Laser activation

Photolysis, luminiscent properties, and laser activity of oxazole derivatives 97MI27. 

Another example of the CVD of TiN is deposition by laser activation using a CO2 laser with N2H2 and TiC reactant gases. Deposition temperatures are not mentioned but presumed to be low. The composition of the film is substoichiometric (N/Ti[Pg.285]

Considerable interest in the subject of C-H bond activation at transition-metal centers has developed in the past several years (2), stimulated by the observation that even saturated hydrocarbons can react with little or no activation energy under appropriate conditions. Interestingly, gas phase studies of the reactions of saturated hydrocarbons at transition-metal centers were reported as early as 1973 (3). More recently, ion cyclotron resonance and ion beam experiments have provided many examples of the activation of both C-H and C-C bonds of alkanes by transition-metal ions in the gas phase (4). These gas phase studies have provided a plethora of highly speculative reaction mechanisms. Conventional mechanistic probes, such as isotopic labeling, have served mainly to indicate the complexity of "simple" processes such as the dehydrogenation of alkanes (5). More sophisticated techniques, such as multiphoton infrared laser activation (6) and the determination of kinetic energy release distributions (7), have revealed important features of the potential energy surfaces associated with the reactions of small molecules at transition metal centers. 

In our laboratory we have utilized multiphoton infrared laser activation of metal ion-hydrocarbon adducts to probe the lowest energy pathways of complex reaction systems (6). Freiser and co-workers have utilized dispersed visible and uv radiation from conventional light sources to examine photochemical processes involving organometallic fragments... 

If the EDA and CT pre-equilibria are fast relative to such a (follow-up) process, the overall second-order rate constant is k2 = eda c e In this kinetic situation, the ion-radical pair might not be experimentally observed in a thermally activated adiabatic process. However, photochemical (laser) activation via the deliberate irradiation of the charge-transfer absorption (hvct) will lead to the spontaneous generation of the ion-radical pair (equations 4, 5) that is experimentally observable if the time-resolution of the laser pulse exceeds that of the follow-up processes (kf and /tBet)- Indeed, charge-transfer activation provides the basis for the experimental demonstration of the viability of the electron-transfer paradigm in Scheme l.21... 

A locally resolved detection of radioactive samples after chromatographic separation can be performed by imaging techniques which work either indirectly with Eu3+- or P-doped sensor plates and laser activated emission or directly by a micro channel array detector which works like an open Geiger-Muller counter. 

UV and/or laser activation of oxsoralen for psoriasis or cutaneous T-Cell lymphoma. 

The mechanism of the iodide formation at platinum immersed in aqueous electrode was recently studied by laser-activated voltammetry in a channel flow cell system [161]. In this technique, solid deposits of iodine are removed from the electrode continuously by short nanosecond high-power laser pulses. By removing deposits on electrode surfaces within a channel flow cell, the voltammetric measurements becomes time independent and data can be analyzed and modeled quantitatively. Laser activation using a 10-Hz pulsed Nd YAG 532-nm laser was shown to remove bulk iodine from the electrode surface so that under sustained pulsed... 

Heterocyclic Compounds as Laser Active Media L. K. Denisov and B. M. Uzhinov, Khim. Geterotsikl. Soedin., 1980, 723-736. 

HOPG, or PG, edge Polished Laser-activated or roughened Easily renewed, strong adsorption Strong adsorption fast kinetics Variable impurities Moderately high background 2... 

Laser-activated ECP Wide solvent compatability easily prepared, rapid in situ renewal Sensitive, selective for cations, fast kinetics Expensive, optical window required in cell High background current Yields fast kinetics 1,2 1,2... 

The scope of the modern science of combustion is significantly broader than it was a few decades ago. Together with the traditional application of combustion in energy installations—to obtain mechanical work, heat, electrical energy, and to maintain transportation systems, etc.—new applications have been developed such as the production of new materials through combustion, use as a source of information about chemical kinetics at high temperatures and pressures, and the production of a high-temperature, laser-active medium. 

There is a possibility that the CO transitions observed in laser activity in CS2-02 mixtures61 could be formed in an analogous reaction. 

An important feature is film activation with micrometer precision by external stimulation with biofriendly near-IR light, which results in controlled release of film-embedded material [98,100], Laser activation of film-supported microcapsules shows remote release of encapsulated dextran by selective stimulation of the capsules with near-IR light (Fig. 6). Destruction of the HA/PLL film functionalized with gold nanoparticles occurs at irradiation with a light power of over 20 mW. Microcapsules modified with nanoparticles keep their integrity under the same conditions but become more permeable. 

The potential for laser activity is not anything we can demand of any atom or molecule. We should regard it as accidental that among the extremely complex sets of energy levels associated with a few atoms or molecules there happens to be one (or more) pairs between which it is possible to produce a population inversion and thereby create a laser. 

An advance in DNA sequencing is the development of automated sequencing instruments that replace the traditional radioactive labels with laser-activated fluorescent labels and that read sequences from gels directly into computer files. The development of automatic sequencers is a promising new strategy for DNA sequencing that increases the speed of data acquisition, but they are still too expensive for most individual laboratories to be able to justify their purchase.17... 

RC-MS stems from the observation that mass spectra of peptides and proteins can be generated by laser activation of chromatographic surfaces placed on MALDI targets. The product application of RC-MS, called surface-enhanced laser desorption ionization-time of fiight (SELDI-TOF), refers to a mass spectrometry method for measuring native proteins adsorbed (retained) on various chemical or biochemical surfaces (Figure 4.11). Although the concept of laser desorption of intact proteins is well established, it has been commercially exploited only recently as a means... 

Electrophoresis is followed by laser activation of the fluorescent dideoxy nucleotides, and detection to distinguish the colours... 

We are going to consider a particular type of laser known as a solid-state laser, which consists of a collection of special laser-active atoms embedded in a solid-state matrix, bounded by partially reflecting mirrors at either end. An external energy source is used to excite or pump the atoms out of their ground states (Figure 3.3.1). 

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