F. Herlemont

Saturated Absorption of C2h4 With a Co2 Waveguide Laser

Abstract Saturated spectroscopy of C 2 H 4 was performed with a CO 2 waveguide laser. Seventeen lines were measured with a precision of the order of 200 kHz. On the basis of these data and of a new highly accurate determination of the ground-state rotational constants a better analysis of the ν 4 , ν 7 , and ν 10 levels was achieved.

Infrared spectroscopy of OCS, SO2, O3 with a CO2 waveguide laser

Abstract Infrared spectroscopy of OCS, SO 2 , and O 3 has been performed with a CO 2 waveguide laser. The spectra observed were analyzed with data available and assignments are proposed.

Microwave spectra of methyl chloride, methyl bromide, and methyl iodide in the ν6 = 1 excited vibrational state

Abstract The rotational spectra of CH 3 35 Cl, CH 3 37 Cl, CH 3 79 Br, CH 3 81 Br, and CH 3 I in the ν 6 state were observed between 8 and 240 GHz. For CH 3 Br and CH 3 I, the present data were combined with the pure quadrupole resonances of Oka et al. to determine the molecular constants. Our measurements have enabled us to notably improve the molecular constants for the ν 6 excited states.

Combined subdoppler laser-Stark and millimeter-wave spectroscopies: Analysis of the ν6 band of CH335Cl

Abstract The ν6 fundamental of CH335Cl has been remeasured by using a Stark-Lamb-dip technique. These Stark resonances were combined with the zero-field microwave spectra to give determinable combinations of the vibration-rotation parameters and the dipole moments: μ″ = 1.89628(23)D and μ′ = 1.89738(19)D.

Doppler-free two-photon spectroscopy of the 2ν3 band of SF6

High-resolution spectroscopy of the 2ν3 band of SF6 is reported by means of Doppler-free two-photon transitions. Parts of spectra are measured with accuracy of 10−9. This technique applied to SF6 should lead to an assignment of the spectra involved.

“Efficiency” of collisions in a microwave infrared four-level system in ammonia

Abstract The increase of microwave lines of NH 3 which do not share a common level with the infrared pumped transition has been observed and interpreted as due to “β type” collisions.The authors give an explanation based upon the “truly resonant collisions” hypothesis to explain the breadth of the monitored microwave signal.

Sub-Doppler study of the v3=2 state of SF6 by infrared–infrared double resonance with a sideband spectrometer

The v3=2 state of SF6 has been investigated using two independently tunable sidebands of a CO2 laser. An electro-optic modulator, based on microstrip concept, is excited by a wave in the range of 0–4 GHz to create a sideband resonant with the cold band transition used as pumping radiation. A second electro-optic modulator working in the 8–18 GHz range is used to monitor the disturbance in the 2ν3−ν3 band. About 250 lines of both the cold band ν3 and the hot band 2ν3–ν3 have been assigned on the basis of a calculated spectrum. Their frequencies have been determined with an accuracy better than 50 kHz. The spectrum is analyzed and the lines are fitted using an effective Hamiltonian developed through the sixth order for the ground state, the seventh order for the v3=1 state and the sixth order for the v3=2 state. The standard deviation is a few tens of kHz for ν3 lines and a few hundreds of kHz for 2ν3–ν3 lines.

Study of rotational relaxation in CH3Br by infrared-microwave double resonance

Abstract Infrared-microwave double resonance has been performed on CH 3 Br with a CO 2 laser. Three coincidences between laser emission and IR absorptions of the gas have been used. The results related to the rotational relaxation are understood on the bases of Δ K (or Δ| K - l |) = 0, Δ l = 0, Δ J = ± 1 and Δ K (or Δ| K - l |) = 3 p coliision induced transitions.

Saturation spectroscopy with a CO2 waveguide laser: Analysis of the ν6 bands of CH3 79Br and CH3 81Br

About 100 Doppler‐free hyperfine resonances arising from rovibrational transitions of methyl bromide have been observed and accurately measured by means of saturation laser spectroscopy using an absorption cell inside the cavity of a CO2 waveguide laser. Most of these transitions have been assigned to the ν6 fundamental bands of CH3 79Br and CH3 81Br. Assignments were deduced from computed spectra and checked with the resolved hyperfine quadrupole structure. An overall fit including recent microwave line frequency measurements, infrared inverted Lamb dip frequencies, infrared laser Stark measurements, and submillimeter emission frequencies yields a set of molecular parameters for the ν6 band of CH3 79Br and CH3 81Br. With respect to previous values, an improvement of one to two orders of magnitude is obtained for all the molecular parameters of the ν6 band. In particular, all the sextic centrifugal distortion constants are obtained significantly from the fit.

Waveguide and diode heterodyne measurements with CO2 laser and assignment of the CW FIR laser emission of OCS

Abstract Heterodyne spectra of carbonyl sulfide have been obtained with saturation in a CO 2 waveguide laser and without saturation with a diode laser. The absolute uncertainties of the measured positions lie between 10 −4 and 7 × 10 −6 cm −1 . The CW submillimeter laser line of OCS at 378 μm has been assigned to the J = 65 → 64 transition in the 02 2 0 e state of 16 O 12 C 32 S, with a pumping through the R (64) line of 02 2 0 e ← 00 0 0, a Δ-Σ transition weakly allowed by the l -type resonance.