51,033 research outputs found
SPECTROSCOPY AND STRUCTURE OF CHAINS TYPE , H and Si
No full textH. Masso, M.L. Senent, P. Rosmus and M. Hochlaf, J.Chem.Phys.J. Goicoechea, J. Cernicharo, H. Masso and M.L. Senent, ApJ.Author Institution: Departamento de Astrofisica Molecular e Infrarroja; Instituto de Estructura de la Materia, C.S.I.C., Madrid 28006, Spain.; Universite Paris-Est, Laboratoire de Modelisation et; Simulation Multi Echelle (FRE 3160 CNRS), Champs sur Marne; F-77454 Marne-la-Vallee,Cedex 2, France.; Departamento de Astrofisica Molecular e Infrarroja; Instituto de Estructura de la Materia, C.S.I.C., Madrid 28006, Spain.; Universidad Andres Bello, Departamento de Quimica; Facultad de Ecologia y Recursos Naturales, Santiago, Chile.Structures, vertical excitation energies to the first electronic states and spectroscopic parameters for the ground electronic state are determined for several small , H and Si astrophysically important molecular species } \underline{\textbf{124}}, 234304 (2006); M.L.~Senent H.~Masso and M.~Hochlaf, \textit{ApJ}, \underline{\textbf{670}}, 1510 (2007); H.~Masso, V.~Veryazov, P.A.~Malmqvist, B.O.~Roos and M.L.~Senent, \textit{J.Chem.Phys.} \underline{\textbf{127}}, 154318 (2007); M.~Hochlaf, C.~Nicolas and L.~Poisson, \textit{J.Chem.Phys.} \underline{\textbf{127}}, 014310 (2007) N.~Inostroza, M.~Hochlaf, M.L.~Senent and J.R.~Letelier (submitted 2008)}. The main aim of these investigations is to help the interpretation of several previous astrophysical observations } \underline{\textbf{609}}, 225 (2004); J.~Cernicharo, J.R.~Goicochea and Y.~Benilan, \textit{ApJ} \underline{\textbf{580}}, L157, 2002.} State-of-the art ab initio calculations are performed for this purpose. All species display isomerism although the inter-transformation processes, that involve various electronic states, are not well known. Anharmonic spectroscopic parameters are computed from full-dimensional Potential Energy Surfaces which are mapped close to their respective local minima. In light of these calculated properties (band positions, spectroscopic parameters, predictions of ro-vibronic effects, spin-spin constants,..) assignments for FIR astrophysical observed bands, are discussed. vspace{1em} \noinden
Ab initio spectroscopic studies of non-rigid molecules: An application to acetic acid
No full textThe torsional levels of various isotopologues of acetic acid are determined from an ab initio potential energy surface using a flexible model depending on the OH-torsion and the methyl-torsion coordinates. Previous calculations for CH3-COOH and CH3-COOD are review and first theoretical energies of the one-deuterated species CH2D-COOH are provided. The zero point vibrational energy correction and an exact definition for the methyl-torsional coordinate have been considered. The levels are compared with previous calculations (Senent in Mol Phys 99:1311, 2001) and experimental data (Havey et al. in J Mol Spectrosc 229:151, 2005). Isotopic effects on the torsional barriers and energies are discussed. For CH2D-COOD, the deuteration splits by 25 cm-1 the zero vibrational energy level. © 2011 Springer Science+Business Media, LLC.The author acknowledges the Ministerio de Ciencia e Innovación of SPAIN for the grants AYA2008-00446 and AYA2009-05801-E/AYA and to CESGA for computing facilities.Peer Reviewe
METHYLAMINE TORSIONAL-WAGGING FIR SPECTRUM HNH BENDING ANGLE DENPENDENCE.
No full text1) Ab-initio determination of the torsional and wagging FIR spectrum of methylamine. Y. G. Smeyers, M. Villa and M. L. Senent. 2) M. Kreglewski and F. Winther, J. Mol Spectrosc., 156, 261 (1992). 3) M. Kreglewski, in Structure and Conformations of Non-Rigid Molecules, (Eds. J. Laane et al), NATO-ASI S., Kluwer Ac., Dordrecht, 1993, pp. 29-43.Author Institution: Instituto de Estructura de la Materia, C.S.I.C., Madrid, Spain; Department de Quimica, U. A. M-I.Av La Purisia y Mechoacan, CP 09340, Mexico D.F., MexicoThe methylamine potential energy function for the torsion and wagging vibration motions depend upon the HNH bendijng angle of the amine groun (1). By using the RHF/MP2 approximation and a 6-31G++(3df, 3pd) basis set the energy potential surface and the kinetic parameters are calculated by considring the HNH angle a constant and considering it as a variable. With the former results the expremental inveraion barrier (2) reported in the literature can be properly reproduced. With a suitable symmetry adupted potential funtion the torssonal-wagging energy levels are calculated and compared with available experimetantal dats (3). The former work introduces the NHN bending angle as a third variable in the torisional-wagging FIR spectrum and is an initial step in considering the methylamine as a three dimensional non-rigid molecule
FP03.04. Dasatinib improves the antitumor activity of anti-pd-1 in nsclc models by inhibiting treg conversion and proliferation
No full textRedin, E., Garmendia, I., Lozano, T., Serrano, D., Senent, Y., Redrado, M., Villalba, M., De Andrea, C. E.
Exposito, F., Ajona, D., Ortiz-Espinosa, S., Remirez, A.
Bertolo, C., Sainz, C., Garcia-Pedrero, J. M., Pio, R., Lasarte, J. J., Agorreta, J., Montuenga, L., Calvo, A
Thermodynamics and kinetics of the nickel(II)-salicylhydroxamic acid system. Phenol rotation induced by metal ion binding
No full textThe kinetics and the equilibria of Ni(II) binding to p-hydroxybenzohydroxamic acid (PHBHA) and salicylhydroxamic acid (SHA) have been investigated in an aqueous solution at 25 degrees C and I = 0.2 M by the stopped-flow method. Two reaction paths involving metal binding to the neutral acid and to its anion have been observed. Concerning PHBHA, the rate constants of the forward and reverse steps are k(1) = (1.9 +/- 0.1) x 10(3) M-1 s(-1) and k(-1) = (1.1 +/- 0.1) x 10(2) s(-1) for the step involving the undissociated PHBHA and k(2) = (3.2 +/- 0.2) x 10(4) M-1 s(-1) and k(-2) = 1.2 +/- 0.2 s(-1) for the step involving the anion. Concerning SHA, the analogous rate constants are k(1) = (2.6 +/- 0.1) x 10(3) M-1 s(-1), k(-1) = (1.3 +/- 0.1) x 10(3) s(-1), k(2) = (5.4 +/- 0.2) x 10(3) M-1 s(-1), and k(-2) = 6.3 +/- 0.5 s(-1). These values indicate that metal binding to the anions of the two acids concurs with the Eigen-Wilkins mechanism and that the phenol oxygen is not involved in the chelation. Moreover, a slow effect was observed in the SHA-Ni(II) system, which has been put down to rotation of the benzene ring around the C-C bond. Quantum mechanical calculations at the B3LYP/lanL2DZ level reveal that the phenol group in the most stable form of the Ni(II) chelate is in trans position relative to the carbonyl oxygen, contrary to the free SHA structure, where the phenol and carbonyl oxygen atoms both have cis configuration. These results bear out the idea that the complex formation is coupled with phenol rotation around the C-C bond
CCSD(T) STUDY OF THE FAR-INFRARED SPECTRUM OF ETHYL METHYL ETHER
No full textM.L. Senent, Mol.Phys.J.R. Durig, Y. Jin, H.V. Phan and D.T. Durig Structural ChemistryI. Medvedev, M. Winnewisser, F.C. de Lucia, E. Herbst, E. Yi, L.P. Leong, R.P.A. Bettens, E. Bialkowska-Jaworska, O. Desyatnyk, L. Psczolkowski and Z. Kisiel, ApJAuthor Institution: Universidad de Burgos, Departamento de Quimica, Plaza Misael Banuelos s/n, 09001 Burgos, Spain; Departamento de Astrofisica Molecular e Infrarroja; Instituto de Estructura de la Materia, C.S.I.C., Madrid 28006, Spain; Departamento de Ingenieria Civil, Catedra de Quimica; E.U.I.T. Obras Publicas, Universidad Politecnica de Madrid, Spain; Departamento de Quimica, UAM-I Purisima y Michoacan, s/n ; CP 09340, Mexico D.F, MEXICOThe molecular structure and the far infrared spectrum of ethyl methyl are investigated using state-of-the-art CCSD(T) ab initio calculations. We provide the geometry of the two conformers (trans and gauche), the corresponding harmonic and anharmonic fundamentals, the torsional barriers and the three dimensional Potential Energy Surface depending on the vibrational motion responsible of the non-rigidity. The dependence of the spectroscopic parameters with the torsional motion is detailed. From the Potential Energy Surface, the rotorsional energy levels are calculated variationally with a flexible model depending on the three large amplitude coordinates } \underline{\textbf{99}}, 1311 (2001)}. We provide the far infrared frequencies and intensities at room temperature and the rotational parameters computed for the lowest torsional energy levels. Results are compared with available experimental data } \underline{\textbf{13}}, 1 (2002)} } \underline{\textbf{148}}, 593 (2003)}. \vspace{1em} \noinden
Quantum-chemical calculation of spectroscopic parameters for rotational spectroscopy: Application to astrophysics and atmospherical systems
No full textQuantum-chemical calculations are a powerful tool for assisting experimental investigations in the field of rotational spectroscopy. High-level calculations can provide reliable values for the corresponding spectroscopic parameters (rotational constants, centrifugal distortion constants, etc.), thus significantly facilitating observations and assignments. Theoretical predictions for the hyperfine parameters (quadrupole coupling constants, spin-rotation tensors, spin-spin couplings, etc.) are often essential for a detailed analysis of the hyperfine structure of the measured rotational spectra.
The theoretical and computational backgrounds for the required quantum-chemical calculations will be reviewed with an emphasis on the adequate treatment of electron correlation (using coupled-cluster techniques), the calculation of molecular properties using analytic derivative techniques, and the treatment of vibrational effects within a perturbational approach.
Examples of astrophysical as well as atmospherical interest will be presented to illustrate the succesfull interplay of theory and experiment in the field of rotational spectroscopy
Weak intramolecular interaction effects on the torsional spectra of ethylene glycol, an astrophysical species
No full text11 pags., 6 figs., 10 tabs.An elaborate variational procedure of reduced dimensionality based on explicitly correlated coupled clusters calculations is applied to understand the far infrared spectrum of ethylene-glycol, an astrophysical species. This molecule can be classified in the double molecular symmetry group G and displays nine stable conformers, gauche and trans. In the gauche region, the effect of the potential energy surface anisotropy due to the formation of intramolecular hydrogen bonds is relevant. For the primary conformer, stabilized by a hydrogen bond, the ground vibrational state rotational constants are computed to be A = 15 369.57 MHz, B = 5579.87 MHz, and C = 4610.02 MHz corresponding to differences of 6.3 MHz, 7.2 MHz, and 3.5 MHz from the experimental parameters. Ethylene glycol displays very low torsional energy levels whose classification is not straightforward and requires a detailed analysis of the torsional wavefunctions. Tunneling splittings are significant and unpredictable due to the anisotropy of the potential energy surface PES. The ground vibrational state splits into 16 sublevels separated ∼142 cm. The splitting of the >G1 sublevels> was calculated to be ∼0.26 cm in very good agreement with the experimental data (0.2 cm = 6.95 MHz). Transitions corresponding to the three internal rotation modes allow assignment of previously observed Q branches. Band patterns, calculated between 362.3 cm and 375.2 cm, 504 cm and 517 cm, and 223.3 cm and 224.1 cm, that correspond to the tunnelling components of the v fundamental (v = OH-torsional mode), are assigned to the prominent experimental Q branches. by AIP Publishing.This research was supported by the MINECO of
Spain grant FIS2013-40626-P. The authors acknowledge
the COST Actions CM1405 “MOLIM” and CM1401 “Our
Astrochemical History”. R.B. acknowledges the grant No.
ECOST-STSMCM1401-020316-071825 and Tunisian Grants.
The authors acknowledge the CTI (CSIC) and CESGA for
computing facilities.Peer Reviewe
Differential Acquisition of m-Sequences using Recursive Soft Sequential Estimation
No full textIn this contribution a novel sequential estimation method is proposed for the acquisition of -sequences. This sequential estimation method exploits the principle of iterative soft-in-soft-out (SISO) decoding for enhancing the acquisition performance, and that of differential pre-processing for the sake of achieving an enhanced acquisition performance, when communicating over various communication environments. Hence the advocated acquisition arrangement is referred to as the Differential Recursive Soft Sequential Estimation (DRSSE) acquisition scheme. The DRSSE acquisition scheme exhibits a low complexity, which is similar to that of an -sequence generator, while achieving an acquisition time that is linearly dependent on the number of stages in the -sequence generator. A low acquisition time is achieved with the advent of the property that the proposed DRSSE scheme is capable of determining the real-time reliabilities associated with the decision concerning a set of, say , consecutive chips. This set of consecutive chips constitutes the sufficient initial condition for enabling the local -sequence generator to produce a synchronized local despreading -sequence replica. Owing to these attractive characteristics, the DRSSE acquisition scheme constitutes a promising initial synchronization scheme for acquisition of long -sequences, when communicating over various propagation environments
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