Visible-laser irradiation

Muniz-Miranda M, Ottaviani ME (2004) Silver nanoclusters in mesoporous silica, as obtained by visible-laser irradiation. Laser Phys 14 1533-1538... 

Different initiation techniques have been investigated in polymerizations induced by iodonium salts, such as visible laser irradiation [32], dual photo- and thermally initiated cationic polymerization [23, 26] and a two-photon photopolymerization initiation system [33,34]. For example, dual photo- and thermal-initiation systems based on selective inhibition of the photoinifiated cationic ring-opening polymerization of epoxides by dialkyl sulfides have been developed [26]. Such a dual system, iodonium salt/dialkyl sulfide, in the... 

In this paper, the authors present the results of studying of the structural and morphological changes that occur after UV and visible laser irradiation of layered organic-inorganic composites zinc and copper synthesized by laser ablation in liquid. The S5mthesized materials are the second and third group composites. Their structural formulas are as follows (M)2(OH)3X x z X H O and (M)(OH)2X x z x H O, where M - divalent metals (Zn, Cu) and X - intercalated anion - alkyl sulfate where n = 12. 

Figure 12. Vibrational action spectra of V (OCO) in the OCO antisymmetric stretch region, (a) Spectrum obtained by monitoring depletion in the photofragment produced by irradiation at the vibronic origin at 15,801 cm The IR absorption near 2391.5 cm removes molecules from V[" = 0, leading to an 8% reduction in the fragment yield, (b) Spectrum obtained by monitoring enhancement in the VO+ photofragment signal as the IR laser is tuned, with the visible laser fixed at 15,777 cm (the Vj = 1 v" = 1 transition). The simulated spectrum gives a more precise value of the OCO antisymmetric stretch vibration in V" (OCO) of 2392.0 cm .

In Raman measurements [57], the 514-nm line of an Ar+ laser, the 325-nm line of a He-Cd laser, and the 244-nm line of an intracavity frequency-doubled Ar+ laser were employed. The incident laser beam was directed onto the sample surface under the back-scattering geometry, and the samples were kept at room temperature. In the 514-nm excitation, the scattered light was collected and dispersed in a SPEX 1403 double monochromator and detected with a photomultiplier. The laser output power was 300 mW. In the 325- and 244-nm excitations, the scattered light was collected with fused silica optics and was analyzed with a UV-enhanced CCD camera, using a Renishaw micro-Raman system 1000 spectrometer modified for use at 325 and 244 nm, respectively. A laser output of 10 mW was used, which resulted in an incident power at the sample of approximately 1.5 mW. The spectral resolution was approximately 2 cm k That no photoalteration of the samples occurred during the UV laser irradiation was ensured by confirming that the visible Raman spectra were unaltered after the UV Raman measurements. 

The observations of complex dynamics associated with electron-stimulated desorption or desorption driven by resonant excitation to repulsive electronic states are not unexpected. Their similarity to the dynamics observed in the visible and near-infrared LID illustrate the need for a closer investigation of the physical relaxation mechanisms of low energy electron/hole pairs in metals. When the time frame for reaction has been compressed to that of the 10 s laser pulse, many thermal processes will not effectively compete with the effects of transient low energy electrons or nonthermal phonons. It is these relaxation channels which might both play an important role in the physical or chemical processes driven by laser irradiation of surfaces, and provide dramatic insight into subtle details of molecule-surface dynamics. 

However, the high frequency of the laser irradiation in the visible region may lead to photochemical reactions in the laser focus. Besides, fluorescence can often cover the whole Raman spectrum. Such problems can be avoided by using an excitation wavelength in the near-infrared (NIR) region, e.g. with an Nd YAG laser operating at 1064 nm. Deficits arising from the v dependence of the Raman intensity and the lower sensitivity of NIR detectors are compensated by the Fourier-Transform (IT) technique, which is widespread in IR spectroscopy . ... 

GW cm ) pulsed CO2 laser radiation shown to result in broad u.v.-visible chemiluminescence Measurement of time-resolved emission spectra in the 618 2—5 p,m region following CO2 laser irradiation of CDF, and mixtures of CDF3-CHF,. Emission from vibrationally excited CDF, and DF observed, the latter being produced in the IRMPD of CDF,... 

Studies at extremely high static pressure can be carried out in diamond anvil cells. Studies of chemical dynamics in gem anvil cells are beginning to be carried out, and some unique chemical synthesis can also occur at these high pressures. For example, a high pressure polymerized phase of carbon monoxide was recently reported to be synthesized using visible laser light to irradiate a carbon monoxide sample at pressures of over 5 GPa in a diamond anvil cell. ... 

In principle, any kinds of organic dyes which undergo photochemical reactions by irradiation with visible laser light (635-830 nm) can be used as the memory media. The photochemical reactions can be detected by changes in refractive index as well as in absorption properties. Although most of photochemical reactions are irreversible, some organic dyes undergo reversible photochemical reactions [photo-chromism) and the photochromic dyes are potentially applicable to erasable optical memory media. 

Irradiation also affects the course of more conventional separation processes. Visible and ultraviolet light have been found to affect plutonium solvent extraction by photochemical reduction of the plutonium (12). Although the results vary somewhat with the conditions, generally plutonium(VI) can be reduced to pluto-nium(IV), and plutonium(IV) to plutonium(III). The reduction appears to take place more readily if the uranyl ion is also present, possibly as a result of photochemical reduction of the uranyl ion and subsequent reduction of plutonium by uranium(IV). Light has also been found to break up the unextractable plutonium polymer that forms in solvent extraction systems (7b,c). The effect of vibrational excitation resulting from infrared laser irradiation has been studied for a number of heterogeneous processes, including solvent extraction (13). 

BPH and BPDH were generated from the photoreduction of BP and BPD in cyclohexane. BP and BPD in the lowest triplet excited states (BP(T ) and BPDCTj)) decayed through the hydrogen abstraction from cyclohexane to produce BPH and BPDH after the first 266-nm nanosecond-laser irradiation. The generated BPH was excited at the visible absorption band using the second laser (532 nm, 30 ps FWHM) with the delay time of 1 ps after the first laser. Upon the excitation, BPH showed fluorescence with a peak at 564 nm. Similarly, fluorescence of BPDH was observed with the second laser irradiation. The measured xf of BPH is 2.0 ns, which is close to the reported value [112-114]. 4-Chloro-, 4,4 -dichloro-, 4-bromo-, 4,4 -dibromo-, and 4-trifluoromethyl-substituted... 

FIGURE 7.5 UV and visible absorption spectra of products resulting from unfocused 355 nm laser irradiation on graphite particles suspended in benzene, toluene, hexafluorobenzene, hexane, or methanol solution. 

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