Rydberg electron attachment to gas-phase isolated uracil molecules and mixed uracil-argon clusters is examined in a crossing beam experiment. By means of reproducible uracil beam conditions, it is possible to control the electron-binding process, which is strongly influenced by solvation. Attachment followed by evaporation of a single argon atom is already sufficient to switch from dipole-bound to valence monomer uracil anions, as demonstrated by field-detachment measurements. The existence of both types of anions is in good agreement with two separate previous theoretical predictions. A DFT calculation of the valence adiabatic electron affinity of uracil provides a small but positive value of 70 meV, close to the measured value of the dipole-bound electron affinity.

The vibrational spectrum of ethanol monomer trapped in argon and nitrogen matrices has been recorded in various conditions of temperature and irradiation. The structures and vibrational properties of the anti and gauche conformers have been investigated by ab initio calculations according to the DFT method. The comparison between observed and calculated frequencies allows an explanation of the matrix data and a proposal of a complete assignment for both conformers. The striking spectral changes observed in nitrogen matrices upon temperature cycling in the range 8−30 K are interpreted in term of anti → gauche conversion. In contrast with these observations, the spectrum obtained in an argon matrix is unsensitive to thermal effects, the anti form being the only one to be stabilized. Monochromatic irradiations in the OH and CO stretching regions were carried out with the purpose of inducing photorotamerization. In all cases only changes of trapping sites were observed, despite an interconversion barrier lower than the energy of the absorbed photons.

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