Excitation laser power

FCS curves for the quantum dots with mono-dispersity were obtained at various excitation laser powers ranging from 10 to 200 j,W. Figure 8.12 shows an autocor-... 

Figure 8.13 Autocorrelation curves for the CdTe quantum dots with diameter 4.9 nm at the excitation laser power from 10-200 XW (a). Comparison of the shapes of these autocorrelation curves by normalization (b).

In Figure 10.12, the TE-CARS signal intensity largely surpasses the background because the number of molecules in the excited volume is enough to induce the large signal. It, however, depends on experimental conditions such as the number of molecules, excitation laser power, and optical density of samples. In other cases, the... 

Figure 4-21 SERS in cytidine-3 -monophosphate (3 -CMP). 3 -CMP concentration 2 x 10 3 M, 0.15 M KC1, 2 x 10 3 M Tris buffer (pH 7.2). 514.5 nm excitation, laser power at the electrode 10 mW, prior activation of the Ag electrode 1x5 mCb between -0.1V and +0.2 V. (a) Adsorption potential E, - 0.1 V vs. Ag/AgCl reference electrode, (b) Adsorption potential E, -0.6 V vs. Ag/AgCl reference electrode. (Reproduced with permission from Ref. 44.)...

It is thus clear that in addition to the sample absorbance and excitation laser power, the thermal lens signal is directly proportional to dn/dT and inversely proportional to the k value of the solvent. Nonpolar, volative organic solvents such as benzene, carbon tetrachloride and hexane, should provide good media for thermal lens measurements owing to their high dn/dT and low k values. Conversely, water, which is the most powerful and widely used solvent in spectrochemical analysis is considered to be the worst mediiun for thermooptical techniques because it has very low dn/dT... 

The first- and second-order TG intensities showed anomalous dependence on the excitation laser power. In particular, the second-order TG... 

It turns out that for some systems, e.g., porphin in -octane the exciting laser power must be chosen so low, to meet condition (35), that detection of the OFID signal is impossible. Also for the case of the lowest 5, transition of naphthalene in durene the factor 4 is so large, that detection of OFID is out of reach. As the photon-echo technique does not suffer from the triplet state bottleneck, this system can be studied using the photon echo, as shown by Aartsma and Wiersma. For the energetically lowest sites of pentacene the situation is particularly favorable, as A is only 9 and OFID detection is easily possible. 

From the laser power dependence of the absorptiontime profiles of the Qq fine particles, it was confirmed that the fast-decaying part appears when the excitation laser power becomes high only the slow-decaying part appears with lower laser power excitation. This finding indicates that the triplet-triplet annihilation process in the fine particles becomes apparent only when the density of the triplet excited states becomes sufficiently high by the higher laser power. 

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