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Mode-specific vibrational excitation and energy redistribution after ultrafast intramolecular electron transfer (2000)

Hogiu, S. ; Werncke, W. ; Pfeiffer, M. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 113 (2000), S. 1587-1594

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Vibrational relaxation in the electronic ground state initiated by intramolecular back-electron transfer (b-ET) of betaine-30 (B-30) is studied by picosecond time-resolved anti-Stokes Raman spectroscopy. Measurements were carried out with B-30 dissolved in slowly as well as in rapidly relaxing solvents. We observed a risetime of the Raman band with the highest frequency near 1600 cm−1 which is close to the b-ET time τb-ET of B-30. For B-30 dissolved in propylene carbonate (τb-ET∼1 ps), the population of this mode exhibits a rise time of 1 ps whereas vibrational populations between 400 and 1400 cm−1 increase substantially slower. In contrast, in glycerol triacetin (τb-ET∼3.5 ps) and in ethanol (τb-ET∼6 ps) rise times of all modes are close to the respective b-ET times. Within the first few picoseconds, direct vibrational excitation through b-ET is favored for modes with the highest frequencies and high Franck–Condon factors. Later on, indirect channels of population due to vibrational energy redistribution (IVR) become effective. Thermal equilibrium populations of the Raman active modes are established within 10 to 15 ps after optical excitation. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.481946

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Imaging Corneal Cells Using Low Power Laser Beams (1998)

Pascu, M. L. ; Carstocea, B. ; Popescu, G. ; [et al.]

Springer

Lasers in medical science 13 (1998), S. 148-154

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ISSN: 1435-604X

Keywords: Keywords: Cell dimensions; Corneal endothelium; Corneal epithelium; Laser imaging

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Physics , Technology

Notes: Abstract. A simple method of characterising epithelial and endothelial corneal cells using laser light is presented. A continuous wave helium-neon laser emitting at a wavelength of 632.8 nm and a continuous wave argon laser emitting at 488 and 514.5 nm were used. The cell images obtained were used to calculate the dimensions of the endothelial corneal cells, a typical value being 34–36 μm diameter, with overall measurement errors of ±21%. An optical mechanism for obtaining images is proposed and comments are made about the possibility of using this method as a diagnostic tool in corneal disease.