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Peters, Mathijs; Hoffmann, D.; Tobiason, J. D.; Walker, Thad

doi:10.1103/physreva.50.r906

Cited by 35 publications

(25 citation statements)

References 14 publications

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“…Although optical collisions have already been studied experimentally in several systems [3], the He͑2 3 S͒ system is in many aspects different from all other systems. He͑2…”

Section: (Received 5 December 1997)mentioning

confidence: 99%

Optical Collisions of Cold, Metastable Helium Atoms

et al. 1998

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We have studied the optical collisions of cold, metastable helium atoms in a magneto-optical trap. We have detected the rate of Penning and associative ionization of two metastable helium atoms at a temperature of 1 mK with and without nearly resonant light. We find that the associative ionization rate is increased with more than a factor 20 due to the presence of the light field. We present a simple, semiclassical model, which accounts for all the observed features, and which agrees, also on an absolute scale, with our experimental results. [S0031-9007(98)06429-1] PACS numbers: 32.80. Pj, 33.80.Eh, 34.50.Rk Because of the breakthrough of laser cooling techniques it is nowadays possible to study collision processes at ultralow temperatures [1]. The study of optical collisions, where during the collisions of two cold atoms a photon is absorbed, has been very successful. It has lead to a wealth of experimental data on the long range interactions in these systems and has been shown to be complementary to molecular spectroscopy [2]. While in the latter case one probes the molecular structures at short range, in the former case one obtains information on the interaction taking place at long range and is able to observe the molecular complex during the reaction.Optical collisions can be induced by irradiation of light detuned below atomic resonance. The transition energy at long range is lowered due to the dipole-dipole attraction C 3 ͞R 3 in the first excited state and the excitation point R c can be selected by the detuning of the light. The study of the ionization rate as a function of the detuning provides information on the dynamics and ionization of the molecular excited states involved. In general, the ionization rate will increase if the laser is tuned closer to resonance, since the number of atomic pairs that can be excited will increase by increasing R c . However, once the detuning becomes too small the ionization rate will decrease for two reasons. First of all, the atomic pairs are excited at such a large distance, that spontaneous emission during the time the molecular system reaches small internuclear distances leads to a "switching off" of the attractive 1͞R 3 potential, thus prohibiting a close collision in which ionization can occur. Second, the attractive potential becomes too weak compared to the relative kinetic energy, so that absorption does not lead to a close collision.We have studied optical collisions using cold, metastable He͑2 3 S͒ atoms. Although optical collisions have already been studied experimentally in several systems [3], the He͑2 3 S͒ system is in many aspects different from all other systems. He͑23 S͒ is a prototype system with only one electron active and no hyperfine structure. This makes it possible to obtain accurate potential curves for the He͑2 3 S͒-He͑2 3 S͒ system, which have been published recently [4]. It is therefore possible to obtain a direct comparison on an absolute scale between experiment and theory for this system. Another difference becomes clear, if one con...

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“…Although optical collisions have already been studied experimentally in several systems [3], the He͑2 3 S͒ system is in many aspects different from all other systems. He͑2…”

Section: (Received 5 December 1997)mentioning

confidence: 99%

Optical Collisions of Cold, Metastable Helium Atoms

et al. 1998

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“…For example, a partially resolved structure has been reported for detunings of only a few hundred MHz in Naz [15,16], and analyzed [43], even though the hyperfine structure is unresolved. But molecular bound-state structure has not yet been reported in trap-loss spectra with a probe (or "catalysis" ) laser detuned up to 1 GHz to the red in Rbz [3,7,44]. The closest distinct resonance known below the dissociation threshold was observed in Rbz at about 4 GHz [12], and a rich resonance structure was seen at 10 GHz and further [17].…”

Section: B Discussion Of Resultsmentioning

confidence: 99%

“…Such a virtual process should not affect the overall energy conservation in the complete optical collision, E'+ AI Ef+ As e, [AF= 6(coF coo)-; F=L or 5] (7) where the detunings 51 and Az are the corresponding channel threshold energies (considering the excited-level channel as the origin in the Floquet energy scale). This virtual emission process should be distinguished from a "true" emission process (like the ficus Iluorescence discussed above).…”

Section: Introductionmentioning

confidence: 99%

Optical collisions in ultracold atom traps: Two-photon distorted-wave theory

1995

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A perturbative distorted-wave theory is presented here for evaluating weak-field two-photon spectra, collision-induced energy redistribution, and radiative escape rates, produced by radiatively damped optical collisions of atoms in ultracold atom traps. This theory complements and corroborates a complex-potential theory developed recently. Illustrations are given of the use of the present theory in producing various features of one-color or two-color photoassociation spectra, such as the excited-level bound-state resonance structure, or Condon diffraction in the continuum of the final level.

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“…With the invention of the magneto-optical trap (MOT), dense and cold samples of atoms are now produced routinely and studied under controlled conditions. Collision dynamics of cold atoms have recently attracted considerable attention experimentally as well as theoretically [3][4][5][6][7][8][9]. When a near resonant light field is introduced into the cold atom cloud the rate coefficient for collisional processes can be dramatically modified [9].…”

Section: Introductionmentioning

confidence: 99%

Photo induced collisions with laser cooled He* atoms

Mastwijk

Rijnbach

Thomsen

et al. 1998

The European Physical Journal D - Atomic, Molecular and Optical

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Abstract. This paper presents an experimental investigation of cold collisions between metastable Helium atoms in an optical trap at 1mK. Penning (PI) and associative (AI) ionization reactions are distinguished using a mass spectrometer and studied under influence of near resonant laser light. Sensitive behavior of the ion rate is observed when the laser is tuned close to resonance. Experimental findings are well described, on an absolute scale, by a semi-classical model we have developed for optical collisions and by a modified Julienne-Vigué model.

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Laser-induced ultracold Rb(5S1/2)+Rb(5P1/2

Cited by 35 publications

References 14 publications

Optical Collisions of Cold, Metastable Helium Atoms

Optical Collisions of Cold, Metastable Helium Atoms

Optical collisions in ultracold atom traps: Two-photon distorted-wave theory

Photo induced collisions with laser cooled He* atoms

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