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Physical Review Letters

Optical-Optical Double Resonance Photoassociative Spectroscopy of Ultracold 39 K Atoms near Highly Excited Asymptotes

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

Published Jun 2, 1997• 46 citations
Publisher

Abstract

We report the first observation of optical-optical double resonance photoassociative spectroscopy of ultracold ${}^{39}$K atoms near the highly excited $^{39}K(4s)+^{39}K(4d,5d,6d,6s,7s)$ asymptotes in a high density magneto-optical trap. Using the ${v}^{\ensuremath{'}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ level of the ${0}_{g}^{\ensuremath{-}}$ ``pure long-range'' state (a localized long-range Franck-Condon window) as the intermediate state, we observe simple and assignable rovibrational progressions dissociating to these asymptotes. The dominant long-range potential constants are determined. Line broadening, presumably due to autoionization, and rotational excitations due to strong field effects are observed.

DOI
10.1103/physrevlett.78.4173

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Long-range interaction of the 39K(4s)+39K(4p) asymptote by photoassociative spectroscopy. I. The g− pure long-range state and the long-range potential constants

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This paper reports on a comprehensive study of the long-range interaction of the K39(4s)+39K(4p) asymptotic system. We present a detailed discussion of the R-dependent angular momentum couplings and correlation between the Hund’s case (a) and case (c) molecular states. Analytical expressions for the 16 adiabatic Hund’s case (c) long-range potential curves are derived including the higher order dispersion forces and the effects of retardation. Experimentally, six Hund’s case (c) long-range molecular states (0u+, 1g, and 0g− dissociating to the 4 2S1/2+4 2P3/2 asymptote and 0u+, 1g, and 0g− to the 4 2S1/2+4 2P1/2 limit) are observed with rovibrational resolution by photoassociative spectroscopy of ultracold K39 atoms in a high density magneto-optical trap (MOT). Among the six observed long-range states, the upper 0g− “pure long-range” state has negligible short-range chemical exchange contributions and the measured molecular binding energies (v=0–26) are used to precisely determine the long-range potential constants of the 4s+4p interaction. We determine: C3Π=8.436(14) a.u., C3Σ=16.872(28) a.u., C6Π=6272(94) a.u., and C6Σ=9365(141) a.u.. Molecular constants for the three special pure long-range states, the 0g− and 1u (dissociating to the 4 2P3/2 limit and with potential minimum) and the 1u (dissociating to the 4 2P1/2 and with potential maximum), are reported. The internal consistency of the theoretical model used in this work is confirmed by the excellent agreement between the long-range potential curve of the 1g state obtained in present work (from the 0g− state) and the long-range portion of the RKR potential curve of the 1 1Πg state previously determined by conventional molecular spectroscopy. The radiative lifetime of the K 4p state derived from the dipole–dipole interaction constant C3Π is also in excellent agreement with a recent fast-beam measurement.

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Precise determination of the dipole matrix element and radiative lifetime of the K39 4p state by photoassociative spectroscopy

H. Wang, J. Li, X. T. Wang +3 more

Rovibrational levels (v=0--30) of the ${0}_{\mathrm{g}}^{\mathrm{\ensuremath{-}}}$ ``pure long-range'' state of $^{39}\mathrm{K}_{2}$ are observed by photoassociative spectroscopy of ultracold potassium atoms prepared in a high-density magneto-optical trap. The measured molecular binding energies are used to precisely determine the long-range dipole-dipole potential constant ${\mathrm{C}}_{3}^{\mathrm{\ensuremath{\Pi}}}$ of the K(4s)+K(4p) asymptote and the radiative lifetime of the 4p state. We determine ${\mathrm{C}}_{3}^{\mathrm{\ensuremath{\Pi}}}$=-5.456(9) zJ ${\mathrm{nm}}^{3}$ (-8.445(14) a.u.), \ensuremath{\tau}(4${\mathrm{}}^{2}$${\mathrm{P}}_{3\mathrm{/}2}$)=26.34(5) ns, and \ensuremath{\tau}(4${\mathrm{}}^{2}$${\mathrm{P}}_{1\mathrm{/}2}$)=26.69(5) ns. Our result is a significant improvement in precision over previous lifetime measurements and agrees well with the recent fast-beam experiment [U. Volz and H. Schmoranzer, Phys. Scr. T65, 48 (1996)].

Physical Review A•Mar 1, 1997•93 citations
We report the first observation of optical-optical double resonance photoassociative spectroscopy of ultracold 39{}^{39}39K atoms near the highly excited 39K(4s)+39K(4d,5d,6d,6s,7s)^{39}K(4s)+^{39}K(4d,5d,6d,6s,7s)39K(4s)+39K(4d,5d,6d,6s,7s) asymptotes in a high density magneto-optical trap. Using the v\ensuremath′=0{v}^{\ensuremath{'}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0v\ensuremath′=0 level of the 0g\ensuremath−{0}_{g}^{\ensuremath{-}}0g\ensuremath−​ ``pure long-range'' state (a localized long-range Franck-Condon window) as the intermediate state, we observe simple and assignable rovibrational progressions dissociating to these asymptotes. The dominant long-range potential constants are determined. Line broadening, presumably due to autoionization, and rotational excitations due to strong field effects are observed.
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 300muK(sim7MHz)300\\mu K (\\sim 7 MHz)300muK(sim7MHz), 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 (Jprimeprime=0,1J^{\\prime\\prime} = 0, 1Jprimeprime=0,1 and 2 in our work on 39K^{39}K39K). Such photoassociative free-bound absorption allows observation of ``pure long-range molecule'' states (Re=28R_{e} = 28Re​=28 and 39 {\\AA} in 39K2^{39}K_{2}39K2​) as well as long-range levels of known short range states with outer classical turning points of sim20−250AA\\sim 20 - 250 {\\AA}sim20−250AA. 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.
This paper reports on a comprehensive study of the long-range interaction of the K39(4s)+39K(4p) asymptotic system. We present a detailed discussion of the R-dependent angular momentum couplings and correlation between the Hund’s case (a) and case (c) molecular states. Analytical expressions for the 16 adiabatic Hund’s case (c) long-range potential curves are derived including the higher order dispersion forces and the effects of retardation. Experimentally, six Hund’s case (c) long-range molecular states (0u+, 1g, and 0g− dissociating to the 4 2S1/2+4 2P3/2 asymptote and 0u+, 1g, and 0g− to the 4 2S1/2+4 2P1/2 limit) are observed with rovibrational resolution by photoassociative spectroscopy of ultracold K39 atoms in a high density magneto-optical trap (MOT). Among the six observed long-range states, the upper 0g− “pure long-range” state has negligible short-range chemical exchange contributions and the measured molecular binding energies (v=0–26) are used to precisely determine the long-range potential constants of the 4s+4p interaction. We determine: C3Π=8.436(14) a.u., C3Σ=16.872(28) a.u., C6Π=6272(94) a.u., and C6Σ=9365(141) a.u.. Molecular constants for the three special pure long-range states, the 0g− and 1u (dissociating to the 4 2P3/2 limit and with potential minimum) and the 1u (dissociating to the 4 2P1/2 and with potential maximum), are reported. The internal consistency of the theoretical model used in this work is confirmed by the excellent agreement between the long-range potential curve of the 1g state obtained in present work (from the 0g− state) and the long-range portion of the RKR potential curve of the 1 1Πg state previously determined by conventional molecular spectroscopy. The radiative lifetime of the K 4p state derived from the dipole–dipole interaction constant C3Π is also in excellent agreement with a recent fast-beam measurement.
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 39K2^{39}\mathrm{K}_{2}39K2​ molecule are observed within 8 ${\mathrm{cm}}^{\ensuremath{-}1}$ below the 42P324^{2}P_{\frac{3}{2}}42P23​​ 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 0u+{0}_{u}^{+}0u+​ and 1g{1}_{g}1g​ 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 1011{10}^{11}1011 ${\mathrm{cm}}^{\ensuremath{-}3}$, increasing our trap loss signals by an order of magnitude compared to a normal MOT.
We have performed high precision photoassociation spectroscopy of ultracold cesium gas. Using trap-loss fluorescence detection and controlling the background cesium pressure we were able to photoassociate atoms into excited states of ultracold molecules with large detunings up to 56 cm(-1) below the Cs(6S(1/2)) + Cs(6P(1/2)) atomic asymptote. Vibrational progressions are assigned to 0(g)(-), 0(u)(+), and 1(g) long-range states. By fitting the spectral data to the LeRoy-Bernstein expression, the effective coefficients of the leading long-range interactions and the vibrational quantum number at dissociation are obtained. In addition we have observed spectral perturbations between states of the same symmetry belonging to different asymptotes (6P(1/2) and 6P(3/2)). The perturbations are manifested through irregular vibrational level spacings and are especially pronounced in the 0(u)(+) symmetry. Many observed rotational levels indicate d- and higher partial wave contributions to the photoassociation cross section in the presence of trapping laser light, while spectral regions with only weak features suggest nodes in the lower state wave functions corresponding to the two ground state atoms asymptote.
In this paper, ultracold cesium molecules are formed through photoassociation technology, which is carried out in a magneto-optical trap. High resolution photoassociaion spectra with the rotational progressions up to J = 7 are obtained. Three rovibrational levels of the long-range 0 u + state of Cs 2 below the (6S 1/2 + 6P 1/2 ) dissociation limit are specifically investigated. By fitting their binding energy intervals to the non-rigid rotational model, the rotational constant of the long-range 0 u + state is determined. A proportional dependence of the value of the rotational constant on the vibrational quantum number is demonstrated.
Rovibrational levels (v=0--30) of the ${0}_{\mathrm{g}}^{\mathrm{\ensuremath{-}}}$ ``pure long-range'' state of 39K2^{39}\mathrm{K}_{2}39K2​ are observed by photoassociative spectroscopy of ultracold potassium atoms prepared in a high-density magneto-optical trap. The measured molecular binding energies are used to precisely determine the long-range dipole-dipole potential constant ${\mathrm{C}}_{3}^{\mathrm{\ensuremath{\Pi}}}$ of the K(4s)+K(4p) asymptote and the radiative lifetime of the 4p state. We determine ${\mathrm{C}}_{3}^{\mathrm{\ensuremath{\Pi}}}$=-5.456(9) zJ nm3{\mathrm{nm}}^{3}nm3 (-8.445(14) a.u.), \ensuremath{\tau}(42{\mathrm{}}^{2}2P3/2{\mathrm{P}}_{3\mathrm{/}2}P3/2​)=26.34(5) ns, and \ensuremath{\tau}(42{\mathrm{}}^{2}2P1/2{\mathrm{P}}_{1\mathrm{/}2}P1/2​)=26.69(5) ns. Our result is a significant improvement in precision over previous lifetime measurements and agrees well with the recent fast-beam experiment [U. Volz and H. Schmoranzer, Phys. Scr. T65, 48 (1996)].