N. Jaidane

Solvation Energies of the Proton in Methanol

pKas, proton affinities, and proton dissociation free energies characterize numerous properties of drugs and the antioxidant activity of some chemical compounds. Even with a higher computational level of theory, the uncertainty in the proton solvation free energy limits the accuracy of these parameters. We investigated the thermochemistry of the solvation of the proton in methanol within the cluster-continuum model. The scheme used involves up to nine explicit methanol molecules, using the IEF-PCM and the strategy based on thermodynamic cycles. All computations were performed at B3LYP/6-31++G(dp) and M062X/6-31++G(dp) levels of theory. It comes out from our calculations that the functional M062X is better than B3LYP, on the evaluation of gas phase clustering energies of protonated methanol clusters, per methanol stabilization of neutral methanol clusters and solvation energies of the proton in methanol. The solvation free energy and enthalpy of the proton in methanol were obtained after converging the partial solvation free energy of the proton in methanol and the clustering free energy of protonated methanol clusters, as the cluster size increases. Finally, the recommended values for the solvation free energy and enthalpy of the proton in methanol are -257 and -252 kcal/mol, respectively.

Quantitative analysis of pathological nails using laser-induced breakdown spectroscopy (LIBS) technique

Laser-induced breakdown spectroscopy (LIBS) has been used as a potential method for simultaneous measurement of the elements Ca, Na, and K, for normal and pathological nails. We compared the measured LIBS spectra of these elements for normal and pathological nails. The

Rotational excitation and de-excitation of C2(X Σ1g+) by para-H2(j=0)

B^{2} sum ^{ + } to {text{X}}^{2} sum ^{ + }

Electronic states of MgO: Spectroscopy, predissociation, and cold atomic Mg and O production

violet band emission spectrum of CN was used for the estimation of the transient temperature of the plasma plume and consequently of the sample surface considering thermodynamic equilibrium.

Theoretical spectroscopic investigations of HNSq and HSNq (q=0,+1,-1) in the gas phase

The local order in liquid N-methylformamide has been studied by using x-ray diffraction and a density functional theory (DFT). Experimental data were analyzed to yield the total structure function SM(q) and the intermolecular pair correlation function gL(r). DFT calculations, using, namely, the standard TZV basis set, were performed to study the relative stability of the two possible isomers (cis and trans) and to examine some possible intermolecular arrangements in the liquid state. X-ray measurements can be interpreted in term of cyclic trimers of cis form molecules where each monomer can establish two N–H⋯O hydrogen bonds that are described.

Structures of protonated methanol clusters and temperature effects

For the van der Waals C(2)(X (1)Sigma(g)(+))-H(2) molecular system, we generated a new ab initio potential energy surface (PES). We mapped this PES at the multireference internally contracted configuration-interaction method including the Davidson correction together with a large diffuse basis set. Then, we incorporated our PES into quantum scattering calculations at the close coupling and infinite order sudden approximation methods to cover collision energies ranging from 0.1 up to 4000 cm(-1). After Boltzmann thermal averaging, rate coefficients for temperatures of up to 1000 K are deduced. Discrepancies between our new rates and those computed previously are noticed. This should induce deviations in astrophysical modeling.

Rotational excitation of HOCO+ by helium at low temperature

Four-dimensional potential energy surface (4D-PES) of the atmospherically relevant CO2-N2 van der Waals complex is generated using the explicitly correlated coupled cluster with single, double, and perturbative triple excitation (CCSD(T)-F12) method in conjunction with the augmented correlation consistent triple zeta (aug-cc-pVTZ) basis set. This 4D-PES is mapped along the intermonomer coordinates. An analytic fit of this 4D-PES is performed. Our extensive computations confirm that the most stable form corresponds to a T-shape structure where the nitrogen molecule points towards the carbon atom of CO2. In addition, we located a second isomer and two transition states in the ground state PES of CO2-N2. All of them lay below the CO2 + N2 dissociation limit. This 4D-PES is flat and strongly anisotropic along the intermonomer coordinates. This results in the possibility of the occurrence of large amplitude motions within the complex, such as the inversion of N2, as suggested in the recent spectroscopic experiments. Finally, we show that the experimentally established deviations from the C2v structure at equilibrium for the most stable isomer are due to the zero-point out-of-plane vibration correction.

Low-Temperature Rate Constants for Rotational Excitation and De-excitation of C3 (X1Σg+) by Collisions with He (1S)

We used multiconfigurational methods and a large basis set to compute the potential energy curves of the valence and valence-Rydberg electronic states of MgO molecule. New bound electronic states are found. Using these highly correlated wave functions, we evaluated their mutual spin-orbit couplings and transition moment integrals. For the bound electronic states of MgO, we deduced an accurate set of spectroscopic constants that agree remarkably well with experimental results. Moreover, our potentials, transition moments, and spin-orbit coupling evolutions are incorporated into Fermi golden rule calculations to deduce the radiative lifetimes of MgO(Bu2009(1)Σ(+)) rovibrational levels and the natural lifetimes of MgO(Au2009(1)Π) vibrational levels, where a good agreement is found with experimental values. Finally, we suggest new routes for the production of cold Mg and O atoms and cold MgO molecules.