32 research outputs found
Frequency shifts in noble-gas magnetometers
Polarized nuclei are a powerful tool in nuclear spin studies and in searches
for beyond-the-standard model physics. Noble-gas comagnetometer systems, which
compare two nuclear species, have thus far been limited by anomalous frequency
variations of unknown origin. We studied the self-interactions in a
He-Xe system by independently addressing, controlling and measuring
the influence of each component of the nuclear spin polarization. Our results
directly rule out prior explanations of the shifts, and demonstrate
experimentally that they can be explained by species dependent
self-interactions. We also report the first gas phase frequency shift induced
by Xe on He.Comment: v.
Development of high-performance alkali-hybrid polarized He-3 targets for electron scattering
Background: Polarized He-3 targets have been used as effective polarized neutron targets for electron scattering experiments for over twenty years. Over the last ten years, the effective luminosity of polarized He-3 targets based on spin-exchange optical pumping has increased by over an order of magnitude. This has come about because of improvements in commercially-available lasers and an improved understanding of the physics behind the polarization process. Purpose: We present the development of high-performance polarized He-3 targets for use in electron scattering experiments. Improvements in the performance of polarized He-3 targets, target properties, and operating parameters are documented. Methods: We utilize the technique of alkali-hybrid spin-exchange optical pumping to polarize the He-3 targets. Spectrally narrowed diode lasers used for the optical pumping greatly improved the performance. A simulation of the alkali-hybrid spin-exchange optical pumping process was developed to provide guidance in the design of the targets. Data was collected during the characterization of 24 separate glass target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. Results: From the data obtained we made determinations of the so-called X-factors that quantify a temperaturedependent and as-yet poorly understood spin-relaxation mechanism that limits the maximum achievable He-3 polarization to well under 100%. The presence of the X-factor spin-relaxation mechanism was clearly evident in our data. Good agreement between the simulation and the actual target performance was obtained by including details such as off-resonant optical pumping. Included in our results is ameasurement of the K-He-3 spin-exchange rate coefficient k(se)(K) = (7.46 +/- 0.62) x 10(-20) cm(3)/s over the temperature range 503 K to 563 K. Conclusions: In order to achieve high performance under the operating conditions described in this paper, the K to Rb alkali vapor density ratio should be about 5 +/- 2 and the line width of the optical pumping lasers should be no more than 0.3 nm. Our measurements of the X-factors under these conditions seem to indicate the He-3 polarization is limited to approximate to 90%. The simulation results, now benchmarked against experimental data, are useful for the design of future targets. Further work is required to better understand the temperature dependence of the X-factor spin-relaxation mechanism and the limitations of our optical pumping simulation
Implementing an electronic sideband offset lock for precision spectroscopy in radium
We demonstrate laser frequency stabilization with at least 6 GHz of offset
tunability using an in-phase/quadrature (IQ) modulator to generate electronic
sidebands (ESB) on a titanium sapphire laser at 714 nm and we apply this
technique to the precision spectroscopy of Ra, and Ra. By
locking the laser to a single resonance of a high finesse optical cavity and
adjusting the lock offset, we determine the frequency difference between the
magneto-optical trap (MOT) transitions in the two isotopes to be
MHz, a factor of 29 more precise than the previously available data. Using the
known value of the hyperfine splitting of the level, we calculate
the isotope shift for the to transition to be
MHz, which is a factor of 8 more precise than the best available
value. Our technique could be applied to countless other atomic systems to
provide unprecedented precision in isotope shift spectroscopy and other
relative frequency comparisons
Hypotension following Patent Ductus Arteriosus Ligation: The Role of Adrenal Hormones
OBJECTIVE: To test the hypothesis that an impaired adrenal response to stress might play a role in the hypotension that follows patent ductus arteriosus (PDA) ligation. STUDY DESIGN: We performed a multicenter study of infants born at <32 weeks gestation who were about to undergo PDA ligation. Serum adrenal steroids were measured three times: before and after a cosyntropin (1.0 microgram/kg) stimulation test (performed prior to the ligation), and at 10–12 hours after the ligation. A standardized approach for diagnosis and treatment of postoperative hypotension was followed at each site. A modified Inotrope Score (1 x dopamine (μg/kg/min) + 1 x dobutamine) was used to monitor the catecholamine support an infant received. Infants were considered to have catecholamine-resistant hypotension if their highest Inotrope Score was >15. RESULTS: Of 95 infants enrolled, 43 (45%) developed hypotension and 14 (15%) developed catecholamine-resistant hypotension. Low post-operative cortisol levels were not associated with the overall incidence of hypotension following ligation. However, low cortisol levels were associated with the refractoriness of the hypotension to catecholamine treatment. In a multivariate analysis: the odds ratio for developing catecholamine-resistant hypotension was OR=36.6, CI=2.8–476, p=0.006. Low cortisol levels (in infants with catecholamine-resistant hypotension) were not due to adrenal immaturity or impairment; their cortisol precursor concentrations were either low or unchanged and their response to cosyntropin was similar to infants without catecholamine-resistant hypotension. CONCLUSION: Infants with low cortisol concentrations following PDA ligation are likely to develop postoperative catecholamine-resistant hypotension. We speculate that decreased adrenal stimulation, rather than an impaired adrenal response to stimulation, may account for the decreased production
Electric dipole moments and the search for new physics
Static electric dipole moments of nondegenerate systems probe mass scales for
physics beyond the Standard Model well beyond those reached directly at high
energy colliders. Discrimination between different physics models, however,
requires complementary searches in atomic-molecular-and-optical, nuclear and
particle physics. In this report, we discuss the current status and prospects
in the near future for a compelling suite of such experiments, along with
developments needed in the encompassing theoretical framework.Comment: Contribution to Snowmass 2021; updated with community edits and
endorsement
Rare Isotope-Containing Diamond Color Centers for Fundamental Symmetry Tests
Detecting a non-zero electric dipole moment (EDM) in a particle would
unambiguously signify physics beyond the Standard Model. A potential pathway
towards this is the detection of a nuclear Schiff moment, the magnitude of
which is enhanced by the presence of nuclear octupole deformation. However, due
to the low production rate of isotopes featuring such "pear-shaped" nuclei,
capturing, detecting, and manipulating them efficiently is a crucial
prerequisite. Incorporating them into synthetic diamond optical crystals can
produce defects with defined, molecule-like structures and isolated electronic
states within the diamond band gap, increasing capture efficiency, enabling
repeated probing of even a single atom, and producing narrow optical
linewidths. In this study, we used density functional theory (DFT) to
investigate the formation, structure, and electronic properties of crystal
defects in diamond containing Pa, a rare isotope that is predicted to
have an exceptionally strong nuclear octupole deformation. In addition, we
identified and studied stable lanthanide-containing defects with similar
electronic structures as non-radioactive proxies to aid in experimental
methods. Our findings hold promise for the existence of such defects and can
contribute to the development of a quantum information processing-inspired
toolbox of techniques for studying rare isotopes
Progress towards the FRIB-EDM3-Frontend: A tool to provide radioactive molecules from isotope harvesting for fundamental symmetry studies
The under-construction FRIB-EDM3-instrument was designed to study polar radioactive molecules (such as RaF) in transparent cryogenic solids by laser spectroscopy. The instrument is divided into a frontend- and a backend section. The frontend accepts an aqueous sample from isotope harvesting and provides a mass-separated molecular ion beam in an ultra-high vacuum environment. In the backend, the ions are guided into alkali-metal vapor and the resulting neutrals are co-deposited in a solid argon matrix to perform laser spectroscopy. This work addresses the frontend of the instrument. The efficient ionization of harvested radioisotopes from aqueous samples is achieved with a spray-ionization method. Subsequently, the molecular ion beam is analyzed by mass-to-charge ratio by a quadrupole mass filter. To verify the feasibility of the approach, numerical simulations with the COMSOL and SIMION packages have been conducted. While the former was applied to study transport in ion funnels, the latter was used to investigate ion beam transmission through the lower pressure sections. Following promising simulation results, a first experimental setup is under construction