Physical Review A

6S1∕2−6P1∕2 transition of Cs atoms in cubic and hexagonal solid He4

A. Hofer, Peter Moroshkin, Simone Ulzega, Daniel Nettels, R. Müller-Siebert, Antoine Weis

Published Aug 8, 2007• 16 citations

Abstract

We present a systematic experimental study of the absorption and fluorescence spectra of the $6{S}_{1∕2}\text{\ensuremath{-}}6{P}_{1∕2}$ transition in Cs atoms isolated in solid $^{4}\mathrm{He}$ matrices. The bubble model developed earlier for alkali-metal atoms in liquid He is revised and applied to the present system. The analysis of the dependencies of absorption and fluorescence wavelengths on He pressure in liquid and solid He (cubic and hexagonal) environments leads us to modify the bubble model by taking the elastic deformation of solid He by the atomic bubble into account.

DOI: 10.1103/physreva.76.022502

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Physical Review A

6S1∕2−6P1∕2 transition of Cs atoms in cubic and hexagonal solid He4

A. Hofer, Peter Moroshkin, Simone Ulzega, Daniel Nettels, R. Müller-Siebert, Antoine Weis

Published Aug 8, 2007• 16 citations

Publisher

Abstract

We present a systematic experimental study of the absorption and fluorescence spectra of the

6{S}_{1∕2}\text{\ensuremath{-}}6{P}_{1∕2}

transition in Cs atoms isolated in solid

^{4}\mathrm{He}

matrices. The bubble model developed earlier for alkali-metal atoms in liquid He is revised and applied to the present system. The analysis of the dependencies of absorption and fluorescence wavelengths on He pressure in liquid and solid He (cubic and hexagonal) environments leads us to modify the bubble model by taking the elastic deformation of solid He by the atomic bubble into account.

DOI: 10.1103/physreva.76.022502

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We report the observation of emission spectra from ${\mathrm{Rb}}^{*}{\mathrm{He}}_{n}$ exciplexes in solid $^{4}\mathrm{He}$ . Two different excitation channels were experimentally identified, viz., exciplex formation via laser excitation to the atomic $5{P}_{3∕2}$ and to the $5{P}_{1∕2}$ levels. While the former channel was observed before in liquid helium, on helium nanodroplets, and in helium gas by different groups, the latter creation mechanism occurs only in solid helium or in gaseous helium above $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ . The experimental results are compared to theoretical predictions based on the extension of a model, used earlier by us for the description of ${\mathrm{Cs}}^{*}{\mathrm{He}}_{n}$ exciplexes. We also report the observation of fluorescence from atomic rubidium in solid helium, and discuss striking differences between the spectroscopic features of $\mathrm{Rb}\text{\ensuremath{-}}\mathrm{He}$ and $\mathrm{Cs}\text{\ensuremath{-}}\mathrm{He}$ systems.We report the observation of emission spectra from ${\mathrm{Rb}}^{*}{\mathrm{He}}_{n}$ exciplexes in solid $^{4}\mathrm{He}$. Two different excitation channels were experimentally identified, viz., exciplex formation via laser excitation to the atomic $5{P}_{3∕2}$ and to the $5{P}_{1∕2}$ levels. While the former channel was observed before in liquid helium, on helium nanodroplets, and in helium gas by different groups, the latter creation mechanism occurs only in solid helium or in gaseous helium above $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The experimental results are compared to theoretical predictions based on the extension of a model, used earlier by us for the description of ${\mathrm{Cs}}^{*}{\mathrm{He}}_{n}$ exciplexes. We also report the observation of fluorescence from atomic rubidium in solid helium, and discuss striking differences between the spectroscopic features of $\mathrm{Rb}\text{\ensuremath{-}}\mathrm{He}$ and $\mathrm{Cs}\text{\ensuremath{-}}\mathrm{He}$ systems.

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Physical Review ANov 1, 199927 citations

We present a systematic experimental study of the absorption and fluorescence spectra of the

6{S}_{1∕2}\text{\ensuremath{-}}6{P}_{1∕2}

transition in Cs atoms isolated in solid

^{4}\mathrm{He}

{\mathit{D}}_{2}

excitation spectra are found to have double peaks, indicating the existence of anisotropic oscillations of the bubble surface. The disappearance of the

{\mathit{D}}_{2}

emission lines and the pressure-dependent quenching of the Rb

{\mathit{D}}_{1}

emission lines are also 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.

We report the observation of emission spectra from

{\mathrm{Rb}}^{*}{\mathrm{He}}_{n}

exciplexes in solid

^{4}\mathrm{He}

. Two different excitation channels were experimentally identified, viz., exciplex formation via laser excitation to the atomic

5{P}_{3∕2}

and to the

5{P}_{1∕2}

levels. While the former channel was observed before in liquid helium, on helium nanodroplets, and in helium gas by different groups, the latter creation mechanism occurs only in solid helium or in gaseous helium above

10\phantom{\rule{0.3em}{0ex}}\mathrm{K}

. The experimental results are compared to theoretical predictions based on the extension of a model, used earlier by us for the description of

{\mathrm{Cs}}^{*}{\mathrm{He}}_{n}

exciplexes. We also report the observation of fluorescence from atomic rubidium in solid helium, and discuss striking differences between the spectroscopic features of $\mathrm{Rb}\text{\ensuremath{-}}\mathrm{He}$ and $\mathrm{Cs}\text{\ensuremath{-}}\mathrm{He}$ systems.

We have studied both theoretically and experimentally the optical pumping of Cs atoms trapped in (body-centered-cubic and hexagonal-close-packed) crystalline

{}^{4}\mathrm{He}

matrices. The theoretical approach is based on rate equations for which time-dependent and asymptotic solutions are obtained in the case of depopulation and repopulation pumping. Comparison with experiments show that repopulation pumping, i.e., a process in which spin polarization in the excited state is not destroyed, is the dominant pumping mechanism in both crystalline phases.