Precise atomic radiative lifetime via photoassociative spectroscopy of ultracold lithium

McAlexander, W. I.; Abraham, E.; Ritchie, N. W. M.; Williams, Carl J.; Stoof, H. T. C.; Hulet, R. G.

doi:10.1103/physreva.51.r871

Cited by 128 publications

(74 citation statements)

References 31 publications

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“…Averaging over the unknown orientation of the molecular axis relative to the polarization axis of the linearly polarized laser field gives a factor of [28]. The free-bound FranckCondon factors are numerically evaluated using molecular potentials determined previously [29,30]. Finally, because of quantum degeneracy, to calculate K p we average the scattering matrix element over a Bose-Einstein energy distribution.…”

Section: P H Y S I C a L R E V I E W L E T T E R S Week Ending 22 Augmentioning

confidence: 99%

Intensity Dependence of Photoassociation in a Quantum Degenerate Atomic Gas

et al. 2003

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We have measured the intensity dependent rate and frequency shift of a photoassociation transition in a quantum degenerate gas of 7 Li. The rate increases linearly with photoassociation laser intensity for low intensities, whereas saturation is observed at higher intensities. The measured rates and shifts agree reasonably well with theory within the estimated systematic uncertainties. Several theoretically predicted saturation mechanisms are discussed, but a theory in which saturation arises because of quantum mechanical unitarity agrees well with the data. DOI: 10.1103/PhysRevLett.91.080402 PACS numbers: 03.75.Nt, 33.20.Kf, 33.70.-w, 34.20.Cf Photoassociation (PA) of ultracold atoms has been a remarkably useful tool for determining scattering lengths characterizing ultracold atom collisions, for producing ultracold molecules, and for providing extremely precise measurements of atomic radiative lifetimes (see Refs. [1,2] for reviews). This utility is largely a consequence of the spectroscopic precision afforded by the small thermal broadening in a laser or evaporatively cooled gas. Quantum degenerate gases are especially interesting because the coherence of the atomic field may enable the formation of a molecular Bose-Einstein condensate (BEC) from an atomic one by coherent Raman transitions [3,4], stimulated Raman adiabatic passage [5], or by other coherent adiabatic population transfer schemes [6,7].There have been extensive theoretical studies of the rate of PA [8][9][10][11][12]. The rate is predicted to increase linearly with intensity at low intensities, while various mechanisms have been proposed that cause saturation of the rate at higher intensities. Among these mechanisms are the quantum mechanical unitarity limit on the rate of atomic collisions [11], a breakdown of the two-mode approximation [4,13] for PA of Bose condensates caused by coupling to noncondensed atomic modes [12,14 -16], and the depletion of the atomic pair correlation function [15]. Photoassociation resonances are also predicted to exhibit a spectral shift proportional to the light intensity caused by coupling to the continuum of free-atom states [11,[17][18][19]. In contrast to theory, there are relatively few experimental measurements, and only two that could be considered ''precise'' (which we define as measurements with uncertainties of less than a factor of 2). We previously measured the spectral light shift using quantum degenerate 7 Li and obtained good agreement with theory [20]. Both the spectral shift and the PA rate constant were recently measured in a Na condensate, and good agreement with two-body theory was found [21]. Saturation was not observed in this experiment. Saturation was observed in two other lower precision experiments [22,23], but these experiments were performed in a magneto-optical trap, where the temperatures were greater than 100 K and the corresponding unitaritylimited rates were quite small, of the order of 1 s ÿ1 or less.We report precise measurements of both the rate of PA and the spectral shift in...

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Section: P H Y S I C a L R E V I E W L E T T E R S Week Ending 22 Augmentioning

confidence: 99%

Intensity Dependence of Photoassociation in a Quantum Degenerate Atomic Gas

et al. 2003

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“…Shortly after the achievement of Bose-Einstein condensation of dilute, magnetically confined alkali atoms, an experimental quest began, seeking to trap and cool fermionic isotopes of lithium and potassium below their Fermi degeneracy temperatures T F [1][2][3][4]. The first realization of a weakly interacting, degenerate Fermi gas of K atoms was reported by DeMarco and Jin [5], and most recently, a mixture of bosonic and fermionic Li isotopes has been sympathetically cooled to about 80% of the corresponding T F [6].…”

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confidence: 99%

Zero-sound density oscillations in Fermi-Bose mixtures

Capuzzi

Hernández

2001

Phys. Rev. A

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Within a mean field plus Random-Phase Approximation formalism, we investigate the collective excitations of a three component Fermi-Bose mixture of K atoms, magnetically trapped and subjected to repulsive s-wave interactions. We analyze both the single-particle excitation and the density oscillation spectra created by external multipolar fields, for varying fermion concentrations. The formalism and the numerical output are consistent with the Generalized Kohn Theorem for the whole multispecies system. The calculations give rise to fragmented density excitation spectra of the fermion sample and illustrate the role of the mutual interaction in the observed deviations of the bosonic spectra with respect to Stringari's rule.

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“…Because of this, new and more accurate ways of measuring excited state lifetimes are constantly being investigated. Previous methods include time-correlated single photon techniques [4,5,6,7,8,9], beam-foil experiments [5], fast beam measurements [10,11], electron-photon delayed coincidence techniques [12,13], luminescent decay [14,15], linewidth measurements [16], photoassociative spectroscopy [17], and quantum jump methods [18].…”

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confidence: 99%

Precision lifetime measurements of a single trapped ion with ultrafast laser pulses

et al. 2006

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We report precision measurements of the excited state lifetime of the 5p 2 P 1/2 and 5p 2 P 3/2 levels of a single trapped Cd + ion. The ion is excited with picosecond laser pulses from a mode-locked laser and the distribution of arrival times of spontaneously emitted photons is recorded. The resulting lifetimes are 3.148 ± 0.011 ns and 2.647 ± 0.010 ns for 2 P 1/2 and 2 P 3/2 respectively. With a total uncertainty of under 0.4%, these are among the most precise measurements of any atomic state lifetimes to date. Here we report excited state lifetime measurements using a time-correlated single photon counting technique on a single atom. This method, designed especially to eliminate common systematic errors, involves selective excitation of a single trapped ion to a particular excited state (lifetime of order nanoseconds) by an ultrafast laser pulse (duration of order picoseconds). Arrival of the spontaneously-emitted photon from the ion is correlated in time with the excitation pulse, and the excited state lifetime is extracted from the distribution of time delays from many such events.By performing the experiment on a single trapped ion, we are able to eliminate prevalent systematic errors, such as: pulse pileup that causes multiple photons to be collected within the time resolution of the detector, radiation trapping or the absorption and re-emission of radiation by neighboring atoms, atoms disappearing from view before decaying, and subradiance or superradiance arising from coherent interactions with nearby atoms. By using ultrafast laser pulses, we eliminate potential effects from applied light during the measurement interval.With this setup, at most one photon can be emitted following an excitation pulse. While this feature is instrumental in eliminating the above systematic errors, it would appear that this signal would require large integration times for reasonable statistical uncertainties. However, with a lifetime of only a few nanoseconds, millions FIG. 1: The experimental apparatus. (a) A picosecond mode locked Ti:Saph laser is tuned to four times the resonant wavelength for either the 5p 2 P 1/2 or the 5p 2 P 3/2 level of Cd + . Each pulse is then frequency-quadrupled through non-linear crystals, filtered from the fundamental and second harmonic, and directed to the ion. An amplified cw diode laser is also frequency quadrupled and tuned just red of the 2 P 3/2 transition for Doppler cooling of the ion within the trap. Acoustooptic modulators (AOM) are used to switch on and off the lasers as described in the text. Photons emitted from the ion are collected by an f /2.1 imaging lens and directed toward a photon-counting photo multiplier tube (PMT). The output of the PMT provides the start pulse for the time to digital converter (TDC), whereas the stop pulse is provided by the reference clock of the mode-locked laser. of such excitations can be performed each second, thus potentially allowing sufficient data for a statistical error of under 0.1% to be collected in a matter of minutes [6].A diagram of th...

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Precise atomic radiative lifetime via photoassociative spectroscopy of ultracold lithium

Cited by 128 publications

References 31 publications

Intensity Dependence of Photoassociation in a Quantum Degenerate Atomic Gas

Intensity Dependence of Photoassociation in a Quantum Degenerate Atomic Gas

Zero-sound density oscillations in Fermi-Bose mixtures

Precision lifetime measurements of a single trapped ion with ultrafast laser pulses

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