Bose–Einstein condensates in dilute atomic gases, which were first realized experimentally in 1995 for rubidium, sodium, and lithium, provide unique opportunities for exploring quantum phenomena on a macroscopic scale. These systems differ from ordinary gases, liquids, and solids in a number of respects, as we shall now illustrate by giving typical values of some physical quantities. The particle density at the centre of a Bose-Einstein condensed atomic cloud is typically 10 13 –10 15 cm −3 . By contrast, the density of molecules in air at room temperature and atmospheric pressure is about 10 19 cm −3 . In liquids and solids the density of atoms is of order 1022 cm −3 , while the density of nucleons in atomic nuclei is about 10 38 cm −3 . To observe quantum phenomena in such low-density systems, the temperature must be of order 10 −5 K or less. This may be contrasted with the temperatures at which quantum phenomena occur in solids and liquids. In solids, quantum effects become strong for electrons in metals below the Fermi temperature, which is typically 10 4 –10 5 K, and for phonons below the De bye temperature, which is typically of order 10 2 K. For the helium liquids, the temperatures required for observing quantum phenomena are of order 1 K. Due to the much higher particle density in atomic nuclei, the corresponding degeneracy temperature is about 10 11 K. The path that led in 1995 to the first realization of Bose–Einstein condensation in dilute gases exploited the powerful methods developed over the past quarter of a century for cooling alkali metal atoms by using lasers.Bose–Einstein condensates in dilute atomic gases, which were first realized experimentally in 1995 for rubidium, sodium, and lithium, provide unique opportunities for exploring quantum phenomena on a macroscopic scale. These systems differ from ordinary gases, liquids, and solids in a number of respects, as we shall now illustrate by giving typical values of some physical quantities. The particle density at the centre of a Bose-Einstein condensed atomic cloud is typically 10 13 –10 15 cm −3 . By contrast, the density of molecules in air at room temperature and atmospheric pressure is about 10 19 cm −3 . In liquids and solids the density of atoms is of order 1022 cm −3 , while the density of nucleons in atomic nuclei is about 10 38 cm −3 . To observe quantum phenomena in such low-density systems, the temperature must be of order 10 −5 K or less. This may be contrasted with the temperatures at which quantum phenomena occur in solids and liquids. In solids, quantum effects become strong for electrons in metals below the Fermi temperature, which is typically 10 4 –10 5 K, and for phonons below the De bye temperature, which is typically of order 10 2 K. For the helium liquids, the temperatures required for observing quantum phenomena are of order 1 K. Due to the much higher particle density in atomic nuclei, the corresponding degeneracy temperature is about 10 11 K. The path that led in 1995 to the first realization of Bose–Einstein condensation in dilute gases exploited the powerful methods developed over the past quarter of a century for cooling alkali metal atoms by using lasers.

Cambridge University Press eBooksNov 29, 20010 citations

Heavy-atom Quantum Tunneling

Sarina R. Chaiken, Elianna Frank, Keaton L. Mertz +1 more

Jan 1, 20180 citations

Rb*Hen exciplexes in solid He4

A. Hofer, Peter Moroshkin, Daniel Nettels +2 more

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.

Physical Review ASep 29, 200620 citations

Dynamical Tunneling of Ultracold Atoms

W. K. Hensinger, Hartmut Häffner, Antoine Browaeys +7 more

NatureJan 1, 200112 citations

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.