SELECTIVE AND TIME-RESOLVED FOURIER TRANSFORM ION SPECTRA.

$^{a}$J.W. Farley, Theory of the resonance line shape in velocity-modulation spectroscopy. J. Chem. Phys. 95, 5590-5602, 1991 N. Picqu\'{e}, G. Guelachvili, High resolution multi-modulation Fourier transform spectroscopy, Applied Optics 38, 1999 (in press). $^{b}$N. Picqu\'{e}, Spectroscopic investigation of the state-to-state dependence of $ArH^{+}$ ion mobility in a Ar/He plasma, Chemical Physics Letters, 1999 (submitted). $^{c}$N.N. Haese, F-S. Pan, and T. Oka, ``Doppler shift and ion mobility measurements of $ArH^{+}$ in a He de glow discharge by infrared laser spectroscopy'', Physical Review Letters 50, 1575-1578, 1983. $^{d}$C.P. Lauenstein, M.J. Bastian, V.M. Bierbaum, S.M. Penn, and S.R. Leone, ``Laser-induced fluorescence measurements of rotationally resolved velocity distributions for $CO^{+}$ drifted in He'', Journal of Chemical Physics 94 7810-7818, 1991. E.B. Anthony, ``Laser probing of transport properties and rotational alignment of $N_{2}$ drifted in $He^{n}$, Ph.D. Thesis, The University of Colorado, 1998.Author Institution: Laboratoire de Photophysique $Mol\acute{e}culaire^{(1)}$, Unit\'{e} Propre du CNRSThis paper illustrates some aspects of the work begun at LPPM in the field of Fourier Transform Ion Spectroscopy. Double-modulation and time-resolved emission FT spectra of molecular ions, created in glow discharges, are presented. The processing of first derivative-type selective $lineshapes^{a}$ is discussed. Results aiming at characterizing the transport properties and the abundance of ions in plasmas are reported. As an illustration, the quantum dependence of the average mobility of $ArH^{+}$ in an Ar/He mixture in an inhomogeneous electric field has been investigated from Doppler-shifts $measurements^{b}$. This fact demonstration extends to wide-band spectroscopy the measurements pioneered by Haese, Pan, and $Oka^{c}$ with diode-lasers, in similar source conditions. Spectroscopic means can now provide high quality state-resolved plasma characterization, as proven with lasers, in homogeneous electric fields, for instance in Leone's $group^{d}$. The determination of the rovibrational intensities of the $\Delta v=1$ sequence of $ArH^{+}$ has been undertaken. First attempts to observe ionic species in C, N, H containing electrical discharges are also reported