Direct laser-induced

So far we have discussed various studies on the relaxation of the population bPo of excited state rovibrational levels in elastic and inelastic collisions. To this end the intensity of fluorescence was measured in one or the other way. If an analysis of the state of polarization of the radiation is performed, one may obtain information on the behavior of alignment and orientation of the molecular angular momenta in elastic and inelastic collisions. If we register, under collisional conditions, the polarization properties of a directly laser-induced rovibrational level of the molecule, then, according to (2.35) and (2.39), it is possible to determine the rates... 

The Direct Laser-Induced Temperature-Jump Method... 

One way to effect a rapid change in the interfacial temperature is by impinging a pulsed laser beam directly onto the electrode [66 71] we will refer to this method as the direct laser-induced temperature-jump method (DLIT). DLIT has several fundamental problems ... 

DLIT Direct laser-induced temperature-jump method... 

Some recent advances in stimulated desorption were made with the use of femtosecond lasers. For example, it was shown by using a femtosecond laser to initiate the desorption of CO from Cu while probing the surface with SHG, that the entire process is completed in less than 325 fs [90]. The mechanism for this kind of laser-induced desorption has been temied desorption induced by multiple electronic transitions (DIMET) [91]. Note that the mechanism must involve a multiphoton process, as a single photon at the laser frequency has insufScient energy to directly induce desorption. DIMET is a modification of the MGR mechanism in which each photon excites the adsorbate to a higher vibrational level, until a suflBcient amount of vibrational energy has been amassed so that the particle can escape the surface. 

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... 

Different analytical techniques are used for detection of the elemental composition of the solid samples. The simplest is direct detection of emission from the plasma of the ablated material formed above a sample surface. This technique is generally referred to as LIBS or LIPS (laser induced breakdown/plasma spectroscopy). Strong continuous background radiation from the hot plasma plume does not enable detection of atomic and ionic lines of specific elements during the first few hundred nanoseconds of plasma evolution. One can achieve a reasonable signal-to-noise ra-... 

Current study in this area is prompted by laser-induced CVD of such volatile gold compounds, permitting direct laser writing in gold [155]. 

Direct laser-assisted myocardial revascularization (DMR) is an approved technique in the US, Europe, and parts of Asia to create numerous myocardial channels. This results in the induction of a massive inflammatory reaction, which in turn induces angiogenesis. The other FDA-approved pro-angiogenic therapy is the use of recombinant human platelet-derived growth factor (Regranex) for use in the treatment of diabetic neuropathic foot ulcer s. 

Direct Measurement of HO, in the Troposphere. Techniques to measure tropospheric concentrations of HO have been reviewed (O Brien Hard, submitted to Advances in Chemistry, 1991) so only a summary will be given here. The most extensively researched technique for [HO ] measurement in the troposphere is based on laser-induced fluorescence (LIF) of HO. This approach has been developed in many configurations directing the laser into the free atmosphere and collecting fluorescence back scatter (LIDAR) (105,106,107) LIF of air sampled at atmospheric pressure... 

Hard et al (reference 110, 125, and submitted to/. Geophys, Res. 1991) have developed a system for the chemical conversion of HO2 to HO via the reaction HO2 + NO —> HO -I- N02. The hydroxyl radical is then measured by their low-pressure laser-induced-fluorescence instrument. Their multi-sample-channel LIF PAGE system is thus capable of simultaneous measurements of [HO ] (directly) and [H02 ] (by conversion to HO ). 

George, L.A. Development of a Direct, Low Pressure, Laser-induced Fluorescence Technique for NO2, Ambient Measurements and Urban NO, Ph.D. Thesis, Portland State University Portland, OR, 1991,1-135. 

Fujikawa, T., Y. Nomura, Y. Hattori, T. Kobayashi, and M. Kanda, Analysis of cycle-by-cycle variation in a direct injection gasoline engine using a laser induced floures-cence technique. International Journal of Engine Research, 4(2) 143-154, 2003. 

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 target molecule C2S 111 was generated by laser-induced photolysis of matrix-isolated C3S2 110 or C3OS 112. Two of the three fundamental vibrations of 111 are observed directly at 1666.6 and 862.7 cm-1, and from an overtone and a combination vibration the position of the missing bending mode in the... 

Concentrations of OH and HO2 were determined, in situ, using Laser Induced Fluorescence (LIF) at low pressure, (FAGE technique). HO2 cannot be detected directly by LIF, and was converted to OH by titration with NO directly below the sampling nozzle. The detection limit for the FAGE instrument during SOAPEX-2, determined by calibration in the field, was 1.4 xlO5 molecule cm-3 for OH and 5.4x 105 molecule cm-3 for HO2. A description of the instrument, as set up in previous field campaigns and dur-... 

Webster and Weissburg (2001) visualized instantaneous versus time-averaged odor plumes by laser-induced fluorescence. The spatially varying plume at any particular point in time matters more to an animal than an average plume shape. The mean direction and speed of airflow may be relatively constant, but the animal may extract information from concentration differences on very small temporal and spatial scales. 

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