Laser physical studies

Long SR, Christesen SD. 1989. Laser ionization studies of organophosphonates and phosphorus oxide radicals. Journal of Physical Chemistry 93(18) 6625-6628. 

In all of these applications, the emphasis to date has been on the use of lasers to study chemically and physically well characterized systems, that is, simple molecules in the gas phase, or in ordered phases such as molecular crystals, or in cryogenic matrices. There are exceptions to this statement, but the basic fact is that the great strides in chemical applications of lasers have been made by the chemical physics and analytical chemistry communities and largely ignored by inorganic, organic, and biological chemists. 

The problem of quenching alkali resonance radiation in E-VR energy-transfer collisions with simple molecules is important as a model case for basic processes in photochemistry and serves its own right for a variety of practical applications, such as in laser physics. It has been studied for many years in the past, but only recent progress has led to information of the final internal energy of the molecule. In particular, crossed-beam experiments with laser-excited atoms allow a detailed measurement of energy-transfer spectra. There can be no doubt that the curve-crossing... 

Summary. In saturated laser fluorescence studies of sodium and lithium in a series of fuel rich H2/02/N2 flames there is evidence for the involvement of laser induced chemical reactions with H20 and H2. Although their reactive probabilities have been shown to be small relative to the corresponding physical quenching interactions they are still sufficient to establish significant... 

Physical Studies of Optically Pumped Dimer Lasers... 

Pancho Tzankov studied laser physics at Sofia University, Bulgaria, and received his Ph.D. in physical chemistry from the Technical University of Munich, Germany. He is now a postdoctoral fellow at the Max Bom Institute in Berhn, Germany. His research activities involve development of new nonhnear optical parametric sources of ultrashort pulses and their apphcation for time-resolved spectroscopy. 

In our laboratory a series of laser-microwave studies has been performed on metastable and short-lived excited states of heliumlike Li. Singly ionized lithium, like all members of the two-electron He isoelectronic sequence, belongs to the fundamental systems in atomic physics. Many of its spectroscopic and quantum-mechanical characteristics have been calcu-... 

Fundamental quantities, such as wavelengths and transition probabilities, determined using spectroscopy, for atoms and molecules are of direct importance in several disciplines such as astro-physics, plasma and laser physics. Here, as in many fields of applied spectroscopy, the spectroscopic information can be used in various kinds of analysis. For instance, optical atomic absorption or emission spectroscopy is used for both qualitative and quantitative chemical analysis. Other types of spectroscopy, e.g. electron spectroscopy methods or nuclear magnetic resonance, also provide information on the chemical environment in which a studied atom is situated. Tunable lasers have had a major impact on both fundamental and applied spectroscopy. New fields of applied laser spectroscopy include remote sensing of the environment, medical applications, combustion diagnostics, laser-induced chemistry and isotope separation. 

In this chapter we will discuss the general principles of lasers and study the most important tunable lasers that are of primary spectroscopic interest. Since many tunable lasers are optically pumped by fixed-frequency lasers we will also describe the most useful types of such lasers. For a more thorough account of laser physics we refer the reader to standard textbooks [8.1-10]. 

TV. Meglinsky, A.N. Bashkatov, E.A. Genina, D.Yu. Churmakov, and V.V. Tuchin, Study of the Possibility of Increasing the Probing Depth by the Method of Reflection Confocal Microscopy upon Immersion Clearing of Near-Surface Human Skin Layers, Laser Physics, vol. 13, no.l, 2003, pp. 

Experimental studies are, undoubtedly, what is needed mostly in the field of stochastic phenomena in Chemistry at the present time. Chemical systems constitute in this respect an ideal substratum, thanks to the possibility to control their characteristic parameters over wide ranges of values, and to excite a large number of closely-packed macroscopic modes (which is much more difficult in laser Physics where, nevertheless, there is ample evidence about the importance of fluctuations). We are convinced that in the coming years we will witness important developments in this field. 

The theory of nonlinear complex systems [6] has become a successful and widely used tool for studying problems in the natural sciences—from laser physics, quantum chaos, and meteorology to molecular modeling in chemistry and computer simulations of cell growth in biology. In recent years, these tools have been used also— at least in the form of scientific metaphors —to elucidate social, ecological, and political problems of mankind or aspects of the working of the human mind. 

Z. Han, Y. Katsumura, et al., Effect of Temperature On the Absorption Spectra of the Solvated Electron in 1-Propanol and 2-Propanol Pulse Radiolysis and Laser Photolysis Studies at Temperatures Up to Supercritical Condition, Radiation Physics and Chemistry, Vol. 77, 409 15 (2008)... 

Many of the fiindamental physical and chemical processes at surfaces and interfaces occur on extremely fast time scales. For example, atomic and molecular motions take place on time scales as short as 100 fs, while surface electronic states may have lifetimes as short as 10 fs. With the dramatic recent advances in laser tecluiology, however, such time scales have become increasingly accessible. Surface nonlinear optics provides an attractive approach to capture such events directly in the time domain. Some examples of application of the method include probing the dynamics of melting on the time scale of phonon vibrations [82], photoisomerization of molecules [88], molecular dynamics of adsorbates [89, 90], interfacial solvent dynamics [91], transient band-flattening in semiconductors [92] and laser-induced desorption [93]. A review article discussing such time-resolved studies in metals can be found in... 

The development of ultrafast spectroscopy has paralleled progress in the teclmical aspects of pulse fomiation [Uj. Because mode-locked laser sources are tunable only with diflSculty, until recently the most heavily studied physical and chemical systems were those that had strong electronic absorption spectra in the neighbourhood of conveniently produced wavelengths. 

The microscopic understanding of tire chemical reactivity of surfaces is of fundamental interest in chemical physics and important for heterogeneous catalysis. Cluster science provides a new approach for tire study of tire microscopic mechanisms of surface chemical reactivity [48]. Surfaces of small clusters possess a very rich variation of chemisoriDtion sites and are ideal models for bulk surfaces. Chemical reactivity of many transition-metal clusters has been investigated [49]. Transition-metal clusters are produced using laser vaporization, and tire chemical reactivity studies are carried out typically in a flow tube reactor in which tire clusters interact witli a reactant gas at a given temperature and pressure for a fixed period of time. Reaction products are measured at various pressures or temperatures and reaction rates are derived. It has been found tliat tire reactivity of small transition-metal clusters witli simple molecules such as H2 and NH can vary dramatically witli cluster size and stmcture [48, 49, M and 52]. 

The crystalline mineral silicates have been well characterized and their diversity of stmcture thoroughly presented (2). The stmctures of siHcate glasses and solutions can be investigated through potentiometric and dye adsorption studies, chemical derivatization and gas chromatography, and laser Raman, infrared (ftir), and Si Fourier transform nuclear magnetic resonance ( Si ft-nmr) spectroscopy. References 3—6 contain reviews of the general chemical and physical properties of siHcate materials. 

Generally, the more intense the available beam source, the shorter the time scales, the weaker the heterogeneities, and the longer the distances that can be probed by a scattering method. Hence, there is a strong drive to utilize high-powered lasers, synchrotrons, and intense neutron somces in research on surfaces, interfaces, and microstmctures. This is particularly tme in the study of liquid materials and of systems that undergo rapid physical transformations or chemical reactions. 

SeUen, DB, Laser Light Scattering Study of Polyacrylamide Gels, Journal of Polymer Science Part B Polymer Physics 25, 699, 1987. 

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