Normalized laser pulse, fluorescence

Figure 2. Normalized laser pulse and fluorescence signal from the directly excited upper level vs. time. The laser is tuned to the Q,(4) line (308.42 nm) and fluorescence is observed from the P,(5) line (310.21 nm). The laser-pulse energy and peak...

Figure 1. Fluorescence spectra (uncorrected for the spectral response) of ZnTPP in EPA at room temperature taken by the 540 nm excitation of a nitrogen pumped dye laser, (a)normal fluorescence spectra, (b)delayed fluorescence spectra taken at 1 s after the laser pulse excitation.

Fig. 3. Upper trace Background corrected and normalized fluorescence signal. Lower trace Time dependence of fluorescence count rate after excitation by the laser pulse...

Figure 2.20. Absorption (black line) and fluorescence spectra of the AXFF in Ar-saturated cyclohexane at room temperature. Fluorescence spectra were obtained during the 266- and 355-nm (dark gray line) or 266- and 532-nm (light gray line) two-color two-laser flash photolysis. The absorption spectrum was obtained during one-laser photolysis (266-nm, black line) of AX (4.0 x 10 4M). The second laser irradiation was at 1 ps after the first laser pulse. All the fluorescence spectra of AXFb were normalized with the corresponding absorption peaks. Inset Kinetic traces of the fluorescence intensity of AXH- at 460 and 645 nm.

Figure 6 displays the phosphorescence spectra of three alkyl polysilylenes obtained from pulsed laser excitation of thin film samples at low temperature. For these spectra, the data was integrated over the period from 200 pseo to 0.01 sec following the laser pulse. All of the alkyl polysilylenes studied show a substantial amount of emission in the region of fluorescence which has essentially the same shape as the normal fluorescence. We interpret this emission as delayed fluorescence resulting from triplet-triplet annihilation. The delayed fluorescence provides a convenient comparison between the fluorescence shape and width and that of the phosphorescence. 

Fig. 86 Fluorescence spectra of a pyrene-implanted PBMA surface as a function of laser pulse number. Pyrene was transferred using ablation of a triazene polymer. Laser flu-ence 100 mj creT2, (a) 5 pulses, (b) 10 pulses, (c) 15 pulses, (d) 20 pulses. The vibrational pyrene emission peaks are denoted (I-V). Inset Normalized fluorescence intensity of the V pyrene peak at 393 nm vs laser pulse number. Data are taken from the spectra in the main figure. REPRINTED WITH PERMISSION OF [Ref. 360], COPYRIGHT (1998) Elsevier Science...

Figure 5. Time-resolved fluorescence of pyranine at the wavelength of maximum

In the present work, a new kinetics configuration utilizing a pulsed laser for photolysis and a quasi-cw, ultraviolet laser for fluorescence excitation has been developed. This technique combines the best features of the two kinetic methods mentioned above. Laser photolysis generally permits greater reactant formation specificity than does flashlamp photolysis. Laser-induced fluorescence detection outperforms resonance fluorescence detection because of its increased fluorescence excitation flux, decreased scattered light signal, and wavelength tunability. Cw fluorescence excitation is desirable over pulsed fluorescence excitation due to its freedom from pulse-to-pulse normalization constraints and, most importantly, because of its efficient duty cycle and the consequent increased density of points obtainable... 

Fig. 9 shows the exponential decay of the fluorescence of molecule C excited by a single 9 ns laser pulse at its resonance frequency. The number of photons counted was averaged over the repetition interval of the laser and normalized to unity at its maximum. The solid curve represents the result of the deconvolution procedure described earlier using a single exponential fit function and a constant background. The lifetime obtained from this fit was 23.9 + 1 ns for molecule C and 24.5 + 1 ns for molecule D. The introduction of an additional exponential function resulted in a... 

The experimental realization is shown schematically in Fig. 11.38. Part of the laser pulse is sent to a fast photodiode. The output pulse of this diode at t = to starts a Time-Amplitude Converter (TAC) which generates a fast rising voltage ramp U(t) = (t-to)Uo. A photomulitplier with a large amplification factor generates for each detected fluorescence photon an output pulse that triggers a fast discriminator. The normalized output pulse of the discriminator stops the TAC at time t. The amplitude U(t) of the TAC... 

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