Saturation effects in photoassociation spectroscopy of strontium-86

Pascal G. Mickelson

Published Jan 1, 2006• 0 citations

Abstract

This work describes intensity saturation of photoassociative transitions of 86Sr at the quantum mechanical unitarity limit. The saturation behavior, which results in a roll-over of the photoassociation rate for intensities greater than the saturation intensity, features interesting physics. Unlike other photoassociation spectroscopy (PAS) experiments, photoassociation occurs in a magneto-optical trap operating on the narrow dipole-forbidden transition at 689 nm. A laser red-detuned from the principal atomic transition at 461 nm by as much as 1300 GHz induces the photoassociation of ground state atoms to excited molecular states. Our previous studies [1] suggest that some of the PAS transitions for 86Sr are sensitive to the intensity of the laser. This work delves more deeply into these high intensity PAS effects, a subject that has not, to our knowledge, been studied experimentally for alkaline-earth atoms.

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Saturation effects in photoassociation spectroscopy of strontium-86

Pascal G. Mickelson

Published Jan 1, 2006• 0 citations

OpenAlex

Abstract

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T. C. Killian, Y. N. Martinez, Pascal G. Mickelson +3 more

Frontiers in OpticsJan 1, 20072 citations

We report photoassociative spectroscopy of

{^{88}\mathrm{S}\mathrm{r}}_{2}

in a magneto-optical trap operating on the $^{1}S_{0}\ensuremath{\rightarrow}^{3}P_{1}$ intercombination line at 689 nm. Photoassociative transitions are driven with a laser red detuned by 600--2400 MHz from the $^{1}S_{0}\ensuremath{\rightarrow}^{1}P_{1}$ atomic resonance at 461 nm. Photoassociation takes place at extremely large internuclear separation, and the photoassociative spectrum is strongly affected by relativistic retardation. A fit of the transition frequencies determines the

^{1}P_{1}

atomic lifetime ($\ensuremath{\tau}=5.22\ifmmode\pm\else\textpm\fi{}0.03\text{ }\text{ }\mathrm{n}\mathrm{s}$) and resolves a discrepancy between experiment and recent theoretical calculations.

We report heteronuclear photoassociation spectroscopy in a mixture of magneto-optically trapped

{}^{6}\mathrm{Li}

and

{}^{7}\mathrm{Li}.

The laser-induced decrease in the

{}^{7}\mathrm{Li}

steady-state particle number, only appearing in the presence of

{}^{6}\mathrm{Li},

gives clear evidence of photoassociation to form

{}^{6}{\mathrm{Li}}^{7}\mathrm{Li}.

Hyperfine resolved spectra of the vibrational level

v=83

of the singlet state ${\mathrm{A}}^{1}{\ensuremath{\Sigma}}_{u}^{+}$ have been taken up to intensities of

1000{\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}.

The absolute resonance frequencies and the rotational constant have been measured. Saturation of the photoassociation rate has been observed for two hyperfine transitions, which can be shown to be due to saturation of the rate coefficient near the unitarity limit. Saturation intensities on the order of

40{\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}

can be determined.

We report the production of ultracold heteronuclear

^{7}\mathrm{Li}^{85}\mathrm{Rb}

molecules in excited electronic states by photoassociation (PA) of ultracold

^{7}\mathrm{Li}

and

^{85}\mathrm{Rb}

atoms. PA is performed in a dual-species

^{7}\mathrm{Li}

^{85}\mathrm{Rb}

magneto-optical trap (MOT) and the PA resonances are detected using trap loss spectroscopy. We identify several strong PA resonances below the Li (2

s

{}^{2}

{S}_{1/2}

) + Rb (5

p

{}^{2}{P}_{3/2}

) asymptote and experimentally determine the long range

{C}_{6}

dispersion coefficients. We find a molecule formation rate (

{P}_{\mathrm{LiRb}}

) of 3.5 \ifmmode\times\else\texttimes\fi{} 10

{}^{7}

s${}^{\ensuremath{-}1}$ and a PA rate coefficient (

{K}_{\mathrm{PA}}

) of 1.3 \ifmmode\times\else\texttimes\fi{} 10${}^{\ensuremath{-}10}$ cm

{}^{3}

/s, the highest among heteronuclear bi-alkali-metal molecules. At large PA laser intensity we observe the saturation of the PA rate coefficient (

{K}_{\mathrm{PA}}

) close to the theoretical value at the unitarity limit.

s+p

) and (

p+p

) manifolds. Based on this theoretical framework, we explain a broad background feature in our data and suggest that double-excitation mechanisms are likely responsible for sharp dips in the ion signal.