Webmaster N. Picqué
(Latest update 2/10/2005)
Lasers and FTS.
| Research: Fourier transform spectroscopy |
| Selective detection. | ||
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We have demonstrated high
resolution double modulation Fourier Transform Spectroscopy (FTS) for
the first time. Two high resolution FT interferograms are
simultaneously recorded. The first one is nonselective, and contains
all the
spectral information from the observed source, when the other one is
made of
the only samples sensitive to a specific source modulation.
The resulting combined advantages of broad spectral coverage and accurate wavenumber determination have for instance proven to be useful for Doppler shifts measurements leading to an investigation on the vibrational and rotational dependence of the average mobility of ArH+ in the positive column of an Ar/He glow discharge. |
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Velocity-modulation Fourier transform emission spectra from a N2O/He discharge plasma recorded between 1 and 5.5 µm surprisingly show Doppler-shifted lines for the E 2S+- D 2S+, C 2P- A 2S+, and D 2S+- A 2S+ Rydberg-Rydberg rovibronic transitions of the nitric oxide neutral molecule. Transitions of other neutral molecules like N2 are also present in the spectra with comparable intensities and remain unshifted. Experimental investigations and simple numerical simulations bring the assumption that NO acquires the observed drift-velocity through momentum transfer from a positively charged ionic collisional partner which might be N2O+. Related www pages of our group :  Fourier
transform spectroscopy:
interferometer Time-resolved
FTS Selective FTS |
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More details may be found in: Instrumental developments: Fast phase-selective detection of transient species with step-scan Fourier transform spectroscopy N. Picqué, Journal of the Optical Society of America B 19, 1706-1710, 2002. High-resolution multimodulation Fourier-transform spectroscopy N. Picqué, G. Guelachvili, Applied Optics, 38, 1224-1230, 1999. Applications: Concentration-modulation FT emission spectroscopy of TiCl4/He plasma. H. Herbin, R. Farrenq, G. Guelachvili, N. Picqué, Fourier Transform Spectroscopy/Hyperspectral Imaging and Sounding of the Environment Topical Meetings on CD-ROM (The Optical Society of America, Washington, DC, 2005), paper FTuD6, 3 pages (2005). Cation-like Doppler shifts from a neutral molecule in an electrical discharge, H. Herbin, R. Farrenq, G. Guelachvili, N. Picqué, Chemical Physics Letters 409, 310-314, 2005. Wide-band spectroscopic investigation of the state-to-state dependence of ArH+ ion average mobility in a Ar/He plasma, N. Picqué, Chemical Physics Letters 310, 183-188, 1999. |
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