RESUMEN
An efficient and simple and convenient technique for transparent samples thickness measurements by Raman spectroscopy is suggested. The elastic scattering can be effectively used for sample border indication if the refractive index changes more than 3%, while it fails to detect an ice-to-water border of floating ice. The alternative is to use Raman spectroscopy to detect the interface between different layers of transparent materials. The difference between the Raman spectra of poly methyl methacrylate (PMMA) and water, and between ice and liquid water were employed to locate the PMMA-water and ice-water interfaces, while elastic scattering was used for air-solid surface detection. This approach yields an error of 2%-5% indicating that it is promising to express a remote and noninvasive thickness measurement technique in field experiments.
RESUMEN
A compact Raman LIDAR system with a spectrograph was used for express ice thickness measurements. The difference between the Raman spectra of ice and liquid water is employed to locate the ice-water interface while elastic scattering was used for air--ice surface detection. This approach yields an error of only 2 mm for an 80 mm thick ice sample, indicating that it is a promising express noncontact thickness measurements technique in field experiments.
RESUMEN
A compact Raman lidar system for remote sensing of sea and drifting ice was developed at the Wave Research Center at the Prokhorov General Physics Institute of the Russian Academy of Sciences. The developed system is based on a diode-pumped solid-state YVO(4):Nd laser combined with a compact spectrograph equipped with a gated detector. The system exhibits high sensitivity and can be used for mapping or depth profiling of different parameters within many oceanographic problems. Light weight (â¼20 kg) and low power consumption (300 W) make it possible to install the device on any vehicle, including unmanned aircraft or submarine systems. The Raman lidar presented was used for study and analysis of the different influence of the open sea and glaciers on water properties in Svalbard fjords. Temperature, phytoplankton, and dissolved organic matter distributions in the seawater were studied in the Ice Fjord, Van Mijen Fjord, and Rinders Fjord. Drifting ice and seawater in the Rinders Fjord were characterized by the Raman spectroscopy and fluorescence. It was found that the Paula Glacier strongly influences the water temperature and chlorophyll distributions in the Van Mijen Fjord and Rinders Fjord. Possible applications of compact lidar systems for express monitoring of seawater in places with high concentrations of floating ice or near cold streams in the Arctic Ocean are discussed.
RESUMEN
We carried out a remote study of ship wakes by optical methods. Both Mie and Raman scattering signals and their evolution were simultaneously recorded by gated detector (intensified CCD). The Mie scattering signal was detectable within 1 min after water disturbance by a high-speed boat. According to an approximation of experimental data, Raman signal fluctuations can be detected for a much longer time under the same conditions. We have demonstrated that Raman spectroscopy is substantially more sensitive to water perturbation compared to conventional acoustic (sonar) technique and can be used for ship wake detection and monitoring.
