Laser excitation fluorescence

Itoh, M. Adachi, T. Transient absorption and two-step laser excitation fluorescence studies of the excited-state proton transfer and relaxation in the methanol solution of 7-hydroxyflavone. J. Am. Chem. Soc. 1984, 106, 4320 -324. 

Itoh, M. Hasegawa, K. Fujiwara, Y. Two-step laser excitation fluorescence study of the ground- and excited-state proton transfer in alcohol solutions of 7-hydroxyisoflavone. J. Am. Chem. Soc. 1986, 108, 5853-5857. 

Personov RI, AT shits LA, Bykovskaja LA (1972) The effect of fine structure appearance in laser-excited fluorescence spectra of organic compounds in solid solutions. Opt Commun 6 169-173... 

Since the CO2 laser line corresponds to a transition between two excited vibrational levels, only those CO2 molecules can be excited by absorption of the laser line which are in the (OOl)-level, populated at 300 ° K with about 1 % of the total number of molecules. In spite of this low population density, the laser-excited fluorescence method is easily achieved because of the large exciting laser intensity. 

D. E. Burton and M. J. Sepaniak, Analysis of B6 vitamers by micellar electrokinetic capillary chromatography with laser-excited fluorescence detection, J. Chromatogr., 24 347 (1986). 

Determination of Flame and Plasma Temperatures and Density Profiles by Means of Laser-Excited Fluorescence... 

Figure 15. Comparison of CH flame emission and laser-excited fluorescence spectrum in an oxy-acetylene slot torch...

Auzinsh, M.P. (1987). Polarization of laser-excited fluorescence of diatomic molecules and the magnetic-field effect, Opt. Spectrosc. 

The use of Raman spectroscopy in the lumber/paper industry has been found to be feasible using the FT-Raman technique. Earlier results using a visible laser were limited due to the laser-induced fluorescence created with most wood samples. Measures to circumvent fluorescence were time-consuming, and the signal-to-noise (S/N) ratio was poor. With most wood samples, using a near-IR laser excitation, fluorescence essentially was eliminated. 

Methane-oxygen mixtures have also been studied by laser-excited fluorescence, as have NO-CH4 mixtures. Yardley and Moore [274] find for the V-V exchange probability from Os to CH4 a value of 2.0 x 10-2 per collision at 297°K. 

The laser-excited fluorescence from dibenzofuran in a biphenyl host at 4.2 K and three different sites in the lattice have been identified. The two-photon excitation spectrum of single crystals of carbazole at 4.2 K has been analysed in detail. Very extensive vibrationally unrelaxed fluorescence is observed following dye-laser excitation of single vibronic levels of naphthazanine and the rates and pathways of relaxation are examined by picosecond emission spectroscopy. The photophysics of rubrene peroxide have been measured for the first time by Bayrakceken. Picosecond fluorescence has been used to study the spectra and kinetics for Sj— So and Si transitions for... 

Observation of Si2 laser-excited fluorescence in the vapour deposition of Si from SiH4... 

The methods range from simple, inexpensive absorption spectroscopy to sophisticated tunable-laser-excited fluorescence and ionization spectroscopies. AAS has been used routinely for uranium and thorium determinations (see for example Pollard et al., 1986). The technique is based on the measurement of absorption of light by the sample. The incident light is normally the emission spectrum of the element of interest, generated in a hollow-cathode lamp. For isotopes with a shorter half life than and Th, this requires construction of a hollow-cathode lamp with significant quantities of radioactive material. Measurement of technetium has been demonstrated in this way by Pollard et al. (1986). Lawrenz and Niemax (1989) have demonstrated that tunable lasers can be used to replace hollow-cathode lamps. This avoids the safety problems involved in the construction and use of active hollow-cathode lamps. Tunable semiconductor lasers were used as these are low-cost devices. They do not, however, provide complete coverage of the spectral range useful for AAS and the method has, so far, only been demonstrated for a few elements, none of which were radionuclides. 

Shirk, J. S., and Bass, A. M., Laser-excited fluorescence of matrix-isolated molecules. Anal. Chem. 41, 103A (1969). 

Fifjure 7. Circular polarization rate aoatod br- an alignmoni to orientation conversion in laser excited fluorescence of the Tc2 molecule due to magnetic intramolecular interactions and magnetic predissociation. 

A number of less commonly used analytical techniques are available for determining PAHs. These include synchronous luminescence spectroscopy (SLS), resonant (R)/nonresonant (NR)-synchronous scan luminescence (SSL) spectrometry, room temperature phosphorescence (RTP), ultraviolet-resonance Raman spectroscopy (UV-RRS), x-ray excited optical luminescence spectroscopy (XEOL), laser-induced molecular fluorescence (LIMP), supersonic jet/laser induced fluorescence (SSJ/LIF), low- temperature fluorescence spectroscopy (LTFS), high-resolution low-temperature spectrofluorometry, low-temperature molecular luminescence spectrometry (LT-MLS), and supersonic jet spectroscopy/capillary supercritical fluid chromatography (SJS/SFC) Asher 1984 Garrigues and Ewald 1987 Goates et al. 1989 Jones et al. 1988 Lai et al. 1990 Lamotte et al. 1985 Lin et al. 1991 Popl et al. 1975 Richardson and Ando 1977 Saber et al. 1991 Vo-Dinh et al. 1984 Vo- Dinh and Abbott 1984 Vo-Dinh 1981 Woo et al. 1980). More recent methods for the determination of PAHs in environmental samples include GC-MS with stable isotope dilution calibration (Bushby et al. 1993), capillary electrophoresis with UV-laser excited fluorescence detection (Nie et al. 1993), and laser desorption laser photoionization time-of-flight mass spectrometry of direct determination of PAH in solid waste matrices (Dale et al. 1993). 

The spectroscopic investigations do not provide sufficient information to elucidate the excited state ordering for all the uranate centres. The ordering appears to be A2(Tig) < E (T ig) in the (UO5 Vp) centre. In a recent paper, Runciman and Wong reported on the absorption and laser excited fluorescence of hexavalent uranium in LiF l. As in the NaF—U system, the relative intensities of various emission line-series in LiF—U depend strongly on the excitation wavelength. The results from temperature dependent decay measurements show that the LiF—U system in this respect also resembles the NaF—U system. 

Experimental data pertinent to the vibrational predisaociation mechanism of two types of van der Waals complex are presented and discussed. First, variations in the infrared band shape for excitation of the ethylene out-of-plane wag, Vy, in the series of molecules CjH tHF, C2H Ne are discussed in terms of structure and relaxation mechanisms. Second, rotationally resolved laser excited fluorescence spectra for NeBr2 and NeCl2 are presented. There is a strong dependence of decay rate on molecular structure.. Relaxation... 

Figure 3. A rotatlonally resolved laser excited fluorescence...

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