Molecular Astrophysics最新文献

{"title":"Structural and spectral properties of astronomical complex organic molecules: 1:1:1 glycine-X-Y and Y-glycine-X","authors":"Anita Kabi,&nbsp;Pradipta K. Behera,&nbsp;Prabhat K. Sahu","doi":"10.1016/j.molap.2020.100086","DOIUrl":"10.1016/j.molap.2020.100086","url":null,"abstract":"<div><p><span>Current research to understand astrochemistry<span> and astrobiology<span> with regard to the weakly bound astronomical complexes including amino acids<span> in the Inter-Stellar Medium (ISM), comets and meteorites at molecular level are flourishing and many new findings are emerging rapidly. Modern experimental techniques and computational investigations assisted by quantum chemical analysis are playing key role towards exploring the evolution of many molecular complexes in astrochemical environment and planetary atmospheres<span> by affecting their stability as well as their structural and spectral properties. The present work deals with weekly bound complexes of glycine with small molecules like water, ammonia and HF as 1:1:1 Glycine-X-Y and Y-Glycine-X. The affects that influence the complexation, mainly involve through non-covalent interactions with these small molecules have been explored, based on various properties of the red shifted hydrogen bonds of the type: O</span></span></span></span></span><img>H<img>O, N<img>H<img>O, F<img>H<img>O, O<img>H<img>N and carbon-cantered blue shifted hydrogen bonds, C<img>H<img><span>O type, for all the stable complexes of 1:1:1 Glycine-X-Y and Y-Glycine-X with respect to their structural properties and spectral characterization<span><span><span>. The computed Ray's asymmetry parameter, κ values for the investigated 1:1:1 Glycine-X-Y and Y-Glycine-X complexes are found to be negative and predicted as prolate-type asymmetric rotor. The computed rotational constants and </span>IR spectra of these different complexes may assist in the interpretation and analysis of observational data and the data obtained in laboratory experiments. The possibilities of formation of such molecular complexes in the </span>interstellar space may provide a direction to explore new possibilities.</span></span></p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"21 ","pages":"Article 100086"},"PeriodicalIF":0.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2020.100086","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89963603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Collision processes, dynamic and kinetic parameters, and energy exchanges of particles in astrochemistry reaction of NH+H2 and deuterated analogs on an interpolated potential energy surface","authors":"Rahman Padash,&nbsp;Shapour Ramazani","doi":"10.1016/j.molap.2020.100085","DOIUrl":"10.1016/j.molap.2020.100085","url":null,"abstract":"<div><p>Collision of NH radical with H₂<span> molecule and their deuterated analogs were studied on an interpolated potential energy surface using </span><em>ab initio</em><span><span> calculation. For this purpose, reactive and non-reactive processes were considered. Reaction probability and cross-section were determined and used for calculating the rate constant. In non-reactive trajectories, the inelastic collision<span> was investigated in order to calculate the scattering angle. The difference between the initial and final energy of each particle was calculated in order to determine the transmitted and converted energy. For all trajectories, the effect of the impact parameter and relative translational energy of particles on the reaction probability, transmitted energy, and scattering angle were determined. </span></span>Isotope effect was used to specify the effect of the mass of the target and incoming particle on the quantity and quality of products and also on the reaction probability and other observable properties.</span></p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"20 ","pages":"Article 100085"},"PeriodicalIF":0.0,"publicationDate":"2020-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2020.100085","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86559356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How does successive hydrogen addition to PAH ions impact their unimolecular chemistry?","authors":"Malick Diedhiou,&nbsp;Brandi J. West,&nbsp;Paul M Mayer","doi":"10.1016/j.molap.2020.100071","DOIUrl":"10.1016/j.molap.2020.100071","url":null,"abstract":"<div><p><span>Hydrogenated polycyclic aromatic hydrocarbons (PAHs) have been proposed to contribute to the formation of interstellar H</span>₂<span> by acting as a surface catalyst for the adsorption of hydrogen atoms and desorption of H</span>₂<span><span> molecules. In the present study, imaging photoelectron<span> photoion coincidence (iPEPICO) spectroscopy and tandem mass spectrometry were employed to examine the unimolecular </span></span>chemistry of four hydrogenated polycyclic aromatic hydrocarbon ions: 9,10-dihydroanthracene (DHA</span>^+•) and 1,2,3,4,5,6,7,8-octahydroanthracene (OHA^+•), having opposite patterns of hydrogenation, and 1,2,3,4-tetrahydrophenanthrene (THP^+•) and 1,2,3,4,9,10-hexahydrophenanthrene (HHP^+•). DHA^+• exhibits the same reactions previously observed for 1,2-dihydronaphthalene and 9,10-dihydrophenanthrene, namely competing loss of H^• and CH₃^•. However, the energy required for H^•<span>-loss, as predicted by RRKM modeling of the iPEPICO results, was lower than the latter ions, presumably due to charge delocalization across the central ring upon dehydrogenation. OHA</span>^+•<span> behaves similarly to ionized tetralin, displaying losses of H</span>^•, CH₃^•, C₂H₄ and C₃H₅^•<span><span> in its collision induced dissociation (CID) </span>mass spectra, but under iPEPICO conditions CH</span>₃^•-loss is not observed. THP^+• and HHP^+• have aspects of both DHA^+• and OHA^+• chemistries, displaying losses of H^•, CH₃^•, C₂H₄ and C₃H₅^•. RRKM modeling produced minimum energies for all observed reaction channels, which were also computationally explored at the B3LYP/6–31+G(d,p) level of theory. The results indicate that small PAH ions may not be effective surfaces for the catalytic formation of H₂ in the ISM, but rather sources of small hydrocarbons.</p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"19 ","pages":"Article 100071"},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2020.100071","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77891354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Line-shape parameters for the first rotational lines of HD in He","authors":"Franck Thibault ,&nbsp;Raúl Z. Martínez ,&nbsp;Dionisio Bermejo ,&nbsp;Piotr Wcisło","doi":"10.1016/j.molap.2020.100063","DOIUrl":"10.1016/j.molap.2020.100063","url":null,"abstract":"<div><p><span><span>We report theoretical and experimental line-shape parameters for He-perturbed pure rotational HD lines that are relevant for the studies of </span>gas giants atmospheres. Besides the usual pressure broadening and shift parameters, we also report their speed dependencies and Dicke parameters. The theoretical values, obtained from quantum dynamical calculations, are for the R(</span><em>j</em>=0-3) lines and S(<em>j</em><span>=0-2) and temperatures from 10 to 500 K. The measurements, performed using stimulated Raman spectroscopy, were done for the S(</span><em>j</em>=0-2) rotational Raman lines at 77, 195 and 298 K. We also compare the results of our calculations with pressure broadening and line shift coefficients available in the literature at 77, 195 and 300 K for the studied R lines. We demonstrate that a simple Voigt profile is insufficient to accurately model the shapes of He-perturbed HD lines at conditions relevant to gas giants atmospheres, and one should incorporate also the speed-dependent effects and velocity-changing collisions.</p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"19 ","pages":"Article 100063"},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2020.100063","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83373458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the possibility of electronically excited states in stable amine anions: Dicyanoamine, cyanoethynylamine, and diethynylamine","authors":"Taylor J. Santaloci,&nbsp;Ryan C. Fortenberry","doi":"10.1016/j.molap.2020.100070","DOIUrl":"10.1016/j.molap.2020.100070","url":null,"abstract":"<div><p>Of the dicyanomine anion (NCNCN<span><math><msup><mrow></mrow><mo>−</mo></msup></math></span>), cyanoethynylamine anion (NCNC₂H<span><math><msup><mrow></mrow><mo>−</mo></msup></math></span>), and diethynylamine anion (HC₂NC₂H<span><math><msup><mrow></mrow><mo>−</mo></msup></math></span>), only the mixed, <em>C_s</em> NCNC₂H<span><math><msup><mrow></mrow><mo>−</mo></msup></math></span><span><span> anion has are large enough dipole moment to support an electronically excited state at 3.0323 eV. This quantum chemical study shows that this value lies 0.0051 eV below the </span>electron binding energy<span><span> (eBE) and may have correlation to early-onset diffuse interstellar bands. None of these three anions possess further valence </span>excited electronic states<span> beyond the singlet ground states, and triplet excited states are all beyond their respective eBEs.</span></span></span></p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"19 ","pages":"Article 100070"},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2020.100070","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74101797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The case for gas-phase astrochemistry without carbon","authors":"Ryan C. Fortenberry","doi":"10.1016/j.molap.2019.100062","DOIUrl":"10.1016/j.molap.2019.100062","url":null,"abstract":"<div><p><span><span>Most carbon in the Universe is tied up in carbon monoxide or in </span>polycyclic aromatic hydrocarbons<span>. Even so, a vast majority of the molecules detected in various astrophysical media contain at least one carbon atom in them. These could nearly all be classified as hydrocarbons. However, only a fraction of the atoms in the Universe heavier than helium are actually carbon. This review will explore the past astronomical detections of molecules that do not contain carbon and will discuss the present workings and future outlooks of pure, inorganic </span></span>astrochemistry. Such molecules have bonding structures that are often “atypical,” have notable spectroscopic intensities, and open the door for new chemical insights. Asking novel questions can lead to novel insights, and inorganic astrochemistry provides a strong motivation for asking the most creative chemical questions.</p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"18 ","pages":"Article 100062"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2019.100062","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76899361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanism and kinetics of astrophysically relevant gas-phase stereoinversion in glutamic acid: A computational study","authors":"Namrata Rani,&nbsp;Vikas","doi":"10.1016/j.molap.2019.100061","DOIUrl":"10.1016/j.molap.2019.100061","url":null,"abstract":"<div><p><span><span><span>Enantiomeric excess of </span>amino acids observed in the meteoritic samples of </span>carbonaceous chondrites has incited many researchers to search for an extra-terrestrial origin of life on prebiotic Earth. However, in a non-catalytic environment, only racemic amino acids are synthesized. This computational quantum-mechanical study explores non-catalytic mechanistic pathways for stereoinversion in proteinogenic </span><em>L</em><span><span><span>-glutamic acid, which may be observable under gas-phase conditions of interstellar medium (ISM). The multi-step stereoinversion pathways proposed in this study are traced through a global reaction route mapping (GRRM) strategy utilizing density-functional and coupled-cluster theories. Notably, a few of the pathways are observed to proceed through simultaneous intramolecular </span>hydrogen atom<span> and proton transfer<span><span> as well as through a proton-coupled electron transfer<span> mechanism. The intermediates explored along the stereoinversion pathways resemble ammonium ylide and </span></span>imine<span>, the key ingredients in Strecker synthesis of amino acids. The thermodynamic and </span></span></span></span>kinetic analysis<span> of the stereoinversion pathways in different temperature regions of ISM are also carried out, predicting the streoinversion to proceed over any dissociation of intermediates and conformers<span> of glutamic acid along the pathways. However, initial step of the pathways involves an unsurmountable energy barrier though the key step responsible for stereoinversion has a very low energy barrier and is predicted to proceeds with significant rates. The work suggests the possibility of observing stereoinversion of glutamic acid in the warmer regions of ISM.</span></span></span></p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"18 ","pages":"Article 100061"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2019.100061","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85332013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reactivity of coronene with O-atoms, a possible route to ketene in the interstellar medium","authors":"Francois Dulieu ,&nbsp;Sabine Morisset ,&nbsp;Abdi-Salam Ibrahim Mohamed ,&nbsp;Leon Boshman ,&nbsp;Stephanie Cazaux ,&nbsp;Dominique Teillet-Billy ,&nbsp;Saoud Baouche ,&nbsp;Nathalie Rougeau","doi":"10.1016/j.molap.2019.100054","DOIUrl":"10.1016/j.molap.2019.100054","url":null,"abstract":"<div><p><span><span>PAHs are one of the important components of the carbonaceous matter of the Universe. They are not detected in the darkest regions of the </span>Interstellar Medium<span> and one possible reason could be their chemical transformation through gas phase reactions In particular, their oxidation was considered ineffective because the reaction barriers appear to be too high, based on combustion studies conducted at high temperatures. For the first time, we experimentally studied the oxidation of </span></span>Coronene<span><span>, a PAH archetype, at low temperature (50 K), as well as the oxidation of hydrogenated Coronenes. It appears that reactivity is higher than expected and that the fragmentation of coronene is a significant channel of the oxidation. Furthermore, hydrogenated coronenes are very reactive to oxygen. To understand the experimental data, DFT calculations were performed. They confirm a low oxidation barrier (0.11 eV) and show that oxygen is preferentially inserted at the periphery of the coronene and propose a reaction mechanism for fragmentation also involving a </span>hydrogen atom. An estimate of the orders of magnitude shows that PAH oxidation may explain part of the decrease in their abundances in warm environments.</span></p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"17 ","pages":"Article 100054"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2019.100054","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73827336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First quantum study of the rotational excitation of HCN by para-H2O: Convergence of quantum results, influence of the potential energy surface, and approximate rate coefficients of interest for cometary atmospheres.","authors":"M.L. Dubernet ,&nbsp;Ernesto Quintas-Sánchez","doi":"10.1016/j.molap.2019.100046","DOIUrl":"10.1016/j.molap.2019.100046","url":null,"abstract":"<div><p><span>The rotational excitation of HCN by H</span>₂<span><span>O, the main perturber in cometary atmospheres, is investigated using quantum methodologies. We provide approximate rotational de-excitation rate coefficients among the first levels of HCN perturbed by thermalized para-water in the temperature range T=5K to T=150K. Because of the novelty of the system for quantum rotational excitation, the current study includes a detailed appreciation of the parameters involved in the convergence of the cross-sections and of rate coefficients calculations. A compromise on the convergence of the rate coefficients with respect to the rotational basis set is taken because of the computing time cost. Moreover, because of the cost also involved in calculating the 5D potential energy surfaces necessary for the current dynamical calculations, several potential energy surfaces of increased quality are tested and it is shown that, within the current approximations on the </span>collisional calculations, average quality potential energy surfaces are sufficient for cometary applications.</span></p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"16 ","pages":"Article 100046"},"PeriodicalIF":0.0,"publicationDate":"2019-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2019.100046","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72449666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theoretical investigation of methanol formation from methane water-ice cluster following ionization","authors":"Sankhabrata Chandra","doi":"10.1016/j.molap.2019.100045","DOIUrl":"10.1016/j.molap.2019.100045","url":null,"abstract":"<div><p>In this article, I have presented quantum mechanical treatment of methanol formation reaction from methane water-ice cluster after ionization with high energy photons. To mimic water ice structure, six water molecules are arranged in hexagonal form. This is the most stable structure formed by six water molecules. Theoretical photodesorption study has been performed on this structure. I have investigated a unique reaction mechanism of methanol formation from methane water ice cluster. I have shown that methanol forms after ionization via two transition states. Hydrogen molecule forms as one of the side product. Initiation of the reaction occurs by dissociation of O<img>H bond in the water cluster followed by C<img>H bond dissociation and formation of C<img>O bond. The timescale of the initial step, which is dissociation of O<img>H bond, has been computed as 50 femtosecond in this article.</p></div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"16 ","pages":"Article 100045"},"PeriodicalIF":0.0,"publicationDate":"2019-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2019.100045","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80317532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}