The spectral features of the light-induced drift (LID) velocity for rubidium atoms ( 85 Rb and 87 Rb) in an argon buffer medium and in binary buffer mixtures of noble gases (Ne + Ar, Ne + Kr, Ne + Xe, He + Ar, He + Kr, and He + Xe) have been investigated theoretically. A strong temperature dependence of the spectral shape of the LID signal for Rb atoms in an Ar atmosphere is predicted in the temperature range 450 K < T < 800 K. It is shown that the anomalous LID of Rb atoms in binary buffer mixtures of noble gases can be observed at almost any temperature (including the room one) depending on the fractions of neon or helium in these mixtures. The results obtained enable a highly accurate testing of the interatomic interaction potentials used to calculate the drift velocity for anomalous LID in LID experiments.
Abstract The relative spin-exchange efficiencies of Cs and Rb remain an important question in the field of hyperpolarized 129 Xe; however, direct experimental comparisons are still limited. We present measurements of the spin-exchange efficiency for 129 Xe–Cs/Rb in 129 Xe: N 2 = 1 : 50 mixtures. Under low-magnetic-field and short-lifetimes van der Waals molecular regime, we determine the spin-exchange efficiencies of 129 Xe–Cs/Rb by measuring the spin-exchange rate coefficient for 129 Xe–Cs/Rb and the Xe-induced spin-relaxation rate of Cs/Rb. Under identical gas composition and pressure conditions, the spin-exchange efficiency of Cs is approximately 1.2–1.5 times higher than Rb. We also derive an expression that enables the prediction of the spin-exchange efficiency for 129 Xe–Cs/Rb in arbitrary 129 Xe– N 2 mixtures.
We present comprehensive determinations of the diffusion coefficients
D at $T=24\phantom{\rule{0.16em}{0ex}}{}^{\ensuremath{\circ}}\mathrm{C}$ for trace amounts of naturally abundant Rb atoms in inert, naturally abundant He, Ne,
N2, Ar, Kr, and Xe buffer gases using a single measurement technique. They have been measured by establishing a spatially periodic population grating in the Rb sample using two laser beams that intersect at a small angle $\ensuremath{\theta}$ of a few milliradians. The atomic population grating decays exponentially in time due to diffusive motion induced by momentum-changing elastic collisions between Rb and buffer gas atoms or molecules. This decay is monitored by observing the scattered field from a readout beam aligned along the direction of one of the excitation beams. We distinguish the contribution of diffusion from other collisional processes by measuring the characteristic ${\ensuremath{\theta}}^{2}$ dependence of the decay rate. We also measure the systematic dependence of the decay rate on the buffer gas pressure over a range of 7000 to
90000 Pa. In this manner, we obtain diffusion coefficients at standard atmospheric pressure of
101325 Pa and at a temperature of $24.0(5)\phantom{\rule{0.16em}{0ex}}{}^{\ensuremath{\circ}}\mathrm{C}$. We use two models to correct for systematic effects due to the transit time, one assuming a rectangular profile of the population distribution and a rectangular readout beam profile, and a second using Gaussian profiles. We obtain weighted averages of 0.33(5), 0.214(14), 0.132(7), 0.123(9), 0.093(9), and
0.073(4)cm2/s for Rb in He, Ne,
N2, Ar, Kr, and Xe, respectively. The number in parentheses represents one standard deviation of the combined statistical and systematic uncertainty. We also compare these data with diffusion coefficients obtained using quantum, classical, and semiclassical theoretical methods based on the most accurate interatomic interaction potentials from the literature. Near room temperature, simulations of
D using classical and quantum methods agree within their intrinsic, sub-1% standard uncertainties. We find that the semiclassical model only gives the correct orders of magnitude for
D. Our computed diffusion coefficients based on the quantum theory agree with the experimental determinations when systematic effects are taken into account. Our measurements and modeling are relevant to the optimization of magnetometers, biomedical imaging using spin-polarized noble gases, tests of collision models based on interatomic potentials, and the development of pressure sensors.