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Accueil > EN > Research Areas > Pure and applied spectroscopy > Pure and applied spectroscopy > Equipments

The Jet-AILES apparatus

par Manuel GOUBET, Thérèse HUET - publié le , mis à jour le


The Jet-AILES apparatus is a supersonic jet coupled to the high resolution infrared spectrometer (FTIR) of the AILES beamline at the synchrotron facility SOLEIL. This set-up has been developed and is now operated by a consortium of 4 teams : Robert Georges and Jonathan Courbe (IPR/Rennes 1), Pierre Asselin and Pascale Soulard (LADIR/Paris VI), Olivier Pirali and Pascale Roy (AILES/SOLEIL), Manuel Goubet and Thérèse Huet (PhLAM/Lille 1). Fully operational, it can be used for spectroscopic analyses through a deposit of scientific project evaluated by a committee of experts (as in the case of all major instruments, deposit every 6 months in the case of SOLEIL).

Supersonic jet in spectroscopy

Pitot mapping of a high pressure expansion of argon

A supersonic jet is obtained by adiabatic expansion of a gas at high pressure through an orifice (hole or slit) to a chamber maintained at low pressure. The multiple collisions that occur during this expansion convert the internal thermal energy (translational, rotational, and vibrational) into kinetic energy of translation along the axis of the nozzle (to learn more, see for example the book : Atomic and Molecular Beam Methods. Vol. I., G. Scoles, Oxford University Press, Inc., New York, 1988).

Samples, diluted in a carrier gas (often monoatomic gas such as argon, neon or helium), may then be observed :

Spectra of the out-of-plane bending of Naphthalene recorded at room temperature (upper trace) and in jet-cooled conditions (lower trace)
  • isolated from any environmental perturbation or controlling them (microsolvation),

  • always in the gas phase whatever is their initial phase (liquid or solid) in standard conditions of temperature and pressure,

  • at temperatures below their condensation point but remaining in the gas phase ; spectra are then remarkably simplified, permitting their analysis often impossible otherwise,

  • as molecular complexes (Van der Waals, hydrogen bond, aggregates) thanks to the energetic stabilization offered by the jet (3 body collisions).

Modelling of a spectrum, determination of an equilibrium structure or understanding the vibrational dynamics of a semi-rigid molecular system (characterized by a large number of degrees of freedom) require an accurate analysis of the low frequency modes. Indeed, these modes are very specific to a given system because they correspond either to deformations of the whole structure or to substructures internal rotations. Such modes are observable in the far-infrared range (15-1000 μ m), spectral region where the synchrotron light extracted by the AILES beamline is up to 30 times brighter than conventional sources, for acquisitions at the highest resolution.

Description of the set-up

Samples are observed in a high pressure supersonic slit jet.

  • Slits of various lengths (3, 6 or 9 cm) and widths (from 10 to 120 μ m) allow a wide range of conditions of expansion. Thus, molecules cooled down at different temperatures up to large aggregates through hydrogen bond complexes can be observed.

  • The injection line is thermally regulated (from ambient to 200°C) and equipped with flow controllers, a controlled evaporation mixer and an oven. Thus, it is possible to control and mix vapors from gaseous, liquid or solid samples.

  • The expansion chamber is evacuated by a set of roots pumps delivering an effective pumping capacity of approximately 1800 m3/h. Thus, it is possible to expand the samples over a wide range of flow rates (from 0.1 to 30 standard liters per min (slm)).

Pictures of the expansion chamber (left), slit nozzles (middle) and the pumping unit (right)

The adiabatic expansion is probed perpendicularly (negligible Doppler broadening of the signals) by the infrared beam from the spectrometer. It is focused at the center of the expansion by two mirrors, one planar (M1) and one toroidal (M2). It is then sent to the detectors compartment, where a second toroidal mirror (M3) and a second planar mirror (M4) redirect and focus the beam towards a photovoltaic detector (for mid-infrared) or towards a bolometer (for far-infrared). Optical compartments are kept under high vacuum together with the spectrometer and isolated from the expansion chamber with optical windows placed as close as possible to the slit (limiting absorption signals form the residual gases).

Publications récentes

  • The (CH2)2O−H2O Hydrogen Bonded Complex. Ab Initio Calculations and Fourier Transform Infrared Spectroscopy from Neon Matrix and a New Supersonic Jet Experiment Coupled to the Infrared AILES Beamline of Synchrotron SOLEIL, M. Cirtog, P. Asselin, P. Soulard, B. Tremblay, B. Madebène, M. E. Alikhani, R. Georges, A. Moudens, M. Goubet, T. R. Huet, O. Pirali and P. Roy, J. Phys. Chem. A 115 2523-2532 (2011)

  • The far infrared spectrum of naphthalene characterized by high resolution synchrotron FTIR spectroscopy and anharmonic DFT calculations, O. Pirali, M. Goubet, T. R. Huet, R. Georges, P. Soulard, P. Asselin, J. Courbe, P. Roy and M. Vervloet, Phys. Chem. Chem. Phys. 15 10141-10150 (2013)

  • Standard free energy of the equilibrium between the trans-monomer and the cyclic-dimer of acetic acid in the gas phase from infrared spectroscopy, M. Goubet, P. Soulard, O. Pirali, P. Asselin, F. Réal, S. Gruet, T.R. Huet, P. Roy, R. Georges, Phys. Chem. Chem. Phys. Vol. 17, 7477-7488 (2015), DOI