Intensity-time diagrams

During the progress of the reaction fluorescence reaction spectra are taken and evaluated in the same way as the absorption spectra. First, fluorescence spectra are recorded at the chosen reaction times, and the intensities at wavelengths with significant changes are plotted versus the reaction time yielding intensity-time diagrams. 

Usually the intermediate s absorption coefficient is not known. Therefore apart from (p (using eq. (S. 145)) no further information can be gained. Accordingly the evaluation of the second slope in the intensity time diagrams only allows an approximation of the third partial quantum yield for known Cg. In any case, however, the two slopes have to differ by at least one... 

Figure 5. Schematic diagram of a time-resolved fluorescence spectrometer using a picosecond laser as an excitation source. Inset diagram intensity/time/ wavelength surface for poly (acenaphthalene) in benzene at 20°C. Excitation wavelength 295 nm. (Reproduced with permission from Ref. 21. Copyright 1987 Chemistry in Australia.)...

Figure 2. Schematic representation of the time-resolved fluorescence spectrometer. Inset diagram intensity/time/ wavelength hypersurface for PACE in benzene at 25°C.

FIGURE 21 In the pump phase the timing diagram for the cavity-dumped case is identical to the Q-switched case. After switching the Pockels cell to enable lasing, the cavity loss now is very small since, for a cavity-dumped architecture, the reflectivity of both resonator mirrors is 100%. Once the power in the cavity has reached the maximum value, the Pockels cell is again switched and ejects the intracavity intensity from the laser in a pulse equal to the round-trip time of the resonator cavity. 

Fig. 1.1. Relationship between spatial pulse length and frequency spectrum. Intensity versus time diagrams (left illustrations) illustrate two pulses with different length k of 1 ps and 2 ps, respectively, and the corresponding spectrum of frequency of 2 MHz and 1 MHz, respectively. The longer pulse (2 ps) generates a narrower bandwidth (1 MHz). (The bandwidth is measured between the 6 dB points of each side of the spectrum)...

This time-dependent population N. (t) can be measured in different ways. One possibility is to pass a weak cw probe laser through the sample and to measure the time-resolved absorption Al = N. (t)aL. Figure 12.12b is a schematic time diagram of pump pulse, lower level relaxation, and probe laser absorption. Another way uses a probe pulse with variable delay T. This probe pulse, which may come either from the same laser as the pump pulse or from another laser, is sent through the pumped region of the sample. The time-integrated fluorescence intensity T+AT T+aT... 

Fig. 4-9. This diagram shows the intensity variation with angle for a rock salt crystal in the region near the Bragg angle, 0q, for an incident monochromatic beam. The area under the mosaic crystal curve could be thirty times greater than the ideal. (After Renninger, Z. Krist. 89, 344.)...

---