Pulsed laser deposition of thin films has besides numerous advantages a major shortcoming which is the presence of particulates of various shapes and dimensions both on surface and inside obtained structures. Indeed, in many key technological applications the use of completely particulates free films is mandatory. We demonstrated that the origin of size and density of particulates depend on specific experimental conditions. Nevertheless, the proper choice of deposition conditions (i.e. ablating laser wavelength and fluence, target-collector separation distance, growing temperature, ambient gas nature and pressure) allows for the decrease under a certain extent of pollution with particulates, but not for their complete elimination. This lecture reports our successful attempts to obtain completely particulates free deposited structures using two synchronized pulsed laser sources. The first, UV laser source was used to ablate the target material. The second, IR laser system was directed parallel to the target surface. The role of the second laser was to heat and vaporize the particulates present in the tail of the plasma ablated by the pulsed UV laser source.
The B 2(Sigma) +->X2(Sigma) + violet band emission spectrum of CN following laser ablation of type I collagen was exploited for the estimation of the transient temperature of the plasma plume and consequently of the sample surface considering thermodynamic equilibrium. The temperature dependence upon experimental parameters, such as laser intensity and wavelength as well as delay of gated detection was obtained. The temperature was found to increase with increasing laser intensity and decrease with increasing gated time delay and laser wavelength.
The concept of a system for continuous express monitoring of coastal sea water areas is presented. According to the suggested concept, the monitoring system should consist, in general, of three parts, in which the key role should belong to laser devices: (1) shore-based lidar that performs continuous monitoring of water surface and sub-surface layer of water (and, possibly, of atmosphere) in the selected water area; (2) patrol boat equipped with submerged portable devices, including laser spectrometer with submerged optical fiber probe; (3) coastal laboratory equipped with devices for detailed (but express enough) analysis of water samples, specially chosen by the results of remote laser sensing and submerged device data. Some features of remote sensing by means of shore-based lidar are considered. The main feature is sliding incidence of laser beam to water surface. The coastal sea waters have much more complex and variable composition than open sea water. The possibilities of different versions of laser fluorimetry in diagnostics of organic compounds in coastal sea waters are analyzed.
Hydroxyl gas-phase reactions play a very important role in air pollution. For the majority of chemical compounds of the atmosphere, the reaction with OH radical s is an intermediate one, part of a long chain reaction. A laser photolysis-laser induced fluorescence technique has been sued to study OH reaction kinetics with dioxane. The apparatus consists of two synchronized pulsed laser systems, a six cross flow/steady gas reactor, a photomultiplier for LIF detection and control electronics. The first laser is used for the production of OH radicals by photolysis. The second laser provides a probe-beam which excites the OH radical electronically. Then, the relative population of OH radicals is monitored time-resolved by laser induced fluorescence. All experiments are performed under pseudo- first order kinetic conditions. The major advantages of this technique are: (1) Capability to measure OH reaction kinetics over an extended temperature range, with different reactants using the same apparatus. (2) Generation of a clean source of OH radicals. (3) Capability of atmospheric pressure measurements. (4) Micro-scale simulation of atmospheric reactions.
The increasing need for the recording and monitoring of the marine pollution, as well as the disadvantages usually presented by the conventional methods to qualitatively and quantitatively determine the pollutants in the marine environment, have led to the development of a new method, which is based on the technique of laser induced fluorescence combined with the use of optical fibers. In this work, we present the basic principle of the method and its improvement referred to the appropriate selection of the wavelength excitation: this permits the qualitative determination of gasoline and jet-oil in water. Furthermore, based on the different life-times, we applied the method of time-resolved spectroscopy and succeeded in identifying anthracene and pyrene, in a mixture of both aromatic compounds, despite their spectral overlap and the weak fluorescence of pyrene.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.