Physical Review Letters

Implantation of neutral atoms into liquid helium by laser sputtering

Akihiro Fujisaki, K. Sano, Toshiya Kinoshita, Yoshiro Takahashi, T. Yabuzaki

Published Aug 16, 1993• 84 citations

Abstract

We have developed a new method for producing a high density of neutral atoms in liquid helium; laser sputtering within liquid helium. When we irradiate samples immersed in liquid helium with a pulsed laser, a large number of clusters are introduced into the liquid. When we further irradiate these clusters with an additional pulse laser, the clusters are sputtered and decomposed, which results in the creation of a high density of isolated atoms in the liquid. For alkaline earth atoms this method is demonstrated, and the results of laser spectroscopy are given.

DOI: 10.1103/physrevlett.71.1039

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Physical Review Letters

Implantation of neutral atoms into liquid helium by laser sputtering

Akihiro Fujisaki, K. Sano, Toshiya Kinoshita, Yoshiro Takahashi, T. Yabuzaki

Published Aug 16, 1993• 84 citations

Publisher

Abstract

DOI: 10.1103/physrevlett.71.1039

Related papers

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AIP conference proceedingsJan 1, 19930 citations

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Lineshapes associated with the absorption and emission spectra of neutral atoms in liquid helium and cold helium gas are discussed. A neutral atom in liquid helium forms a microcavity due to a strong short-range repulsive force between the helium and impurity atoms, producing very broad and largely blueshifted absorption bands and relatively narrow emission lines with much smaller shifts. A broad and weak emission band observed by exciting the D2 line of Ag atoms in liquid helium has confirmed the hypothesis that quenching of D2 emission lines for heavy group 1a and 1b atoms are due to the formation of exciplex. In cold helium gas, sudden decrease of the emission lifetimes below 5.2 K by the excitation of the D2 line of Ag atoms is attributed to the condensation of He atoms on the metastable 2D5/2 state. Very narrow absorption lines of Eu innershell electron transitions have revealed that superfluid helium behaves as a static and highly homogeneous low temperature matrix.Lineshapes associated with the absorption and emission spectra of neutral atoms in liquid helium and cold helium gas are discussed. A neutral atom in liquid helium forms a microcavity due to a strong short-range repulsive force between the helium and impurity atoms, producing very broad and largely blueshifted absorption bands and relatively narrow emission lines with much smaller shifts. A broad and weak emission band observed by exciting the D2 line of Ag atoms in liquid helium has confirmed the hypothesis that quenching of D2 emission lines for heavy group 1a and 1b atoms are due to the formation of exciplex. In cold helium gas, sudden decrease of the emission lifetimes below 5.2 K by the excitation of the D2 line of Ag atoms is attributed to the condensation of He atoms on the metastable 2D5/2 state. Very narrow absorption lines of Eu innershell electron transitions have revealed that superfluid helium behaves as a static and highly homogeneous low temperature matrix.

International Conference on Spectral Line Shapes (ICSLS)Jan 1, 19990 citations

Production of slow atoms from a moving drop

Kenneth C. Harvey

High densities of low velocity atoms or molecules may be produced from moving liquid drops. This technique can be useful for filling to high density neutral atom traps that have small well depths. If a drop travels at or near the mean thermal velocity of the atoms that are evaporating from the surface of the drop, the atoms that evaporate in the direction opposite the velocity of the drop have a velocity in the laboratory reference frame greatly reduced by the motion of the drop. These slow atoms may be further cooled in the trap by laser radiation. If the drop is rapidly heated by a laser pulse, the velocity distribution is compressed and the density of the low velocity atoms can be increased. Also the velocity distributions of the atoms evaporating from small drops may be interrogated by their Doppler-shifted resonance lines. This may give new information about liquids with small dimensions.High densities of low velocity atoms or molecules may be produced from moving liquid drops. This technique can be useful for filling to high density neutral atom traps that have small well depths. If a drop travels at or near the mean thermal velocity of the atoms that are evaporating from the surface of the drop, the atoms that evaporate in the direction opposite the velocity of the drop have a velocity in the laboratory reference frame greatly reduced by the motion of the drop. These slow atoms may be further cooled in the trap by laser radiation. If the drop is rapidly heated by a laser pulse, the velocity distribution is compressed and the density of the low velocity atoms can be increased. Also the velocity distributions of the atoms evaporating from small drops may be interrogated by their Doppler-shifted resonance lines. This may give new information about liquids with small dimensions.

Annual Meeting Optical Society of AmericaJan 1, 19890 citations

We report a study of implantation and optical spectroscopy of foreign atoms in a solid-helium matrix. With a sample of more than

{10}^{9}

Ba atoms in 1

{\mathrm{cm}}^{3}

, a storage time in excess of 5 hours has been demonstrated. Laser-induced fluorescence studies favor the assumption that the isotropy of the trapping site for the implanted atoms is preserved during the liquid-to-solid phase transition.

{4f}^{13}{(}^{2}{F}_{7/2}^{o}{)6s}^{2}

, which indicates that the transition between the inner shells is weakly perturbed by surrounding helium atoms. The pressure dependence of the emission wavelength suggests that the symmetry of helium atoms distributed around a thulium atom in the solid phase is similar to that in the liquid phase. The emission intensity was stable and large in the solid phase since thulium atoms were trapped at a density of 10

{}^{10}

--10

{}^{11}

atoms/cm

{}^{3}

. The lifetime of the excited state was measured to be $7.09\ifmmode\pm\else\textpm\fi{}0.04$ $\ensuremath{\mu}$s, which was longer than that of the

{4f}^{12}{(}^{3}{H}_{6}{)5d}_{5/2}{6s}^{2}

{(6,5/2)}_{7/2}

state of free thulium atoms. The excited state is expected to be a mixed state of the

{4f}^{12}{5d6s}^{2}

and

{4f}^{13}6s6p

configurations. The metastable state

{4f}^{13}{(}^{2}{F}_{5/2}^{o}{)6s}^{2}

is populated by a radiative transition from this excited state and relaxes to the ground state through a magnetic dipole transition. The lifetime of the metastable state of a neutral thulium atom was measured to be $75\ifmmode\pm\else\textpm\fi{}3$ ms.