Physical Review Letters

Fine-Structure Predissociation of Ultracold Photoassociated K239 Molecules Observed by Fragmentation Spectroscopy

H. Wang, P. L. Gould, William C. Stwalley

Published Jan 19, 1998• 30 citations

Abstract

We report the first observation of fragmentation spectra of the fine-structure predissociated long-range ${1}_{g}$ and ${0}_{u}^{+}$ $(b^{3}\ensuremath{\Pi}_{{0}^{+}u})$ states of ultracold $(T<1\mathrm{mK})$ ${}^{39}{\mathrm{K}}_{2}$ molecules. The ${1}_{g}$ state predissociates via the curve crossing at long range $(R\ensuremath{\sim}23\AA{})$ with the repulsive ${0}_{g}^{+}$ state. The ${0}_{u}^{+}$ state, however, predissociates predominantly through molecular fine-structure mixing at short range with the $b^{3}\ensuremath{\Pi}_{1u}$ component. Our technique of fragmentation spectroscopy is a sensitive and selective tool for ultracold photoassociation and fine-structure-changing collisions.

DOI: 10.1103/physrevlett.80.476

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PHOTOASSOCIATION OF ULTRACOLD ATOMS: A NEW TOOL FOR MOLECULAR SPECTROSCOPY

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Jan 1, 19980 citations

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Photoassociative spectroscopy of ultracold K39 atoms in a high-density vapor-cell magneto-optical trap

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Physical Review Letters

Fine-Structure Predissociation of Ultracold Photoassociated K239 Molecules Observed by Fragmentation Spectroscopy

H. Wang, P. L. Gould, William C. Stwalley

Published Jan 19, 1998• 30 citations

Publisher

Abstract

We report the first observation of fragmentation spectra of the fine-structure predissociated long-range

{1}_{g}

and

{0}_{u}^{+}

(b^{3}\ensuremath{\Pi}_{{0}^{+}u})

states of ultracold

(T<1\mathrm{mK})

{}^{39}{\mathrm{K}}_{2}

molecules. The

{1}_{g}

state predissociates via the curve crossing at long range

(R\ensuremath{\sim}23\AA{})

with the repulsive

{0}_{g}^{+}

state. The

{0}_{u}^{+}

state, however, predissociates predominantly through molecular fine-structure mixing at short range with the

b^{3}\ensuremath{\Pi}_{1u}

component. Our technique of fragmentation spectroscopy is a sensitive and selective tool for ultracold photoassociation and fine-structure-changing collisions.

DOI: 10.1103/physrevlett.80.476

Related papers

PHOTOASSOCIATION OF ULTRACOLD ATOMS: A NEW TOOL FOR MOLECULAR SPECTROSCOPY

William C. Stwalley

The field of laser cooling and trapping of atoms has had a profound impact on many areas of atomic, molecular and optical science. In particular, ultracold atoms colliding in magneto-optical traps typically have relative kinetic energies of $300\\mu K (\\sim 7 MHz)$ , so free-bound absorption lines are as sharp as bound-bound lines. Moreover, because of very long range centrifugal barriers, only a few collisional partial waves are important ( $J^{\\prime\\prime} = 0, 1$ and 2 in our work on $^{39}K$ ). Such photoassociative free-bound absorption allows observation of ``pure long-range molecule'' states ( $R_{e} = 28$ and 39 {\\AA} in $^{39}K_{2}$ ) as well as long-range levels of known short range states with outer classical turning points of $\\sim 20 - 250 {\\AA}$ . Such spectra have been observed by ``trap loss'' (decrease in atomic fluorescence), molecular ionization, and fragment ionization. Optical-optical double resonance (OODR), e.g. through the ``Franck-Condon windows'' of the ``pure long-range'' states, produces readily assignable spectra at higher asymptotes as well. Further extensions of ultracold photoassociative spectroscopy and applications to determination of long range potentials, atomic properties, and Bose-Einstein condensate stability will be presented.The field of laser cooling and trapping of atoms has had a profound impact on many areas of atomic, molecular and optical science. In particular, ultracold atoms colliding in magneto-optical traps typically have relative kinetic energies of $300\\mu K (\\sim 7 MHz)$, so free-bound absorption lines are as sharp as bound-bound lines. Moreover, because of very long range centrifugal barriers, only a few collisional partial waves are important ($J^{\\prime\\prime} = 0, 1$ and 2 in our work on $^{39}K$). Such photoassociative free-bound absorption allows observation of ``pure long-range molecule'' states ($R_{e} = 28$ and 39 {\\AA} in $^{39}K_{2}$) as well as long-range levels of known short range states with outer classical turning points of $\\sim 20 - 250 {\\AA}$. Such spectra have been observed by ``trap loss'' (decrease in atomic fluorescence), molecular ionization, and fragment ionization. Optical-optical double resonance (OODR), e.g. through the ``Franck-Condon windows'' of the ``pure long-range'' states, produces readily assignable spectra at higher asymptotes as well. Further extensions of ultracold photoassociative spectroscopy and applications to determination of long range potentials, atomic properties, and Bose-Einstein condensate stability will be presented.

Jan 1, 19980 citations

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Jie Ma, Wang Xiao-Feng, Xin Tong-Yu +5 more

Photoassociation spectroscopy with high resolution for 0u+(6P3/2) long-range state of ultracold cesium molecules has been measured experimentally using the modulated trap loss fluorescence spectroscopy technology. The spectral range has been extended over 60 cm-1 below the 6S1/2 + 6P3/2 dissociation limit as compared with other groups. twenty-five new observations of the Cs2 0u+ in long-range state are reported. The vibrational binding energies of these states are analyzed by using the LeRoy-Bernstein formula. The long-range parameter C3 in molecular 0u+(6P3/2) state is derived for 16.1030.010, and the corresponding molecular potential curve is depicted.Photoassociation spectroscopy with high resolution for 0u+(6P3/2) long-range state of ultracold cesium molecules has been measured experimentally using the modulated trap loss fluorescence spectroscopy technology. The spectral range has been extended over 60 cm-1 below the 6S1/2 + 6P3/2 dissociation limit as compared with other groups. twenty-five new observations of the Cs2 0u+ in long-range state are reported. The vibrational binding energies of these states are analyzed by using the LeRoy-Bernstein formula. The long-range parameter C3 in molecular 0u+(6P3/2) state is derived for 16.1030.010, and the corresponding molecular potential curve is depicted.

Acta Physica SinicaJan 1, 20152 citations

Ultracold photoassociation spectroscopy: Long-range molecules and atomic scattering

K. M. Jones, Eite Tiesinga, Paul D. Lett +1 more

Photoassociation is the process in which two colliding atoms absorb a photon to form an excited molecule. The development of laser-cooling techniques for producing gases at ultracold $(<1\phantom{\rule{0.3em}{0ex}}\mathrm{mK})$ temperatures allows photoassociation spectroscopy to be performed with very high spectral resolution. Of particular interest is the investigation of molecular states whose properties can be related, with high precision, to the properties of their constituent atoms with the ``complications'' of chemical binding accounted for by a few parameters. These include bound long-range or purely long-range vibrational states in which two atoms spend most or all of their time at large internuclear separations. Low-energy atomic scattering states also share this characteristic. Photoassociation techniques have made important contributions to the study of all of these. This review describes what is special about photoassociation spectroscopy at ultracold temperatures, how it is performed, and a sampling of results including the determination of scattering lengths, their control via optical Feshbach resonances, precision determinations of atomic lifetimes from molecular spectra, limits on photoassociation rates in a Bose-Einstein condensate, and briefly, production of cold molecules. Discussions are illustrated with examples on alkali-metal atoms as well as other species. Progress in the field is already past the point where this review can be exhaustive, but an introduction is provided on the capabilities of photoassociation spectroscopy and the techniques presently in use.Photoassociation is the process in which two colliding atoms absorb a photon to form an excited molecule. The development of laser-cooling techniques for producing gases at ultracold $(<1\phantom{\rule{0.3em}{0ex}}\mathrm{mK})$ temperatures allows photoassociation spectroscopy to be performed with very high spectral resolution. Of particular interest is the investigation of molecular states whose properties can be related, with high precision, to the properties of their constituent atoms with the ``complications'' of chemical binding accounted for by a few parameters. These include bound long-range or purely long-range vibrational states in which two atoms spend most or all of their time at large internuclear separations. Low-energy atomic scattering states also share this characteristic. Photoassociation techniques have made important contributions to the study of all of these. This review describes what is special about photoassociation spectroscopy at ultracold temperatures, how it is performed, and a sampling of results including the determination of scattering lengths, their control via optical Feshbach resonances, precision determinations of atomic lifetimes from molecular spectra, limits on photoassociation rates in a Bose-Einstein condensate, and briefly, production of cold molecules. Discussions are illustrated with examples on alkali-metal atoms as well as other species. Progress in the field is already past the point where this review can be exhaustive, but an introduction is provided on the capabilities of photoassociation spectroscopy and the techniques presently in use.

Reviews of Modern PhysicsMay 22, 2006873 citations

Photoassociative spectroscopy of ultracold K39 atoms in a high-density vapor-cell magneto-optical trap

H. Wang, P. L. Gould, William C. Stwalley

We have performed photoassociative spectroscopy of ultracold potassium atoms in a high-density vapor-cell magneto-optical trap (MOT) in which atoms are confined predominantly in "dark" hyperfine levels that do not interact with the trapping light. Three well-resolved vibrational series (one strong and two weak) of the $^{39}\mathrm{K}_{2}$ molecule are observed within 8 ${\mathrm{cm}}^{\ensuremath{-}1}$ below the $4^{2}P_{\frac{3}{2}}$ atomic limit. One of the series is identified as the ${0}_{g}^{\ensuremath{-}}$ pure long-range state and the other two are assigned to the ${0}_{u}^{+}$ and ${1}_{g}$ states. These photoassociative spectra are obtained by measuring reductions in the trap fluorescence due to trap loss induced by an intense photoassociation laser. By using a vapor-cell-dark MOT technique, we achieve atomic densities greater than ${10}^{11}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, increasing our trap loss signals by an order of magnitude compared to a normal MOT.We have performed photoassociative spectroscopy of ultracold potassium atoms in a high-density vapor-cell magneto-optical trap (MOT) in which atoms are confined predominantly in "dark" hyperfine levels that do not interact with the trapping light. Three well-resolved vibrational series (one strong and two weak) of the $^{39}\mathrm{K}_{2}$ molecule are observed within 8 ${\mathrm{cm}}^{\ensuremath{-}1}$ below the $4^{2}P_{\frac{3}{2}}$ atomic limit. One of the series is identified as the ${0}_{g}^{\ensuremath{-}}$ pure long-range state and the other two are assigned to the ${0}_{u}^{+}$ and ${1}_{g}$ states. These photoassociative spectra are obtained by measuring reductions in the trap fluorescence due to trap loss induced by an intense photoassociation laser. By using a vapor-cell-dark MOT technique, we achieve atomic densities greater than ${10}^{11}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, increasing our trap loss signals by an order of magnitude compared to a normal MOT.

Physical Review AMar 1, 199688 citations

Long-Range Predissociation in Two-Color Photoassociation of Ultracold Na Atoms

Peter Molenaar, P. van der Straten, H G M Heideman

We report two-color photoassociative ionization of sodium in a magneto-optical trap. The experimental results yield information on both singly and doubly excited states. We find that the highest bound vibrational levels ( $v>20$ ) of the singly excited ${0}_{g}^{\ensuremath{-}}$ state predissociate into the ${3}^{2}{P}_{3/2}{+3}^{2}{S}_{1/2}({F}_{g}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1)$ dissociation continuum due to avoided crossings of the hyperfine components of this potential with other molecular symmetries. Based on symmetry and energy consideration we argue that a doubly excited ${1}_{u}$ state remains autoionizing even when excited only a few GHz above the dissociation continuum.We report two-color photoassociative ionization of sodium in a magneto-optical trap. The experimental results yield information on both singly and doubly excited states. We find that the highest bound vibrational levels ( $v>20$) of the singly excited ${0}_{g}^{\ensuremath{-}}$ state predissociate into the ${3}^{2}{P}_{3/2}{+3}^{2}{S}_{1/2}({F}_{g}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1)$ dissociation continuum due to avoided crossings of the hyperfine components of this potential with other molecular symmetries. Based on symmetry and energy consideration we argue that a doubly excited ${1}_{u}$ state remains autoionizing even when excited only a few GHz above the dissociation continuum.

Physical Review LettersAug 19, 199637 citations

Near-threshold photoassociation of 87Rb2

M. Kemmann, Ivan Mistrík, S. Nußmann +3 more

Photoassociation of cold ${}^{87}\mathrm{Rb}{(5s,f}_{b}=2)$ atom pairs is studied within 13 GHz of the dissociation limits ${}^{87}\mathrm{Rb}{(5p}_{3/2}{,f}_{a}{)+}^{87}\mathrm{Rb}{(5s,f}_{b}=2).$ Vibrational levels in the long range, hyperfine manifolds of the ${0}_{g}^{\ensuremath{-}}$ and ${1}_{g}$ states arising from the ${}^{87}\mathrm{Rb}{(5p}_{3/2})$ fine structure limit are identified to lead to the formation of stable molecules in the photoassociation process. The vibrational bands are observed to break off, at positions matching the energetic location of potential-energy barriers predicted in the hyperfine manifolds at about 1 GHz above the ${}^{87}\mathrm{Rb}{(5p}_{3/2}{,f}_{a}{=3)+}^{87}\mathrm{Rb}{(5s,f}_{b}=1)$ dissociation limit. Empiricial potential-energy curves are derived from the data. These are found to be in agreement with predictions based on the long-range hyperfine recoupling of the excited molecular states. The selectivity of the excitation process and predissociation mechanisms are discussed.Photoassociation of cold ${}^{87}\mathrm{Rb}{(5s,f}_{b}=2)$ atom pairs is studied within 13 GHz of the dissociation limits ${}^{87}\mathrm{Rb}{(5p}_{3/2}{,f}_{a}{)+}^{87}\mathrm{Rb}{(5s,f}_{b}=2).$ Vibrational levels in the long range, hyperfine manifolds of the ${0}_{g}^{\ensuremath{-}}$ and ${1}_{g}$ states arising from the ${}^{87}\mathrm{Rb}{(5p}_{3/2})$ fine structure limit are identified to lead to the formation of stable molecules in the photoassociation process. The vibrational bands are observed to break off, at positions matching the energetic location of potential-energy barriers predicted in the hyperfine manifolds at about 1 GHz above the ${}^{87}\mathrm{Rb}{(5p}_{3/2}{,f}_{a}{=3)+}^{87}\mathrm{Rb}{(5s,f}_{b}=1)$ dissociation limit. Empiricial potential-energy curves are derived from the data. These are found to be in agreement with predictions based on the long-range hyperfine recoupling of the excited molecular states. The selectivity of the excitation process and predissociation mechanisms are discussed.

Physical Review AFeb 26, 200437 citations

We report the first observation of fragmentation spectra of the fine-structure predissociated long-range

{1}_{g}

and

{0}_{u}^{+}

(b^{3}\ensuremath{\Pi}_{{0}^{+}u})

states of ultracold

(T<1\mathrm{mK})

{}^{39}{\mathrm{K}}_{2}

molecules. The

{1}_{g}

state predissociates via the curve crossing at long range

(R\ensuremath{\sim}23\AA{})

with the repulsive

{0}_{g}^{+}

state. The

{0}_{u}^{+}

state, however, predissociates predominantly through molecular fine-structure mixing at short range with the

b^{3}\ensuremath{\Pi}_{1u}

component. Our technique of fragmentation spectroscopy is a sensitive and selective tool for ultracold photoassociation and fine-structure-changing collisions.

300\\mu K (\\sim 7 MHz)

, so free-bound absorption lines are as sharp as bound-bound lines. Moreover, because of very long range centrifugal barriers, only a few collisional partial waves are important (

J^{\\prime\\prime} = 0, 1

and 2 in our work on

^{39}K

). Such photoassociative free-bound absorption allows observation of ``pure long-range molecule'' states (

R_{e} = 28

and 39 {\\AA} in

^{39}K_{2}

) as well as long-range levels of known short range states with outer classical turning points of

\\sim 20 - 250 {\\AA}

. Such spectra have been observed by ``trap loss'' (decrease in atomic fluorescence), molecular ionization, and fragment ionization. Optical-optical double resonance (OODR), e.g. through the ``Franck-Condon windows'' of the ``pure long-range'' states, produces readily assignable spectra at higher asymptotes as well. Further extensions of ultracold photoassociative spectroscopy and applications to determination of long range potentials, atomic properties, and Bose-Einstein condensate stability will be presented.

Photoassociation is the process in which two colliding atoms absorb a photon to form an excited molecule. The development of laser-cooling techniques for producing gases at ultracold

(<1\phantom{\rule{0.3em}{0ex}}\mathrm{mK})

temperatures allows photoassociation spectroscopy to be performed with very high spectral resolution. Of particular interest is the investigation of molecular states whose properties can be related, with high precision, to the properties of their constituent atoms with the ``complications'' of chemical binding accounted for by a few parameters. These include bound long-range or purely long-range vibrational states in which two atoms spend most or all of their time at large internuclear separations. Low-energy atomic scattering states also share this characteristic. Photoassociation techniques have made important contributions to the study of all of these. This review describes what is special about photoassociation spectroscopy at ultracold temperatures, how it is performed, and a sampling of results including the determination of scattering lengths, their control via optical Feshbach resonances, precision determinations of atomic lifetimes from molecular spectra, limits on photoassociation rates in a Bose-Einstein condensate, and briefly, production of cold molecules. Discussions are illustrated with examples on alkali-metal atoms as well as other species. Progress in the field is already past the point where this review can be exhaustive, but an introduction is provided on the capabilities of photoassociation spectroscopy and the techniques presently in use.

^{39}\mathrm{K}_{2}

molecule are observed within 8 ${\mathrm{cm}}^{\ensuremath{-}1}$ below the

4^{2}P_{\frac{3}{2}}

atomic limit. One of the series is identified as the ${0}_{g}^{\ensuremath{-}}$ pure long-range state and the other two are assigned to the

{0}_{u}^{+}

and

{1}_{g}

states. These photoassociative spectra are obtained by measuring reductions in the trap fluorescence due to trap loss induced by an intense photoassociation laser. By using a vapor-cell-dark MOT technique, we achieve atomic densities greater than

{10}^{11}

${\mathrm{cm}}^{\ensuremath{-}3}$, increasing our trap loss signals by an order of magnitude compared to a normal MOT.

v>20

) of the singly excited ${0}_{g}^{\ensuremath{-}}$ state predissociate into the

{3}^{2}{P}_{3/2}{+3}^{2}{S}_{1/2}({F}_{g}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1)

dissociation continuum due to avoided crossings of the hyperfine components of this potential with other molecular symmetries. Based on symmetry and energy consideration we argue that a doubly excited

{1}_{u}

state remains autoionizing even when excited only a few GHz above the dissociation continuum.

Photoassociation of cold

{}^{87}\mathrm{Rb}{(5s,f}_{b}=2)

atom pairs is studied within 13 GHz of the dissociation limits

{}^{87}\mathrm{Rb}{(5p}_{3/2}{,f}_{a}{)+}^{87}\mathrm{Rb}{(5s,f}_{b}=2).

Vibrational levels in the long range, hyperfine manifolds of the ${0}_{g}^{\ensuremath{-}}$ and

{1}_{g}

states arising from the

{}^{87}\mathrm{Rb}{(5p}_{3/2})

fine structure limit are identified to lead to the formation of stable molecules in the photoassociation process. The vibrational bands are observed to break off, at positions matching the energetic location of potential-energy barriers predicted in the hyperfine manifolds at about 1 GHz above the

{}^{87}\mathrm{Rb}{(5p}_{3/2}{,f}_{a}{=3)+}^{87}\mathrm{Rb}{(5s,f}_{b}=1)

dissociation limit. Empiricial potential-energy curves are derived from the data. These are found to be in agreement with predictions based on the long-range hyperfine recoupling of the excited molecular states. The selectivity of the excitation process and predissociation mechanisms are discussed.