Laser, ablation irradiation

We use laser photofragment spectroscopy to study the vibrational and electronic spectroscopy of ions. Our photofragment spectrometer is shown schematically in Eig. 2. Ions are formed by laser ablation of a metal rod, followed by ion molecule reactions, cool in a supersonic expansion and are accelerated into a dual TOE mass spectrometer. When they reach the reflectron, the mass-selected ions of interest are irradiated using one or more lasers operating in the infrared (IR), visible, or UV. Ions that absorb light can photodissociate, producing fragment ions that are mass analyzed and detected. Each of these steps will be discussed in more detail below, with particular emphasis on the ions of interest. 

Nondestructive radiation techniques can be used, whereby the sample is probed as it is being produced or delivered. However, the sample material is not always the appropriate shape or size, and therefore has to be cut, melted, pressed or milled. These handling procedures introduce similar problems to those mentioned before, including that of sample homogeneity. This problem arises from the fact that, in practice, only small portions of the material can be irradiated. Typical nondestructive analytical techniques are XRF, NAA and PIXE microdestructive methods are arc and spark source techniques, glow discharge and various laser ablation/desorption-based methods. On the other hand, direct solid sampling techniques are also not without problems. Most suffer from matrix effects. There are several methods in use to correct for or overcome matrix effects ... 

There are several sample introduction methods that are used in conjunction with ICP, including nebulization, electrothermal evaporation, gas chromatography, hydride generation, and laser ablation [30]. Laser ablation combined with ICP (LA-ICP) is useful for analysis of solids. In such a source the sample is positioned in a chamber prior to the ICP source, the ablation cell. Argon gas at atmosperic pressure flows through the cell towards the ICP source. The sample is irradiated by a laser beam and... 

By fluorescence analyses just upon laser ablation and of ablated surface, Molecular aspects of ablation echanisa were elucidated and a characterization of ablated Materials was perforaed. Laser fluence dependence of poly(N-vinylcarbazole) fluorescence indicates the iaportance of Mutual interactions between excited singlet states. As the fluence was increased, a plasna-like eaission was also observed, and then fluorescence due to diatonic radicals was superinposed. While the polyner fluorescence disappeared Mostly during the pulse width, the radicals attained the naxinun intensity at 100 ns after irradiation. Fluorescence spectra and their rise as well as decay curves of ablated surface and its nearby area were affected to a great extent by ablation. This phenonenon was clarified by probing fluorescence under a Microscope. 

Figure 21-26 Emission from a plasma produced by laser irradiation of the high-temperature superconductor YBCI2CU3O7. Solid is vaporized by the laser and excited atoms and molecules such as YO emit light at characteristic wavelengths. [From w.a. warmer. "Plasma Emission from Laser Ablation of YBa2Cuj07." Appf. Phys. Lett. 1988, 52.2171]...

Iwanaga S, Akiyama Y, Kikuchi A et al (2005) Fabrication of a cell array on ultrathin hydrophilic polymer gels utilising electron beam irradiation and UV excimer laser ablation. Biomaterials 26(26) 5395-5404... 

Electron beam irradiation and laser ablation has been successful in producing the metal dichalcogenide nanotubes. Laser ablation of MoS2 and WS2 targets produces substantial amounts of inorganic fullerenes and nanotubes.64 Electron beam irradiation of bulk WS2 powder yields various nanostructures of WS2 including inorganic fullerenes, nanotubes and nanorods.65... 

Laser ablation is one of the modem and frequently used methods. The disadvantage of broad size distribution could be improved by the so-called laser-induced size reduction . For instance, in the case of gold nanoparticles, their well expressed plasmon resonance around 520 nm can be used to influence the size and shape of the particles.Thus, more or less monodisperse gold particles of 1.7nm and 3.4nm could be generated with a 532-nm pulsed laser irradiation of gold metal plates in diluted sodium dodecylsulfate solutions. ... 

Russian group of Derjaguin et al., by irradiating ultrafine graphite powder with a CO laser beam, and was later confirmed by Roy et al. Various other researchers have reported diamond synthesis by similar techniques (e.g., 24-27). Diamond formation by laser ablation of graphite too has been claimed (e.g., 28, 29). 

The laser ablation apparatus consists of a quartz tube inside which a composite graphite disk is placed for laser irradiation. A furnace enwraps the quartz tube, thereby supplying a high... 

The performance of ablation lasers depends largely on two factors, namely the nominal laser wavelength and intensity, and whether the continuous or pulsed mode of irradiation is used. Studies on the first two factors have yielded controversial results that can be ascribed to differences in sample nature or grain size. Thus, ruby (694 nm), Nd YAG (1064, 532, 266 and, recently, 213 nm) and excimer (308, 248, 222, 193 and, recently, 157 nm) lasers have been used for laser ablation (LA). A comparison of the Nd YAG laser operating at 1064 nm and 266 nm revealed better absorption of UV wavelength by most types of samples and also decreased fractionation. The particle sizes produced during ablation were smaller with 266 than with 1064 nm, which was possibly the reason for the reduced... 

The sudden increase in crater depth observed during high irradiance (> 10 W/cm ) laser ablation of silicon [17], which has been ascribed to phase explosion, can be used to establish a new threshold the threshold irradiance for phase explosion. This threshold depends on two laser parameters, viz. beam spot size and wavelength. The larger the beam size and the longer the incident wavelength are, the higher is the laser irradiance required to cause phase explosion. 

Fig. 9.6. Schematic diagram of the experimental system for laser ablation-assisted radio-frequency atomization excitation. (I) Sample holder, (2) tantalum lid, (3) graphite cup, (4) graphite disc, (5) rf power source, (6) different types of sample holder for sintered ceramics, (7) NdiYAG laser, (8) laser beam-focusing lens, (9) spectrometer, (10) quartz window for laser irradiation, (11) central electrode, (12) discharge chamber, (13) quartz window for optical observation. (Reproduced with permission of the Royal Society of Chemistry.)...

In addition to chemical methods variety of physical methods has been employed for the synthesis of AuNPs. UV irradiation is used to improve the quality of the AuNPs when it is used in synergy with micelles or seeds [32,33], Near-IR laser irradiation provokes an enormous size growth of thiol-stabilized AuNPs [34], The presence of an ultrasonic field (200 kHz) allowed the control of the rate of AuC14" reduction in an aqueous solution containing only a small amount of 2-propanol and the sizes of the formed AuNPs are controlled by varying the parameters such as the temperature of the solution, the intensity of the ultrasound, and the positioning of the reactor [35,36], Sonochemistry was also used for the synthesis of AuNPs within the pores of silica and for the synthesis of Au/Pd bimetallic particles [37,38], Radiolysis has been used to control the size of AuNPs [39], Laser photolysis has been used to form AuNPs in block copolymer micelles. Laser ablation is another technique of AuNP synthesis that has been used under various conditions whereby size control can be induced by the laser [40,41],... 

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