Generation and spectroscopy of atoms and molecules in metastable states

We report on the use of multistage Zeeman deceleration to generate beams of ${\mathrm{He}}_{2}$ molecules in the metastable $a\phantom{\rule{0.16em}{0ex}}{}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ state with velocities tunable down to 100 m/s. The metastable molecules are generated by striking a discharge in a supersonic expansion of pure helium gas from a pulsed valve held at cryogenic temperature. The velocity and internal-state distributions of the metastable ${\mathrm{He}}_{2}$ molecules are measured for nozzle temperatures of 300, 77, and 10 K by high-resolution photoelectron and photoionization spectroscopy. The deceleration process does not exhibit any rotational state selectivity with rotational levels up to ${N}^{\ensuremath{'}\ensuremath{'}}=21$ being populated, but eliminates molecules in spin-rotational sublevels with ${J}^{\ensuremath{'}\ensuremath{'}}={N}^{\ensuremath{'}\ensuremath{'}}$ from the beam, where ${J}^{\ensuremath{'}\ensuremath{'}}$ and ${N}^{\ensuremath{'}\ensuremath{'}}$ are the total and the rotational angular momentum quantum number, respectively. The lack of rotational state selectivity is attributed to the fact that the Paschen-Back regime of the Zeeman effect in the rotational levels of ${\mathrm{He}}_{2}$ is already reached at fields of only 0.1 T.We report on the use of multistage Zeeman deceleration to generate beams of ${\mathrm{He}}_{2}$ molecules in the metastable $a\phantom{\rule{0.16em}{0ex}}{}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ state with velocities tunable down to 100 m/s. The metastable molecules are generated by striking a discharge in a supersonic expansion of pure helium gas from a pulsed valve held at cryogenic temperature. The velocity and internal-state distributions of the metastable ${\mathrm{He}}_{2}$ molecules are measured for nozzle temperatures of 300, 77, and 10 K by high-resolution photoelectron and photoionization spectroscopy. The deceleration process does not exhibit any rotational state selectivity with rotational levels up to ${N}^{\ensuremath{'}\ensuremath{'}}=21$ being populated, but eliminates molecules in spin-rotational sublevels with ${J}^{\ensuremath{'}\ensuremath{'}}={N}^{\ensuremath{'}\ensuremath{'}}$ from the beam, where ${J}^{\ensuremath{'}\ensuremath{'}}$ and ${N}^{\ensuremath{'}\ensuremath{'}}$ are the total and the rotational angular momentum quantum number, respectively. The lack of rotational state selectivity is attributed to the fact that the Paschen-Back regime of the Zeeman effect in the rotational levels of ${\mathrm{He}}_{2}$ is already reached at fields of only 0.1 T.

arXiv:1401.7774Physical Review AApr 21, 201439 citations

Experimental Studies of Metastable Atoms and Molecules.

C. H. Dugan

Jan 1, 19630 citations

Accurate Determination of the Scattering Length of Metastable Helium Atoms Using Dark Resonances between Atoms and Exotic Molecules

Steven Moal, M. Portier, J. Kim +4 more

We present a new measurement of the $s$ -wave scattering length $a$ of spin-polarized helium atoms in the $2\text{ }^{3}S_{1}$ metastable state. Using two-photon photoassociation spectroscopy and dark resonances, we measure the energy ${E}_{v=14}=\ensuremath{-}91.35\ifmmode\pm\else\textpm\fi{}0.06\text{ }\text{ }\mathrm{MHz}$ of the least-bound state $v=14$ in the interaction potential of the two atoms. We deduce a value of $a=7.512\ifmmode\pm\else\textpm\fi{}0.005\text{ }\text{ }\mathrm{nm}$, which is at least 100 times more precise than the best previous determinations and is in disagreement with some of them. This experiment also demonstrates the possibility to create exotic molecules binding two metastable atoms with a lifetime of the order of $1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$.We present a new measurement of the $s$-wave scattering length $a$ of spin-polarized helium atoms in the $2\text{ }^{3}S_{1}$ metastable state. Using two-photon photoassociation spectroscopy and dark resonances, we measure the energy ${E}_{v=14}=\ensuremath{-}91.35\ifmmode\pm\else\textpm\fi{}0.06\text{ }\text{ }\mathrm{MHz}$ of the least-bound state $v=14$ in the interaction potential of the two atoms. We deduce a value of $a=7.512\ifmmode\pm\else\textpm\fi{}0.005\text{ }\text{ }\mathrm{nm}$, which is at least 100 times more precise than the best previous determinations and is in disagreement with some of them. This experiment also demonstrates the possibility to create exotic molecules binding two metastable atoms with a lifetime of the order of $1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$.

arXiv:cond-mat/0509286Physical Review LettersJan 20, 200692 citations

Sources of Metastable Atoms and Molecules

T. J. Gay

Experimental methods in the physical sciencesJan 1, 199610 citations

Trapping Cold Ground State Argon Atoms

P. D. Edmunds, P. F. Barker

We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable $4s[3/2{]}_{2}$ state to be $(7.3\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}39}\text{ }\text{ }\mathrm{C}\text{ }{\mathrm{m}}^{2}/\mathrm{V}$. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be $(3.3\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$.We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable $4s[3/2{]}_{2}$ state to be $(7.3\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}39}\text{ }\text{ }\mathrm{C}\text{ }{\mathrm{m}}^{2}/\mathrm{V}$. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be $(3.3\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$.

arXiv:1406.2503Physical Review LettersOct 30, 201413 citations

We report on the use of multistage Zeeman deceleration to generate beams of

{\mathrm{He}}_{2}

molecules in the metastable $a\phantom{\rule{0.16em}{0ex}}{}^{3}{\ensuremath{\Sigma}}_{u}^{+}$ state with velocities tunable down to 100 m/s. The metastable molecules are generated by striking a discharge in a supersonic expansion of pure helium gas from a pulsed valve held at cryogenic temperature. The velocity and internal-state distributions of the metastable

{\mathrm{He}}_{2}

molecules are measured for nozzle temperatures of 300, 77, and 10 K by high-resolution photoelectron and photoionization spectroscopy. The deceleration process does not exhibit any rotational state selectivity with rotational levels up to ${N}^{\ensuremath{'}\ensuremath{'}}=21$ being populated, but eliminates molecules in spin-rotational sublevels with ${J}^{\ensuremath{'}\ensuremath{'}}={N}^{\ensuremath{'}\ensuremath{'}}$ from the beam, where ${J}^{\ensuremath{'}\ensuremath{'}}$ and ${N}^{\ensuremath{'}\ensuremath{'}}$ are the total and the rotational angular momentum quantum number, respectively. The lack of rotational state selectivity is attributed to the fact that the Paschen-Back regime of the Zeeman effect in the rotational levels of

{\mathrm{He}}_{2}

is already reached at fields of only 0.1 T.

We present a new measurement of the

s

-wave scattering length

a

of spin-polarized helium atoms in the

2\text{ }^{3}S_{1}

metastable state. Using two-photon photoassociation spectroscopy and dark resonances, we measure the energy ${E}_{v=14}=\ensuremath{-}91.35\ifmmode\pm\else\textpm\fi{}0.06\text{ }\text{ }\mathrm{MHz}$ of the least-bound state

v=14

in the interaction potential of the two atoms. We deduce a value of $a=7.512\ifmmode\pm\else\textpm\fi{}0.005\text{ }\text{ }\mathrm{nm}$, which is at least 100 times more precise than the best previous determinations and is in disagreement with some of them. This experiment also demonstrates the possibility to create exotic molecules binding two metastable atoms with a lifetime of the order of $1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$.

4s[3/2{]}_{2}

state to be $(7.3\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}39}\text{ }\text{ }\mathrm{C}\text{ }{\mathrm{m}}^{2}/\mathrm{V}$. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be $(3.3\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$.