Quantum and quasi-classical calculations for the S+ + H2(v,j) → SH+(v′,j′) + H reactive collisions

10 págs; 14 figs.; 2 tabs.State-to-state cross-sections for the S + H(v,j) → SH(v′,j′) + H endothermic reaction are obtained using quantum wave packet (WP) and quasi-classical (QCT) methods for different initial ro-vibrational H(v,j) over a wide range of translation energies. The final state distribution as a function of the initial quantum number is obtained and discussed. Additionally, the effect of the internal excitation of H on the reactivity is carefully studied. It appears that energy transfer among modes is very inefficient that vibrational energy is the most favorable for the reaction, and rotational excitation significantly enhances the reactivity when vibrational energy is sufficient to reach the product. Special attention is also paid to an unusual discrepancy between classical and quantum dynamics for low rotational levels while agreement improves with rotational excitation of H. An interesting resonant behaviour found in WP calculations is also discussed and associated with the existence of roaming classical trajectories that enhance the reactivity of the title reaction. Finally, a comparison with the experimental results of Stowe et al. for S + HD and S + D reactions exhibits a reasonably good agreement with those results.O. R. and N. B. acknowledge CSIC for the travelling grant I-LINK0775. Financial support from the Scientific and Technological Research Council of TURKEY (TUBITAK) (Project No. TBAG- 112T827) and the Ministerio de Economía e Innovación (Spain), for grants CSD2009-00038 and FIS2014-52172-C2, is gratefully acknowledged. The computations have been performed on the High Performance and Grid Computing Center (TR-Grid) at ULAKBIM/TURKEY and CESGA computer center. We also thank the support from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007- 2013)/ERC Grant Agreement no. 610256 (NANOCOSMOS). We also acknowledge the COST action CM1401 ‘Our Astrochemical History’.Peer Reviewe

Formation of interstellar SH+^+ from vibrationally excited H2_2: Quantum study of S+^+ + H2_2 ⇄\rightleftarrows SH+^+ + H reactions and inelastic collisions

The rate constants for the formation, destruction, and collisional excitation of SH$^+$ are calculated from quantum mechanical approaches using two new SH$_2^+$ potential energy surfaces (PESs) of $^4A''$ and $^2A''$ electronic symmetry. The PESs were developed to describe all adiabatic states correlating to the SH$^+$ ($^3\Sigma^-$) + H($^2S$) channel. The formation of SH$^+$ through the S$^+$ + H$_2$ reaction is endothermic by $\approx$ 9860 K, and requires at least two vibrational quanta on the H$_2$ molecule to yield significant reactivity. Quasi-classical calculations of the total formation rate constant for H$_2$($v=2$) are in very good agreement with the quantum results above 100K. Further quasi-classical calculations are then performed for $v=3$, 4, and 5 to cover all vibrationally excited H$_2$ levels significantly populated in dense photodissociation regions (PDR). The new calculated formation and destruction rate constants are two to six times larger than the previous ones and have been introduced in the Meudon PDR code to simulate the physical and illuminating conditions in the Orion bar prototypical PDR. New astrochemical models based on the new molecular data produce four times larger SH$^+$ column densities, in agreement with those inferred from recent ALMA observations of the Orion bar.Comment: 8 pages, 7 figure

Tailoring the optical and spectroscopic properties of ascorbic acid via solvation with DMSO: A theoretical study using different quantum models

The anti-oxidizing properties and physiological action of ascorbic acid have recently attracted considerable research attention. This study employs dimethyl sulfoxide (DMSO) solvent to examine the interaction of solvent molecules and the resulting structural modifications in ascorbic acid through trial and error with three quantum solvation models (CPCM, IEFPCM, and SMD). DMSO was selected from the models to analyze changes in the optical bandgap and spectroscopic properties using first-principles methods. Geometry optimization was performed at two different levels of theory: Hartree-Fock (HF) and density functional theory (DFT). The DFT method was employed with a 6–311 G/B3LYP basis set to yield the ground-state energy. The electronic orientation was investigated through potential energy mapping, while spectroscopic analysis encompassed ultraviolet (UV–VIS) and nuclear magnetic resonance (NMR) techniques. Additionally, Fourier transform infrared spectroscopy was used to gain a deeper understanding of the chemical structures of the compound. The findings shed light on the DMSO-Ascorbic acid interactions and revealed structure-property correlation. © 2023 The Author(s

A detailed quantum mechanical and quasiclassical trajectory study on the dynamics of the H(+) + H2 --> H2 + H(+) exchange reaction

13 pages, 11 figures.-- PACS nrs.: 82.30.Hk; 82.30.Nr.The H(+) + H2 exchange reaction has been studied theoretically by means of a different variety of methods as an exact time independent quantum mechanical, approximate quantum wave packet, statistical quantum, and quasiclassical trajectory approaches. Total and state-to-state reaction probabilities in terms of the collision energy for different values of the total angular momentum obtained with these methods are compared. The dynamics of the reaction is extensively studied at the collision energy of E(coll) = 0.44 eV. Integral and differential cross sections and opacity functions at this collision energy have been calculated. In particular, the fairly good description of the exact quantum results provided by the statistical quantum method suggests that the dynamics of the process is governed by an insertion mechanism with the formation of a long-lived collision complex.Two of the authors (O.R. and T.G.L.) thank the Spanish Ministry of Education (MEC) for financial support through Grants Nos. FIS2004-02461 and CTQ2004-02415. One of the authors (T.G.L.) would like to acknowledge support from the program Ramón y Cajal of Spanish MEC and EU Grant No. MERG-CT-2004-513600. Two other authors (F.J.A. and L.B.) acknowledge financial support through MEC Grant No. CTQ2005-08493-C02-01 and Universidad Complutense- Comunidad de Madrid Grant No. 910729. Another author (N.B.) thanks a postdoctoral fellowship by Spanish MEC under the program "Estancias de jóvenes doctores y tecnólogos extranjeros en España". One of the authors (F.J.A.) thanks the financial support by the programme of "Sabáticos Complutenses" of the Universidad Complutense de Madrid. The EQM calculations were performed on a NEC-SX5 vector supercomputer, through a grant from the "Institut du Développement des Ressources en Informatique Scientifique" (IDRIS-CNRS) in Orsay (France).Peer reviewe

A Bimodal Extension of the Generalized Gamma Distribution

A bimodal extension of the generalized gamma distribution is proposed by using a mixing approach. Some distributional properties of the new distribution are investigated. The maximum likelihood (ML) estimators for the parameters of the new distribution are obtained. Real data examples are given to show the strength of the new distribution for modeling data.Una extensión bimodal de la distribución gamma generalizada es propuesta a través de un enfoque de mixturas. Algunas propiedades de la nueva distribución son investigadas. Los estimadores máximo verosímiles (ML por sus siglas en inglés) de los parámetros de la nueva distribución son obtenidos. Algunos ejemplos con datos reales son utilizados con el fin de mostrar las fortalezas de la nueva distribución en la modelación de datos

The Evaluation of Contralateral Breast Lesions in Breast Cancer Patients Using Reduction Mammoplasty

Purpose: This study evaluated the importance of routine pathological examination of contralateral breast specimens in breast cancer patients using reduction mammoplasty. Methods: The weight of breast tissue resected from the contralateral breast in 71 patients and the number of slices used for pathological evaluation were recorded. Breast lesions found in the contralateral breast and accompanying lesions with tumors were examined. Results: High risk proliferative lesions were reported in the contralateral breast of eight (11.2%) patients, and low-risk lesions were detected in 18 (25%). While the mean age of the patients with high-risk lesions was 45.6, it was 52.8 for the other patients (p = 0.036). Conclusion: Bilateral reduction mammoplasty may be beneficial to delineate some pathologies in contralateral breasts even in those patients with normal clinical and radiological findings. The incidental discovery of these pathologies is much more likely in young breast cancer patients

Crystallinity Improvement of Co3O4 by Adding Thiourea

Tricobalt tetraoxide (Co3O4) samples having different thiourea/Co molar ratio of 0, 5 and 10 were prepared by wet chemical synthesis. The effects of thiourea content on the crystal structure-related parameters of Co3O4 were determined. The increase in the amount of thiourea caused a gradual decrease in the lattice parameters and specific surface area and an increase in the crystallinity and crystallite size. The experimental analysis results showed that thiourea content can be used to control the crystal structure-related parameters of Co3O4

Synthesis and Structural Characterization of Y-doped Pyramidal ZnO Powders

The present study focuses on the structural changes in ZnO powder induced by doping of a rare earth metal of Y. For this aim, we synthesized four ZnO samples with different Y-content using the combustion reaction method. X-ray powder diffraction (XRPD) technique and scanning electron microscopy (SEM) results confirm that the as-investigated structural parameters and morphology of the ZnO structure were affected directly by the concentration of Y dopant. For each Y-doped sample, randomly-oriented pyramidal morphology and the formation of a minority phase of Y2O3 were observed. A gradual increase in both lattice parameters and unit cell volume was detected with increasing Y content. All samples were found to be thermally stable in the temperature interval of 25-950 °C

Gas phase Elemental abundances in Molecular cloudS (GEMS) VIII. Unlocking the CS chemistry: the CH + S→\rightarrow CS + H and C2_2 + S→\rightarrow CS + C reactions

We revise the rates of reactions CH + S -> CS + H and C_2 + S -> CS + C, important CS formation routes in dark and diffuse warm gas. We performed ab initio calculations to characterize the main features of all the electronic states correlating to the open shell reactants. For CH+S we have calculated the full potential energy surfaces for the lowest doublet states and the reaction rate constant with a quasi-classical method. For C_2+S, the reaction can only take place through the three lower triplet states, which all present deep insertion wells. A detailed study of the long-range interactions for these triplet states allowed to apply a statistic adiabatic method to determine the rate constants. This study of the CH + S reaction shows that its rate is nearly independent on the temperature in a range of 10-500 K with an almost constant value of 5.5 10^{-11} cm^3/s at temperatures above 100~K. This is a factor \sim 2-3 lower than the value obtained with the capture model. The rate of the reaction C_2 + S depends on the temperature taking values close to 2.0 10^{-10} cm^3/s at low temperatures and increasing to 5. 10^{-10} cm^3/s for temperatures higher than 200~K. Our modeling provides a rate higher than the one currently used by factor of \sim 2. These reactions were selected for involving open-shell species with many degenerate electronic states, and the results obtained in the present detailed calculations provide values which differ a factor of \sim 2-3 from the simpler classical capture method. We have updated the sulphur network with these new rates and compare our results in the prototypical case of TMC1 (CP). We find a reasonable agreement between model predictions and observations with a sulphur depletion factor of 20 relative to the sulphur cosmic abundance, but it is not possible to fit all sulphur-bearing molecules better than a factor of 10 at the same chemical time.Comment: 13 pages, 10 figure