Laser alkali

In electrical porcelains (often called steatite bodies), high purity talc products with low levels of alkali metals ate preferred. A typical steatite is made from 85% talc, 10% plastic kaolin, and 5% BaCO. Steatites ate used as insulators on high voltage equipment such as automotive starters, microwave oven generators, and laser generators. 

Other. Alkali chiorochromate compounds, including cesium chiorochromate, CsCrCl, are ferromagnetic substances being studied for potential apphcation in optically-read computer memory devices. Cesium has also been used in vapor glow lamps (44), vapor rectifiers, and high energy lasers (qv)... 

The material evaporated by the laser pulse is representative of the composition of the solid, however the ion signals that are actually measured by the mass spectrometer must be interpreted in the light of different ionization efficiencies. A comprehensive model for ion formation from solids under typical LIMS conditions does not exist, but we are able to estimate that under high laser irradiance conditions (>10 W/cm ) the detection limits vary from approximately 1 ppm atomic for easily ionized elements (such as the alkalis, in positive-ion spectroscopy, or the halogens, in negative-ion spectroscopy) to 100—200 ppm atomic for elements with poor ion yields (for example, Zn or As). 

Since the demonstration by Schumacher et al ) of the use of alkali metal vapor inclusion into a supersonic beam to produce clusters, there have been a number of attempts to generalize the approach. It has recently been recognized that instead of high temperature ovens, with their concommitant set of complex experimental problems, an intense pulsed laser beam focused on a target could be effectively used to produce metal atoms in the throat of a supersonic expansion valve. ) If these atoms are injected into a high pressure inert gas, such as helium, nucleation to produce clusters occurs. This development has as its most important result that clusters of virtually any material now can be produced and studied with relative ease. 

Sato et al. " measured the viscosities of some binary and ternary alkali carbonates. Since melt creep must be prevented, a highly sintered alumina crucible was used instead of a gold-plated nickel crucible. Homogeneity of a mixture sample was achieved by gas bubbling. A laser beam is combined with a computer-assisted time counter to obtain the logarithmic decrement. Roscoe s equationi3i has been used for calculation of the viscosity, while it has been claimed by Abe et al. that the viscosities calculated from Roscoe s equation are 0.6-1.5% lower than those from more rigorous equations. 

Thomas JB, Bodnar RJ, Shimizu N, Sinha AK (2002) Determination of zircon/melt trace element partition coefficients from SIMS analysis of melt inclusions in zircon. Geochim Cosmochim Acta 66 2887-2901 Thompson GM, Malpas J (2000) Mineral/melt partition coefficients of oceanic alkali basalts determined on natural samples using laser ablation-inductively eouple plasma-mass spectrometry (LAM-ICP-MS). Mineral Mag 64 85-94... 

Jackson SE, Gunther D (2003) The nature and sources of laser induced isotopic fractionation in laser ablation-multicollector-inductively coupled plasma-mass spectrometry. J Anal At Spectrom 18 205-212 Jiang S-J, Houk RS, Stevens MA (1988) Alleviation of overlap interferences for determination of potassium isotope ratios by Inductively-Coupled Plasma Mass Spectrometry. Anal Chem 60 1217-1220 Lam JWH, Horlick G (1990) A comparison of argon and mixed gas plasmas for inductively coupled plasma-mass spectrometry. Spectrochim Acta Part B 45 1313-1325 Langmuir I, Kingdon KH(1925) Thermionic effects caused by vapours of alkali metals. Phil Trans R Soc A107 61-79... 

In general, two types of tunable solid state lasers have been developed those based on color centers in alkali halide crystals, and those based on transition metal ions (3d) in a crystalhne host. In both cases, the tunabihty rehes on the large spectral gain profile provided by the active center. 

Chapter 6 is devoted to discussing the main optical properties of transition metal ions (3d" outer electronic configuration), trivalent rare earth ions (4f 5s 5p outer electronic configuration), and color centers, based on the concepts introduced in Chapter 5. These are the usual centers in solid state lasers and in various phosphors. In addition, these centers are very interesting from a didactic viewpoint. We introduce the Tanabe-Sugano and Dieke diagrams and their application to the interpretation of the main spectral features of transition metal ion and trivalent rare earth ion spectra, respectively. Color centers are also introduced in this chapter, special attention being devoted to the spectra of the simplest F centers in alkali halides. 

In spite of the fact that in alkali vapors, which contain about 1 % diatomic alkali-molecules at a total vapor-pressure of 10 torr, the atoms cannot absorb laser lines (because there is no proper resonance transition), atomic fluorescence lines have been observed 04) upon irradiating the vapor cell with laser light. The atomic excited states can be produced either by collision-induced dissociation of excited molecules or by photodissociation from excited molecular states by a second photon. The latter process is not improbable, because of the large light intensities in the exciting laser beam. These questions will hopefully be solved by the investigations currently being performed in our laboratory. 

Polarized Raman spectra from the alkali fluorides LiF, NaF and CsF habe been observed with argon laser excitations by Evans and Fitchen 09). These spectra are of interest as an extreme test of lattice dynamics theories and polarizability models. 

The author also studied the possibility of enhancing the electron density and temperature of an alkali-seeded plasma by pumping the resonance lines of the alkali atoms with a suitably tuned laser 283)... 

The development of matrix-assisted laser desorption ionization (MAEDI) has advanced the entire field of mass spectrometry. To use this ionization method, the sample is mixed into a matrix that absorbs the laser wavelength extremely well (approximately 10,000 1 matrix analyte) and the mixture is placed on a solid substrate. Absorption of the laser causes the matrix to explode, ejecting the intact, nonvolatile molecules of interest into the gas phase. Proton exchange or alkali metal attachment occurs in the gas plume and the ionized species can be detected. 

Keki, S., Deak, G., and Zsuga, M., Fragmentation study of rutin, a naturally occurring flavone glycoside cationized with different alkali metal ions, using post-source decay matrix-assisted laser desorption/ionization mass spectrometry, J. Mass Spectrom., 36, 1312, 2001. 

Despite these widespread applicahons, ILM is not equally well suited for all classes of analytes. Due to the need for increased laser energies/fluences for the ionizahon/desorption process, ILMs may only be of restricted suitability for some classes of analytes. For example for proteins, an extensive peak broadening caused potenhally by the combination of extended neutral losses (e.g., of ammonia or water) and alkali-ion-adduct formation can be observed. On the other hand, the increased tendency of the ILM to favor sodium and potassium adduct formation makes it ideally suited for the measurement of carbohydrates [38,40], whereas in proteomics, this tendency of adduct formahon is again an unwanted effect. 

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