Jean-Claude Cornut

Vibrational Spectra of Fluoronium Ions, FH2+, FD2+, and FHD+

The first direct observation of fluoronium ions, FH2+, FD2+, and FHD+, is reported. The method of production of the fluoronium salts is described, and their infrared spectra are analyzed. The structure of the fluoronium ions is shown to be angular. The force constants have been evaluated. In the presence of liquid hydrogen fluoride, the fluoronium ions are strongly solvated by hydrogen bonds in the form (HF)nH+.

A Sample Holder for Raman Spectroscopic Studies of Crystals at Low Temperatures. Application: Phase Transition in Succinonitrile

A device to improve the thermal exchange between the cold tail, in a Raman cryostat working at liquid helium temperatures, and the crystalline sample is described and a side-reference method for the temperature measurement is used. The method is then applied to the study of the phase transition in succinonitrile.

Infrared spectral profile of hydrogen fluoride diluted in deuterium fluoride

A special infrared spectral profile with an intense band and two satellites on each side is observed for hydrogen fluoride hydrogen bonded to deuterium fluoride molecules in the solid state. The sidebands are interpreted as the result of a combination of the FH stretching vibration with the stretching and bending modes of the hydrogen bond⋅⋅⋅F–H⋅⋅⋅F. This interpretation is confirmed by the temperature dependence of the intensity of the sidebands. The experimental result also reveals a strong mechanical anharmonicity in the coupling between the high frequency vibration and the low frequency modes and a strong electrical anharmonicity of the hydrogen‐bond vibrations.

The interconversion of the zwitterion and the uncharged form of γ‐aminobutyric acid (GABA) at low temperatures

The infrared spectra of γ‐aminobutyric acid (GABA) in the solid state and inert gas matrices at several temperatures and concentrations have been analyzed. Evidence of a neutral molecular form of GABA is shown for the first time; this compound was known until now only in its zwitterionic or cationic forms. The intermolecular mechanism is also established for the formation of the GABA zwitterion. This final step is shown to be preceeded by hydrogen‐bonded intermediates.

A variable-temperature hydrostatic pressure cell for Raman scattering experiments

A variable-temperature hydrostatic high-pressure cell for Raman scattering experiments is presented; it can be commonly used for pressures up to about 6 kbars, in the temperature range between 340 and 80 K. Examples of applications are given, concerning conformational equilibriums in liquid tridecane on the one hand, and structural phase transitions in crystalline (CH3)4NMnCl3(TMMC) and (CH3)4NCdCl3 (TMCC), on the other hand.

A Newly Designed Cryostat for Absorption Spectroscopic Studies of Liquids, Solids, and the Interphases

A double jacket cryostat based on thermal convection between a gaseous cold stream filled in a freezing chamber and the sample cell is described. This device is designed for absorption spectroscopy in the infrared and in the UV-visible regions for gases, liquids, liquefied gases, and solids, as well as for the transitions between these phases or between phases in the solid state, over the range 85 to 340 K, at variable thicknesses and under a pressure of up to 10 bars.