Physical Review A

Spectroscopy of barium atoms in liquid and solid helium matrices

Victor Lebedev, Peter Moroshkin, Antoine Weis

Published Aug 3, 2011• 14 citations

Abstract

We present an exhaustive overview of optical absorption and laser-induced fluorescence lines of Ba atoms in liquid and solid helium matrices in visible and near-infrared spectral ranges. Due to the increased density of isolated atoms, we have found a large number of spectral lines that were not observed in condensed helium matrices before. We have also measured the lifetimes of metastable states. The lowest ${}^{3}{D}_{1}$ metastable state has lifetime of 2.6 s and can be used as an intermediate state in two-step excitations of high-lying states. Various matrix-induced radiationless population transfer channels have been identified.

DOI: 10.1103/physreva.84.022502

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Physical Review A

Spectroscopy of barium atoms in liquid and solid helium matrices

Victor Lebedev, Peter Moroshkin, Antoine Weis

Published Aug 3, 2011• 14 citations

Publisher

Abstract

{}^{3}{D}_{1}

metastable state has lifetime of 2.6 s and can be used as an intermediate state in two-step excitations of high-lying states. Various matrix-induced radiationless population transfer channels have been identified.

DOI: 10.1103/physreva.84.022502

Related papers

Laser spectroscopy of thulium atoms implanted in liquid and solid 4 He

Kiyoshi Ishikawa, A. Hatakeyama, Koichi Gosyono-o +3 more

The excitation, emission spectra, and decay curves of the emission intensity of thulium atoms implanted in liquid and solid helium were observed in the presence and absence of an external magnetic field. The observed narrow line (width $\ensuremath{\sim}0.1$ nm) of the excitation spectrum at 590.60 nm is assigned as a zero-phonon transition from the electronic ground state ${4f}^{13}{(}^{2}{F}_{7/2}^{o}{)6s}^{2}$ , 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.The excitation, emission spectra, and decay curves of the emission intensity of thulium atoms implanted in liquid and solid helium were observed in the presence and absence of an external magnetic field. The observed narrow line (width $\ensuremath{\sim}0.1$ nm) of the excitation spectrum at 590.60 nm is assigned as a zero-phonon transition from the electronic ground state ${4f}^{13}{(}^{2}{F}_{7/2}^{o}{)6s}^{2}$, 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.

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Energy pooling in barium with state excitation

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Energy-pooling collisions between low-lying excited states of Ba have been studied. We have used a CW dye laser to excite the level in Ba. Radiative decay and collisions with Ba or buffer-gas atoms (Ar, He) populate also the , and metastable levels. The spatial density distributions of these excited levels were measured by the absorption of lines from a Ba hollow-cathode lamp as a function of laser frequency. When the laser was on the exact atomic resonance we observed fluorescence from the , , , , , , and states populated by energy-pooling collisions of Ba( , ). By changing the buffer gas pressure the fluorescence intensity ratio between - and - transitions changes dramatically. This is found to be due to redistribution of population among metastable levels, both in magnitude and space. In addition, we have found that the and metastable levels are also populated when the laser is tuned to the blue from the 553.5 nm line under which conditions a pronounced red-shifted light cone (cone emission) is observed.Energy-pooling collisions between low-lying excited states of Ba have been studied. We have used a CW dye laser to excite the level in Ba. Radiative decay and collisions with Ba or buffer-gas atoms (Ar, He) populate also the , and metastable levels. The spatial density distributions of these excited levels were measured by the absorption of lines from a Ba hollow-cathode lamp as a function of laser frequency. When the laser was on the exact atomic resonance we observed fluorescence from the , , , , , , and states populated by energy-pooling collisions of Ba( , ). By changing the buffer gas pressure the fluorescence intensity ratio between - and - transitions changes dramatically. This is found to be due to redistribution of population among metastable levels, both in magnitude and space. In addition, we have found that the and metastable levels are also populated when the laser is tuned to the blue from the 553.5 nm line under which conditions a pronounced red-shifted light cone (cone emission) is observed.

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arXiv:1410.2624Physical Review AFeb 10, 201540 citations

Pressure shift and broadening of the resonance line of barium atoms in liquid helium

S. I. Kanorsky, Markus Arndt, R. Dziewior +2 more

We have measured the pressure broadening and shift of the excitation and emission lines of the 6 ${\mathit{s}}^{2}$ $^{1}$ ${\mathit{S}}_{0}$ \ensuremath{\rightarrow}6s6p $^{1}$ ${\mathit{P}}_{1}$ transition of Ba atoms implanted in liquid and solid helium at 1.5 K. The observed spectra are quantitatively explained within the adiabatic line-broadening theory by assuming a bubble structure of the trapping sites for the Ba atoms. The evolution of the bubble shape and size in the optical excitation-deexcitation cycle is modeled theoretically.We have measured the pressure broadening and shift of the excitation and emission lines of the 6${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$\ensuremath{\rightarrow}6s6p $^{1}$${\mathit{P}}_{1}$ transition of Ba atoms implanted in liquid and solid helium at 1.5 K. The observed spectra are quantitatively explained within the adiabatic line-broadening theory by assuming a bubble structure of the trapping sites for the Ba atoms. The evolution of the bubble shape and size in the optical excitation-deexcitation cycle is modeled theoretically.

Physical review. B, Condensed matterSep 1, 199474 citations

{}^{3}{D}_{1}

{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.

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.

{\mathrm{Ba}}^{+}

deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of fewer than or equal to

{10}^{4}

Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.

We have measured the pressure broadening and shift of the excitation and emission lines of the 6

{\mathit{s}}^{2}

^{1}

{\mathit{S}}_{0}

\ensuremath{\rightarrow}6s6p

^{1}

{\mathit{P}}_{1}

transition of Ba atoms implanted in liquid and solid helium at 1.5 K. The observed spectra are quantitatively explained within the adiabatic line-broadening theory by assuming a bubble structure of the trapping sites for the Ba atoms. The evolution of the bubble shape and size in the optical excitation-deexcitation cycle is modeled theoretically.