Molecular Spectroscopy and Structure

The IR spectra of nonionized glycine and its deuterated derivatives isolated in the low-temperature argon matrices have been measured, and for the first time the infrared spectral characteristics of the three most stable conformers have been determined and assigned. Correlated level ab initio and density functional th…

Terahertz (THz) spectroscopic investigations of condensed-phase biological samples are reviewed ranging from the simple crystalline forms of amino acids, carbohydrates and polypeptides to the more complex aqueous forms of small proteins, DNA and RNA. Vibrationally resolved studies of crystalline samples have revealed…

• OKAN ESENTÜRK

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• ALİ TÜRKCAN

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• AHMET NECATİ ÖZSEZEN

The relaxation of the higher-energy cis conformer of formic acid to the lower-energy trans form by a tunneling mechanism has been investigated in low-temperature rare gas matrices. In the temperature range 8–60 K, the tunneling takes place dominantly from the vibrational ground state of the cis form and the temperatur…

• RUI FAUSTO MARTINS RIBEIRO DA SILVA LOURENÇO

The high-energy conformer of acetic acid (cis-AA) is produced in an Ar matrix by vibrational excitation of the OH stretching overtone of the ground conformational state (trans-AA). IR-absorption spectroscopy provides a clear identification of the reaction product. cis-AA converts back to trans-AA in a time scale of mi…

• RUI FAUSTO MARTINS RIBEIRO DA SILVA LOURENÇO

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• RUI FAUSTO MARTINS RIBEIRO DA SILVA LOURENÇO

Five different orientations of the acetylene-benzene dimer including the T-shaped global minimum structure are used to assess the accuracy of the density functional theory combined with symmetry adapted perturbation theory (DFT-SAPT) approach in its density-fitting implementation (DF-DFT-SAPT) for the study of CH-pi a…

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• RUI FAUSTO MARTINS RIBEIRO DA SILVA LOURENÇO

Formic acid (HCOOH, FA) and acetic acid (CH(3)COOH, AA) are studied in a nitrogen matrix. The infrared (IR) spectra of cis and trans conformers of these carboxylic acids (and also of the HCOOD isotopologue of FA) are reported and analyzed. The higher-energy cis conformer of these molecules is produced by narrowband ne…

• RUI FAUSTO MARTINS RIBEIRO DA SILVA LOURENÇO

Rotational isomerization of acetic acid (CH3COOH) is studied in Ar, Kr, and Xe matrices. The light-induced trans-->cis reaction is promoted using resonant excitation of a number of modes in the 3500-7000 cm(-1) region, and the quantum yields for this process are measured for various acetic acid isotopologues and matri…

• RUI FAUSTO MARTINS RIBEIRO DA SILVA LOURENÇO

The conformational behavior and infrared spectrum of l-phenylalanine were studied by matrix-isolation infrared spectroscopy and DFT [B3LYP/6-311++G(d,p)] calculations. The fourteen most stable structures were predicted to differ in energy by less than 10 kJ mol(-1), eight of them with abundances higher than 5% at the…

• RUI FAUSTO MARTINS RIBEIRO DA SILVA LOURENÇO