Physical Review A

Spectroscopy of autoionizing doubly excited states in ultracold Na2 molecules produced by photoassociation

Arjen Amelink, K. M. Jones, Paul D. Lett, P. van der Straten, H G M Heideman

Published Mar 9, 2000• 25 citations

Abstract

We have performed photoassociation spectroscopy to study the doubly excited states of ${\mathrm{Na}}_{2}$ involved in the associative ionization of colliding $\mathrm{Na}(3P)$ atoms. Rovibrational levels of two doubly excited potentials connected to the ${P}_{3/2}{+P}_{3/2}$ asymptote, one of ${0}_{u}^{\ensuremath{-}}$ and one of ${1}_{u}$ symmetry, have been identified. These two doubly excited potentials dominate the route to ionization used in photoassociation experiments of cold Na. Binding energies and rotational constants for all the vibrational levels with binding energies $<50\mathrm{GHz}$ have been measured. The asymptotic potentials and short-range ionization probabilities are extracted from the data.

DOI: 10.1103/physreva.61.042707

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Photoassociation of atoms in ultracold collisions probed by wave-packet dynamics

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Physical Review ADec 1, 199450 citations

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

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Physical Review A

Spectroscopy of autoionizing doubly excited states in ultracold Na2 molecules produced by photoassociation

Arjen Amelink, K. M. Jones, Paul D. Lett, P. van der Straten, H G M Heideman

Published Mar 9, 2000• 25 citations

Publisher

Abstract

We have performed photoassociation spectroscopy to study the doubly excited states of

{\mathrm{Na}}_{2}

involved in the associative ionization of colliding

\mathrm{Na}(3P)

atoms. Rovibrational levels of two doubly excited potentials connected to the

{P}_{3/2}{+P}_{3/2}

asymptote, one of

{0}_{u}^{\ensuremath{-}}

and one of

{1}_{u}

symmetry, have been identified. These two doubly excited potentials dominate the route to ionization used in photoassociation experiments of cold Na. Binding energies and rotational constants for all the vibrational levels with binding energies

<50\mathrm{GHz}

have been measured. The asymptotic potentials and short-range ionization probabilities are extracted from the data.

DOI: 10.1103/physreva.61.042707

Related papers

Photoassociation of atoms in ultracold collisions probed by wave-packet dynamics

Mette Machholm, Annick Giusti-Suzor, Frederick H. Mies

Photoassociation in laser-assisted collisions of ultracold alkali atoms has been used recently to perform high-precision spectroscopy of very-long-range states. Rovibrational spectra close to the Na(3 $^{2}$ S)+ ${\mathrm{Na}}^{\mathrm{*}}$ (3 $^{2}$ ${\mathit{P}}_{3/2}$ ) dissociation limit have been obtained by monitoring an enhanced ${\mathrm{Na}}_{2}^{+}$ ion signal. We propose the use of pump-probe techniques to study the dynamics of the ionization process. At very large distances (typically 70 a.u.) two colliding Na atoms absorb a photon and form a coherent vibrational wave packet. We follow the packet in time and probe two possible mechanisms that are proposed to yield molecular ions: photoionization, where the second photon is absorbed at a small internuclear distance R directly ionizing the molecule, and associative ionization with excitation at intermediate R to the nuclear continuum of a doubly excited state followed by a half collision and autoionization at small R. The latter event can also lead to dissociation of the complex. The two mechanisms lead to distinct differences in the ion signals as a function of delay time between the pump and the probe pulses. Estimates of the ion rates to be expected in actual pump-probe experiments are given, which tend to favor the autoionization mechanism as the dominant reaction path.Photoassociation in laser-assisted collisions of ultracold alkali atoms has been used recently to perform high-precision spectroscopy of very-long-range states. Rovibrational spectra close to the Na(3 $^{2}$S)+${\mathrm{Na}}^{\mathrm{*}}$(3 $^{2}$${\mathit{P}}_{3/2}$) dissociation limit have been obtained by monitoring an enhanced ${\mathrm{Na}}_{2}^{+}$ ion signal. We propose the use of pump-probe techniques to study the dynamics of the ionization process. At very large distances (typically 70 a.u.) two colliding Na atoms absorb a photon and form a coherent vibrational wave packet. We follow the packet in time and probe two possible mechanisms that are proposed to yield molecular ions: photoionization, where the second photon is absorbed at a small internuclear distance R directly ionizing the molecule, and associative ionization with excitation at intermediate R to the nuclear continuum of a doubly excited state followed by a half collision and autoionization at small R. The latter event can also lead to dissociation of the complex. The two mechanisms lead to distinct differences in the ion signals as a function of delay time between the pump and the probe pulses. Estimates of the ion rates to be expected in actual pump-probe experiments are given, which tend to favor the autoionization mechanism as the dominant reaction path.

Physical Review ADec 1, 199450 citations

Spectroscopy of Na2 by photoassociation of laser-cooled Na

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We have observed the spectrum of long range molecular states of singly excited ${\mathrm{Na}}_{2}$ formed by photoassociation during ultracold associative ionization collisions of laser-cooled Na atoms. The low kinetic energy of the collision allows us to obtain very high resolution spectra and to observe states close to the dissociation limit. The spectrum shows regular vibrational series characteristic of the 1/ ${\mathit{R}}^{3}$ long range portion of the ${1}_{\mathit{g}}$ potential (asymptotically ${\mathit{S}}_{1/2}$ + ${\mathit{P}}_{3/2}$ ) as well as molecular hyperfine structure within these peaks. We extract potential parameters and compare with recent theory.We have observed the spectrum of long range molecular states of singly excited ${\mathrm{Na}}_{2}$ formed by photoassociation during ultracold associative ionization collisions of laser-cooled Na atoms. The low kinetic energy of the collision allows us to obtain very high resolution spectra and to observe states close to the dissociation limit. The spectrum shows regular vibrational series characteristic of the 1/${\mathit{R}}^{3}$ long range portion of the ${1}_{\mathit{g}}$ potential (asymptotically ${\mathit{S}}_{1/2}$+${\mathit{P}}_{3/2}$) as well as molecular hyperfine structure within these peaks. We extract potential parameters and compare with recent theory.

Physical Review LettersOct 4, 1993227 citations

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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

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Arjen Amelink, K. M. Jones, Paul D. Lett +2 more

We have measured the rate of production of ${\mathrm{Na}}_{2}^{+}$ ions in collisions of ultracold Na atoms held in a magneto-optical trap (MOT) as a function of probe laser detuning using a single-color probe beam. The ion rate is measured with the atoms mainly in the $3S(f=2)$ level (``bright MOT'') or the $3S(f=1)$ level (``dark MOT''). Using recent experimental information about the doubly excited autoionizing states of ${\mathrm{Na}}_{2},$ we find that the large structures in the first 5 GHz red of the atomic transition frequency are due to a doubly resonant excitation process with levels in the ${0}_{g}^{\ensuremath{-}}$ potential (asymptotically connected to ${3S}_{1/2}{+3P}_{3/2})$ as the intermediate states, and levels in the ${0}_{u}^{\ensuremath{-}}$ and ${1}_{u}$ potentials (asymptotically connected to ${3P}_{3/2}{+3P}_{3/2})$ as the final autoionizing states. We can account for nearly all of the observed structure in this region of the spectra for both the bright and dark MOT.We have measured the rate of production of ${\mathrm{Na}}_{2}^{+}$ ions in collisions of ultracold Na atoms held in a magneto-optical trap (MOT) as a function of probe laser detuning using a single-color probe beam. The ion rate is measured with the atoms mainly in the $3S(f=2)$ level (``bright MOT'') or the $3S(f=1)$ level (``dark MOT''). Using recent experimental information about the doubly excited autoionizing states of ${\mathrm{Na}}_{2},$ we find that the large structures in the first 5 GHz red of the atomic transition frequency are due to a doubly resonant excitation process with levels in the ${0}_{g}^{\ensuremath{-}}$ potential (asymptotically connected to ${3S}_{1/2}{+3P}_{3/2})$ as the intermediate states, and levels in the ${0}_{u}^{\ensuremath{-}}$ and ${1}_{u}$ potentials (asymptotically connected to ${3P}_{3/2}{+3P}_{3/2})$ as the final autoionizing states. We can account for nearly all of the observed structure in this region of the spectra for both the bright and dark MOT.

Physical Review AJun 13, 20008 citations

Two-colour photoassociation spectroscopy of ultracold sodium

K. M. Jones, S. Maleki, L. P. Ratliff +1 more

We demonstrate a number of two-colour spectroscopy techniques where the first step is the photoassociation of laser-cooled and trapped sodium atoms to form bound states of . High-resolution spectra of are obtained. Spectra of the `purely long-range' state demonstrates the use of two-colour spectroscopy to open up an ionization channel for detecting the occurrence of photoassociation. The utility of photoassociation as a technique for producing cold molecular samples in a well defined rovibrational state is demonstrated with spectra showing and (Condon internal diffraction) transitions after the photoassociation. Starting from states in the and potentials, these transitions include upward transitions to autoionizing potentials dissociating near 3P + 3P and downward transitions back to the 3S + 3S ground-state potentials. Spectroscopic constants for six levels of a doubly excited state of are given.We demonstrate a number of two-colour spectroscopy techniques where the first step is the photoassociation of laser-cooled and trapped sodium atoms to form bound states of . High-resolution spectra of are obtained. Spectra of the `purely long-range' state demonstrates the use of two-colour spectroscopy to open up an ionization channel for detecting the occurrence of photoassociation. The utility of photoassociation as a technique for producing cold molecular samples in a well defined rovibrational state is demonstrated with spectra showing and (Condon internal diffraction) transitions after the photoassociation. Starting from states in the and potentials, these transitions include upward transitions to autoionizing potentials dissociating near 3P + 3P and downward transitions back to the 3S + 3S ground-state potentials. Spectroscopic constants for six levels of a doubly excited state of are given.

Journal of Physics B Atomic Molecular and Optical PhysicsJan 28, 199744 citations

Highly Excited States of Ultracold Molecules: Photoassociative Spectroscopy of Na2

James P. Shaffer, Witek Chalupczak, N. P. Bigelow

We describe the spectroscopy of highly excited states of ultracold ${\mathrm{Na}}_{2}$ molecules using a new photoassociative approach based on resonantly enhanced multiphoton ionization. We excite a remarkable number of ${\mathrm{Na}}_{2}$ rotational states providing a rich rovibrational spectrum. We thereby extract not only the first order quadrupole-quadrupole ( ${C}_{5}$ ) and the van der Waals constants ( ${C}_{6}$ ) but also sensitive atom-atom interaction parameters such as spin-spin, spin-orbit, and perturbative constants.We describe the spectroscopy of highly excited states of ultracold ${\mathrm{Na}}_{2}$ molecules using a new photoassociative approach based on resonantly enhanced multiphoton ionization. We excite a remarkable number of ${\mathrm{Na}}_{2}$ rotational states providing a rich rovibrational spectrum. We thereby extract not only the first order quadrupole-quadrupole ( ${C}_{5}$) and the van der Waals constants ( ${C}_{6}$) but also sensitive atom-atom interaction parameters such as spin-spin, spin-orbit, and perturbative constants.

Physical Review LettersNov 1, 199915 citations

We have performed photoassociation spectroscopy to study the doubly excited states of

{\mathrm{Na}}_{2}

involved in the associative ionization of colliding

\mathrm{Na}(3P)

atoms. Rovibrational levels of two doubly excited potentials connected to the

{P}_{3/2}{+P}_{3/2}

asymptote, one of

{0}_{u}^{\ensuremath{-}}

and one of

{1}_{u}

<50\mathrm{GHz}

have been measured. The asymptotic potentials and short-range ionization probabilities are extracted from the data.

^{2}

S)+

{\mathrm{Na}}^{\mathrm{*}}

^{2}

{\mathit{P}}_{3/2}

) dissociation limit have been obtained by monitoring an enhanced

{\mathrm{Na}}_{2}^{+}

ion signal. We propose the use of pump-probe techniques to study the dynamics of the ionization process. At very large distances (typically 70 a.u.) two colliding Na atoms absorb a photon and form a coherent vibrational wave packet. We follow the packet in time and probe two possible mechanisms that are proposed to yield molecular ions: photoionization, where the second photon is absorbed at a small internuclear distance R directly ionizing the molecule, and associative ionization with excitation at intermediate R to the nuclear continuum of a doubly excited state followed by a half collision and autoionization at small R. The latter event can also lead to dissociation of the complex. The two mechanisms lead to distinct differences in the ion signals as a function of delay time between the pump and the probe pulses. Estimates of the ion rates to be expected in actual pump-probe experiments are given, which tend to favor the autoionization mechanism as the dominant reaction path.

We have observed the spectrum of long range molecular states of singly excited

{\mathrm{Na}}_{2}

formed by photoassociation during ultracold associative ionization collisions of laser-cooled Na atoms. The low kinetic energy of the collision allows us to obtain very high resolution spectra and to observe states close to the dissociation limit. The spectrum shows regular vibrational series characteristic of the 1/

{\mathit{R}}^{3}

long range portion of the

{1}_{\mathit{g}}

potential (asymptotically

{\mathit{S}}_{1/2}

{\mathit{P}}_{3/2}

) as well as molecular hyperfine structure within these peaks. We extract potential parameters and compare with recent theory.

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 have measured the rate of production of

{\mathrm{Na}}_{2}^{+}

ions in collisions of ultracold Na atoms held in a magneto-optical trap (MOT) as a function of probe laser detuning using a single-color probe beam. The ion rate is measured with the atoms mainly in the

3S(f=2)

level (``bright MOT'') or the

3S(f=1)

level (``dark MOT''). Using recent experimental information about the doubly excited autoionizing states of

{\mathrm{Na}}_{2},

we find that the large structures in the first 5 GHz red of the atomic transition frequency are due to a doubly resonant excitation process with levels in the ${0}_{g}^{\ensuremath{-}}$ potential (asymptotically connected to

{3S}_{1/2}{+3P}_{3/2})

as the intermediate states, and levels in the ${0}_{u}^{\ensuremath{-}}$ and

{1}_{u}

potentials (asymptotically connected to

{3P}_{3/2}{+3P}_{3/2})

as the final autoionizing states. We can account for nearly all of the observed structure in this region of the spectra for both the bright and dark MOT.

We describe the spectroscopy of highly excited states of ultracold

{\mathrm{Na}}_{2}

molecules using a new photoassociative approach based on resonantly enhanced multiphoton ionization. We excite a remarkable number of

{\mathrm{Na}}_{2}

rotational states providing a rich rovibrational spectrum. We thereby extract not only the first order quadrupole-quadrupole (

{C}_{5}

) and the van der Waals constants (

{C}_{6}

) but also sensitive atom-atom interaction parameters such as spin-spin, spin-orbit, and perturbative constants.