Search

We report on the operation of co-located ${}^{129}$Xe and ${}^{131}$Xe nuclear spin masers with an external feedback scheme, and discuss the use of ${}^{131}$Xe as a comagnetometer in measurements of the ${}^{129}$Xe spin precession frequency. By applying a correction based on the observed change in the ${}^{131}$Xe frequency, the frequency instability due to magnetic field and cell temperature drifts are eliminated by two orders of magnitude. The frequency precision of 6.2 $\mu$Hz is obtained for a 10$^4$ s averaging time, suggesting the possibility of future improvement to $\approx$ 1 nHz by improving the signal-to-noise ratio of the observation., Comment: 8 pages, 5 figures

We demonstrate spin-exchange optical pumping of 129Xe atoms with our newly made laser system. The new laser system was prepared to provide higher laser power required for the stable operation of spin maser oscillations in the 129Xe EDM experiment. We studied the optimum cell temperature and pumping laser power to improve the degree of 129Xe spin polarization. The best performance was achieved at the cell temperature of 100 ◦C with the presently available laser power of 1 W. The results show that a more intense laser is required for further improvement of the spin polarization at higher cell temperatures in our experiment.

Co-magnetometry enables the elimination of systematic errors arising from the long-term drift in the magnetic field, and is essential for a precision measurement of spin precession frequency in experiments searching for electric dipole moment (EDM). $^{131}$Xe nuclear spin maser shows great promise as a co-magnetometer in a Xe EDM experiment, because the systematic error originating from the Xe-Rb interaction, which virtually limits the sensitivity in a case of a $^3$He co-magnetometer, will be cancelled out. The performance of a cell which contains both $^{129}$Xe and $^{131}$Xe was investigated. In the best cell among those fabricated this time, the signal-to-noise ratio in a free induction decay experiment turned out to be large enough for the operation as co-existing $^{129}$Xe-$^{131}$Xe masers.

A system for the spin-polarization measurement of unstable nuclei has been developed, in which the alternation of nuclear spins takes place by adiabatically rotating a holding magnetic field for the preservation of spin polarization, without applying a resonant oscillating magnetic field for NMR. The performance of the system was studied with spin-polarized 20F ( I π = 2 + , T 1 / 2 = 11.163 s) produced in the 19 F ( d → , p ) 20 → F reaction at E/A = 7 MeV at the RIKEN RIBF facility. In the measurement, the magnitude of 20F spin polarization | P ( 20 F ) | = 1.6 ( 2 ) % was successfully observed with the new system.

Radiative capture rates of thermal $\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}+\mathrm{\ensuremath{\Xi}}N$ states into a H dibaryon are calculated in the novel imaginary time method. The H dibaryon is assumed to be a bound state of $\mathrm{\ensuremath{\Xi}}N$ with spin ${J}^{\ensuremath{\pi}}={0}^{+}$, isospin $I=0$ and strangeness $\ensuremath{-}2$. We consider the $E1$ transition to H from $\mathrm{\ensuremath{\Xi}}N (L=1)$ scattering states which mix with $\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}(L=1)$. In order to calculate the transition rates, we formulate a coupled-channel imaginary time method by extending the one-channel formula originally proposed by Yabana and Funaki. The imaginary time method allows us to avoid the sum over all the excited thermal initial states, and thus to save computational time significantly. The transition rates are given as a function of temperature and the unknown binding energy of the H dibaryon, which we take as a parameter. It is found that the transition rate is not sensitive to the choices of the H binding energy or the strengths of the channel coupling for temperatures 3 MeV or higher.

Uncertainty in the frequency precision of the planned experiment to search for a 129 Xe atomic electric dipole moment is dominated by drifts in the frequency shift due to contact interaction of 129 Xe with polarized Rb valence electrons. In order to suppress the frequency shift, a double-cell geometry has been adopted for the confinement of 129 Xe gas. A new process has been identified to take part in the optical detection of spin pre- cession. The parameters controlling the oscillation of the maser in this new double-cell arrangement were optimized. As a result, the frequency shift has been reduced by a factor of 10 or more from the former single-cell geometry.

An experimental search for an electric dipole moment in the diamagnetic atom 129 Xe is in progress through the precision measurement of spin precession frequency using an active nuclear spin maser. A 3 He comagnetometer has been incorporated into the active spin maser system in order to cancel out the long-term drifts in the external magnetic field. Also, a double-cell geometry has been adopted in order to suppress the frequency shifts due to interaction with polarized Rb atoms. The first EDM measurement with the 129 Xe active spin maser and the 3 He comagnetometer has been conducted.

We aim to measure the electric dipole moment (EDM) of a diamagnetic atom 129Xe using an optical-detection nuclear spin maser technique. The relation of EDM in a diamagnetic atom to nuclear Schiff moment and fundamental sources generating it is discussed, and the present status for the development of our experimental setup is presented.