Lucien Henry

Analysis of high resolution fourier transform and diode laser spectra of the ν9 band of ethane

Abstract Fourier transform measurements with an apodized apparatus function up to 0.002 cm−1 are reported for the ν9 band (ρu) of ethane in the 12-μm region, together with an integrated band strength obtained from intensity measurements on selected Q-branch lines recorded using a diode laser spectrometer. Since the ν9 band falls in an atmospheric window, these data may be useful in studies of the ethane concentration in the atmosphere of Jupiter and other outer planets. Torsional splittings in the ν9 level caused by a higher-order Coriolis interaction with the close lying 3ν4 state (a1u) have been analyzed in a global least squares fit of 2206 Fourier transform lines and 58 diode splittings to a molecular Hamiltonian containing 20 parameters, with a standard deviation of 0.35 × 10−3 cm−1. Rotational levels of one component of the torsionally split 3ν4 state cross interacting rotational levels of the ν9 state for K = 17, and the spectrum is followed to K = 19 on the pP subband side to permit inclusion of ν9 levels beyond this crossing. No transitions to 3ν4 levels were observed. The theoretical treatment presented here makes use of standard symmetric top formalism and of the G 36 † double-group formalism for ethane.

Extension to third-order Coriolis terms of the analysis of ν10, ν7, and ν4 levels of ethylene on the basis of Fourier transform and diode laser spectra

Abstract The ν 7 , ν 10 , and ν 4 levels of ethylene have been studied based on waveguide laser, Fourier transform, and diode laser spectra in the range from 798 to 1091 cm −1 . The absolute calibration of these spectra is better than 0.0002 cm −1 . To deal with so many and so accurate experimental data, we have developed in our analysis programs the Watson Hamiltonian up to the sextic centrifugal distortion coefficients and the interaction Hamiltonian up to the third-order Coriolis resonance terms. The molecular parameters of the vibrational ground state have been significantly improved on the basis of more than 4000 GSCD. In the analysis of ν 7 , ν 10 , and ν 4 levels, we had to introduce the ν 12 level, which contributes to the indirect coupling of ν 7 and ν 4 through strong Coriolis interactions. We obtain a statistical agreement with all experimental data with an estimated standard deviation equal to 0.84. The intrinsic intensity of the ν 10 band has been determined to be 16 500 ± 2500 times lower than the intensity of the ν 7 band.

Temperature dependence of the diffusion and accommodation coefficients in nitrous oxide and carbon dioxide excited into the (00°1) vibrational level

We have studied the temperature dependence of the relaxation rates in nitrous oxide and carbon dioxide excited into the (00°1) level by absorption of the radiation of a Q‐switched laser. The relaxation constant β has been determined by measuring the decay time of the fluorescence emitted by the gas. Measurements were performed in the temperature range between room temperature up to 1000 °K and at gas pressures low enough to determine the diffusion coefficient of the excited molecules and their wall‐deexcitation probability versus temperature.

Vibrational energy transfer from the (00°1) level of 14N2O and 12CO2 to the (m, nl, 1) levels of these molecules and of their isotopic species

We have studied versus temperature the fast vibvrational energy transfers which occur between two nitrous oxide molecules, or two carbon dioxide molecules, initially excited by a laser pulse into the (00°1) level. These transfers occur upon near−resonant collisions of the type M(m, nl, 1) + M(m′, n′l′, 0) ? M(m, nl, 0) + M(m′, n′l′, 1) with M = 14N2O) or 12CO2. The rates of these V−V transfers have been measured from room temperature up to 900 K by the laser−induced fluorescence method. These exchanges can play an important role in the kinetics of the fast V−V transfers which occur in gaseous mixtures involving these molecules. This is particularly the case for the transfers occurring between different isotopic species of CO2 and N2O, such as 12CO2−13CO2, and mixtures of 14N2O with 14N15NO, 15N14NO, and 15N2O, also studied in this work. The transfer rates for the isotopic mixtures of nitrous oxide have been measured versus temperature. The experimental results are compared with the values calculated on th...

The ν2 band of 15NH3

Abstract High-resolution Fourier transform sepctra of the ν 2 band of 15 NH 3 have been recorded in the region 725–1250 cm −1 with a precision better than 0.0003 cm −1 . A simultaneous weighted least-squares analysis of these data, together with previously published data, has been carried out, to yield molecular parameters which fit the data within the limits of their experimental accuracies.

Temperature dependence of the vibrational relaxation of CO (v=1) by NO, O2, and D2, and of the self‐relaxation of D2

Rate constants for the vibrational de‐excitation of CO(v=1) by NO, O2, and D2 have been measured as a function of the temperature using the laser‐induced vibrational fluorescence technique. In the temperature range from 100 to 700 K considered in our experiments, far‐from‐resonance V–V energy transfers occur between CO and the collision partners. In CO–NO and CO–O2 samples, the CO fluorescence decay curves are single exponentials; only the total de‐excitation rates χCO–M=kCO–M+kMCO of CO(v=1) by M=NO or O2 may be experimentally deduced, kCO–M being V–V transfer rate and kCOM the V–TR de‐excitation rate. In the CO–D2 system, the fluorescence exhibits a double exponential decay; the V–V transfer rate kCO–D2 is found to be much greater than the V–TR de‐excitation rate kCOD2, and the self‐relaxation rate kD2 of deuterium has also been deduced from measurements. The V–V transfer rates kCO–M calculated from a semiclassical method derived from that of Shin, and using a Morse potential, have been compared to the ...

Calcul de l'influence de la diffusion inélastique des électrons sur les images de monocristaux

Abstract CALCULATION OF THE INFLUENCE OF INELASTIC SCATTERING OF ELECTRONS ON ELECTRON MICROSCOPE IMAGES OF SINGLE CRYSTALS Taking inelastic scattering by plasmons into consideration in the calculation of the intensity distribution in images of single crystals, common experimental observations in electron microscopy are accounted for.

Amino wagging and inversion in hydrazine: K'=1 levels in the first excited state of the antisymmetric wagging vibration

Abstract The infrared absorption spectrum of NH 2 NH 2 vapor has been observed in the region 899–1077 cm −1 , where the antisymmetric wagging band ( v a = 1 ← 0) appears, by the use of a Fourier transform spectrometer with a practical resolution of 0.003 cm −1 . In the region 925.0–925.6 cm −1 , the spectrum was also observed with a tunable diode laser, and a component, β, of the p Q 2 cluster has been further resolved. Most of the absorption lines assignable to β - p P 2 ( J ″), γ - p P 2 ( J ″), β - p Q 2 ( J ″), γ - r Q 0 ( J ″), β - r R 0 ( J ″), and γ - r R 0 ( J ″), where J ″ = 2 ∼ 15, have been identified. From these observed transition frequencies, in combination with the ground state energy levels given by microwave spectroscopy, the energy level structure of the K ′ = 1 rotational states was determined. From this, the following molecular parameters for the v a = 1 state were determined: molecular asymmetry, B ′- C ″ = 0.00017 cm −1 ; a parameter q 5 describing an umbrella motion Coriolis interaction ( q 5 K ) about the a axis, q 5 = −0.0030 cm −1 ; its J ( J + 1) variation, q 5 j = 0.00014 cm −1 ; and a parameter describing an umbrella-motion K -type doubling g 5 J ( J + 1), g 5 = 0.000021 cm −1 .

High-resolution Fourier transform spectra and rotational analysis of monoisotopic H374Ge35Cl and H374Ge37Cl in the ν2/ν5/2ν3 region near 850 cm−1

Abstract The gas phase infrared spectra of the monoisotopic germyl chloride species H374Ge35Cl (7435) and H374Ge37Cl (7437) in the ν2/ν5/2ν3 region near 850 cm−1 have been studied with a resolution (fwhm) of ca. 0.002 cm−1 employing a Fourier transform spectrometer. A total of 4628 and 3461 transitions of (7435) and (7437), respectively, have been assigned with Kmax = 15 and Jmax = 80 for ν2(a1) and ν5(e). For 2ν3 of (7435), Kmax and Jmax were 6 and 61, respectively. Precise J-dependent ground state constants up to sextic coefficients have been determined from a fit (σ ⋍ 1.3 × 10−4 cm−1) of 1635 and 751 combination differences for (7435) and (7437), respectively. One pair of excited state levels split by Δl = ±1, Δ k = ⊣2 interactions has been observed, and A0 (in connection with DK0 determined previously) of (7437) has been obtained from the related normal and perturbation-allowed transitions. Strong Coriolis interaction, |ζ 2,5 i | ⋍ 0.65 , i = x, y, with positive intensity perturbation occurs between ν2(a1) and ν5(e). For (7437), the perturbation by 2ν3(A1) is local and restricted to the (kl) = −8 sublevels of ν5. In contrast, ν2 and 2ν3 are sufficiently close in (7435) that extended Fermi interactions, |W233F| = 1.27 cm−1, negative intensity perturbation, become dominant. The observed transitions have been fitted, σ ⋍ 1.3 × 10−4 cm−1, to excited state parameters, and a model taking into account Fermi, Δl = Δk = ±1, Δl = Δk = ±2 and Δl = ±1, Δ k = ⊣2 interactions has been employed. The following rounded vibrational frequencies ( 7435 7437 ) have been determined: ν20, 847.650 847.456 , ν50, 873.844 873.833 , and 2ν30, 843.070 827.607 cm −1 .

Rotational constants of C2D6 in the ground and v4=1 vibrational states

Abstract A high-resolution Fourier transform infrared spectrum of C 2 D 6 , in the region of the ν 6 and ν 8 fundamental vibration-rotation bands, has been partially analyzed, and the wavenumbers of the assigned transitions of the ν 8 and ( ν 4 + ν 8 ) − ν 4 bands have been used to determine the rotational parameters B , D JK , and D J of the ground and v 4 = 1 vibrational states. The observation of additional transitions, made detectable by the effect of locally resonant level couplings, allows the establishment of relations between the values of the rotational constants A and D K in the mentioned vibrational states. It is found that the available values of the quartic centrifugal distortion parameters, including D K , determined by a harmonic force field, are highly reliable; therefore accurate values of A 0 and A 4 can be evaluated.