Search results for " Molecular*"
showing 10 items of 14081 documents
Refractive index controlled by film morphology and free carrier density in undoped ZnO through sol-pH variation
2018
Abstract Zinc oxide thin films, prepared by the sol-gel process, were deposited on glass substrate using spin coating technique. The sol-pH effect on the optical parameters was studied for alkaline sol. The surface roughness was investigated by atomic force microscopy (AFM) and varied from 20 to 40 nm. The optical transmission measurements were carried out to evaluate the behavior of the extinction coefficient and the refractive index. An exponential decay of the refractive index ‘n’ as a function of wavelength was observed. The refractive index increases slightly when the pH increases to pH = 9.5 where it reaches its maximum. Beyond this value, it decreases sharply. This behavior has been …
Ultrasonic nebulization inductively coupled plasma optical emission spectrometry method for wine analysis
2020
Abstract A methodology was developed to determine mineral elements in wines using Inductively Coupled Plasma Optical Emission Spectrometry combined with ultrasonic nebulization. The concentration of 36 elements (Al, B, Ba, Bi, Ca, Cd, Ce, Co, Cr, Dy, Er, Eu, Fe, Gd, K, La, Lu, Mg, Mn, Mo, Na, Nd, Ni, Pb, Pr, Sb, Sc, Sm, Sr, Tb, Ti, Tm, V, Y, Yb, and Zn) was determined in 59 wine samples and used to distinguish between Brazilian and Spanish wines. The best conditions for the plasma were selected using a two-level factorial design: radiofrequency power 1500 W; plasma gas flow rate 15 L min−1; auxiliary 0.70 L min−1; and nebulizer 0.40 L min−1. An exploratory multivariate analysis by Principal…
Ab initio multi-reference perturbation theory calculations of the ground and low-lying electronic states of the KRb molecule
2016
The potential energy curves of the low-lying electronic states correlating up to the limit K(4p) + Rb(5s) of KRb molecule have been calculated using the multi-reference perturbation theory method at the CASSCF/ XMCQDPT2 level of theory without and with spin–orbit coupling. The calculated parameters of the ground X 1 R + state are in the best agreement among all previously performed ab initio calculations for the KRb molecule. The calculated vibrational intervals of the ground electronic term of the 39 K 85 Rb molecule describe the experiment with the accuracy within ±1 cm ?1 . The calculated intensities of the 2 1 R + (v 0 = 3, J 0 = 26) ? X 1 R + (v 00 = 0...24, J 00 = 25, 27) transitions …
Carbonyl-functionalized quaterthiophenes: a study of the vibrational Raman and electronic absorption/emission properties guided by theoretical calcul…
2011
This work investigates the evolution of the molecular, vibrational, and optical properties within a family of carbonyl-functionalized quaterthiophenes: 5,5'''-diheptanoyl-2,2':5',2'':5'',2'''-quaterthiophene (1), 5,5'''-diperfluorohexylcarbonyl-2,2':5',2'':5'',2'''-quaterthiophene (2), and 2,7-[bis(5-perfluorohexylcarbonylthien-2-yl)]-4H-cyclopenta[2,1-b:3,4-b']-dithiophene-4-one (3). The analysis is performed by Raman and UV/Vis absorption/excitation/fluorescence spectroscopy in combination with density functional calculations. Theoretical calculations show that substitution with carbonyl groups and perfluorohexyl chains induces progressive quinoidization of the π-conjugated backbone in co…
Coupled-Cluster study of ‘no-pair’ bonding in the tetrahedral Cu4 cluster
2011
Abstract Ab initio Coupled-Cluster calculations with single and double excitations and perturbative correction to the triple, CCSD(T), have been carried out for the high-spin electronic state, ( 5 A 2 ) , of the copper cluster Cu 4 in its tetrahedral arrangement. Like alkali metals clusters, tetrahedral Cu 4 presents a bound quintet state, i.e., a situation where all the valence electrons are unpaired. This rather exotic wavefunction, also known as no-pair bonding state, is examined in detail. The influence of the basis set is also analyzed, as well as the importance of the core correlation and the effect of the basis-set superposition errors.
Theoretical investigation of the potential energy surface of the van der Waals complex CH4-N-2
2009
International audience; The interaction potential energy surface of the van der Waals CH4-N-2 complex has been calculated for a broad range of intermolecular separations and configurations in the approximation of rigid interacting molecules at the CCSD(T) and MP2 levels of theory using the correlation consistent aug-cc-pVTZ basis set. The BSSE correction was taken into account for all the calculations. The most stable configurations of the complex were found. Binding energies were calculated in the CBS limit with accounting for the molecular deformations. The harmonic and anharmonic fundamental vibrational frequencies and rotational constants for the ground and first excited vibrational sta…
Germanium Dicarbide: Evidence for a T-Shaped Ground State Structure
2017
The equilibrium structure of germanium dicarbide GeC2 has been an open question since the late 1950s. Although most high-level quantum calculations predict an L-shaped geometry, a T-shaped or even a linear geometry cannot be ruled out because of the very flat potential energy surface. By recording the rotational spectrum of this dicarbide using sensitive microwave and millimeter techniques, we unambiguously establish that GeC2 adopts a vibrationally averaged T-shaped structure in its ground state. From analysis of 14 isotopologues, a precise r0 structure has been derived, yielding a Ge–C bond length of 1.952(1) A and an apex angle of 38.7(2)°.
Introduction to the special issue on molecular spectroscopy, atmospheric composition and climate change
2018
International audience
Spin-orbit ZORA and four-component Dirac-Coulomb estimation of relativistic corrections to isotropic nuclear shieldings and chemical shifts of noble …
2015
Hartree-Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange-correlation functionals were used for nonrelativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton, and xenon dimers and free atoms. Relativistic corrections were calculated with the scalar and spin-orbit zeroth-order regular approximation Hamiltonian in combination with the large Slater-type basis set QZ4P as well as with the four-component Dirac-Coulomb Hamiltonian using Dyall's acv4z basis sets. The relativistic corrections to the nuclear magnetic shieldings and chemical shifts are combined with nonrelativistic coupled cluster singles and doubles …
Gas-Phase Synthesis of the Elusive Trisilicontetrahydride Species (Si3H4)
2016
The bimolecular gas-phase reaction of ground-state atomic silicon (Si; 3P) with disilane (Si2H6; 1A1g) was explored under single-collision conditions in a crossed molecular beam machine at a collision energy of 21 kJ mol–1. Combined with electronic structure calculations, the results suggest the formation of Si3H4 isomer(s) along with molecular hydrogen via indirect scattering dynamics through Si3H6 collision complex(es) and intersystem crossing from the triplet to the singlet surface. The nonadiabatic reaction dynamics can synthesize the energetically accessible singlet Si3H4 isomers in overall exoergic reaction(s) (−93 ± 21 kJ mol–1). All reasonable reaction products are either cyclic or …