LASER INDUCED SPECTROSCOPY

The steady-state luminescence of water-organic complexes is strong and conceals the weaker characteristic luminescence of uranium containing centers, which can be detected by the difference in decay times only. The reason is that the decay time of water-organic complexes is characterized by two time intervals less then 30 ns and more then 10 ms. Since the uranium centers have decay times in the microseconds range, it is possible to detect them by time-resolved spectroscopy. In the time-delayed laser-induced spectroscopy, the luminescence spectra are recorded at a fixed moment after a laser pulse. These spectra maybe different from the integrated steady-state ones since after a certain time short luminescence will be practically absent. 

The Applications of Laser-induced Time-resolved Spectroscopic Techniques chapter starts with a short description of laser-induced spectroscopies, which may be used in combination with laser-induced luminescence, namely Breakdown, Raman and Second Harmonic Generation. The chapter contains several examples of the application of laser-based spectroscopies in remote sensing and radiometric sorting of minerals. The proljlem of minerals as geomaterials for radioactive waste storage is also considered. 

To assess this qnestion in the present case, we characterized in detail the laser-induced spectroscopy of PM567 dye both in liquid and solid solutions with and without POSS nanoparticles, pumped rmder the same experimental conditions. The pump pulses were now incident on the samples at a 30° angle and the laser excitation energy was gradually increased from 0.9 to 6 mJ/pulse. The emission from the front-face of the sample was collected with an optical fiber, sent to an spectrometer with 0.1 nm resolution and detected with a CCD camera. 

Laser-Induced Spectroscopy of a Messenger-Tagged Ionic Cluster... 

The Chapter 6 describes of laser-induced spectroscopies, which may be used in combination with laser-induced luminescence, namely, Breakdown, Raman. 

Geipel G. Some aspects of actinide speciation by laser-induced spectroscopy. Coord Chem Rev. 2006 250 844-854. 

New to the fourth edition are the topics of laser detection and ranging (LIDAR), cavity ring-down spectroscopy, femtosecond lasers and femtosecond spectroscopy, and the use of laser-induced fluorescence excitation for stmctural investigations of much larger molecules than had been possible previously. This latter technique takes advantage of two experimental quantum leaps the development of very high resolution lasers in the visible and ultraviolet regions and of the supersonic molecular beam. 

COLORANTS FORFOOD, DRUGS, COSTffiTICS AND TffiDICAL DEVICES] (Vol 6) -analysis using laser-induced fluorescence [SPECTROSCOPY, OPTICAL] (Vol 22) -drinkingwater [ANALYTICALTffiTHODS - PTYPHENATED INSTRUTffiNTS] (Vol 2)... 

The hydrolysis of the uranyl(VI) ion, UO " 2> has been studied extensively and begins at about pH 3. In solutions containing less than lO " M uranium, the first hydrolysis product is the monomeric U02(OH)", as confirmed using time-resolved laser induced fluorescence spectroscopy. At higher uranium concentrations, it is accepted that polymeric U(VI) species are predominant in solution, and the first hydrolysis product is then the dimer, (U02)2(0H) " 2 (154,170). Further hydrolysis products include the trimeric uranyl hydroxide complexes (U02)3(0H) " 4 and (1102)3(OH)(154). At higher pH, hydrous uranyl hydroxide precipitate is the stable species (171). In studying the sol-gel U02-ceramic fuel process, O nmr was used to observe the formation of a trimeric hydrolysis product, ((U02)3( -l3-0)(p.2-0H)3) which then condenses into polymeric layers of a gel based on the... 

Different analytical techniques are used for detection of the elemental composition of the solid samples. The simplest is direct detection of emission from the plasma of the ablated material formed above a sample surface. This technique is generally referred to as LIBS or LIPS (laser induced breakdown/plasma spectroscopy). Strong continuous background radiation from the hot plasma plume does not enable detection of atomic and ionic lines of specific elements during the first few hundred nanoseconds of plasma evolution. One can achieve a reasonable signal-to-noise ra-... 

Kim, J. 1., Stumpe, R., and Klenze, R. Laser-induced Photoacoustic Spectroscopy for the Speciation ofTransuranic Elements in Natural Aquatic Systems. 157,129-180 (1990). 

More recently, Scaiano et al. (1991) observed (Zs)->(Z)-isomerization of 1,3-di-phenyltriazene also in methanol by using flash photolysis, transient spectroscopy, and laser-induced optoacoustic calorimetry (LIOAC). The interpretation of the data is consistent with the mechanism shown in Scheme 13-4, involving two solvent molecules. 

Daily, J.W., Laser induced fluorescence spectroscopy in flames. Prog. Energy Combust. Sci., 23,133,1997. 

Schoemaecker Moreau, C. et al.. Two-color laser-induced incandescence and cavity ring-down spectroscopy for sensitive and quantitative imaging of soot and PAHs in flames, Appl. Phys. B, 78,485,2004. 

Dreyer, C.B., Spuler, S.M., and Linne, M., Calibration of laser induced fluorescence of the OH radical by cavity ringdown spectroscopy in premixed atmospheric pressure flames. Combust. Sci. Tech., 171,163, 2001. 

In addition, a 532 (visible) or 355 (UV region) nm laser-induced photoisomerization of allylic alcohols to aldehydes catalyzed by [Fe3(CO)i2] or [Fe(CO)4PPh3] was developed by Fan [176]. In this reaction, key intermediates such as the 7i-allyl hydride species [FeH(CO)3(q -C3H3ROH)] (R = H, Me) were detected by pulsed laser FTIR absorption spectroscopy. These results strongly support the 7i-allyl mechanism of photoisomerization of allyl alcohols. 

Yamakata, A., Uchida, T., Kubota, J. and Osawa, M. (2006) Laser-induced potential jump at the electrochemical interface probed by picosecond time-resolved surface-enhanced infrared absorption spectroscopy./. Phys. Chem. B, 110, 6423-6427. 

In order to relate material properties with plasma properties, several plasma diagnostic techniques are used. The main techniques for the characterization of silane-hydrogen deposition plasmas are optical spectroscopy, electrostatic probes, mass spectrometry, and ellipsometry [117, 286]. Optical emission spectroscopy (OES) is a noninvasive technique and has been developed for identification of Si, SiH, Si+, and species in the plasma. Active spectroscopy, such as laser induced fluorescence (LIF), also allows for the detection of radicals in the plasma. Mass spectrometry enables the study of ion and radical chemistry in the discharge, either ex situ or in situ. The Langmuir probe technique is simple and very suitable for measuring plasma characteristics in nonreactive plasmas. In case of silane plasma it can be used, but it is difficult. Ellipsometry is used to follow the deposition process in situ. 

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