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A novel technique for coherent anti-Stokes Raman spectroscopy (CARS) measurements in multiple points is presented. With a system of cylindrical lenses, each laser beam is split into several focused beams, yielding separate planar boxcars configurations. Spectrally resolved CARS signals are detected at different heights on the CCD chip. With dual-broadband rotational CARS the setup is demonstrated
Pure rotational coherent anti-Stokes Raman scattering (CARS) experiments have been performed in acetylene for temperatures ranging from 294 to 582 K, and in mixtures of acetylene and nitrogen in the mole fraction range of 0.06-0.32 for acetylene at room temperature. The experimental spectra are evaluated by a least-square fitting to libraries of theoretically calculated spectra using two different
Rotational CARS (Coherent anti-Stokes Raman Spectroscopy) was used to measure temperature and relative oxygen concentrations in the exhaust gas of a catalytic combustor. This laser technique has the general advantages of such techniques, i.e. possibility of performing in-situ measurements with high spatial and temporal resolution, and non-intrusiveness. Profiles of temperature and oxygen concentra
A common experimental problem with rotational coherent anti-Stokes Raman spectroscopy (CARS) is undesired spectral interference that is due to stray light from the primary laser beams. Also, for the most developed approach, dual-broadband rotational CARS, practical measurements often suffer from stray light interference from the narrow-band laser, inasmuch as the CARS signal is produced inherently
The accuracy and precision of oxygen concentration and temperature measured by dual-broadband rotational Coherent Anti-Stokes Raman Spectroscopy (CARS) were investigated in nitrogen-oxygen mixtures at atmospheric pressure and temperatures between 290 and 1410 K. The relative standard deviation of temperatures evaluated from pure oxygen rotational CARS spectra was found to be around 5%, and the mea
Strategies for spatially resolved soot volume-fraction measurements have been investigated in sooting laboratory flames with known soot characteristics. Two techniques were compared: Laser-Induced Fluorescence in C2 from Laser-Vaporized Soot (LIF(C2)LVS), and Laser-Induced Incandescence of soot (LII). The LII signal is the increased temperature radiation from soot particles which have been heated
This is the first report of pure rotational coherent anti-Stokes Raman spectroscopy (CARS) measurementsin an internal combustion (IC) engine. Single-shot, dual-broadband rotational CARS (DB-RCARS) spectra were recorded both prior to ignition and in the postcombustion gases. From these spectra, both temperature and relative oxygen concentrations were evaluated. The pressure was registered simultane
Laser diagnostic techniques have during the last decade been successfully applied for diagnostics of combustion processes. The main advantages with these techniques are that they are inherently non-intrusive and that spatially as well as temporally resolved information can be achieved. The current paper will exemplify two different laser spectroscopic techniques. Laser-Induced Fluorescence (LIF),
Coherent anti-Stokes Raman scattering of pure rotational transitions, rotational CARS, is demonstrated as an efficient method for temperature determination in sooting flames. The dual broadband CARS approach was used to measure temperature profiles in premixed, sooting ethylene flames at atmospheric pressure by probing the nitrogen gas. The recorded spectra were of equally high quality in non-soot
Swan band emission of C2. which had been produced and excited (d3∏x←a 3∏u, Δ v = 0) by focused, tunable, visible laser radiation, was studied in sooting ethylene flames. The C2signal from the sooting regions of the flames was found to be proportional to the measured volume fractions of soot, indicating laser-vaporized soot to be the source of the signal, and as such it can be used as a diagnostic
Laser-induced fluorescence from carbon atoms, excited at the two-photon resonances around 280 nm, has been detected in fuel-rich hydrocarbon flames together with Swan band emission from the C2 radical, which was non-resonantly excited at the same wavelengths. The emission from the C atom and from the C2 molecule exhibited several similarities, indicating a possible common photo-chemical origin.
Recent developments in rotational CARS thermometry and critical issues when comparing vibrational and rotational CARS thermometry are described. In particular, the development of dual broadband rotational CARS and the noise characteristics of this approach are emphasized. The difficulty with unambiguous temperature determination in vibrational CARS with unknown parameters, in particular the nonres
High elevations of groundwater at Mosul city is a very big problem and may cause mass destructions to the environment, health and building foundations due to the closing of groundwater near ground surface. From field investigations for 43 large diameter shallow wells, the water elevations were measured 14 times through 7 months. Utilizing raster based GIS operations with automated parameter estima
A model for calculating the noise in nonlinear optical processes arising from (nonquantum) stochastic fluctuations (mode beating) in and between the lasers participating in the nonlinear interaction has been previously developed. Assuming that all individual laser mode phases and laser modes are (statistically) independent (Gaussian statistics) and that the nonlinear interaction can be expressed a
