Excitation conditions

The interpretation of emission spectra is somewhat different but similar to that of absorption spectra. The intensity observed m a typical emission spectrum is a complicated fiinction of the excitation conditions which detennine the number of excited states produced, quenching processes which compete with emission, and the efficiency of the detection system. The quantities of theoretical interest which replace the integrated intensity of absorption spectroscopy are the rate constant for spontaneous emission and the related excited-state lifetime. 

From such a treatment, we may derive explicit expressions for the nonlinear radiation in tenns of the linear and nonlinear response and the excitation conditions. For the case of nonlinear reflection, we obtain an irradiance for the radiation emitted at the nonlinear frequency of... 

Ach antages. DOR works well if the quadnipolar interaction is dominant and the sample is highly crystalline, with some extremely impressive gains in resolution. Provided that the conect RF-excitation conditions are employed the spectral infonuation is directly quantitative. 

S-S annihilation phenomena can be considered as a powerful tool for investigating tire exciton dynamics in molecular complexes [26]. However, in systems where tliat is not tire objective it can be a complication one would prefer to avoid. To tliis end, a measure of suitably conservative excitation conditions is to have tire parameter a< )T < 0.01. Here x is tire effective rate of intrinsic energy dissipation in tire ensemble if tire excitation is by CW light, and T = IS tire... 

Recent tlieoretical [35, 36 and 37] and experimental [38] research has revealed anomalous behaviour of tire dimer anisotropy under certain excitation conditions. If tire dimer is excited by broadband light tliat covers botli excitonic transitions, or by a relatively narrow band properly positioned between tire maxima of tire excitonic transitions, tire... 

To maintain reproducible excitation conditions in the glow discharge source, the working conditions (e. g. argon pressure, dc-current or rf-power) are carefully controlled. 

The quantification algorithm most commonly used in dc GD-OES depth profiling is based on the concept of emission yield [4.184], Ri] , according to the observation that the emitted light per sputtered mass unit (i. e. emission yield) is an almost matrix-independent constant for each element, if the source is operated under constant excitation conditions. In this approach the observed line intensity, /ijt, is described by the concentration, Ci, of element, i, in the sample, j, and by the sputtering rate g, ... 

Figure 10-10. (a) Semilogarillnnic plol of ihc stimulated emission transients for various excitation pulse energies measured for LPPP on glass. The excitation pulses have a duration of 150 fs and are centered at 400 nm. The probe pulse were spectrally filtered (Ao=500nin, Aa=l0nm). (b) Emission spectra recorded for the same excitation conditions. The spectra are normalized at the purely electronic emission baud (according lo Ref. [181). 

Excitation conditions and threshold vulues for lasing in different conjugated polymers. Different resonator structures are used to achieve real lasing. Note that it is in some cases difficult to compare the values due to the different laser pulse duration used in the experiments. indicates the wavelength for excitation, r(,u< is the pulse duration of the exciting laser pulse atu A the urea of the spot on the sample. 

Reference Material and resonator Excitation conditions Threshold for lasing... 

The chapter is organized as follows in Section 8.2 a brief overview of ultrafast optical dynamics in polymers is given in Section 8.3 we present m-LPPP and give a summary of optical properties in Section 8.4 the laser source and the measuring techniques are described in Section 8.5 we discuss the fundamental photoexcitations of m-LPPP Section 8.6 is dedicated to radiative recombination under several excitation conditions and describes in some detail amplified spontaneous emission (ASE) Section 8.7 discusses the charge generation process and the photoexcitation dynamics in the presence of an external electric field conclusions are reported in the last section. 

If the excitation conditions are kept constant and the sample composition is varied over a narrow range, the energy emitted for a given spectral line of an... 

In the internal standard method the intensity of the unknown line is measured relative to that of an internal standard line. The internal line may be a weak line of the main constituent. Alternatively, it may be a strong line of an element known not to be present in the sample and furnished by adding a fixed small amount of a compound of the element in question to the sample. The ratios of the intensities of these lines — the unknown line and the internal standard line — will be unaffected by the exposure and development conditions. This method will provide lines of suitable wavelength and intensity by variations of the added element and the amount added, due regard being paid to the relative volatility of the selected internal standard element. It is important to use as internal standard pairs only those lines of which the relative intensities are insensitive to variations in excitation conditions. The line selected as standard should have a wavelength close to that of the unknown and should, if possible, have roughly the same intensity. 

Figure 9.3. Illustration of the approach to steady-state conditions for the populations of states So, Si, and Ti under the continuous excitation conditions of Example 9.5...

The single inequahty is used, simply because we want to reduce the necessary laser intensity as much as possible. Equation (188) now provides the nearly complete excitation condition. 

Figure 8.2a-c shows optical transmission images of organic microcrystals of perylene, anthracene, and pyrene, excited at a laser power of 1.7 nj pulse under similar excitation conditions as in Figure 8.1c. The bright spots <2 pm in diameter at the center of each microcrystal were areas irradiated with the NIR laser pulse.

In Sect. 4.9.1, experimental rationalization was provided for the W value of ionization in gaseous and liquid water, giving respectively 30.0 and 20.8 eV. The corresponding ionization potentials are respectively 12.6 and 8.3 eV. For the purpose of diffusion and stochastic kinetics, one often requires the statistical distribution P(i,j) of the number of ionizations i and excitations j, conditioned on i ionizations, for a spur of energy . Pimblott and Mozumder (1991) write P(i, j) = r(i) 2(j i), where F(i) is the probability of having i ionizations and 2(j i) is the probability of having j excitations conditioned on i ionizations. These probabilities are separately normalized to unity. 

Must essentially achieve reproducible excitation conditions of various samples. 

The laser microprobe employs a pulsed laser to vaporize minute amounts of the sample. The vapor temperature, however, in the case of low-power lasers is not sufficient to provide adequate excitation for spectrochemical analysis. The sample vapor is therefore further excited as it passes between two auxiliary electrodes above the sample. The optimum excitation conditions have been examined by Quillfeldt using the commercial laser-microspectral analyzer LMA 1 (Carl Zeiss, Jena). Spectrochemical determinations of Fe,... 

Each y-ray energy emission connecting two excited states corresponds to the difference between the disintegration energy associated with the two a decays, which lead to the two limiting excited conditions. 

As with radical polymerization, some studies have used well-established IP-initiators under 2P excitation conditions. For example, the commercially available photoacid generator p.l (Fig. 18), which has a peak cross section of only 16 GM at a photon wavelength of 5 3 0 nm [ 169 ], has b een used to fabricate... 

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