Dyes, photoionization

Another point subject to criticism from this work is the apparent absence of DC photocurrents upon constant illumination. Although the responses in Fig. 13(c) appear effectively in phase at the chopping frequency, it is possible that slow photoinduced perturbation of accumulated charge at the interface can be connected with these photoresponses, e.g., photoionization of the dye [72]. In this respect, clearer evidence of photo-induced ET was introduced by Brown et al. for the reaction [49]... 

Since the second laser ionizes the excited atom in DLI, this step may be accomplished by an off-resonant photon (see Fig. 1). If a nitrogen laser-pumped dye laser provides the resonant photon, a fraction of the nitrogen laser beam can conveniently ionize the atom from the laser-excited state 14,15). It is theoretically possible to photoionize every atom in the periodic table except helium and neon using five RIS ionization schemes involving stepwise and/or multiphoton excitation4). Presumably these... 

Andreoni et al. 49,83) investigated a selective photodamage of dye molecules bound to polynucleotides. The experiments were based on a time-delayed two-step photoionization the experimental set up is shown in Fig. 19. The two-step excitation was performed with a nitrogen laser (337 nm) and a dye laser (pumped by the nitrogen laser) at 430 nm. The selectivity arises from the fact that the lifetime of the first excited electronic state of the dye may be sensitive to the binding site (Chapter 4.2.2). Two complexes with different lifetimes Tj and t2 (tj < x2) are irradiated with two laser pulses (Fig. 20). The second pulse is delayed with rD against the first pulse. If xt < xD < t2 the second pulse (frequency v2) will find a smaller singlet-state... 

Excitation using high-intensity 532 nm laser pulses led to photoionization of these dyes [67]. The transient absorption recorded following the laser flash excitation of 3 is shown in Fig. 5. The linear dependence of the absorption at... 

After the light is removed from solutions of leuconitriles, the color slowly fades in the dark, giving rise to the colorless products dye leuconitrile, dye car-binol base [20] where water is present, and dye ether base [21] in alcohols [22]. The carbinol and ether bases, which are called leucohydwxide and leucoether, respectively, undergo efficient photoionization as well [11, 23-27]. 

The second harmonic output of an excimer (Lambda Physik EMG 201 MSC) pumped-dye laser (Lambda Physik FL 3002) is focused into the photoionization region by a 2(X)-mm, focal-length, fused-silica lens. The wavelength calibration is made using the known ZEKE spectrum of atomic sulfur [194], which is produced by the multiphoton laser photodissociation of HjS. 

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