Ethanol laser spectroscopy

S. E. Braslavsky, R. M. Ellul, R. G. Weiss, H.Al-Ekabi, K. Schaffner. Photoprocesses in Biliverdin Dimethyl Ester in Ethanol Studied by Laser-Induced Optoacoustic Spectroscopy (.LIOAS). Tetrahedron 1983, 39, 1909-1913. 

Site-selection spectroscopy Maximum selectivity in frozen solutions or vapor-deposited matrices is achieved by using exciting light whose bandwidth (0.01-0.1 cm-1) is less than that of the inhomogeneously broadened absorption band. Lasers are optimal in this respect. The spectral bandwidths can then be minimized by selective excitation only of those fluorophores that are located in very similar matrix sites. The temperature should be very low (5 K or less). The techniques based on this principle are called in the literature site-selection spectroscopy, fluorescence line narrowing or energy-selection spectroscopy. The solvent (3-methylpentane, ethanol-methanol mixtures, EPA (mixture of ethanol, isopentane and diethyl ether)) should form a clear glass in order to avoid distortion of the spectrum by scatter from cracks. 

Photoprocesses in biliverdin dimethyl ester in ethanol have been studied by laser-induced optoacoustic spectroscopy." The picosecond kinetics of excited-state relaxation of this ester have also been reported." " Isophorcarubin is a conformationally restricted and highly fluorescent bilirubin." " The phototherapy for neonatal jaundice has stimulated investigations of configurational isomers of bilirubin" and of stereospecific and regioselective photoisomerization of bilirubin." ... 

Braslavsky, S.E., Ellul, R.M., Weiss, R.G., Al-Ekabi, H., and Schaffner, K. (1983) Pytochrome model 7 photoprocessesin biliverdin dimethyl ester in ethanol studied by laser-induced optoacoustic spectroscopy (LIOAS), Tetrahedron, 39, 1909-1913. 

Besides fluorescence spectroscopy, time-resolved spectroscopy can rely on the measurement of excited (singlet or triplet) state absorption. Similarly to ground-state absorption, the spectral and absorbance properties may be altered by CyD complexation and yield information about the behavior of the complex in the excited state in addition, the time dependence (formation and decay) of the excited state absorption yields information about the kinetics and dynamics of the system. This is illustrated by the behavior of the lowest triplet state of naphthalene as measured by nanosecond spectroscopy using a Q-switched Nd YAG laser at 266 nm for excitation [21]. The triplet-triplet absorption spectra were measured in neat solvents (water and ethanol) and in the presence of a- and -CyD (Fig. 10.3.3). The spectra in ethanol and H2O had the same absorption maximum, but the transition was considerably weaker and broadened in H2O. Both CyDs induced a red shift, and a-CyD additionally narrowed the main band considerably. Fig. 10.3.4 shows the effect of a-CD concentration on the time evolution of the triplet-triplet absorption at 416 nm in the microsecond range. Triplet decay was caused by O2 quenching a detailed kinetic analysis of the time dependence yielded two main components which could be assigned to the free guest and the 1 2 complex, in full... 

Rhodamine B H3C. A common fluoix hore and laser dye, used in A bs 460-600 nm — 0.65 in fluorescence correlation spectroscopy and basic ethanol, 0.49 in ethanol. is ELISA. Often used as a tracer dye to tenqrecature dependent (119, 20]. determine the rate and direction of flow and transport. A concentrated solution in glycerol is used as a quantum counter out to 600 nm. 

For symmetric carbocyanines the experimental and theoretical data of the ground-state potential energy surface are in agreement. In laser-induced optoacoustic spectroscopy studies, Braslavsky and her group found that the molecular volume change due to photoisomerization of T2 in ethanol-water is 52 ml mok and that of 02 (iodide) is zero. A combination with semiempirical calculations indicates mainly rearrangement of solvent molecules. ... 

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