Characterizing the dark state in thymine and uracil by double resonant spectroscopy and quantum computation.

We report on gas phase double resonant spectroscopy of both the ground state and the dark excited state in isolated uracil and thymine. We also report lifetimes of the dark state for different excitation wavelengths. In combination with ab initio calculations the results suggest that the dark state is of triplet ((3)ππ*) character

Characterizing the dark state in thymine and uracil by double resonant spectroscopy and quantum computation.

We report on gas phase double resonant spectroscopy of both the ground state and the dark excited state in isolated uracil and thymine. We also report lifetimes of the dark state for different excitation wavelengths. In combination with ab initio calculations the results suggest that the dark state is of triplet ((3)ππ*) character

Hydrogen adsorption on the zeolite Ca-A: DFT and FT-IR investigation

[EN] Adsorption of H(2) on the zeolite Ca-A was investigated by a combination of variable temperature IR spectroscopy and calculations at the periodic DFT level. Calculations showed that adsorption complexes can be formed on two types of adsorption sites: Ca(2+) in the center of six-member rings and Ca(2+) in eight-member rings. Only the former adsorption complexes were experimentally observed in IR spectra; they are characterized by H-H stretching frequency of 4083 cm (1) and Delta H(0) = -12 kJ/mol in agreement with calculated results. The most likely explanation for not observing the adsorption complex on Ca(2+) in 8-member rings is that the geometry of the complex does not render the H-H stretching mode IR active. (C) 2009 Published by Elsevier B. V.Work in Prague was supported by research projects 203/09/0143 (GA C. R), MSM0021620857 and LC512 (MSMT C. R). AP acknowledges the support from Spanish MICINN (post-doctoral fellowship). The Spanish MICINN and FEDER funds are gratefully acknowledged for financial support to the work done at the UIB (Projects MAT2008-00089 and PCI2006-A7-0618). The access to the META Centrum computing facilities provided under the research intent MSM6383917201 is acknowledged.Otero Arean, C.; Turnes Palomino, G.; Llop Carayol, MR.; Pulido Junquera, MA.; Rubes, M.; Bludsky, O.; Nachtigall, P. (2009). Hydrogen adsorption on the zeolite Ca-A: DFT and FT-IR investigation. Chemical Physics Letters. 447(1-3):139-143. https://doi.org/10.1016/j.cplett.2009.06.058S1391434471-

Combined Experimental and Theoretical Investigations of Heterogeneous Dual Cation Sites in Cu,M-FER Zeolites

Carbon monoxide is frequently used as a probe molecule for characterization of adsorption sites in zeolites by means of infrared (IR) spectroscopy. IR spectra of carbonyl species in zeolites are usually understood within a concept of CO adsorption on a single cation site. This concept, however, is not sufficient in microporous materials when the concentration of cationic sites increases. Adsorption complexes formed on homogeneous dual cation sites were recently described (J. Phys. Chem. B 2006, 110, 22542) based on a combination of experimental and theoretical investigations. The concept of dual cation sites is extended for the situation where CO is strongly bound on the Cu+ cation and it also interacts with the extra-framework alkali-metal cation. The existence and properties of theCOadsorption complexes on such heterogeneous dual cation sites are discussed for Cu,M-FER zeolites (M =H, Na, K, Cs) having various compositions. Based on a good agreement between theoretical (periodic density functional theory) and experimental (IR, microcalorimetry, TPD) results, the interpretation of some IR features is offered.Bulanek, R.; Frolich, K.; Cicmanec, P.; Nachtigallova, D.; Pulido Junquera, MA.; Nachtigall, P. (2011). Combined Experimental and Theoretical Investigations of Heterogeneous Dual Cation Sites in Cu,M-FER Zeolites. Journal of Physical Chemistry C. 115(27):13312-13321. doi:10.1021/jp200293yS13312133211152