Surface Laser Irradiation

In order to move the samples under the laser beam, the stainless steel (SS) disks were mounted on a precise, computer-controlled ZABERT-LS80 X-Y translation stage. The power of the incident laser beam was adjusted in the range of 5 to 1700 mW and the scanning speed varied from 250 to 1850pm/s. The samples were irradiated at normal incidence in air and then subjected to an ultrasonic bath for 2 min in acetone to remove all the debris off the patterned surface. 

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Surface photochemistry can drive a surface chemical reaction in the presence of laser irradiation that would not otherwise occur. The types of excitations that initiate surface photochemistry can be roughly divided into those that occur due to direct excitations of the adsorbates and those that are mediated by the substrate. In a direct excitation, the adsorbed molecules are excited by the laser light, and will directly convert into products, much as they would in the gas phase. In substrate-mediated processes, however, the laser light acts to excite electrons from the substrate, which are often referred to as hot electrons . These hot electrons then interact with the adsorbates to initiate a chemical reaction. 

The possible mechanism of ionization, fragmentation of studied compound as well as their desoi ption by laser radiation is discussed. It is shown that the formation of analyte ions is a result of a multi stage complex process included surface activation by laser irradiation, the adsoi ption of neutral analyte and proton donor molecules, the chemical reaction on the surface with proton or electron transfer, production of charged complexes bonded with the surface and finally laser desoi ption of such preformed molecules. 

Other topics recently studied by XPS include the effects of thermal treatment on the morphology and adhesion of the interface between Au and the polymer trimethylcy-clohexane-polycarbonate [2.72] the composition of the surfaces and interfaces of plasma-modified Cu-PTFE and Au-PTFE, and the surface structure and the improvement of adhesion [2.73] the influence of excimer laser irradiation of the polymer on the adhesion of metallic overlayers [2.74] and the behavior of the Co-rich binder phase of WC-Co hard metal and diamond deposition on it [2.75]. 

Noguchi, H., Okada, T, Onda, K., Kano, S. S., Wada, A. and Domen, K. (2003) Time-resolved SFG study of formate on a Ni(lll) surface under irradiation of picosecond laser pulses. Surf. Sci., 528, 183-188. 

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. 

Polyvinyl chloride has been modified by photochemical reactions in order to either produce a conductive polymer or to improve its light-stability. In the first case, the PVC plate was extensively photochlorinated and then degraded by UV exposure in N2. Total dehydrochlorination was achieved by a short Ar+ laser irradiation at 488 nm that leads to a purely carbon polymer which was shown to exhibit an electrical conductivity. In the second case, an epoxy-acrylate resin was coated onto a transparent PVC sheet and crosslinked by UV irradiation in the presence of both a photoinitiator and a UV absorber. This superficial treatment was found to greatly improve the photostability of PVC as well as its surface properties. 

D.M. Zehner, Surface Studies of Pulsed Laser Irradiated Semiconductors D.H. Lowndes, Pulsed Beam Processing of Gallium Arsenide R.B. James, Pulsed C02 Laser Annealing of Semiconductors R. T. Young and R.F. Wood, Applications of Pulsed Laser Processing... 

The origin of lead present in individual calcite particles could be ascribed by the LAMMA (laser microprobe mass analysis) technique. At low laser irradiances, the desorption mode, information is gathered on metallic species adsorbed on the surface of the particle. At high irradiances the particle is evaporated, revealing the components that coprecipitated with calcite111. 

As a whole, our set of measurements therefore shows that, contrary to what is usually observed under low contrast conditions [21, 71], BWD protons originating from the laser-irradiated surface have practically the same characteristics as the FWD protons from the target rear side, suggesting a quasi-symmetrical TNSA acceleration in the two directions. 

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. 

The Ru(NH3)j+ moiety can be attached to histidine-83 on the azurin surface. It can then be oxidized to Ru(III) without altering the conformation of the protein. This ruthenated protein is mixed with Ru(bpy)3+ and laser irradiated. The sequence of events which occurs is shown in the scheme... 

Laser irradiation onto the insulating (EDO)2PF6 crystal induces a phase transition to the highly conductive state within a few picoseconds [162, 180]. The crystal surface was excited by laser irradiation with a pulse width of 0.12 ps. The excitation photon energy (1.55 eV) was nearly resonant to the CT band at 11.1 x 10 cm (1.37 eV), directly reflecting the excitation of the charge ordered state. 

Thus the effect of ELBI on the aorta and vein endothehocytes depends on the duration of irradiation. Irradiation for 15 and 30 min caused reversible changes which were expressed in changes of the normal cell forms, appearance of craterlike depressions and surface defects, swelling of nuclei and oedema. Irradiation for 60 min had a more pronounced effect on the inner surface of blood vessels resulting in detachment of endothehocytes from the basal membrane and their desquamation. Restoration of the endothelial structure after 15 and 30 min of laser irradiation... 

LA-ICP mass spectrometry is becoming the method of the choice for trace and isotope analysis of solid samples and is already the most important laser induced technique in inorganic mass spectrometry due to the advantage of direct solid sampling by focused laser irradiation on the sample surface and its ability to provide microscale information. 

The experiments demonstrate that femtosecond laser pulses offer new opportunities for multiple-photon ionization of bioorganic molecules on surface. The fast femtosecond excitation makes it possible to produce molecular and fragmentation ions directly on the surface being irradiated. The two-photon excitation with an intense femtosecond pulse allows the selectivity of ionization of the chromophore (tryptophan in our case) in large molecules... 

At suitably high laser irradiances at the solid surface, a plasma is formed as mentioned above. With properly chosen irradiation parameters, this plasma shows features, comparable to those of HF-spark sources, commonly used in mass spectrometry of inorganic solid samples. From results, reported in the literature (1, 2, 3), it can be deduced that the laser source may offer some advantages over classical spark sources with respect to sample preparation (nonconductors), reproducibility, collection efficiency and uniformity of elemental sensitivity factors. The laser in addition... 

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