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A study was conducted relating to research on the vibrational spectrum of ethanol monomers and the issue of the rotational isomerism of ethanol was conducted. The experiment aimed to demonstrate that the comparison between spectra calculated according to the DFT method for both conformers and the observed ones enable researchers to conclude that either one or the other species can be stabilized according to the nature of the matrix. Results of the study are discussed.

The simultaneous existence of valence and dipole-bound states of the uracil anion was investigated in a cross beam experiment. Specifically, Rydberg electron attachment to gas-phase isolated uracil molecules and mixed uracil-argon clusters was analyzed. Field-detachment measurements showed that attachment and evaporation of a single argon atom is enough to switch from dipole-bound to valence monomer uracil anions. The results were consistent with two previous theoretical predictions.

The prediction accuracy of second-order Moller-Plesset theory MP2 and density functional theory DFT-(D) with and without empirical dispersion correction within the resolution of identity approximation (ri) have been investigated for the assignment of infrared spectra of gas-phase peptides. A training set of 17 conformers of phenylalanine containing capped peptides have been used to establish mode-specific local scaling factors. Inclusion of dispersion terms at the DFT level turns to significantly improve the accuracy of predicted IR spectra. At the DFT-D level, the nonhybrid generalized gradient approximation functional B97-D (TZVP basis set) provides even better results than the popular hybrid functional B3LYP (6-31+G* basis set) while reducing the computational cost by almost 1 order of magnitude. Besides, MP2 (SVP basis set) outperforms all other tested methods in terms of reliability and transferability to larger molecular systems with typical prediction errors of about 5 cm(-1).

A set of transferable local scaling factors is established for assignment of infrared spectra of molecular systems of biological interest experimentally recorded under gas-phase conditions. Each scaling factor is specific for an experimentally observable vibrational mode chosen among those bringing significant structural information. Those factors are provided for harmonic calculations at the DFT B3LYP and DFT B3PW91 levels respectively with 7 and 2 different basis sets. The used training set of neutral molecules comprises nucleobases, aminoacids, peptides, sugars, and neurotransmitters. The proposed specific scaling factors usable for unambiguous conformer assignments lead to typical prediction errors ca. 10 cm(-1) for free and moderately hydrogen-bonded group frequencies with red-shifts up to 200 cm(-1).