Search results for "Number"
showing 10 items of 3939 documents
High resolution spectroscopy and potential determination of the (3)1Pi state of NaCs.
2006
The (3)(1)Pi state of the NaCs molecule was studied by high resolution Fourier-transform spectroscopy. The (3)(1)Pi--X (1)Sigma(+) laser induced fluorescence was excited by an Ar(+) ion laser or by a single-mode frequency-doubled cw Nd:YAG laser. The presence of argon buffer gas yielded rich rotational relaxation spectra allowing to enlarge the data set for the (3)(1)Pi state term values, as well as to observe Lambda splittings in a wide range of vibrational (v(')) and rotational (J(')) quantum numbers. The data field includes about 820 energy levels of (3)(1)Pi NaCs in the range from v(')=0 to 37 and from J(')=3 to 190, which corresponds to ca. 95% of the potential well depth. Direct fit o…
Hydration of agarose double helix: A monte carlo simulation
2009
The structure of the water around agarose double helix is analyzed with ab initio quantum mechanical calculations and Monte Carlo simulations. The potential surface is sampled by computing the interaction energy between fragments of agarose and a water molecule placed at 221 different orientations and/or positions. These energy values are fitted to a simple analytical expression representing atom-atom pair potentials for a water molecule interacting with agarose. A preliminary understanding of the agarose-water interaction is obtained from isoenergy contour maps at planar cross sections, perpendicular to the long axis of the double helix, and for cylindrical surfaces enclosing the double he…
On a topological interpretation of electronic and vibrational molecular energies
1998
Abstract A relationship between Randic's connectivity index and various quantum mechanical parameters derived from the Huckel Molecular Orbital (HMO) approach is demonstrated. When applied to conjugated hydrocarbons, this index represents the measure of the global π electron molecular energy and, therefore, of the resonance energy. Moreover, the development of the procedure, allows the introduction of a new definition of the bond order which, in turn, makes possible a better prediction not only for bond lengths of naphtalene but also for the resonance integral and conjugation energy for butadiene. Also, a corrected value for the Randic index is deduced, which allows for the reduction of the…
Extended Fourier-transform spectroscopy studies and deperturbation analysis of the spin-orbit coupled A1Σ+ and b3Π states in RbCs.
2014
The article presents a study of the strongly spin-orbit coupled singlet A(1)Σ(+) and triplet b(3)Π states of the RbCs molecule, which provide an efficient optical path to transfer ultracold molecules to their rovibrational ground state. Fourier-transform A(1)Σ(+) - b(3)Π → X(1)Σ(+) and (4)(1)Σ(+) → A(1)Σ(+) - b(3)Π laser-induced fluorescence (LIF) spectra were recorded for the natural mixture of the (85)Rb(133)Cs and (87)Rb(133)Cs isotopologues produced in a heat pipe oven. Overall 8730 rovibronic term values of A(1)Σ(+) and b(3)Π states were determined with an uncertainty of 0.01 cm(-1) in the energy range [9012, 14087] cm(-1), covering rotational quantum numbers J ∈ [6, 324]. An energy-ba…
ChemInform Abstract: Getting Discriminant Functions of Antibacterial Activity from Physicochemical and Topological Parameters.
2010
Linear discriminant analysis has been demonstrated to be a very useful tool in the selection and design of new drugs. Up to now we have used it through the search of a topological pattern of activity. In this work our goal is to calculate a complete set of physicochemical parameters using semiempirical (quantum chemical) calculations as well as topological indices (TIs) and try to find out any discriminant function for antibacterial activity through the combined use of both types of descriptors. The physicochemical parameters, such as heat of formation, HOMO, LUMO, dipole moment, polarizability, hyperpolarizability, PM3 generated IR vibrational frequencies, etc., were calculated using PM3 H…
The infrared spectrum of CH 3 D between 900 and 3200 cm −1 : extended assignment and modeling
2000
Abstract The high resolution infrared spectrum of CH 3 D in the region from 900 to 3200 cm −1 has been analyzed on the basis of Fourier transform spectra recorded at Kitt Peak and at Giessen. A theoretical model for an effective hamiltonian in terms of irreducible tensor operators recently adapted to symmetric top molecules has been used in order to consider simultaneously all available transitions between the lowest three polyads of the molecule: the Ground State (G.S.), the Triad (three interacting fundamental bands in the 8 μm region) and the Nonad (nine interacting bands in the 4 μm region). A preliminary simultaneous fit of 3467 Triad–G.S., 5208 Nonad–G.S., and 2487 Nonad–Triad (hot ba…
Adsorption of 3d Transition Elements on a TiO2(110) Surface.
2008
International audience; A first-principles study on the adsorption of 3d transition metal atoms on a stoichiometric TiO2(110) surface is reported. For all 3d elements except Cu, the most stable on-surface adsorption site is a site where the adatom binds to two twofold and one threefold surface oxygen atoms. For Ti, V, and Cr, however, a subsurface site, where the adatom substitutes a sixfold Ti atom, is more stable. The adatoms are oxidized in all cases. The charge transfer to the substrate is larger for the substitutional site than for the on-surface adsorption sites and decreases with atomic number along the 3d series. The relative stabilities of the adsorption sites are discussed in term…
Calculations on solvents and co-solvents of single-wall carbon nanotubes:cyclopyranoses
2005
The (10, 10) single-wall carbon nanotube (SWNT) presents consistency between relatively small solubility, and large partition coefficients and kinetic stability. The solubility of SWNTs is investigated in a variety of solvents, finding a class of non-hydrogen-bonding Lewis bases that provides good solubility. The organic solvent–water partition and hydrophobic moment of lysozyme show that the main contribution to the water-accessible surface area of helices is the hydrophobic term, while the hydrophilic part dominates in the sheet, which is related to the 1-octanol–, cyclohexane– and chloroform–water partition coefficients Po−ch−cf of helices, which are greater than those of the sheet. The …
Graphical representation of polynuclear acid-base and complex equilibria.
1983
Abstract A calculation procedure for diagrams of log CM = ƒ(pL) at various values of the ratio of analytical concentrations, CL/CM, in polynuclear binary systems is described. The diagrams are useful in the resolution of analytical problems of practical interest involving acid-base equilibria (such as the preparation of buffer solutions) and complex equilibria. The presence of a solid phase is also considered.
Structures and EPR spectra of binary sulfur–nitrogen radicals from DFT calculations
2007
Abstract The scattered electron paramagnetic resonance (EPR) spectroscopic data for binary sulfur–nitrogen (S,N) radicals have been compiled and critically assessed.Many of these are inorganic rings or cages.For each species, possible equilibrium structures in the gas phase and the EPR hyperfine coupling (hfc) constants have been calculated with DFT using the B3LYP functional and basis sets of triple-ζ (or better) quality.Good agreement is obtained between calculated and measured values for the well characterized [S3N2]+ , a planar π-radical for which the s-component of the orbitals is likely to be reasonably independent of minor geometrical changes between gas-phase and condensed-phase sta…