0000000000113091
AUTHOR
B. Lavorel
Temperature measurement in gas mixtures by femtosecond Raman-induced polarization spectroscopy
European Conference on Nonlinear Optical Spectroscopy (ECONOS) MAR 30-APR 01, 2003 BESANCON, FRANCE; The potential of femtosecond Raman-induced polarization spectroscopy (RIPS) for the simultaneous determination of temperature and concentrations was investigated. These measurements were related to the rotational time response of the molecular gas mixture, which was measured as a function of the pump-probe time delay. The change of the polarizability anisotropy with respect to the vibrational levels was taken into account. The results of temperature measurements in pure CO2 showed good agreement with the values obtained by a thermocouple. The RIPS technique was also applied to a CO2-N2 gas m…
Study of Collisional Effects on Band Shapes of the v1/2v2 Fermi Dyad in CO2 Gas with Stimulated Raman-Spectroscopy .1. Rotational and Vibrational-Relaxation in the 2v2 Band
0021-9606
Laser induced molecular alignment of ethylene
Talk given by O. Faucher
Measurements of Collisional Line Widths in the Stimulated Raman Q-Branch of the v1 Band of Silane
0377-0486; Self-broadened widths of 28SiH4 in the v1 Q-branch have been measured at room temperature (295 K) using high-resolution stimulated Raman spectroscopy. These collisional widths have been obtained by fitting a superposition of Voigt profiles to the experimental spectra in the pressure range 28-154 Torr. No evidence for line mixing within the tetrahedral components of a Q(J) line has been found. The line broadening coefficients for J up to 13 depend weakly on the rotational quantum number. The mean value is 103.7 x 10(-3) cm-1 atm-1.
La molécule d'éthylène soumise à des impulsions laser femtosecondes : spectroscopie rotationnelle et alignement
Talk given by B. Lavorel
A direct study of the vibrational bending effect in line mixing: The hot degenerate 11(1)0<-01(1)0 transition of CO2
0022-4073; The study of the isotropic Raman Q-branch of a hot band Pi <-- Pi allows one to establish a direct connection between the vibration-rotation angular momentum coupling and the resulting spectra. Due to the l-doubling, the Q-branch is split into two subbranches characterized by either even or odd rotational quantum number j. The vibrational bending reduces the rotational transfer rates inside each of these subbranches by a factor of about two and induces an inter-subbranch coupling. The expected propensity rule towards conservation of the parity index for high rotational levels is well observed. Calculated spectra are in excellent agreement with CARS experiments for the nu(1) + nu(…
Wavelengths Measurements of Continuous Wave Lasers with a Wavemeter - Applications to High-Resolution Raman-Spectra Calibration
0150-536X
Study of Rotational Relaxation Fitting Laws from Calculation of SRS N2 Q-Branch
0301-0104
Relative line intensity measurement in absorption spectra using a tunable diode laser at 1.6 um: application to the determination of (13CO2)/(12CO2) isotope ratio
0946-2171; The measurement of relative intensities in CO2 combination bands spectrum is performed using wavelength modulation spectroscopy (WMS) and a DFB (distributed feedback) diode laser operating at 1.6 mum. The diode laser is stabilized with an external Fabry-Perot interferometer and absorption spectroscopy is performed in a multipass gas cell. A spectrum containing spectral lines of both 13CO2 and 12CO2 isotopic species is recorded. The variation of laser power during frequency scanning and the line shape are taken into account to accurately extract line intensities from experimental data. The isotopic concentration ratio is deduced from the intensity ratio. Both ratios are measured w…
Accurate Spectroscopic Constants of Nitrogen Determined from Stimulated Raman Spectra of the Fundamental and 1st Hot Bands
0377-0486; Nitrogen specta of the Q-branch of the fundamental and the first hot bands were recorded with a high-resolution stimulated Raman spectrometer at atmospheric pressure and ca. 1300 K. The absolute frequencies of the Raman lines were measured with high accuracy, leading to a refinement of spectroscopic constants. A temperature estimation was also performed from the Raman intensities.
Collisional Line Broadening and Line Shifting in N2-CO2 Mixture Studied by Inverse Raman-Spectroscopy
0301-0104
High-Resolution Nonlinear Raman-Spectroscopy of Small Molecules
0022-2860
Collisional shifting and broadening coefficients for the rovibrational anisotropic lines of the v1/2v2 Fermi dyad in CO2 gas studied by stimulated Raman spectroscopy
0377-0486; High-resolution stimulated Raman spectroscopy was applied to the study of collisional broadening and shifting for rovibrational anisotropic Raman Lines of the Fermi dyad of molecular carbon dioxide, The O(J) lines of the v1 band and the S(J) lines of the 2v2 band were recorded at 295 K. The pressure-induced line shifts were obtained and compared with the overall shift of the high-density Raman Q-branch, A rotational quantum number dependence of the rovibrational line broadening coefficients was observed. The experimental line broadening coefficients were used in order to check the ability of two theoretical methods (random phase approximation and sum rule) for calculating the lin…
Collisional Broadening, Line Shifting, and Line Mixing in the Stimulated Raman 2-v2 Q-Branch of CH4
0021-9606; Self-, argon-, and helium-broadening coefficients have been measured for 13 lines in the 2v2 Raman Q branch of CH4 using stimulated inverse Raman spectroscopy. The linewidths clearly show the symmetry-state dependence characteristic of pressure broadening, and inelastic processes in general, involving spherical-top molecules. Pressure-induced line shifts have also been measured for these features in pure methane. The pressure-shift coefficients do not display the symmetry-state dependence found for the linewidths. By applying the Rosenkranz perturbation treatment to a pair of collisionally mixed lines, we have been able to obtain an estimate of individual state-to-state contribut…
Study of the Density and Temperature Dependences of the Vibrational Raman Transition in Compressed Liquid N2
0021-9606; Accurate values of linewidth and line shift in the isotropic vibrational Raman spectrum of compressed liquid N2 have been obtained by using inverse Raman spectroscopy. Experiments have been performed for eight isotherms, from the normal boiling point to the critical point temperatures of N2, the number density varying between the value on the coexistence line, and the maximum value of 2.1 x 10^22 cm-3. Minima of the linewidth have been observed above 86 K, showing the increasing influence of vibration-rotation coupling (motional narrowing) competing with the broadening due to pure vibrational dephasing. Moreover, for the first time, maxima of the red line shifts have been found, …
Control of rotational wave packets using phase-modulated ultrashort laser pulses
8th Colloquium on Lasers and Quantum Optics SEP 03-05, 2003 Toulouse, FRANCE INSA Toulouse, Univ Paul Sabatier, CNRS, CNES, DGA, ONERA, Minist Rech & Nouvelles Technologies, Soc Francaise Opt, Soc Francaise Phys
High-Resolution Nonlinear Rotation-Vibrational Raman-Spectroscopy of Gases
0033-4545
Dunham Coefficients of 14N2 from CARS Measurements of High Vibrational-States in a Low-Pressure Discharge
0377-0486
Control and optimization of postpulse molecular alignment by shaped laser pulse
Talk given by O. Faucher; International audience
Raman Intensities of the ν1/ν3 Dyad of 28SiH4
0022-2852; The stimulated Raman spectrum of 28SiH4 has been recorded in the ν1/ν3 region between 2182 and 2190 cm(-1). The intensities of the Raman transitions were modeled using a dyad scheme for the two interacting bands with a first-order polarizability expansion. The involved polarizability parameter; have been adjusted to fit about 800 measured intensities of transitions reaching upper states up to J = 18. The resulting standard deviation is about 10%. (C) 1994 Academic Press, Inc.
Laser-induced field-free alignment of OCS molecule
International audience; We investigate the dynamical alignment of jet-cooled OCS molecules induced by a short laser pulse. The alignment is measured through the orientational contribution of the optical Kerr effect using a second weak laser pulse as a probe. Maximum alignment is observed at conditions close to saturation of ionization. The results are analysed with a quantum mechanical model solving for the rotational dynamics.
Rotational Relaxation of Nitrogen in Ternary Mixtures N2-CO2-H2O - Consequences in Coherent Anti-Stokes-Raman Spectroscopy Thermometry
0021-9606; The influence of CO2 and H2O on the rotational relaxation processes of N2 in ternary mixtures N2-CO2-H2O is investigated. The efficiency of these perturbers is responsible for significant modifications of the state-to-state relaxation rates and broadening coefficients. Flame data are well reproduced by taking into account these modifications. The role of these minor species in the determination of temperatures in premixed flames is analyzed. The present relaxation model allows us to understand why the discrepancy between observed and calculated coherent anti-Stokes Raman spectroscopy (CARS) spectra in flames is sometimes resolved by empirically adding a dephasing component to pur…
Enhancement of Sensitivity in High-Resolution Stimulated Raman-Spectroscopy of Gases - Application to the 2v2 (1285 cm-1) Band of CO2
0377-0486