Hyperfine structure measurement of
87Rb atoms injected into superfluid helium as highly energetic ion beam
In this paper, we report on a laser spectroscopy measurement of ${}^{84\ensuremath{-}87}\mathrm{Rb}$ isotopes in superfluid helium (He ii) at 1.8 K using laser--radio-frequency double-resonance spectroscopy. Rb ion beams
(>60 MeV/u) provided by the RIKEN projectile fragment separator (RIPS) were injected and trapped into He ii. The stopping position of atoms in He ii was precisely confirmed by laser spectroscopy. By optically pumping the trapped Rb isotopes, large atomic spin polarization (up to 40%) of each observed isotope in the ground state was achieved. The laser--radio-frequency double-resonance spectra were observed for stable
85,87Rb isotopes as well as for unstable isotopes
84,84m,86Rb by scanning a weak magnetic field with a fixed-frequency RF field. From the measured Zeeman splitting, nuclear spin values for ${}^{84m,84\ensuremath{-}87}\mathrm{Rb}$ isotopes were determined with reasonable accuracy. The number of ions injected into He ii for the resonance spectra measurement was on the order of
104 particles per second. This work may open new opportunities for the study of various particles trapped in condensed helium in several fields.
We present new results on the properties of Celsium and Rubidium atoms trapped in crystalline helium matrices. We have extended the measurements of optical excitation spectra and excited state lifetimes, previously performed in superfluid helium, to solid helium. Cs atoms in the hcp phase of 4He exhibit several distinctive features, such as dipole-forbidden transitions and zero-field magnetic resonance lines. We interpret these features as being due to static quadrupolar deformations of the local trapping sites (atomic bubbles). The degree of deformation of the bubbles can be obtained by comparing hyperfine coupling constants in the cubic and hexagonal phases. We have investigated in detail optical pumping of Cs in solid helium, and have gained new insights into the pumping mechanism. We have also succeeded, for the first time, in detecting Rb and Rb in solid helium, by applying an absorption technique, based on driven spin precession.