Laser vaporization, inducing

An alternative approach to trace analyte detection results from the measurement of chemiluminescence in a laser-generated plume of plasma, formed when the laser beam evaporates a small amount of sample (43). In these experiments, a pulsed excimer laser-induced-plasma, formed by laser vaporization and ionization, is probed direcdy to measure ion intensity. Ground state sodium atoms, excited state copper atoms, and sodium dimer molecules have all been monitored using this technique. This laser enhanced ionization may well be one of a very few techniques which can be used to probe extremely dense plasmas with good spatial and temporal resolution. 

The Al4 system is both a-aromatic and Ti-aromatic. However, a conflicting nature has been exhibited by the rectangular which is simultaneously TT-antiaromatic and a-aromatic The LisAljcluster, containing the Al4 unit, has been synthesized by laser vaporization and analyzed by photoelectron spectroscopy and ab initio calculations Conflicting results have been reported through different aromaticity measures, e.g., the and magnetic field induced current density ... 

Every effort is made here to achieve the highest possible absolute power of detection. Microdistribution analysis represents the primary field of application for microprobe techniques based on beams of laser photons, electrons, or ions, including electron microprobe analysis (EPMA), electron energy-loss spectrometry (EELS), particle-induced X-ray spectrometry (PIXE), secondary ion mass spectrometry (SIMS), and laser vaporization (laser ablation). These are exploited in conjunction with optical atomic emission spectrometry and mass spectrometry, as well as various forms of laser spectrometry that are still under development, such as laser atomic ab.sorption spectrometry (LAAS), resonance ionization spectrometry (RIS). resonance ionization mass spectrometry (RIMS), laser-enhanced ionization (LEI) spectrometry, and laser-induced fluorescence (LIF) spectrometry [36]-[44],... 

Preferred methods in trace determination of the elements include atomic absorption spectrometry (AAS), optical emission spectrometry (OES) with any of a wide variety of excitation sources [e.g., sparks, arcs, high-frequency or microwave plasmas (inductively coupled plasma, ICP microwave induced plasma, MIP capacitively coupled micro-wave plasma, CMP), glow discharges (GD). hollow cathodes, or laser vaporization (laser ablation)], as well as mass spectrometry (again in combination with the various excitation sources listed), together with several types of X-ray fluorescence (XRF) analysis [51]. 

In Surface Analysis by Laser Ionization (SALI), a probe beam such as an ion beam, electron beam, or laser is directed onto a surfiice to remove a sample of material. An untuned, high-intensity laser beam passes parallel and close to but above the sur-fiice. The laser has sufficient intensity to induce a high degree of nonresonant, and hence nonselective, photoionization of the vaporized sample of material within the laser beam. The nonselectively ionized sample is then subjected to mass spectral analysis to determine the nature of the unknown species. SALI spectra accurately reflect the surface composition, and the use of time-of-flight mass spectrometers provides fast, efficient and extremely sensitive analysis. 

Bauerle, D., Laser Induced Chemical Vapor Deposition, mLaser Processing and Diagnostics, (D. Bauerle, ed.), Springer-Verlag, New York (1984)... 

Carver, G. E., and Seraphin, B., Chemical Vapor Deposition Molybdenum Thin Films for High-Power Laser Mirrors, mLaser Induced Damage in Optical Materials, Publ. of National Bureau of Standards (Oct 1979)... 

The last problem of this series concerns femtosecond laser ablation from gold nanoparticles [87]. In this process, solid material transforms into a volatile phase initiated by rapid deposition of energy. This ablation is nonthermal in nature. Material ejection is induced by the enhancement of the electric field close to the curved nanoparticle surface. This ablation is achievable for laser excitation powers far below the onset of general catastrophic material deterioration, such as plasma formation or laser-induced explosive boiling. Anisotropy in the ablation pattern was observed. It coincides with a reduction of the surface barrier from water vaporization and particle melting. This effect limits any high-power manipulation of nanostructured surfaces such as surface-enhanced Raman measurements or plasmonics with femtosecond pulses. 

The increasing application of laser ablation or induced techniques for local and bulk analysis, whereby either the sampled vapor or the excited light becomes trans-... 

No information was found on the transformation of diisopropyl methylphosphonate in the atmosphere. Based on the results of environmental fate studies of diisopropyl methylphosphonate in distilled water and natural water, photolysis (either direct or indirect) is not important in the transformation of diisopropyl methylphosphonate in aquatic systems (Spanggord et al. 1979). The ultraviolet and infrared laser-induced photodegradation of diisopropyl methylphosphonate in both the vapor or liquid phase has been demonstrated (Radziemski 1981). Light hydrocarbon gases were the principal decomposition products. Hydrogen, carbon monoxide (CO), carbon dioxide (C02), and water were also detected. 

The laser induces instantaneous vaporization of a microvolume (called a plume), and a mixture of ionized matrix and analyte molecules is released into the vacuum of the ion source. The relationship between the laser irradiance, I ascn and the number of molecules formed, Gma di, is most peculiar. There exists a threshold irradiance, peculiar to each matrix, below which ionization is not observed. Above this level, the ion production increases in a very strong, nonlinear, manner (often Gma di grows as Ilaser is raised to the eighth power). 

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