We report on hyperpolarization of quadrupolar (I=3/2) 131Xe via spin-exchange optical pumping. Observations of the 131Xe polarization dynamics show that the effective alkali-metal/131Xe spin-exchange cross-sections are large enough to compete with 131Xe spin relaxation. 131Xe polarization up to 7.6 p/m 1.5 percent was achieved in ca. 8.5EE20 spins--a ca. 100-fold improvement in the total spin angular momentum--enabling applications including measurement of spin-dependent neutron-131Xe s-wave scattering and sensitive searches for time-reversal violation in neutron-131Xe interactions beyond the Standard Model.
We consider the degree of conservation of nuclear spin polarization in the process of optical pumping under typical spin-exchange optical pumping conditions. Previous analyses have assumed that negligible nuclear spin precession occurs in the brief p
eriods of time the alkali-metal atoms are in the excited state after absorbing photons and before undergoing quenching collisions with nitrogen molecules. We include excited-state hyperfine interactions, electronic spin relaxation in collisions with He and N_2, spontaneous emission, quenching collisions, and a simplified treatment of radiation trapping.
The spin polarization of electrons from multiphoton ionization of Xe by 395 nm circularly polarized laser pulses at $6cdot10^{13}$ W/cm$^2$ has been measured. At this photon energy of 3.14 eV the above threshold ionization peaks connected to Xe$^+$ i
ons in the ground state ($J=3/2$, ionization potential $I_p=12.1$ eV) and the first exicted state ($J=1/2$, $I_p=13.4$ eV) are clearly separated in the electron energy distribution. These two combs of ATI peaks show opposite spin polarizations. The magnitude of the spin polarization is a factor of two higher for the $J=1/2$ than for the $J=3/2$ final ionic state. In turn the data show that the ionization probability is strongly dependent on the sign of the magnetic quantum number.
We detail the design and operation of a compact, discharge light polarimeter for metastability exchange optical pumping of 3He gas near 1 torr under a low magnetic field. The nuclear polarization of 3He can be discerned from its electron polarization
, measured via the circular polarization of 668 nm discharge light from an RF excitation. This apparatus measures the circular polarization of this very dim discharge light using a nematic liquid crystal wave retarder (LCR) and a high-gain, transimpedance amplified Si photodiode. We outline corrections required in such a measurement, and discuss contributions to its systematic error.
We demonstrate that spin-exchange dephasing of Larmor precession at near-earth-scale fields is effectively eliminated by dressing the alkali-metal atom spins in a sequence of AC-coupled 2-pi pulses, repeated at the Larmor precession frequency. The co
ntribution of spin-exchange collisions to the spectroscopic line width is reduced by a factor of the duty cycle of the pulses. We experimentally demonstrate resonant transverse pumping in magnetic fields as high as 0.1 Gauss, present experimental measurements of the suppressed spin-exchange relaxation, and show enhanced magnetometer response relative to a light-narrowed scalar magnetometer.
Through solution of the multielectron, semi-relativistic, time-dependent Schr{o}dinger equation, we show that angular streaking produces strongly spin-polarized electrons in a noble gas. The degree of spin polarization increases with the Keldysh para
meter, so that angular streaking -- ordinarily applied to investigate tunneling -- may be repurposed to generate strongly spin-polarized electron bunches. Additionally, we explore modifications of the angular streaking scheme that also enhance spin polarization.
Michael J. Molway
,Liana Bales-Shaffer
,Kaili Ranta
.
(2021)
.
"Two-Orders-of-Magnitude Improvement in the Total Spin Angular Momentum of 131Xe Nuclei Using Spin Exchange Optical Pumping"
.
Boyd Goodson
هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا