Fluorescence delay time

Temporal characteristics at early stages were elucidated by measuring fluorescence intensity with the gate time of 1.74 ns as a function of the delay time. Compared to the laser pulse, the time where the maximum intensity is attained shifts to the early stage as the laser fluence becomes high. Of course, we could not find out any decay component with intrinsic fluorescence lifetime of 17 and 35 ns. It is concluded that an Si - Si annihilation occurs quite efficiently during the pulse width. 

The LS-3B is a fluorescence spectrometer with separate scanning monochromators for excitation and emission, and digital displays of both monochromator wavelengths and signal intensity. The LS-5B is a ratioing luminescence spectrometer with the capability of measuring fluorescence, phosphorescence and bio- and chemiluminescence. Delay time (t) and gate width (t) are variable via the keypad in lOps intervals. It corrects excitation and emission spectra. 

The intensity of the sum frequency light /sum at a given delay time r between the probe pulse and the fluorescence beam co( is proportional to the correlation function of the fluorescence intensity with the intensity of the probe pulse co ... 

Figure 8.9. Time-resolved fluorescence spectra of 9,10-diphenylanthracene, recorded wi th time-correlated single photon counting, Aa = 360 nm. Parameters gate width and delay time relative to the intensity maximum of the excitation pulse.

Most common lock-in amplifiers can be operated at frequencies ranging from a few Hz up to 100 kHz. This fact is important in analyzing the temporal evolution of optical signals for example, fluorescence decay time measurements. Although this particular application of lock-in amplifiers is beyond the scope of this section, it is instructive to mention that this can be done by tuning the relative phase (the time delay) between the signal intensity and the reference signal provided by the chopper. 

In a third method for lifetime measurements, the levels to be investigated are excited by a short pulse and subsequently the number of fluorescence quanta is counted as a function of the delay time (e.g. with a multichannel analyzer and a time-to-pulse height converter). The experimental procedure is described by Bennet 2 and has been perfected by several authors using light pulses 22) or electron pulses 23) for excitation. 

The flnorescence dynamics imaging was carried ont by monitoring time-resolved fluorescence at 530 nm, where the rise of the tetracene fluorescence is observed, at different positions of the microcrystal. The np-converted fluorescence data were recorded every 1 pm distance. To shorten the measnrement time at each point, the up-converted signal was sampled at only fonr delay time points (- 5, 5,15, 30 ps), and then the energy transfer time, x, was evalnated by htting with the following single-exponential fnnction ... 

The typical luminescence in natural apatite is connected with a band peaking at 569 nm (Fig. 4.1e) with a delay time of 5 ms. Various laser hnes were used to excite the luminescence but the spectra were all very similar. All portions of the curve have the same decay time and the spectra were found to be identical for different delay times and gate widths. All of this suggests that we a dealing with a simple single-ion fluorescence. Red apatite has unusual for a natural sample luminescence of Eu " and in Ca(II) instead of Ca(I)... 

Generation of M in solution includes one-electron transfer and should be accompanied with ion pair formation, e.g., M -M, M -anion, etc. in any processes. Absorption spectroscopy of M are not sufficiently sensitive to distinguish ion pair from free ion, while fluorescence spectroscopy is enough sensitive. The delay time (10-1000 nsec) decreased rapidly during PR-LFP of TMB in DCE... 

Figure 23 Fluorescence spectrum of DMP measured at 100 nsec after e. Energy of / V532, 130 mJ. Inset a plot of the integrated fluorescence intensity of DMP as a function of the delay time of hv532 relative to eT (open circle) is superimposed with a plot of AO.D.575 (solid circle).

Fig. 1-left gives a general overview of the differential absorption spectra recorded for the free chromophore, oxyblepharismin, dissolved in DMSO for reference the steady-state absorption and (uncorrected) fluorescence spectra are also given below, in dotted lines. At all pump-probe delay times, the overall picture is a superposition of the structured bleaching and gain bands, as expected from the steady-state spectra, and broad transient absorption bands around 530 nm and 750 nm (weaker). These apparently homothetic spectra are very similar to... 

Fig. 1. Top Reference spectra for femtosecond transient absorption measurements S-S abs. in solution (thin solid lines), oxidized dye (dye+) abs. in solution (thick solid line), fluorescence for solution (dotted line), steady-state absorption ofNKX-2311/ZnO (dotted-dashed line), and absorption of electrons in the conduction band (dashed line). Bottom Transient absorption spectra of NKX-23ll/ZnO in the spectral range between 600 and 1350 nm at the 2 (thick solid line), 10 (dotted line), 100 ps (thin solid line) delay times after excitation at 540 nm by the femtosecond pulse with the intensity of about 10 pJ.

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