Time-Resolved Studies of Ultracold Ionizing Collisions

Orzel, Chad; Bergeson, Scott; Kulin, S. A.; Rolston, S. L.

doi:10.1103/physrevlett.80.5093

Cited by 21 publications

(8 citation statements)

References 14 publications

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“…+ z Collisions between two cold atoms are extremely sensitive to the long-range part of interatomic potentials. For example, recent experiments in cold optical collisions observed in real time [1,2] have shown the effects of the resonant dipole-dipole interaction. In these experiments, respectively, with rubidium and xenon trapped atoms, photoexcitation of pairs of atoms at relatively short internuclear distance [R ϳ ͑10 400͒a 0 ] gives rise, respectively, to trap loss [1] and associative ionization [2].…”

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confidence: 98%

Long-Range Forces between Cold Atoms

et al. 1999

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Long-range interactions can substantially modify collision or interaction processes among cold atoms. We are able to monitor their effects on two different systems: Cs atoms which undergo photoassociation and highly excited Cs Rydberg atoms. Although the length and the time scales of the interactions are quite different, their effects can be described with the same resonant dipole picture.[S0031-9007(99)08564-6] PACS numbers: 34.50. Rk, 32.80.Pj, 34.60. + z Collisions between two cold atoms are extremely sensitive to the long-range part of interatomic potentials. For example, recent experiments in cold optical collisions observed in real time [1,2] have shown the effects of the resonant dipole-dipole interaction. In these experiments, respectively, with rubidium and xenon trapped atoms, photoexcitation of pairs of atoms at relatively short internuclear distance [R ϳ ͑10 400͒a 0 ] gives rise, respectively, to trap loss [1] and associative ionization [2]. As such processes depend on the flux of colliding particles arriving at short distance, they can be enhanced (shielded) by exciting at large distance [R exc ϳ ͑1000 3000͒a 0 ] the atomic pairs to an attractive (repulsive) branch of the excited molecular potential curve.The dynamical effects of long-range forces should be ubiquitous in experiments with cold atoms. Here we report two very different manifestations of essentially similar resonant dipole-dipole forces, in which the modified atomic dynamics at long range clearly affects the outcome of the reactions.The first effect is the photoassociation (PA) of cold Cs atoms [3] into relatively high rotational states of the Cs 2 excited molecule. In alkali PA spectroscopy [4], two free colliding atoms resonantly absorb one photon to form an excited dimer in a rovibrational state. The rotational number J is a direct signature of the partial waves involved in the collisional process. In our experiment, by exciting at long range atom pairs to an attractive excited state, we can increase the number of partial waves participating in the collision and observe PA into higher rotational levels.The second effect is the distortion in the resonances of dipole-dipole energy transfer between cold Cs Rydberg atoms [5,6]. In this case pairs of atoms, separated by roughly 2 3 10 4 a 0 , are moved slightly either closer together or farther apart by the dipole-dipole force over several microseconds. The resulting change in the dipoledipole interaction strength distorts the resonances.Although the systems and magnitudes of the involved quantities are very different, the dynamical effects are comparable and are due to the same resonant dipole-dipole interaction with the R 23 dependence.The paper is organized as follows. The essential idea of the long-range forces is developed for the PA experiment, followed by a description of the experiment. Then we describe the cold Rydberg atom system and the effects of the resonant dipole force in this case.Long-range forces in the PA of Cs can be understood with the help of the level diagram in F...

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Long-Range Forces between Cold Atoms

et al. 1999

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“…A long-lived ground-state shape resonance has been probed by timedependent photoassociation [10,11], and laser-induced collisions have been followed in real time [12,13]. Motivated by earlier predictions [14], photoassociative ionization dynamics on the nanosecond time scale have been probed with picosecond pulses [15].…”

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Control of Ultracold Collisions with Frequency-Chirped Light

Wright

Gensemer²,

Vala

et al. 2005

Phys. Rev. Lett.

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We report on ultracold atomic collision experiments utilizing frequency-chirped laser light. A rapid chirp below the atomic resonance results in adiabatic excitation to an attractive molecular potential over a wide range of internuclear separation. This leads to a transient inelastic collision rate which is large compared to that obtained with fixed-frequency excitation. The combination of high efficiency and temporal control demonstrates the benefit of applying the techniques of coherent control to the ultracold domain. DOI: 10.1103/PhysRevLett.95.063001 PACS numbers: 32.80.Pj, 32.80.Qk, 34.50.Rk The ability to control the dynamics of microscopic systems has been a major motivation in physics and chemistry in recent years [1]. The development of ultrafast lasers and pulse-shaping techniques has allowed selective bond breaking and coherent control of chemical reactions [2]. At the other temporal extreme, slow collisions between ultracold atoms [3,4] can be controlled by long-range laser excitation because the colliding atoms have minimal kinetic energy and their trajectories are easily manipulated. In the present work, we adapt the techniques of coherent control to the nanosecond time scale and use frequencychirped light to control inelastic collisions between ultracold atoms. The combination of adiabatic excitation and the large number of atom pairs addressed by the chirp leads to a large transient collision rate. Such extensions of coherent control to the ultracold domain may significantly benefit processes such as ultracold molecule formation [5,6]. As an example, chirped two-photon Raman photoassociation [7,8] may provide an attractive alternative to magnetic Feshbach resonances for the coherent conversion of an atomic Bose-Einstein condensate into a molecular one. Because light can be controlled much faster than magnetic fields, the chirped excitation techniques developed here may allow the probing of quantum gases on much shorter time scales than previously achieved [9].There have been a number of experiments exploring the temporal dynamics of ultracold collisions. A long-lived ground-state shape resonance has been probed by timedependent photoassociation [10,11], and laser-induced collisions have been followed in real time [12,13]. Motivated by earlier predictions [14], photoassociative ionization dynamics on the nanosecond time scale have been probed with picosecond pulses [15]. In ultracold highly excited Rydberg atoms, the microsecond-scale evolution of resonant energy transfer has been observed via field ionization [16,17]. Our use of rapidly frequency-chirped laser light brings a new dimension to these studies. The temporal evolution of the light can lead to an efficient and robust adiabatic transfer of population to the excited state. Also, the wide range of frequencies spanned by the chirp leads to excitation of atom pairs over a wide range of internuclear separations. The advantages of chirped excitation have been discussed in the context of ultracold atom photoassociation with picosecond puls...

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“…This means that spontaneous emission can occur during the course of collision and may significantly alter the atomic collision dynamics [11,12]. Cold atom phenomena are also being merged with cavity quantum electrodynamics to realize single atom lasers [13][14][15].…”

Section: Physical Motivationmentioning

confidence: 99%

“…Possible applications of the Maxwell-Schrödinger theory lie in photon-electron-phonon dynamics in semiconductor quantum wells [10], spontaneous emission in cold atom collisions [11,12], atom-photon interaction in single atom laser cavities [14,15], and photon-exciton dynamics in fluorescent polymers [16].…”

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confidence: 99%