Gas in Scattering Media Absorption Spectroscopy - GASMAS

An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied. Transport of gas in porous media can readily be studied by first immersing the material in, e. g., pure nitrogen, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen. Also other dynamic processes such as drying of materials can be studied. The techniques have also been extended to remote-sensing applications (LIDAR-GASMAS)

Atomic Spectroscopy by Resonance Scattering

Resonance scattering techniques are very useful for high-resolution atomic spectroscopy. The applicability of these techniques has been much extended, particularly through the rapid development of tunable-laser technology. The use of a narrowband tunable laser, acting on a collimated atomic beam, gives a direct method enabling, for example, hyperfine structure and isotope shift studies. The intensity of lasers allows stepwise excitations to be performed, and with the two-photon absorption technique, Doppler-free measurements on thermal gases are also possible. By using pulsed lasers, time-resolved measurements yielding radiative life-times and structural information can be performed. The basic resonance scattering methods can be combined with radiofrequency and coherence techniques to yield a resolution, limited only by the uncertainty relation. Optical double resonance and level-crossing techniques, not requiring a narrow-band light source, have been extensively used. Several examples of the application of resonance scattering methods are given

The predominant cultivable dental plaque flora of beagle dogs with gingivitis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66319/1/j.1600-0765.1980.tb00266.x.pd

Disordered, strongly scattering porous materials as miniature multipass gas cells

Spectroscopic gas sensing is both a commercial success and a rapidly advancing scientific field. Throughout the years, massive efforts have been directed towards improving detection limits by achieving long interaction pathlengths. Prominent examples include the use of conventional multipass gas cells, sophisticated high-finesse cavities, gas-filled holey fibers, integrating spheres, and diffusive reflectors. Despite this rich flora of approaches, there is a continuous struggle to reduce size, gas volume, cost and alignment complexity. Here, we show that extreme light scattering in porous materials can be used to realise miniature gas cells. Near-infrared transmission through a 7 mm zirconia (ZrO2) sample with a 49% porosity and subwavelength pore structure (on the order of 100 nm) gives rise to an effective gas interaction pathlength above 5 meters, an enhancement corresponding to 750 passes through a conventional multipass cell. This essentially different approach to pathlength enhancement opens a new route to compact, alignment-free and low-cost optical sensor systems

Edson, Gary. Shamanism: A Cross-Cultural Study of Beliefs and Practices

E DSON, GARY. Shamanism: A Cross-Cultural Study of Beliefs and Practices. Jefferson, North Carolina, and London: McFarland & Company, 2008. Pp 287.ISBN: 978-0-7864-3409-1

Real-World Applications of Laser Spectroscopy

Laser spectroscopic techniques are powerful tools for monitoring real-world phenomena. A wide variety of methods for establishing spectroscopic contact with a species exist: Absorption, emission, fluorescence, Raman scattering, acousto-optic, and opto-galvanic phenomena. Extreme sensitivity and specificity characterize the methods, which can be used for in situ monitoring and, in some cases, for remote sensing. Combustion diagnostics and atmospheric pollution monitoring are examples of gas-phase applications, while vegetation studies and early cancer detection illustrate interactions with solids