Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

As currently implemented, magnetic resonance imaging (MRI) relies on the protons of water molecules in tissue to provide the NMR signal. Protons are, however, notoriously difficult to image in some biological environments of interest, notably the lungs and lipid bilayer membranes such as those in the brain. Here we show that 129Xe gas can be used for high-resolution MRI when the nuclear-spin polarization of the atoms is increased by laser optical pumping and spin exchange. This process produces hyperpolarized 129Xe, in which the magnetization is enhanced by a factor of about 10(5). By introducing hyperpolarized 129Xe into mouse lungs we have obtained images of the lung gas space with a speed and a resolution better than those available from proton MRI or emission tomography. As xenon (a safe general anaesthetic) is rapidly and safely transferred from the lungs to blood and thence to other tissues, where it is concentrated in lipid and protein components, images of the circulatory system, the brain and other vital organs can also be obtained. Because the magnetic behaviour of 129Xe is very sensitive to its environment, and is different from that of 1H2O, MRI using hyperpolarized 129Xe should involve distinct and sensitive mechanisms for tissue contrast.

Biological magnetic resonance imaging using laser-polarized 129Xe

The realization of superfluidity in a dilute gas of fermionic atoms, analogous to superconductivity in metals, represents a long-standing goal of ultracold gas research. In such a fermionic superfluid, it should be possible to adjust the interaction strength and tune the system continuously between two limits: a Bardeen–Cooper–Schrieffer (BCS)-type superfluid (involving correlated atom pairs in momentum space) and a Bose–Einstein condensate (BEC), in which spatially local pairs of atoms are bound together. This crossover between BCS-type superfluidity and the BEC limit has long been of theoretical interest, motivated in part by the discovery of high-temperature superconductors. In atomic Fermi gas experiments superfluidity has not yet been demonstrated; however, long-lived molecules consisting of locally paired fermions have been reversibly created. Here we report the direct observation of a molecular Bose–Einstein condensate created solely by adjusting the interaction strength in an ultracold Fermi gas of atoms. This state of matter represents one extreme of the predicted BCS–BEC continuum.

Emergence of a molecular Bose-Einstein condensate from a Fermi gas

https://escholarship.org/content/qt16g3d6mk/qt16g3d6mk.pdf

Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials, and organisms.

NMR imaging methods are provided for determining the spatial petrophysical properties of materials. These methods employ the generation of separate Mo, T1 and T2 images from which various petrophysical characteristics may be obtained, such as free fluid index, porosity, pore sizes and distributions, capillary pressure, permeability, formation factor and clay content.

NMR imaging of materials

The theory of spin exchange between optically pumped alkali-Inetal atoms and noble-gas nuclei is presented. Spin exchange with heavy noble gases is dominated by interactions in long-lived van der Waals molecules. The main spin interactions are assumed to be the spin-rotation interactions yN S between the rotational angular momentum N of the alkali-metal — noble-gas pair and the electron spin S of the alkali-metal atom, and the contact hyperfine interaction aK S between the nuclear spin K of the noble-gas atom and the electron spin S. Arbitrary values for EC and for the nuclear spin I of the alkali-metal atom are assumed. Precise formal expressions for spin transfer coefficients are given along with convenient approximations based on a perturbation expansion in powers of (o.'/yX), a quantity which has been shown to be small by experiment.

/pdf/polarization-of-the-nuclear-spins-of-noble-gas-atoms-by-spin-23i0fqcmbp.pdf

Polarization of the nuclear spins of noble-gas atoms by spin exchange with optically pumped alkali-metal atoms

https://wvanwijngaarden.info.yorku.ca/files/Publications/Before1990/WvW1983.pdf

Wall relaxation of spin polarized 129Xe nuclei

This pedagogical paper introduces the basic ideas of optical pumping. Some of the various optical pumping mechanisms are discussed, and illustrated by diagrams showing the experimental apparatus. The density matrix formalism is introduced and used to quantitatively examine the effects of optical pumping. Next some of the various spin relaxation mechanisms such as collisions and spin exchange between electrons and nuclei, are discussed. A good knowledge of elementary quantum mechanics is needed to follow the article.

https://wvanwijngaarden.info.yorku.ca/files/Publications/Before1990/WvW-1987b.pdf

An optical pumping primer

Over one-quarter billion hourly values of temperature and relative humidity observed at 309 stations located across North America during 1948–2010 were studied. The water vapor pressure was determined and seasonal averages were computed. Data were first examined for inhomogeneities using a statistical test to determine whether the data were fit better to a straight line or a straight line plus an abrupt step, which may arise from changes in instruments and/or procedure. Trends were then found for data not having discontinuities. Statistically significant warming trends affecting the Midwestern United States, Canadian prairies, and the western Arctic are evident in winter and to a lesser extent in spring while statistically significant increases in water vapor pressure occur primarily in summer for some stations in the eastern half of the United States. The temperature (water vapor pressure) trends averaged over all stations were 0.30 (0.07), 0.24 (0.06), 0.13 (0.11), 0.11 (0.07) °C decade−1 (hPa d...

https://wvanwijngaarden.info.yorku.ca/files/Publications/2012/WvW-2012b.pdf

Surface Water Vapor Pressure and Temperature Trends in North America during 1948–2010

The isotope and hyperfine shifts for the Yb 1S0(6s2) → 3P1(6s6p) transition were determined with an acousto-optic modulator used to frequency shift part of a laser beam The frequency-shifted and -unshifted laser beams were superimposed and excited an atomic beam The laser was scanned across the transition while fluorescence produced by the radiative decay of the excited state was detected by a photomultiplier Each isotope generated two peaks in the spectrum separated by the acousto-optic shift, which permitted the frequency to be calibrated This relatively simple method yields results that agree well with the most accurate existing data, which were obtained by measurement of frequency shifts with a Fabry–Perot etalon whose length was stabilized with a helium–neon laser locked to an iodine line

/pdf/measurement-of-isotope-shifts-and-hyperfine-splittings-of-59rl3phglj.pdf

W. A. van Wijngaarden

Papers

Polarization of the nuclear spins of noble-gas atoms by spin exchange with optically pumped alkali-metal atoms

Wall relaxation of spin polarized 129Xe nuclei

An optical pumping primer

Surface Water Vapor Pressure and Temperature Trends in North America during 1948–2010

Measurement of isotope shifts and hyperfine splittings of ytterbium by means of acousto-optic modulation