Search results for "Pumping"
showing 10 items of 198 documents
Compression of Polarized 3He
1991
This article gives a status report on the polarized 3He target development work at Mainz. It is based on the optical pumping of the 3S1 state of 3He with subsequent metastability spin exchange to the ground state atoms. This pumping scheme is very efficient at 3He pressures of about 1 Torr; for high density targets, however, a mechanical compression of the polarized gas is needed in a second step. First results with a Toepler compression pump look promising and will be discussed in the following.
Non-Linear Optical Properties of Hybridized Surface Plasmon Polaritonic Crystals: Observation of Optical Bistability
2007
Summary form only given. The use of surface plasmons (SP) is recognized as being central to the development of nanoscale assemblies of photonic and opto-electronic devices. This is motivated by the spatially confined nature of these electromagnetic waves as well as their resonant behavior. Amongst plasmonic supporting structures, surface plasmonic crystals (SPCs) draw particular interest because of their tailored optical properties. A geometry common to SPCs consists in a periodic arrangement of holes or slits in a metal film. Their complex optical response is then governed by coherent interactions between Bloch modes at the film's interfaces and modes supported by the holes or slits. These…
Mg isotopes and the disappearance of magic N=20 Laser and β-NMR studies
2007
Collinear laser spectroscopy and β-NMR spectroscopy with optical pumping were applied at ISOLDE/CERN to measure for the first time the magnetic moments of neutron-rich 27Mg, 29Mg, 31Mg and 33Mg, along with the spins of the two latter. The magnetic moment of 27Mg was derived from its hyperfine structure detected in UV fluorescent light, whereas the nuclear magnetic resonance observed in β-decay asymmetry from a polarised ensemble of nuclei gave the magnetic moment of 29Mg. For 31Mg and 33Mg, the hyperfine structure and nuclear magnetic resonance gave the spin and the magnetic moment. The preliminary results for 27Mg and 29Mg are consistent with a large neutron shell gap at N=20, whereas data…
Novel spectra in the supercontinuum generation with applications in the biodiversity conservation
2014
This paper presents some spectra of the supercontinuum generation obtained with microstructured fibers and tapered fiber devices excited with quasi-continuous pumps. These spectra are part of a group (collection) of multiple configurations that were studied and evaluated by our working group, and that could be very useful in LIDAR as well as bio-imaging applications. This work is limited to present some spectra that could be useful in applications of biodiversity conservation. The prototypes for specific applications will be evaluated in future research.
Laser spectroscopy of niobium fission fragments: first use of optical pumping in an ion beam cooler buncher.
2009
A new method of optical pumping in an ion beam cooler buncher has been developed to selectively enhance ionic metastable state populations. The technique permits the study of elements previously inaccessible to laser spectroscopy and has been applied here to the study of Nb. Model independent mean-square charge radii and nuclear moments have been studied for $^{90,90\text{ }\mathrm{m},91,91\text{ }\mathrm{m},92,93,99,101,103}\mathrm{Nb}$ to cover the region of the $N=50$ shell closure and $N\ensuremath{\approx}60$ sudden onset of deformation. The increase in mean-square charge radius is observed to be less than that for Y, with a substantial degree of $\ensuremath{\beta}$ softness observed …
Excited-state absorption in erbium-doped silica fiber with simultaneous excitation at 977 and 1531 nm
2009
We report a study of the excited-state absorption (ESA) in erbium-doped silica fiber (EDF) pumped at 977 nm, when the fiber is simultaneously excited by signal radiation at 1531 nm. We show, both experimentally and theoretically, that ESA efficiency at 977 nm gets strongly enhanced only in the presence of signal power. Experimentally, this conclusion is supported through the detection of upconversion emission, a “fingerprint” of the ESA process, and through the measurements of the EDF nonlinear transmission coefficient for the pump wavelength, which is sensitive to the ESA value. It is shown that the experimental data are precisely modeled with an advanced five-level Er3+ model developed fo…
Hyperfine shifts for cesium in Argon at high density
1974
An optical pumping experiment was performed to obtain precise hfs shifts for Cs in Argon. The shifts measured include a term quadratic in the densityρ and a large temperature coefficient. The coefficients of the expansionδv/v0=a ρ+bρ2 area(80 °C)=−29.8(6)x10−9(Torr−1(0°C))b(80 °C)=+11(2)x10−14(Torr−2(0 °C)).
Very high sensitivity in collinear laser spectroscopy: resonance detection by particle counting techniques
1992
Abstract Fast-beam collinear laser spectroscopy with resonance detection by counting of fluorescence photons provides a versatile tool for precise determinations of nuclear ground-state properties. The intrinsic high sensitivity of this method can be further increased by almost three orders of magnitude if measuring schemes based on ion or atom counting are introduced. The optical pumping from one atomic state to another at an appreciably different excitation energy is detected via state-selective collisional charge exchange processes and charge-state separated atom or ion counting. Applications of these techniques on alkaline earth, noble gas, mercury and thallium beams is examined.
Quadrupole moments of odd-A 53−63Mn: Onset of collectivity towards N=40
2016
Physics letters / B 760, 387 - 392 (2016). doi:10.1016/j.physletb.2016.07.016
MRI of the lungs using hyperpolarized noble gases
2002
The nuclear spin polarization of the noble gas isotopes (3)He and (129)Xe can be increased using optical pumping methods by four to five orders of magnitude. This extraordinary gain in polarization translates directly into a gain in signal strength for MRI. The new technology of hyperpolarized (HP) gas MRI holds enormous potential for enhancing sensitivity and contrast in pulmonary imaging. This review outlines the physics underlying the optical pumping process, imaging strategies coping with the nonequilibrium polarization, and effects of the alveolar microstructure on relaxation and diffusion of the noble gases. It presents recent progress in HP gas MRI and applications ranging from MR mi…