Isotopic difference in trap loss collisions of laser cooled rubidium atoms

Wallace, C. D.; Dinneen, T.; Tan, Kit-Yan N.; Grove, Timothy; Gould, Phillip L.

doi:10.1103/physrevlett.69.897

Cited by 120 publications

(93 citation statements)

References 11 publications

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“…Collisions in an optical trap are an important loss process limiting attainable density, and studies of total trap-loss rates [6,7] have confirmed the essentially molecular nature of photon absorption during the collisional encounter.…”

Section: Pacs Number(s): 3280pjmentioning

confidence: 90%

Ultracold photoassociative ionization collisions in a magneto-optical trap: The optical-field-intensity dependence in a radiatively dissipative environment

et al. 1993

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We report here measurements of two-body associative-ionization collisions between sodium atoms confined in a magneto-optic trap. These collisions represent a kind of "open" or dissipative collision for which the energy of the atom plus applied light field subsystem need not be conserved due to spontaneous-emission coupling to the vacuum modes of the radiation field. The experiment measures the photoassociative-ionization-rate constant as a function of the optical field intensity from about 40 to 260 mWcm . These results are in reasonable agreement with the predictions of an optical-Blochequation theory [Y. B. Band and P. S. Julienne, Phys. Rev. A 46, 330 (1992)],but differ strongly from the predictions of a local-equilibrium theory [A. Gallagher, Phys. Rev. A 44, 4249 (1991)]. PACS number(s): 32.80.PjWe report here studies of collisions between sodium atoms optically confined and cooled by the dissipative spontaneous-light force to temperatures well below T, (=65 mK for sodium), the point at which a collision duration becomes longer than the spontaneous-emission lifetime. Ultracold collisions involving excited states are truly novel because, at the extremely long time and distance scales inherent in this regime, radiative coupling and spontaneous decay become significant, and inelastic collision probabilities can be manipulated by intensity, frequency, and polarization of applied optical fields. Ultracold collisions represent a fundamentally new kind of low-pressure, gas-phase process -an "open" or dissipative one in which the fluctuating, stochastic force of spontaneous emission to the vacuum modes of the radiation field can result in energy nonconservation within the subsystem comprised of the colliding atoms plus applied laser field. Density-matrix methods rather than wavefunction methods must be used to describe the collision, and crucial experimental tests are needed to develop an understanding of the collision dynamics. Such collisions serve as prototype and paradigm systems for studying the properties of nonequilibrium open systems coupled to reservoirs, e.g. , conductance and transport in mesoscopic and macroscopic systems in which irreversibility is present.Reports of atom optical cooling [1] inspired early calculations of photon-stimulated two-body association reactions [2], and the observation of associative ionization (AI) between optically cooled sodium atoms [3] demonstrated the ability to manipulate the inelastic rate constant with radiation field intensity. Recent experiments[4] sweeping the frequency of a dipole optical trap to =4 GHz to the red side of the Na atomic resonance line have revealed structure in the AI production rate and have been interpreted [5] using a model that identifies the specific transient molecular states of the collision intermediate. Collisions in an optical trap are an important loss process limiting attainable density, and studies of total trap-loss rates [6,7] have confirmed the essentially molecular nature of photon absorption during the collisional encounter.In this...

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Section: Pacs Number(s): 3280pjmentioning

confidence: 90%

Ultracold photoassociative ionization collisions in a magneto-optical trap: The optical-field-intensity dependence in a radiatively dissipative environment

et al. 1993

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“…Theory is facilitated in the case of lithium by the relatively well-known interatomic potentials, which are well described by ab initio calculation [10]. In addition, the excited 2P3/2 state hyperfine structure of lithium is small (comparable to the radiative linewidth) and inverted, unlike for the heavier alkali-metal species, where excited-state hyperfine structure is thought to play an important role in trap-loss collisions [5,6]. Finally, since EFs (E"s/ktt=0.…”

Section: Measurementsmentioning

confidence: 99%

Trap-loss collisions of ultracold lithium atoms

et al. 1995

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Accurate measurements are presented of the rate of trap-loss-producing collisions between ultracold magneto-optically trapped Li atoms for a range of trap laser intensities and frequencies. Intensities from near the atomic saturation intensity to well above it are investigated. At low intensities, fine-structure-changing collisions cause trap loss with a rate constant of -10 ' cm /s. At sufficiently high intensity, the trap can be deep enough to effectively freeze out the dominant fine-structure-changing collisions as a loss mechanism, [11].This ability to separate the contributions of RE and FS greatly simplifies the interpretation of the experiment. In this paper, we present measurements of the RE and FS rates in I i for a range of trap laser intensities and detunings. The measured rates are compared with calculations that account for the variation of ET with laser intensity and detuning.The experimental apparatus and procedure are similar to other measurements of collisional loss in a MOT [2,4]. The MOT consists of six near-resonant laser beams along the three orthogonal axes that provide for dissipation of the atomic kinetic energy, and, when combined with an inhomogeneous magnetic field, also produce a restoring force [1].The six beams are produced by a dye laser that is frequency locked relative to a saturated absorption feature of Li in an absorption cell to provide long-term frequency stability and a relative frequency reference. The waist (1/e intensity radius) of the laser beams is 0.64 cm. A pair of anti-Helmholtz configured coils generates an axial magnetic-field gradient of 3 mT/cm and a radial gradient of 1.5 mT/cm. To ensure a near-spherically-symmetric cloud of trapped atoms, the intensities of the four radial laser beams are equal, while the intensity of an axial beam is -60% of the intensity of a radial beam. Transitions from both I' = 1 and 2 ground-state hyperfine levels to the excited states are driven with equal intensity using the upper and lower first-order sidebands produced by a standing-wave electro-optic modulator, modulated at 406.4 MHz. The lower first-order sideband is de-

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“…We then make use of the curved wavefront technique to collimate our atomic beam in two dimensions [35] before it enters the Zeeman slower. Due to its lighter mass 3 He atoms emerge from the source with a greater mean velocity than 4 He atoms and in order to achieve a large flux of both 3 He* and 4 He* atoms we have increased the capture velocity of our Zeeman slower [19,24]. Our ultra-high vacuum chamber maintains an operational pressure of 7×10 −10 mbar (with a partial presure of 6.5×10 −10 mbar, ground state He atoms from the atomic beam are the major contribution to this) and is based upon the design of our next-generation BEC chamber [36].…”

Section: Methodsmentioning

confidence: 99%

“…Since then, numerous investigations, both experimental and theoretical, have been made into the collisional properties of many different homonuclear [2,3,4,5,6,7,8,9,10,11,12,13] and (later) heteronuclear [14,15,16,17,18,19] systems. Collisional studies are in themselves interesting, leading to an in-depth understanding of the various scattering mechanisms present at such low kinetic energies and methods by which we can have some measure of control over elastic and inelastic collisions.…”

Section: Introductionmentioning

confidence: 99%

Heteronuclear ionizing collisions between laser-cooled metastable helium atoms

et al. 2007

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We have investigated cold ionizing heteronuclear collisions in dilute mixtures of metastable (2 3 S1) 3 He and 4 He atoms, extending our previous work on the analogous homonuclear collisions [R. J. W. Stas et al., PRA 73, 032713 (2006)]. A simple theoretical model of such collisions enables us to calculate the heteronuclear ionization rate coefficient, for our quasi-unpolarized gas, in the absence of resonant light (T = 1.2 mK): K (th) 34 = 2.4×10 −10 cm 3 /s. This calculation is supported by a measurement of K34 using magneto-optically trapped mixtures containing about 1×10 8 atoms of each species, K (exp) 34 = 2.5(8)×10 −10 cm 3 /s. Theory and experiment show good agreement.

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Isotopic difference in trap loss collisions of laser cooled rubidium atoms

Cited by 120 publications

References 11 publications

Ultracold photoassociative ionization collisions in a magneto-optical trap: The optical-field-intensity dependence in a radiatively dissipative environment

Ultracold photoassociative ionization collisions in a magneto-optical trap: The optical-field-intensity dependence in a radiatively dissipative environment

Trap-loss collisions of ultracold lithium atoms

Heteronuclear ionizing collisions between laser-cooled metastable helium atoms

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