Polarization and relaxation of radon

Investigations of the polarization and relaxation of $^{209}$Rn by spin exchange with laser optically pumped rubidium are reported. On the order of one million atoms per shot were collected in coated and uncoated glass cells. Gamma-ray anisotropies were measured as a signal of the alignment (second order moment of the polarization) resulting from the combination of polarization and quadrupole relaxation at the cell walls. The temperature dependence over the range 130$^\circ$C to 220$^\circ$C shows the anisotropies increasing with increasing temperature as the ratio of the spin exchange polarization rate to the wall relaxation rate increases faster than the rubidium polarization decreases. Polarization relaxation rates for coated and uncoated cells are presented. In addition, improved limits on the multipole mixing ratios of some of the main gamma-ray transitions have been extracted. These results are promising for electric dipole moment measurements of octupole-deformed $^{223}$Rn and other isotopes, provided sufficient quantities of the rare isotopes can be produced.Comment: 4 pages, 4 figure

Temperature Dependence of Rb 5P Fine-Structure Transfer Induced By \u3csup\u3e4\u3c/sup\u3eHe Collisions

Employing ultrafast laser excitation and time-correlated single-photon counting, we have measured the fine-structure transfer between Rb 5P states induced by collisions with 4He buffer gas at temperatures up to 150°C. The temperature dependence of the binary cross section agrees with earlier measurements. Our data show that the temperature dependence of the three-body rate is about the same as that of the binary rate. The three-body rate can be described as arising from the reduction of the rubidium fine-structure splitting due to nearby helium atoms. (C) 2012 Optical Society of Americ

Enhancement of Rb Fine-Structure Transfer in \u3csup\u3e4\u3c/sup\u3eHe Due to Three-Body Collisions

Using ultrafast laser excitation and time-correlated single-photon counting techniques, we have measured the collisional mixing rates between the rubidium 52P fine-structure levels in the presence of 4He gas. A nonlinear dependence of the mixing rate with 4He density is observed. We find Rb fine-structure transfer is primarily due to binary collisions at 4He densities of ≤1019cm-3, while at greater densities, three-body collisions become significant. We determine a three-body collisional transfer rate coefficient (52P3/2 → 52P1/2) of 1.25(9) × 10-32cm6/s at 22°C

Collisional Excitation Transfer Between Rb(5P) States in 50-3000 Torr of He-4

Measurements of the mixing rates and cross sections for collisional excitation transfer between the 5P(1/2) and 5P(3/2) states of rubidium (Rb) in the presence of He-4 buffer gas are presented. Selected pulses from a high repetition rate, mode-locked femtosecond laser are used to excite either Rb state with the fluorescence due to collisional excitation transfer observed by time-correlated single-photon counting. The time dependence of this fluorescence is fitted to the solution of rate equations which include the mixing rate, atomic lifetimes and any quenching processes. The variation in the mixing rate over a large range of buffer gas densities allows the determination of both the binary collisional transfer cross section and a three-body collisional transfer rate. We do not observe any collisional quenching effects at He-4 pressures up to 6 atm and discuss in detail other systematic effects considered in the experiment

Polarization and relaxation of ^209Rn

The study of the nuclear polarization of radon is motivated by the expected large enhancement of sensitivity to a CP-violating electric dipole moment (EDM) in isotopes with octupole deformation or vibrational strength. In preparation for EDM measurements, the polarization of radon by spin exchange with laser-polarized alkali metals is studied. The measurement of the alignment of 209Rn using HPGe detectors to observe the resulting anisotropy in the 337 and 745 keV gamma rays emitted following electron-capture decay of 209Rn to 209At is demonstrated. Radon is polarized via spin-exchange collisions with rubidium atoms in an uncoated Pyrex optical pumping cell. Anisotropy measurements at several temperatures are used to study polarization and relaxation