the ground state by a beat from the other direction. Each absorption/stimulated emission cycle imparts an i...

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Bichromatic force on metastable argon for atom-trap trace analysis

Cited by 6 publications

References 15 publications

Coherent Bichromatic Force Deflection of Molecules

Coherent Bichromatic Force Deflection of Molecules

All-optical atom trap as a target for MOTRIMS-like collision experiments

Deflection of a molecular beam using the bichromatic stimulated force

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