Ludovic Biennier

High Resolution Absorption Spectroscopy of the ν1=2-6 Acetylenic Overtone Bands of Propyne: Spectroscopy and Dynamics

The rotationally resolved nν1 (n=2–6) overtone transitions of the CH acetylenic stretching of propyne (CH3–C≡C–H) have been recorded by using Fourier transform spectroscopy (n=2), various intracavity laser absorption spectrometers (n=3, 4, and 6) and cavity ring down spectroscopy (CRDS) (n=5). The 2ν1, 3ν1, and 6ν1 bands exhibit a well-resolved and mostly unperturbed J-rotational structure, whose analysis is reported. The 5ν1 band recorded by pulsed CRDS shows an unresolved rotational envelope. In the region of 12u200a700 cm−1, an anharmonic interaction is confirmed between 4ν1 and 3ν1+ν3+ν5. The band at a higher wave number in this dyad exhibits a partly resolved K-structure, whose analysis is reported. The mixing coefficient of the two interacting states is determined consistently using different procedures. The 1/35 anharmonic resonance evidenced in the 4ν1 manifold induces weaker intensity borrowing from the 2ν1 and 3ν1 levels to the ν1+ν3+ν5 and 2ν1+ν3+ν5 level, respectively, which have been predicted an...

Rotationally resolved absorption spectrum of the O2 dimer in the visible range

Abstract The rotationally resolved absorption spectrum of two bands of the oxygen dimer near 630 and 578 nm have been recorded by intracavity laser absorption spectroscopy both in a supersonic slit expansion of pure O 2 and in a cell cooled at 77 K. These bands correspond to the transitions [ O 2 ( 1 Δ g ) v=0 ] 2 ←[ O 2 ( 3 Σ g − ) v=0 ] 2 and [ O 2 ( 1 Δ g ) v=0 – O 2 ( 1 Δ g ) v=1 ]←[ O 2 ( 3 Σ g − ) v=0 ] 2 . From the extension of the highly congested rotational structure, the dissociation energy of the ground and excited states are estimated to be 80 and 40 cm −1 , respectively. These values agree reasonably well with the results of ab initio calculations of the potential energy surface.

Ultraviolet cavity ring-down spectroscopy of free radicals in etching plasmas

Abstract Many reactive species of interest in technological plasmas absorb light in the UV spectral region (200–300 nm). Measurement of these weak absorbances (typically 10 −2 –10 −4 for a single pass) allows us to determine their absolute concentration. Low-resolution absorption spectra of these systems have previously been obtained by broad-band absorption spectroscopy. Here we present spectra obtained using laser cavity ring-down spectroscopy, which has much higher spectral resolution, and potentially higher sensitivity. Spectra were obtained for CF, CF 2 , AlF and SiF 2 radicals in capacitively-coupled radio-frequency plasmas in fluorocarbon gases. This technique offers the possibility of real-time (1 s) absolute concentration measurements during wafer processing.

THE ABSORPTION SPECTRUM OF 12C2H2 BETWEEN 12 800 AND 18 500 CM-1. II. ROTATIONAL ANALYSIS

The rotational structure of the vibrational bands of 12C2H2 is investigated in three spectral energy regions not previously systematically explored at high resolution, 12800–13500 cm−1, 14000–15200 cm−1 and 16500–18360 cm−1, on the basis of new spectral data recorded by intracavity laser absorption spectroscopy. The rotational analysis of 17 new absorption bands arising from the ground state is reported (11 Σu + − Σg + bands and 6Πu − Σg + bands). Four bands in the range studied show strong perturbations affecting both the line positions and intensities. Their detailed analysis is performed in order to determine the nature of the coupling schemes, the vibrational species and the rotational constants of the perturber states. Altogether, the vibration-rotation parameters of 21 newly observed vibrational states are derived.

The visible absorption spectrum of 12C2H2 III. The region 14 500-17 000 cm-1

The absorption spectrum of 12C2 H2 has been recorded at high resolution by intracavity laser absorption spectroscopy between 14 500 cm-1 and 17 000 cm-1. Among the 32 bands which have been rotationally analysed 15 are newly observed, and improved rovibrational parameters are obtained for the others. The new resulting set of 26 vibrational levels is assigned by extrapolating the cluster model built from lower energy data (Abbouti Temsamani, M., and Herman, M., 1995, J. chem. Phys., 102, 6371) which allows vibrational energies and Bv rotational constants to be predicted. Intensity features are also discussed.