Ab Initio Calculations and High-Resolution Spectroscopy of the Bending Pentad of SiH2D2 in the 10–16 um Region

International audience; The SiH2D2 asymmetric top has nine vibrational modes, five of them forming a pentad strongly perturbed by Coriolis interactions. High-level ab initio calculations of SiH2D2 have been performed which yield numerous spectroscopic parameters related to the harmonic and anharmonic force fields. The bending pentad comprising v4(A1), v7(B1), v5(A2), v9(B2), and v3(A1) has been studied by high-resolution Fourier transform spectroscopy; the region 600 –1050 cm-1 has been investigated with a resolution of ca. 4 x 10-3 cm-1. Raman BOXCARS spectroscopy has been used for the infrared inactive v5 band. The Raman apparatus function was 0.0054 cm-1. Assignments of about 4000 transi…

Experimental investigation of the optical Kerr effect at large laser intensity: impact on the propagation of a short and intense laser pulse

Talk given by O. Faucher; International audience

Molecular alignment in CO2 mixtures induced by a short nonresonant intense pulse : effect of collisional relaxation

Quantifying alignment with transient grating technique

Higher-order Kerr terms allow ionization-free filamentation in gases

Talk given by J. Kasparian; International audience; Higher-order nonlinear indices, rather than plasma, provide the main defocusing contribution to filamentation in gases at 800 nm. Developing generalized Miller formulae, we discuss the generality of this as a function of the laser wavelength

Field-free molecular alignment of ethylene

Talk given by O. Faucher; International audience

Stratégies de contrôle pour la manipulation spatiale de molécules

Talk given by E. Hertz; National audience

Observation d'effets Kerr d'ordres élevés (HOKE) dans les gaz

Talk given by O. Faucher; National audience

Analysis of Infrared and Raman-Spectra of 116SnH4 in the 1900 cm-1 Region - Study of the 1000, 0010 Interacting States

0022-2852

Optical rotary power at the resonance of the terbium F-7(6)-> D-5(4) line in terbium gallium garnet

0038-1101; The Tb3+ absorption line F-7(6)-->D-5(4) Of the Terbium Gallium Garnet crystal is excited with an Argon ion laser. The Verdet's constant has been determined and reported against 1/lambda(2), showing no significant resonant behaviour at absorption resonance. The utility and the constraints of the crystal at this particular resonant wavelength are pointed out. (C) 1998 Elsevier Science Ltd. All rights reserved.

Stimulated Raman-Spectroscopy as the Essential Tool for Studying Collisional Effects - Application to Combustion

3rd International Conference: Laser M2P DEC 08-10, 1993 LYON, FRANCE FEDERAT LASER CTR, RHONE ALPES REG; The main purposes of this paper are to give an overview of coherent Raman techniques with a particular emphasis on Stimulated Raman Spectroscopy (SRS) because this process can be considered as an essential tool for investigating collisional processes.

Alignement moléculaire sous impulsions laser ultracourtes

Talk given by O. Faucher; National audience

High-Resolution Nonlinear Raman-Spectroscopy in Gases

0377-0486; The resolution in the Raman spectra of gases has been greatly improved by the development of the different methods of non-linear Raman scattering. When two laser beams, one of which has a tunable frequency, are focused in a sample, a stimulated Raman process occurs as soon as the frequency difference between the two lasers is equal to a Raman-active rovibrational or rotational transition frequency. The Raman resonance can be detected in different ways: by coherent anti-Stokes Raman scattering (CARS) or the corresponding Stokes process (CSRS), by a gain in one of the beams (stimulated Raman gain spectroscopy, SRGS) or a loss in the other (inverse Raman spectroscopy, IRS), or even …

High-Resolution Photoacoustic Raman-Spectroscopy of Gases

0377-0486; A high-resolution photoacoustic Raman spectroscopy experiment is described. The resolution achieved by using two single-mode pulsed lasers is about 0.0054 cm-1 (full width at half maximum intensity). The experiment was tested first on the v1/2v2 bands of CO2 and gave an increase of at least about one order of magnitude in the signal-to-noise ratio with respect to stimulated Raman spectroscopy at low pressure (ca. 10 Torr almost-equal-to 13 kPa). The sensitivity is also demonstrated by the study of the weak hot band v1 + v2 - v2 of CO2. In both cases, the experimental line shape is well reproduced by taking into account Doppler and collisional effects. A comparison with CARS spect…

Line mixing in the stimulated Raman spectrum of the ν1 band of SiH4 at 0.4-1.0 bar

International audience; The stimulated Raman spectrum of the ν1 band of SiH4 has been recorded at 0.4 and 1.0 bar pressures and room temperature. Line mixing of the fine structure components of this spectrum was taken into account in a calculated profile by considering coupling between the main transitions and using a simple model (strong collision model, SCM) for the relaxation matrix.

A Powerful Tool to Study Collisional Phenomena and for Combustion Applications - the High-Resolution Stimulated Raman-Spectroscopy

0302-0738

Determination of concentrations in ternary and quaternary molecular gas mixtures using femtosecond Raman spectroscopy

European Conference on Nonlinear Optical Spectroscopy MAR 18-19, 2002 VILLIGEN, SWITZERLAND; Measurements of concentrations in gas mixtures of three and four molecular components are presented. They rely on a femtosecond time-resolved pump-probe technique based on Raman-induced polarization spectroscopy. The rotational time response of the molecular gas mixture is measured as a function of the pump-probe time delay. No selective frequency tunability is needed as the molecular rotational spectra are excited within the laser bandwidth. The results obtained from experiments performed at room temperature in N2O-CO2-N2 and N2O-CO2-O2-N2 mixtures are presented and the accuracy of the method is di…

Study of Collisional Effects on Band Shapes of the v1/2v2 Fermi Dyad in CO2 Gas with Stimulated Raman-Spectroscopy .2. Simultaneous Line Mixing and Dicke Narrowing in the v1 Band

0021-9606

Line Coupling Effects in Anisotropic Raman Q-Branches of the ν1/2ν2 Fermi Dyad in CO2

0021-9606; The generalized energy corrected sudden model is used to calculate the Q branch of the anisotropic coherent anti-Stokes Raman scattering spectra corresponding to the v1 and 2v2 transitions of the Fermi dyad of CO2. The corresponding experimental spectra have been recorded for pressures leading to a consistent overlapping between the rotational components. This leads to a new experimental evaluation of the relaxation time of the second-order tensor associated with the rotational angular momentum. The value is in excellent agreement with that already obtained from the study of the infrared absorption Q branch, the Rayleigh scattering, and the viscomagnetic effect. (C) 1995 American…

Pressure and Temperature Evolution of Fundamental Vibrational Transition of Liquid Nitrogen Using Inverse Stimulated Raman Spectroscopy

CONF ON LASERS AND QUANTUM OPTICS ( COLOQ-1 ) SEP 11-13, 1989 VILLETANEUSE, FRANCE SOC SPECTRA PHYS, SOC OPLILAS, SOC PHOTON SCI INSTRUMENTS, SOC PHOTONET COHERENT SCI, SOC QUANTEL Suppl. 2

Stimulated Raman-Spectroscopy of the Q-Branch of Nitrogen at High Pressure - Collisional Narrowing and Shifting in the 150-6800 Bar Range at Room Temperature

0026-8976; The Raman Q branch of N2 has been recorded at room temperature in the pressure range 150-6800 bar, which corresponds to densities from 135 to 800 amagat. In this domain, the Raman Q branch profile is mainly determined by the well-known collisional narrowing. The experimental data have been obtained by means of a high resolution stimulated Raman spectrometer. The linewidth and line shift of the band have been accurately measured as functions of the density, and their density dependences have been fitted by polynomials. The minimum of the linewidth and the maximum of the red shift have been clearly observed at respectively 735.8 and 532.3 amagat. The lineshape was found to be Loren…

Rotationally Inelastic Rates for N2-N2 System from a Scaling Theoretical Analysis of the Stimulated Raman Q-Branch

0021-9606

Higher-order Kerr terms allow ionization-free filamentation in gases

International audience; We show that higher-order nonlinear indices (n4 , n6 , n8 , n10) provide the main defocusing contribution to self-channeling of ultrashort laser pulses in air and Argon at 800 nm, in contrast with the previously accepted mechanism of filamentation where plasma was considered as the dominant defocusing process. Their consideration allows to reproduce experimentally observed intensities and plasma densities in self-guided filaments.

High-Resolution Stimulated Raman-Spectroscopy with a 3 MHz Accuracy Wavemeter

0302-0738

Mesure de l'effet Kerr d'ordre élevé des constituants de l'air

Talk given by V. Loriot

Study of Collisional Effects on Band Shapes of the ν1/2ν2 Fermi Dyad in CO2 Gas with Stimulated Raman-Spectroscopy .3. Modeling of Collisional Narrowing and Study of Vibrational Shifting and Broadening at High-Temperature

0021-9606; High resolution stimulated Raman spectra (SRS) of the ν1/2ν2 Fermi dyad of CO2 have been recorded in the 0.4-22. amagat density range at 700 K and in the 0.6-16 amagat density range at 900 K. The data have been successfully analyzed with a theoretical model taking into account both rotational line mixing through the energy corrected sudden-polynomial (ECS-P) law for the relaxation matrix and vibrational line broadening gamma(v) and line shifting delta(v). The two vibrational parameters have been accurately determined from fit to the experimental spectra. These new high temperature data together with previous data obtained at 295 and 500 K [B. Lavorel et al., J. Chem. Phys. 93, 21…

Preliminary-Analysis of the Pentad of 13CH4 from Raman and Infrared-Spectra

0022-2852

Self-Density Frequency-Shift Measurements of Raman N2 Q-Branch Transitions

0030-4018

Determination of Temperature by Stimulated Raman Scattering of Molecular Nitrogen, Oxygen, and Carbon-Dioxide

0721-7269; We have determined the temperature from SRS spectra of N2-N2, N2-CO2, O2-O2, and CO2-CO2 recorded in wide pressure and temperature ranges. The fitting procedure takes simultaneously into account the Dicke effect and motional narrowing. We have quantified the accuracy of the MEG and ECS-P models for rotational relaxation. The temperature extracted from each model is compared with thermocouple measurements. The influence of vibrational broadening and shifting is discussed in detail.

Study of Collisional Broadening in Oxygen Lines by High-Resolution Coherent Anti-Stokes Raman-Spectroscopy

0008-4204

Laser induced field-free molecular alignment

Talk given by O. Faucher; International audience

Nonlinear Raman Spectroscopy in Gases

0022-2860; Recent progress in high-resolution non-linear coherent Raman spectroscopy in the gas phase is reviewed. An instrumental spectral resolution of less than 100 MHz can be routinely achieved. It is limited by the convoluted linewidths of the lasers used for excitation and is of particular advantage in the gas phase, where the rotational structure of vibrational bands is to be resolved. It also allows the measurement of linewidths and line positions with an accuracy of 60 MHz when an appropriate wavemeter is used for calibration. After a short overview of the various techniques being used, examples of recent results of the evaluation of measurements on nitrogen, oxygen, carbon dioxide…

Negative and positive Kerr nonlinearity of air calibrated with transient molecular alignment

Talk given by O. Faucher; International audience; Nonlinear electronic Kerr index of the major air constituents has been measured up to high order terms using transient molecular alignment as a reference. Sign reversal associated to negative nonlinearity is observed above a pulse intensity of 26 TW/cm^.2

Study of ν1/ν3 interacting bands of silane : analysis of infrared and Raman spectra

International audience; The ν1/ν3 interacting bands of natural silane have been studied by Fourier transform spectroscopy and stimulated Raman spectroscopy, respectively, in the regions 2040–2320 and 2180–2187 cm−1. These data combined with available microwave observations have been analyzed using a reduced effective Hamiltonian developed through the fifth order for 28SiH4 and through the fourth order for 29SiH4 and 30SiH4. The observed infrared and Raman transitions have been very well reproduced with a standard deviation of about 0.0004 cm−1 for 28SiH4. Some anomalies in the Hamiltonian expansion have been found, but they did not perturb the analysis.

Fitting and scaling laws for high temperature Q branch collapse in the O2 stimulated Raman spectra in O2-H2O mixtures

0021-9606

Collisional Raman Linewidths of Nitrogen at High-Temperature (1700-2400 K)

0146-9592; New high-temperature measurements of collisional linewidths of the Roman Q branch of nitrogen have been performed at 1700-2400 K with stimulated Raman spectroscopy in a tungsten filament. We fitted these data together with previous data obtained in the 295-1500-K range to redetermine the parameters of the relaxation models used in coherent anti-Stokes Raman spectroscopy thermometry. The improvement in the accuracy of the temperature measurement has been checked. Semiclassical calculations of linewidths in the 1700-2400-K range agree with the experimental data and have been extended to even higher temperatures.

Inverse Raman-Spectrum of Cyclopropane in the Region 3000-3050 cm-1

International audience

Density and Temperature-Dependence of the Isotropic Vibrational Raman Spectrum of Compressed Liquid N2

0009-2614

Line mixing in the ν1 and 2ν2 isotropic Raman Q-branch of CO2 perturbed by argon and helium

0021-9606; The shapes of the ν1 and 2ν2 isotropic Raman Q-branch of CO2 perturbed by argon and helium have been measured by Stimulated Raman Spectroscopy (SRS) or coherent anti-Stokes Raman Spectroscopy (CARS) techniques. The data have been successfully analyzed with an energy corrected sudden (ECS) approximation model based on basic rates determined independently. Finally comparison of the present data with time resolved double resonance experiments allows us to discuss the physical origin of the two empirical constants which account for the shift and broadening of the branch due to vibrational effects. (C) 1999 American Institute of Physics. [S0021-9606(99)00344-X].

High-order Kerr nonlinearity of air calibrated with transient molecular alignment

Talk given by O. Faucher; International audience; Nonlinear electronic Kerr index of the major air constituents has been measured up to high order terms using transient molecular alignment as a reference. Sign reversal associated to negative nonlinearity is observed above a pulse intensity of 26 TW/cm^2.