Aldo Millemaggi

Observation of the rotational spectra of van der Waals complexes by free jet absorption millimeter wave spectroscopy: pyridine-argon

Abstract A free jet millimeter wave spectrometer has been modified in order to observe the rotational spectra of van der Waals molecular complexes. Here the free jet millimeter wave spectrum of the pyridine-argon molecular complex, as investigated in the 60–78 GHz frequency range, is reported.

A microwave free jet absorption spectrometer and its first applications

Abstract A free jet absorption microwave spectrometer working in the frequency range 50–80 GHz has recently been built in our laboratory. Different experiments can be performed with the system: the microwave radiation can be focussed on the supersonic expansion either with a lens corrected horn system or with a semiconfocal Fabry-Perot interferometer. The microwave radiation can be either parallel or perpendicular to the jet, and Stark modulation or double resonance experiments (MWMW or RFMW, respectively) are possible. As first applications, studies on complicated conformational equilibria, tautomeric equilibria and molecules with puzzling nuclear hyperfine structure (for example, a molecule containing two iodine atoms) have been performed.

Free jet rotational spectrum and ab initio calculations of acetanilide

Formanilide has been investigated by free-jet millimeter-wave absorption spectroscopy. The rotational spectrum of the conformer with the formyl hydrogen anti to the phenyl group has been assigned. Several rotational transitions of the ground state have been measured for both normal and ND isotopic species. All the atoms of the peptidic group are coplanar to the ring. Copyright 2001 Academic Press.

Rotational spectra and dynamics of the van der Waals adducts of neon and argon with 1,1-difluoroethylene

The free jet millimeter wave spectra of the complexes of Ne and Ar with 1,1-difluoroethylene are reported. Information on the equilibrium configurations, dynamics, and dissociation energies of these weakly bonded complexes are obtained from their nonrigidity. The vibrational doubling (0.78 MHz) of the rotational transitions of 1,1-difluoroethylene–Ne has been useful in scaling the ab initio potential energy function calculated for the tunneling of Ne above and below the plane of 1,1-difluoroethylene. This motion is hindered by a barrier of about 36 cm−1 at the planar C2v configuration.

Free jet rotational spectra in natural abundance of the 13C and 15N isotopic species, structures and ab initio calculations of equatorial and axial pyrrolidine ☆

Abstract The rotational spectra of all singly substituted 13 C and 15 N isotopic species of the equatorial form of pyrrolidine and all singly substituted 13 C isotopic species of the axial form have been measured in natural abundance with millimeter-wave free jet technique and r s and r 0 heavy atom geometries have been determined. Various sets of ab initio calculations give contrasting results for the energy difference between the two conformers.

Free jet absorption millimeter wave spectrum of benzene sulphonyl chloride

Abstract The free jet millimeter wave spectrum of benzene sulphonyl chloride has been investigated in the 60–66 GHz frequency range. The rotational spectra of the 35 Cl and 37 Cl isotopomers have been assigned, allowing the determination of the equilibrium configuration: the Cl atom is perpendicular to the benzene ring.

Rotational spectrum of the imidazole–argon complex

Abstract The free jet millimeter-wave spectrum of the imidazole–argon molecular complex has been investigated in the 60–78 GHz frequency range. Estimates of the Van der Waals stretching force constant and of the dissociation energy are given.