| 1. |
- Andersson, Mats, et al.
(författare)
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Laser spectroscopy of gas in scattering media at scales ranging from kilometers to millimeters
- 2007
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Ingår i: Laser Physics. - 1054-660X. ; 17:7, s. 893-902
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Tidskriftsartikel (refereegranskat)abstract
- Free gases are characterized by their narrow line width, and they can conveniently be studied by laser spectroscopy. The present paper discusses the monitoring of such ambient pressure gases, which are dispersed in scattering media such as aerosol-laden atmospheres, solids, or liquids. Atmospheric work basically constitutes the well-known field of differential absorption lidar (DIAL), while the study of free gas in solids and liquids was initiated more recently under the name of GASMAS (GAs in Scattering Media Absorption Spectroscopy). We discuss the connections between the two techniques, which are extensively used in our labortory. Thus, we span the field from trace-gas mapping of gases in the lower atmosphere to gas studies in construction materials, food products, and the human body. We show that the basic ideas are very similar, while the spatial and temporal scales vary greatly.
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| 2. |
- Andersson, Mats, et al.
(författare)
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Spectroscopic studies of wood-drying processes
- 2006
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Ingår i: Optics Express. - 1094-4087. ; 14:8, s. 3641-3653
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Tidskriftsartikel (refereegranskat)abstract
- By the use of wavelength-modulation diode laser spectroscopy, water vapor and oxygen are detected in scattering media nonintrusively, at 980 nm and 760 nm, respectively. The technique demonstrated is based on the fact that free gases have extremely sharp absorption structures in comparison with the broad features of bulk material. Water vapor and oxygen measurements have been performed during the drying process of wood. The results suggest that the demonstrated technique can give information about the drying process of wood to complement that of commercially available moisture meters. In particular, the time when all the free water has evaporated from the wood can be readily identified by a strong falloff in the water vapor signal accompanied by the reaching of a high-level plateau in the molecular oxygen signal. Furthermore, the same point is identified in the differential optical absorption signal for liquid water, with a sharp increase by an order of magnitude in the ratio of the signal intensities at 980 nm and 760 nm.
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| 3. |
- Grönlund, Rasmus, et al.
(författare)
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Studies of free gas in scattering media at micro- and macroscopic scales
- 2006
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Ingår i: Proceedings of International Symposium on Biophotonics, Nanophotonics and Metamaterials. ; , s. 42-45
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Konferensbidrag (refereegranskat)abstract
- Free gases in scattering media and different techniques for such studies are discussed in the present paper. Connections between two techniques that constitute a major research area at our laboratory are presented. One of the techniques concerns measurements of free gas in scattering media, such as human tissue and food products, on a small scale, while the other one is a technique for trace-gas measurements in the lower atmosphere. We show that the basic ideas are very similar and that, by applying the knowledge obtained on one scale to the other, little differences exist. This study motivates us to perform a measurement linking the two techniques.
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| 4. |
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| 5. |
- Persson, Linda, et al.
(författare)
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Tunable diode laser spectroscopy for gas detection inside scattering media
- 2005
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Ingår i: 2005 Conference on Lasers and Electro-Optics Europe. - 0780389743 ; , s. 646-646
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Konferensbidrag (refereegranskat)abstract
- The present communication is mainly focused on molecular oxygen detection in porous organic matter, through a tunable diode laser spectroscopy. Initial measurements on wood were preformed in order to illustrate the influence of the density and anisotropy of the sample on the GASMAS-signal. Additional measurements were performed on horticultural produces, in which the concentration of the molecular oxygen gas is of crucial importance for the ripening process and the quality of the produces. The methodology presented is general and can be applied to a large number of problems concerning gas exchange in porous materials, which can be of interest in applications ranging from biological and medical to industrial and pharmaceutical
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| 6. |
- Sjöholm, Mikael, et al.
(författare)
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Analysis of gas dispersed in scattering media
- 2001
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Ingår i: Optics Letters. - 0146-9592. ; 26:1, s. 16-18
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring of free gas embedded in scattering media, such as wood, fruits, and synthetic materials, is demonstrated by use of diode laser spectroscopy combined with sensitive modulation techniques. Gas detection is made possible by the contrast of the narrow absorptive feature of the free-gas molecules with the slow wavelength dependence of the absorption and scattering cross sections in solids and liquids. An absorption sensitivity of 2.5 x 10(-4), corresponding to a 1.25-mm air column, is demonstrated by measurements of dispersed molecular oxygen. These techniques open up new possibilities for characterization and diagnostics, including internal gas pressure and gas-exchange assessment, in organic and synthetic materials. (C) 2001 Optical Society of America. OCIS codes: 300.6360, 290.7050, 290.5820, 170.3660, 020.3690, 160.4890.
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| 7. |
- Somesfalean, Gabriel, et al.
(författare)
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Concentration measurement of gas embedded in scattering media by employing absorption and time-resolved laser spectroscopy
- 2002
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Ingår i: Applied Optics. - 2155-3165. ; 41:18, s. 3538-3544
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Tidskriftsartikel (refereegranskat)abstract
- Diode-laser-based absorption spectroscopy for the evaluation of embedded gas concentrations in porous materials is demonstrated in measurements of molecular oxygen dispersed throughout scattering polystyrene foam, used here as a generic test material. The mean path length of light scattered in the material is determined with the temporal characteristics of the radiation transmitted through the sample. This combined with sensitive gas-absorption measurements employing wavelength-modulation spectroscopy yields an oxygen concentration in polystyrene foam of 20.4% corresponding to a foam porosity of 98%, which is consistent with manufacturing specifications. This feasibility study opens many possibilities for quantitative measurements by using the method of gas-in-scattering-media absorption spectroscopy. (C) 2002 Optical Society of America.
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