Relaxation time constants of electron polarization, 〈Sz〉, for optically pumped rubidium atoms in a drifilm coated glass cell have been investigated with the Faraday rotation method. The dependence of the 〈Sz〉 relaxation time on pump cell temperature, rubidium density and applied magnetic field has been determined with high precision. The measurements allow the determination of the local magnetic field on the surface, alkali-wall binding energy and wall-dwell time. Furthermore, the change of relaxation time caused by admixtures of molecular hydrogen, nitrogen and oxygen has been investigated. No influence due to the addition of hydrogen could be detected up to a density of 3.3×1014 cm−3 at typical rubidium densities of several 1011 cm−3. The cross section for depolarizing collisons with molecular oxygen has been determined to be 7.50×10−15 cm2. The corresponding cross section for nitrogen was found to be two orders of magnitude lower. The experimental results are discussed in respect to the performance of spin exchange sources for nuclear polarized hydrogen and deuterium.
We measure the transverse relaxation of the spin state of an ensemble of ground-state rubidium atoms trapped in solid parahydrogen at cryogenic temperatures. We find the spin dephasing time of the ensemble (
T2∗) is limited by inhomogeneous broadening. We determine that this broadening is dominated by electrostaticlike interactions with the host matrix, and can be reduced by preparing nonclassical spin superposition states. Driving these superposition states gives significantly narrower electron paramagnetic resonance lines and the longest reported electron spin
T2∗ in any solid-phase system other than solid helium.
A new optical method for studying the spin relaxation of optically aligned rubidium vapor is described. In this method, the pumping radiation, consisting of circularly polarized
D1 resonance radiation, is suddenly shut off and then turned on again after a known time interval. The relaxation which takes place during the interval of darkness causes the vapor to become more opaque to the pumping radiation at a rate which is determined by the relaxation time. A large degree of alignment, as well as a relaxation time of about 80 milliseconds, were observed in a closed-off evacuated cylindrical glass cell completely lined, except for
2001 of the wall area, with a thin film of tetracontane (
C40H82). The variation of relaxation time with buffer gas pressure was studied in this cell and in an unlined glass cell. From the observations with the unlined cell, diffusion coefficients for rubidium in neon and argon of 0.31
cm2/sec and 0.24
cm2/sec, respectively, can be deduced. Observed cross sections for disorientation collisions between aligned ground-state rubidium atoms and neon, argon, krypton, and xenon atoms are 5.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}23}$
cm2, 3.7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}22}$
cm2, 5.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$
cm2, and 1.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}20}$
cm2, respectively. In the evacuated tetracontane-lined cell, the relaxation time decreased by 30% for a tenfold increase in rubidium vapor pressure. An explanation for this relatively weak dependence is suggested. The longest observed relaxation time was approximately 0.4 seconds in a tetracontanelined cell filled with neon to a pressure of 3 cm Hg.
It is known from ensemble measurements that rubidium atoms trapped in solid parahydrogen have favorable properties for quantum sensing of magnetic fields. To use a single rubidium atom as a quantum sensor requires a technique capable of efficiently measuring the internal state of a single atom, such as laser-induced fluorescence. In this work we search for laser-induced fluorescence from ensembles of rubidium atoms trapped in solid parahydrogen and, separately, in solid neon. In parahydrogen we find no evidence of fluorescence over the range explored, and we place upper limits on the radiative branching ratio. In neon, we observe laser-induced fluorescence, measure the spectrum of the emitted light, and measure the excited-state lifetime in the matrix. Bleaching of atoms from the excitation light is also reported.
In this work, we optically resolve and detect individual rubidium atoms trapped in solid neon. Additionally, we optically pump the rubidium's spin state using polarized light and measure the spin state via laser-induced fluorescence. When combined with the previously demonstrated magnetic field sensing capabilities of matrix-isolated rubidium atoms, these results are very promising for nanoscale sensing and for performing nuclear magnetic resonance (NMR) spectroscopy of individual molecules cotrapped in the matrix. Published by the American Physical Society 2024