Fluorescence lasers

Zare R N and Dagdigian P J 1974 Tunable laser fluorescence method for product state analysis Science 185 739-46... 

Figure B2.3.9. Schematic diagram of an apparatus for laser fluorescence detection of reaction products. The dye laser is syncln-onized to fire a short delay after the excimer laser pulse, which is used to generate one of the reagents photolytically.

The fluorescence signal is linearly proportional to the fraction/of molecules excited. The absorption rate and the stimulated emission rate 1 2 are proportional to the laser power. In the limit of low laser power,/is proportional to the laser power, while this is no longer true at high powers 1 2 <42 j). Care must thus be taken in a laser fluorescence experiment to be sure that one is operating in the linear regime, or that proper account of saturation effects is taken, since transitions with different strengdis reach saturation at different laser powers. 

Figure B2.3.15. Laser fluorescence excitation spectrum of the A S -X ff (1,3) band for the OH product, in the V = 3 vibrational level, from tire H + NO2 reaction [44]- (By pemrission from AIP.)...

This book presents a detailed exposition of angular momentum theory in quantum mechanics, with numerous applications and problems in chemical physics. Of particular relevance to the present section is an elegant and clear discussion of molecular wavefiinctions and the detennination of populations and moments of the rotational state distributions from polarized laser fluorescence excitation experiments. 

Piezoelectric buzzer LED laser Fluorescent tube EL display... 

Riboflavin can be assayed by chemical, en2ymatic, and microbiological methods. The most commonly used chemical method is fluorometry, which involves the measurement of intense yeUow-green fluorescence with a maximum at 565 nm in neutral aqueous solutions. The fluorometric deterrninations of flavins can be carried out by measuring the intensity of either the natural fluorescence of flavins or the fluorescence of lumiflavin formed by the irradiation of flavin in alkaline solution (68). The later development of a laser—fluorescence technique has extended the limits of detection for riboflavin by two orders of magnitude (69,70). 

Fig. 36. Laser fluorescence excitation spectrum of 7-azoindole dimer (6.1).

A number of investigations of the copper-group oxides and dioxygen complexes have been reported. The electronic spectra of CuO, AgO, and AuO were recorded in rare-gas matrices (9), and it was found that the three oxides could be formed effectively by cocondensation of the metal atoms with a dilute, oxygen matrix, followed by near-ultraviolet excitation. The effective wavelengths for CuO or AgO formation were X > 300 nm and for AuO was X > 200 nm. In addition, the laser fluorescence spectrum of CuO in solid Ar has been recorded (97). 

Liu, J., Hsieh, Y.-Z., Wiesler, D., Novotny, M., Design of 3-(4-carboxybenzoyl)-2-quinolinecarboxaldehyde as a reagent for ultrasensitive determination of primary amines by capillary electrophoresis using laser fluorescence detection, Anal. Chem., 63, 408, 1991. 

Eukaryotic cells utilize an efficient transport system that delivers macromolecules fast and secure to their destination. In the case of the small GTP binding proteins of the Ras family the modified C-terminus seems to be sufficient for addressing the polypeptide to its target membrane (in the case of Ras itself the plasma membrane). Lipopeptides with the C-terminal structure of N-Ras (either a pen-tamer with a C-terminal carboxymethylation and farnesylation or a heptapeptide with a palmitoyl thioester in addition) and a N-terminal 7-nitrobenz-2-oxa-l,3-diazolyl (NBD) fluorophore were microin-jected into NIH3T3 fibroblast cells and the distribution of the fluorophore was monitored by confocal laser fluorescence microscopy. Enrichment of the protein in the plasma membrane was efficient only for peptides with two hydrophobic modification sites, while the farnesylated but not palmitoylated peptide was distributed in the cytosol.1121... 

Soper SA, Mattingly QL (1994) Steady-state and picosecond laser fluorescence studies of nonradiative pathways in tricarbocyanine dyes implications to the design of near-IR fluor-ochromes with high fluorescence efficiencies. J Am Chem Soc 116 3744—3752... 

Using laser fluorescence measurements on fuel-rich H2/02/N2 flames seeded with H2S, Muller et al. [43] determined the concentrations of SH, S2, SO, S02, and OH in the post-flame gases. From their results and an evaluation of rate constants, they postulated that the flame chemistry of sulfur under rich conditions could be described by the eight fast bimolecular reactions and the two three-body recombination reactions given in Table 8.4. 

Crosley, D. R., Laser Fluorescence Detection of Atmospheric Hydroxyl Radicals, in Problems and Progress in Atmospheric Chemistry (J. R. Barker, Ed.), Advanced Series in Physical Chemistry (C.-Y. Ng, Ed.), Vol. 3, World Scientific, Singapore, 1995b. 

Fig. 7. Potential mechanisms of actinide (represented by Cm(ni)) interaction with colloids as interpreted from laser fluorescence spectroscopy (TRLFS) experiments. Spectra are taken from Stumpf et al. (2001o, b) and Chung et al. (1998).

Chung, K. H., Klenze, R., Park, K. K., Paviet-Hartmann, P. Kim, J. I. 1998. A study of the surface sorption process of Cm(III) on silica by time-resolved laser fluorescence spectroscopy (I). Radiochimica Acta, 82, 215-219. 

Stumpf, Th., Bauer, A., Coppin, F. Kim, J. I. 200]a. Time-resolved laser fluorescence spectroscopy study of the sorption of Cm(III) onto smectite and kaolinite. Environmental Science and Technology, 35, 3691 -3694. 

Stumpf, Th. Fanghanel, Th. 2002. A time-resolved laser fluorescence spectroscopy (TRLFS) study of the interaction of trivalent actinides (Cm(III)) with calcite. Journal of Colloid and Interface Science, 249, 119-122. 

TCLP TDB TDF THC TBP TEM TLM TM-AFM TOC TRLFS TRU TSP TST TVS Toxicity characteristics leaching procedure Thermodynamic database Tyre-derived fuel Total hydrocarbon Tri-n-butyl phosphate Transmission electron microscopy Triple layer model Tapping mode atomic force microscopy Total organic carbon Time-resolved laser fluorescence spectroscopy Transuranic Total suspended particles Transition state theory Transportable vitrification system... 

HO measurement techniques in the troposphere are the principal focus of this chapter. All reported fluorescence measurements of HO in the troposphere have used lasers. Most of the early tropospheric laser fluorescence work used a frequency-doubled Nd.YAG laser to pump a Rh6G dye laser that was also frequency-doubled and tuned to either the Px( 1) line or the QiU + R23 line group of the A2 v = l X2 v" = 0 band of HO at 282 nm. Fluorescence is detected from the A2X v = 0 —> X2 v" = 0 band at 309 nm. Although the three groups to report tropospheric HO data by this method have often used similar lasers and have usually pumped the same transitions, the air sampling configurations have been quite different. 

Reaction (44a) is analogous to the 02-reaction of the vinyl radical leading to HCO and HCHO as reported by Gutman and co-workers [118,119], Evidence for the occurrence of reaction (44b) was based on the observation of a-dicarbonyl products in the absence of NO. Schmidt et al. [120] have recently observed the regeneration of HO from the HO + C2H2 reaction by means of a laser fluorescence technique. The branching ratios for the two unimolecular dissociation channels typified by reactions (44a) and (44b) were estimated to be 0.4 0.1 and 0.7 + 0.3 (acetylene), 0.12 + 0.02 and 0.53 0.03 (propyne), and 0.12 + 0.87 0.07 (2-butyne), respectively. In any case, the formation of acidic products as well as the a-dicarbonyl products from these reactions is of potential importance in the atmosphere. 

Earlier methods for the determination of uranium in soils employed spectrophotometry of the chromophore produced with arsenic(III) at 655 nm [237 ] and neutron activation analysis [238]. More recently, laser fluorescence [239] and in situ laser ablation-inductively coupled plasma atomic emission spectrometry [240] have been employed to determine uranium in soil. D Silva et al. [241] compared the use of hydrogen chloride gas for the remote dissolution of uranium in soil with microwave digestion. 

Chemical state characterization IR and Raman Spectroscopy, FT-IR, EELS, XPS, SIMS, ESDIAD, ellipsometry, and laser fluorescence... 

While the independent techniques do not give the exact same concentration measurements they are similar enough to be highly encouraging. The laser fluorescence technique is many orders of magnitude more sensitive than the best absorption measurements and it is a point sampling technique. 

Eckbreth, A.C. Bonczyk, P.A. and Shirley, J.A. "Experimental Investigations of Saturated Laser Fluorescence and CARS Spectroscopic Techniques for Practical Combustion Diagnostics", Technical Report R78-952665-18 United Technologies Research Center, East Hartford. Conn., p. 58. EPA-600/7-78-104, June... 

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