Sub-Doppler spectroscopy in a thin film of resonant vapor

Briaudeau, S.; Bloch, Daniel; Ducloy, M.

doi:10.1103/physreva.59.3723

Cited by 82 publications

(108 citation statements)

References 15 publications

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“…This relaxation time is of the same order as the mean free time between collisions of atoms with the cell surfaces, where the spin polarization is supposed to be completely destroyed. It is interesting to point out that the spectral width should become much narrower with decreasing laser intensity than that determined by the mean free time, because of selective polarization and detection of atoms that have long free flight times (and hence have long spin relaxation times) [11]. We show in Fig.…”

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confidence: 99%

Motion-Induced Magnetic Resonance of Rb Atoms in a Periodic Magnetostatic Field

et al. 2005

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We demonstrate that transitions between Zeeman-split sublevels of Rb atoms are resonantly induced by the motion of the atoms (velocity: ∼ 100 m/s) in a periodic magnetostatic field (period: 1 mm) when the Zeeman splitting corresponds to the frequency of the magnetic field experienced by the moving atoms. A circularly polarized laser beam polarizes Rb atoms with a velocity selected using the Doppler effect and detects their magnetic resonance in a thin cell, to which the periodic field is applied with the arrays of parallel current-carrying wires.PACS numbers: 32.30. Dx, 32.80.Bx By applying an electromagnetic (EM) wave to an atom at rest, one can resonantly induce transition between two atomic energy levels whose frequency difference coincides with the EM wave frequency. This resonance transition is one of the most extensively studied and widely utilized phenomena in atomic physics and also in other various fields. Also in the reversed configuration, that is, by an atom moving in a static periodic field, an internal transition can be made when the periodic perturbation experienced by the atom has a frequency equal to the transition frequency. The resonance transition of this kind, quite simple in principle and applicable to any particle with internal states, however, has been clearly demonstrated only in the phenomenon called "resonant coherent excitation" (RCE) [1] using channeled fast ion beams in periodic electric fields of crystals. RCE has attracted much attention [2,3] since the first proposal by Okorokov [4]. Recent progress made by using the high-energy beams of highly charged ions shows the possibility of high resolution spectroscopy of highly charged ions in an x-ray region of keV or 10 18 Hz [5]. The order of this transition frequency is determined by an ion velocity (∼ 10 8 m/s) and a lattice constant (∼ 10 −10 m).We report in this Letter on the resonance transition that is based on the same principles as RCE but is induced by a different type of interaction in a quite different energy range of neV or 10 5 Hz: magnetic resonance between the Zeeman sublevels of Rb atoms with a z velocity component v z of ∼ 100 m/s in a static magnetic field that is periodic in the z direction (period: a = 1 mm). This resonance transition, called motioninduced resonance in this Letter, was observed in a thin cell containing Rb vapor, with the periodic magnetic field applied with the arrays of parallel current-carrying wires sandwiching the cell. The atoms with a velocity selected using the Doppler effect were polarized by optical pumping with circularly polarized laser light slightly detuned from the D 2 line. The magnetic resonance between the ground state sublevels was optically detected with the same laser beam. We confirmed that the resonance occurs when the Zeeman splitting frequency coincides with v z /a, namely the frequency of the field experienced by the moving atoms. We successfully obtained the resonance spectra very similar to those of standard rf magnetic resonance. Our clear demonstration of motion-ind...

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confidence: 99%

Motion-Induced Magnetic Resonance of Rb Atoms in a Periodic Magnetostatic Field

et al. 2005

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“…When a cell of dilute gas is so thin that atomic (or molecular) trajectories are mostly from wall-to-wall, sub-Doppler spectral lineshapes can be obtained in a variety of processes (optical pumping, ...) under normal incidence : this results from a specific enhancement of the slow atoms contribution (see [2] and refs. therein), with respect to the transient nature of the atom-light interaction.…”

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“…indeed, the successive 1-photon processes cannot eliminate the Doppler-broadening when two different 1 k and 2 k axes are involved, so that the stepwise excitation process cannot strongly interfere with the 2-photon process. As a counterpart of the large pump detuning, the pump intensity can be high, as the condition Ω 1 , Ω 2 << ∆ required by the 3 rd order perturbation expansion, that imposes a Stark shift much smaller than ∆, remains easily respected.…”

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Dicke coherent narrowing in two-photon and Raman spectroscopy of thin vapor cells

Dutier¹,

Todorov²,

Hamdi³

et al. 2005

Phys. Rev. A

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The principle of coherent Dicke narrowing in a thin vapour cell, in which sub-Doppler spectral lineshapes are observed under a normal irradiation for a λ/2 thickness, is generalized to two-photon spectroscopy. Only the sum of the two wave vectors must be normal to the cell, making the two-photon scheme highly versatile. A comparison is provided between the Dicke narrowing with copropagating fields, and the residual Doppler-broadening occurring with counterpropagating geometries. The experimental feasibility is discussed on the basis of a first observation of a two-photon resonance in a 300 nm-thick Cs cell. Extension to the Raman situation is finally considered.

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“…large values of ). Note also that in the two works mentioned above, the surface was simple polished glass, and the experiments are far from providing "universal" evidences of the effectiveness of a "cos" law.A blooming of sub-Doppler resolution spectroscopy techniques in a thin film of dilute vapor at thermal equilibrium has been noted in the last decades, including selective reflection spectroscopy at an interface [22,26], and confined vapor spectroscopy in microor nano-cells [22,[27][28][29][30][31][32][33][34]. The Doppler broadening, associated to the distribution of random 7 atomic velocities, can be eliminated for well-chosen signals note by the way that the early observation of a sub-Doppler contribution in selective reflection [35], before the laser era, was originally attributed to the contribution of specular atomic collisions onto the surface, so that the first modern theory [36] of selective reflection spectroscopy also includes the specific contributions of atoms having undergone specular reflection.…”

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“…A natural consequence of an assumed M-B distribution of atomic velocities is that the distribution of "slow" atoms (for the normal component v  , i.e. atoms moving parallel to the wall) should be flat around null velocity.However, when pretending to use those atoms moving nearly parallel to a cell window, intrinsic difficulties arise: the long-range atom-surface (van der Waals type) attraction may curve the atomic trajectories, and this should particularly affects atoms moving parallel to the wall [22,33]; also, the local roughness of the window, which often largely exceeds an atomic step, may prevent very parallel motion to the window plane.In the principle, the development of experiments involving linear spectroscopy of a vapor close to an interface [22][23][24][29][30][31], even when limited to relatively broad subDoppler transitions, should have indicated to which extent the velocity distribution is flat for velocities around the selected velocities, currently 5-10 m/s. This should require analyzing the signal amplitude as a function of the broadening (e.g.…”

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Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell

Todorov

Bloch

2017

The Journal of Chemical Physics

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2 For a gas at thermal equilibrium, it is usually assumed that the velocity distribution follows an isotropic 3-dimensional Maxwell-Boltzmann (M-B) law. This assumption classically implies the assumption of a "cos ~85°-88.5° from the normal to the surface and no deviation from the M-B law is found within the limits of our elementary set-up. Finally we suggest tracks to explore more parallel velocities, when surface details -roughness or structureand the atom-surface interaction should play a key role to restrict the applicability of a M-B-type distribution.3 I. The Maxwell-Boltzmann distribution of atomic velocities in a dilute gas and the signature of atoms moving close to a wall container.It is usually unquestioned, in the field of Atomic and Molecular Physics, that the atomic velocity distribution in a gas at thermal equilibrium is governed by a MaxwellBoltzmann (M-B) distribution for kinetic energy, with a 3-dimensional isotropy. This is even the basis for proposals aiming to measure the Boltzmann constant by the Doppler broadening of a thermal gas, in view of a redefinition of the temperature scale [1].However, in the vicinity of a wall, the isotropy is locally lost in a region, often called the Knudsen layer [2], where the atom-wall collisions modify the behavior of the gas. The microscopic description of an atom-surface collision or interaction is a rich field, which has been addressed experimentally for a long time. The possibility of a velocity distribution depending upon the vessel shape, has been sometimes considered, although the proofs for self-consistency seem delicate [3]. Despite the variety of behaviors found microscopically at the frontier of the gas, it remains usually assumed that the overall gas behavior obeys a M-B distribution (see e.g. [4]).As recalled in detail in the review by Comsa and David [5], which includes a significant historical approach, the distribution of atomic velocities established by Maxwell for an isotropic volume of a gas with molecules undergoing numerous collisions (the basis for the ideal gas kinetics) has been founded upon questionable hypotheses concerning the effect of the surface. The Maxwell model assumes that a fraction f of the molecules sticks onto the wall, for further scattering or "desorption" according to the expected "gas law", while the remaining fraction (1-f) just undergoes an ideal (specular) reflection on the wall.Retrospectively, it is clear that specular atomic reflection cannot be considered as a general 4 phenomenon for an unprepared surface and a high atomic density. Rather, quantum reflection on a wall potential is an effect well identified but difficult to observe, and applies to atoms cooled to extremely slow motion [6] (along the normal), while requiring perfectly polished surfaces [7]. For the desorption process, occurring on considerably longer time scale, arguments based upon conservation laws of the flux to and from the surface, combined with the assumed isotropic M-B distribution in the surrounding gas, lead to the cos law (Knudsen l...

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Sub-Doppler spectroscopy in a thin film of resonant vapor

Cited by 82 publications

References 15 publications

Motion-Induced Magnetic Resonance of Rb Atoms in a Periodic Magnetostatic Field

Motion-Induced Magnetic Resonance of Rb Atoms in a Periodic Magnetostatic Field

Dicke coherent narrowing in two-photon and Raman spectroscopy of thin vapor cells

Testing the limits of the Maxwell distribution of velocities for atoms flying nearly parallel to the walls of a thin cell

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