Molecular Astrophysics最新文献_第3页

Computational rotational–vibrational spectroscopic analysis of isomeric species in the interstellar gas-phase stereoinversion of amino acid threonine 氨基酸苏氨酸星际气相立体转化中异构体的计算旋转-振动光谱分析

Molecular Astrophysics Pub Date : 2019-06-01 DOI: 10.1016/j.molap.2019.04.002

Namrata Rani, Vikas

{"title":"Computational rotational–vibrational spectroscopic analysis of isomeric species in the interstellar gas-phase stereoinversion of amino acid threonine","authors":"Namrata Rani, Vikas","doi":"10.1016/j.molap.2019.04.002","DOIUrl":"10.1016/j.molap.2019.04.002","url":null,"abstract":"<div>The gas-phase stereoinversion of amino acid threonine under the condition of interstellar medium (ISM) has been predicted to proceed through isomeric species with diverse chemistry. These species including ammonium ylides, epoxides, contain a variety of functional groups such as geminal-diol, triol besides alkenyl, carboxy, keto, hydroxy, and amino groups. The detection of these species in ISM can help in unravelling the enantiomeric excess observed in meteoritic samples. Towards this, the present work reports rotational and vibrational spectroscopic data computed for the conformers and isomeric intermediates predicted along the stereoinversion pathways of proteinogenic threonine under conditions akin to ISM. The rotational parameters are computed using quantum mechanical methods employing Møller–Plesset perturbation theory whereas for the vibrational analysis, density functional computations are performed using dispersion corrected exchange-correlation functionals. The anharmonic corrections are also computed using vibrational second-order perturbation theory, which, however, fails to account for the hydrogen bonded interactions in the species investigated. The rotational and vibrational transitions predicted for the conformers of threonine are observed to be in good agreement with the available experimental data. The gas-phase spectroscopic data computed for other isomeric species of threonine is quite reliable and can be used to search threonine or other amino acids in ISM by resolving the astrophysical data observed in the microwave and mid-infrared regions.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"15 ","pages":"Pages 8-16"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2019.04.002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82293601","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}

引用次数: 4

LVG analysis of amidogen radical (NH2) found in interstellar medium and in cometary material 星际介质和彗星物质中氨基自由基(NH2)的LVG分析

Molecular Astrophysics Pub Date : 2019-06-01 DOI: 10.1016/j.molap.2019.04.001

Mohit K. Sharma

{"title":"LVG analysis of amidogen radical (NH2) found in interstellar medium and in cometary material","authors":"Mohit K. Sharma","doi":"10.1016/j.molap.2019.04.001","DOIUrl":"10.1016/j.molap.2019.04.001","url":null,"abstract":"<div>Amidogen (NH2), a b-type asymmetric top molecule with electric dipole moment 1.82  ±  0.05 Debye, is detected in Sgr B2, in high-mass star-forming regions W31C (G10.6−0.4), W49N (G43.2−0.1), W51 (G49.5−0.4), G34.3+0.1, and in several comets. Because of two hydrogen atoms, each with nuclear spin 1/2, its rotational energy levels can be classified into ortho and para groups. We have not considered for fine structure splitting and hyper-fine structure splitting of rotational levels. For 15 rotational levels in the ground vibrational state, having energy up to 400 cm<math><mrow><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo>,</mo></mrow></math> for each specie, the energies of rotational levels, and Einstein A and B coefficients for radiative transitions between the levels are calculated, using accurate values of spectroscopic data. These radiative transition probabilities along with the collisional rate coefficients (obtained from a scaling law) are employed as input parameters for solving a set of statistical equilibrium equations coupled with the equations of radiative transfer for each group. Several emission lines produced by amidogen are found. For each species of NH2, we have considered some strongest emission lines along with the observed one, which may help for identification of NH2 in the interstellar medium (ISM) and in the cometary material.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"15 ","pages":"Pages 1-7"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2019.04.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86564973","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}

引用次数: 7

Hydrogenation reactions and adsorption : From CO to methanol on a graphene surface 氢化反应和吸附:从一氧化碳到甲醇在石墨烯表面

Molecular Astrophysics Pub Date : 2019-03-01 DOI: 10.1016/j.molap.2019.02.001

Sabine Morisset, Nathalie Rougeau, Dominique Teillet-Billy

引用次数: 5

Formation of acetamide in interstellar medium 星际介质中乙酰胺的形成

Molecular Astrophysics Pub Date : 2018-11-01 DOI: 10.1016/j.molap.2018.06.002

Lois Foo , Attila Surányi , Andrea Guljas , Milán Szőri , John Justine Villar , Béla Viskolcz , Imre G. Csizmadia , Anita Rágyanszki , Béla Fiser

{"title":"Formation of acetamide in interstellar medium","authors":"Lois Foo , Attila Surányi , Andrea Guljas , Milán Szőri , John Justine Villar , Béla Viskolcz , Imre G. Csizmadia , Anita Rágyanszki , Béla Fiser","doi":"10.1016/j.molap.2018.06.002","DOIUrl":"10.1016/j.molap.2018.06.002","url":null,"abstract":"<div>Acetamide (C2H5NO) is the largest molecule containing a peptide bond, which is an amine (-NH2) group bonded to a carbonyl (C = O) group, that has yet been detected in interstellar medium (ISM). It is also considered to be a precursor for amino acids (the building blocks of proteins). Formation of acetamide in ISM is believed to occur due based on evidence for the existence of the molecule itself and its component smaller species in ISM. A case study of acetamide is presented here, to introduce a new method to determine its possible formation reaction pathways in ISM based on the molecular formula of a species. All possible species with the same molecular formula as acetamide (C2H5NO) but with different connectivity, the so-called constitutional isomers of the molecule (198 structures, 91 unique species), were created and studied under the extreme conditions of dense molecular clouds. Acetamide was found to be the most stable of the C2H5NO isomer family. Based on the stability of the uni- and bimolecular species, eight reactions were proposed which could led to the formation of acetamide in ISM.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"13 ","pages":"Pages 1-5"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2018.06.002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81030199","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}

引用次数: 6

Ro-vibrational analysis of SiO in UV-irradiated environments 紫外辐射环境下SiO的反振动分析

Molecular Astrophysics Pub Date : 2018-11-01 DOI: 10.1016/j.molap.2018.09.001

Ziwei E. Zhang , R.S. Cumbee , P.C. Stancil , G.J. Ferland

{"title":"Ro-vibrational analysis of SiO in UV-irradiated environments","authors":"Ziwei E. Zhang , R.S. Cumbee , P.C. Stancil , G.J. Ferland","doi":"10.1016/j.molap.2018.09.001","DOIUrl":"10.1016/j.molap.2018.09.001","url":null,"abstract":"<div>SiO emission lines are important probes of chemical processes in diverse astrophysical environments, commonly observed in shocks associated with the outflows of young stellar objects, both low- and high-mass, and in the envelopes of evolved stars. Modelling SiO emission for conditions of non-local thermodynamic equilibrium (NLTE) requires collisional rate coefficients due to H2, H, and He impact, with the first of these of limited availability. Unknown collisional rate coefficients are often estimated from known systems. For the case of SiO-H2, rate coefficients have previously been adapted from a different collider, He, based on a reduced-mass scaling approach. Here, we construct comprehensive SiO collisional rate coefficients data with multiple colliders (H2, He and H) and rovibrational transitions up to <math><mrow><mi>v</mi><mo>=</mo><mn>5</mn></mrow></math> and <math><mrow><mi>J</mi><mo>=</mo><mn>39</mn></mrow></math>. A reduced-potential scaling approach is used to estimate unknown collisional data. Using RADEX and Cloudy, we investigate the rotational and rovibrational SiO emission in various astrophysical environments, including photodissociation regions (PDR) and the envelope of VY Canis Majoris.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"13 ","pages":"Pages 6-21"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2018.09.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72936855","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}

引用次数: 2

Catalytic conversion of methanol to larger organic molecules over crystalline forsterite: Laboratory study and astrophysical implications 甲醇催化转化为更大的有机分子的结晶forsterite:实验室研究和天体物理意义

Molecular Astrophysics Pub Date : 2018-11-01 DOI: 10.1016/j.molap.2018.09.002

Li Q. , Dai W. , Liu B.S. , Sarre P.J. , Xie M.H. , Cheung A.S-C.

{"title":"Catalytic conversion of methanol to larger organic molecules over crystalline forsterite: Laboratory study and astrophysical implications","authors":"Li Q. , Dai W. , Liu B.S. , Sarre P.J. , Xie M.H. , Cheung A.S-C.","doi":"10.1016/j.molap.2018.09.002","DOIUrl":"10.1016/j.molap.2018.09.002","url":null,"abstract":"<div>Laboratory catalytic reactions of methanol over heated crystalline silicates (forsterite) lead to the formation of gas-phase olefinic and polycyclic aromatic hydrocarbon (PAH) molecules, and are of potential importance in astrophysical environments including hot molecular cores, protoplanetary disks and shocks. In our experiments the methanol reagent, together with intermediate and product gas-phase molecular species were detected using time-of-flight mass-spectrometry (TOF-MS). A solid deposited on the crystalline forsterite surface was examined subsequently using high-resolution transmission electron microscopy and thermal gravimetric techniques and found to comprise amorphous and graphitic carbon. The chemical players in this work – gas-phase methanol, crystalline silicates and PAHs, have been identified spectroscopically in a range of astrophysical environments including young and evolved stars, protoplanetary disks, comets, captured dust particles and meteorites. It is envisaged that reactions on bare dust grains as studied here both experimentally and theoretically through DFT calculations, can have implications for chemical transformations and conversions, in forming PAH molecules and potentially in the synthesis of prebiotic molecules.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"13 ","pages":"Pages 22-29"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2018.09.002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73057892","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}

引用次数: 3

A theoretical investigation of the reaction between the amidogen, NH, and the ethyl, C2H5, radicals: a possible gas-phase formation route of interstellar and planetary ethanimine 氨基NH和乙基C2H5自由基之间反应的理论研究:星际和行星乙胺的可能气相形成途径

Molecular Astrophysics Pub Date : 2018-11-01 DOI: 10.1016/j.molap.2018.10.001

Nadia Balucani , Dimitrios Skouteris , Cecilia Ceccarelli , Claudio Codella , Stefano Falcinelli , Marzio Rosi

{"title":"A theoretical investigation of the reaction between the amidogen, NH, and the ethyl, C2H5, radicals: a possible gas-phase formation route of interstellar and planetary ethanimine","authors":"Nadia Balucani , Dimitrios Skouteris , Cecilia Ceccarelli , Claudio Codella , Stefano Falcinelli , Marzio Rosi","doi":"10.1016/j.molap.2018.10.001","DOIUrl":"10.1016/j.molap.2018.10.001","url":null,"abstract":"<div>The reaction between the amidogen, NH, radical and the ethyl, C2H5, radical has been investigated by performing electronic structure calculations of the underlying doublet potential energy surface. Rate coefficients and product branching ratios have also been estimated by combining capture and RRKM calculations. According to our results, the reaction is very fast, close to the gas-kinetics limit. However, the main product channel, with a yield of ca. 86–88% in the range of temperatures investigated, is the one leading to methanimine and the methyl radical. The channels leading to the two E-, Z- stereoisomers of ethanimine account only for ca. 5–7% each. The resulting ratio [E-CH3CHNH]/[Z-CH3CHNH] is ca. 1.2, that is a value rather lower than that determined in the Green Bank Telescope PRIMOS radio astronomy survey spectra of Sagittarius B2 North (ca. 3). Considering that ice chemistry would produce essentially only the most stable isomer, a possible conclusion is that the observed [E-CH3CHNH]/[Z-CH3CHNH] ratio is compatible with a combination of gas-phase and grain chemistry. More observational and laboratory data are needed to definitely address this issue.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"13 ","pages":"Pages 30-37"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2018.10.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75038681","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}

引用次数: 18

Polarizability of isomeric and related interstellar compounds in the aspect of their abundance 同分异构体及相关星际化合物在丰度方面的极化性

Molecular Astrophysics Pub Date : 2018-09-01 DOI: 10.1016/j.molap.2018.05.001

Denis Sh. Sabirov , Ralia R. Garipova , Franco Cataldo

{"title":"Polarizability of isomeric and related interstellar compounds in the aspect of their abundance","authors":"Denis Sh. Sabirov , Ralia R. Garipova , Franco Cataldo","doi":"10.1016/j.molap.2018.05.001","DOIUrl":"10.1016/j.molap.2018.05.001","url":null,"abstract":"<div>Currently, about 100 carbon-containing molecules have been detected in interstellar and circumstellar environments, and this list includes isomeric substances. In most cases, the minimum energy principle is able to explain the ratio of abundances of the isomeric compounds but in some cases is not. Trying to rationalize the questions unsolved within the energetic approach, we have theoretically studied the polarizability of isomeric and related compounds detected or proposed in interstellar conditions. As we found, in general both energy and polarizability provide the consistent estimates for the ratio of the isomers (e.g., for the isomers having generic formulae CHO, CHN, C3H, C3H2, CHNO, C2H3N, C2H6O, etc.). In the case of the C4H3N isomers, the most abundant isomer (cyanoallene) is not the most stable but the least polarizable that is in a good agreement with relevant experimental study. We assume that the efficiency of the use of polarizability is due to its relevance to the molecules’ response to the external electric fields, i.e., more polarizable molecules are more responsive, more reactive, and, hence, less abundant. Further, we have analyzed the polarizabilities of polycyclic aromatic hydrocarbons, fullerene hydrides (fulleranes), polyynes, and their derivatives with respect to their possible detection under interstellar conditions.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"12 ","pages":"Pages 10-19"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2018.05.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85740884","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}

引用次数: 18

Strengths of rotational lines from H2CC molecule: Addressing tentative detection H2CC分子旋转线的强度:解决试探性检测

Molecular Astrophysics Pub Date : 2018-09-01 DOI: 10.1016/j.molap.2018.06.001

M.K. Sharma , M. Sharma , S. Chandra

{"title":"Strengths of rotational lines from H2CC molecule: Addressing tentative detection","authors":"M.K. Sharma , M. Sharma , S. Chandra","doi":"10.1016/j.molap.2018.06.001","DOIUrl":"10.1016/j.molap.2018.06.001","url":null,"abstract":"<div>Though H2C, H2CCC, H2CCCC, H2CCO, H2CO, H2CS molecules have been identified in cool interstellar clouds, identification of H2CC is still awaited. Formation of H2CC in the interstellar medium is quite probable as the cosmic abundance of carbon is 20 times larger than that of the sulphur, and the molecule H2CS has already been identified in the interstellar medium. To our knowledge, no laboratory study for H2CC is available in literature. Physical conditions in the interstellar medium are quite different as compared to those in a terrestrial laboratory. Using the rotational and centrifugal distortion constants for H2CC, we have calculated the energies of rotational levels and the strengths of lines between the levels up to 270 cm<math><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. We have found that 88 and 87 lines of ortho-H2CC and para-H2CC, respectively have Einstein A-coefficient larger than 10<math><msup><mrow></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup></math> s<math><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. These lines may help in the identification of H2CC in the interstellar medium. Tentative detection of H2CC has been addressed.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"12 ","pages":"Pages 20-24"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2018.06.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72671136","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}

引用次数: 7

Semiempirical breakdown curves of C2N(+) and C3N(+) molecules; application to products branching ratios predictions of physical and chemical processes involving these adducts C2N(+)和C3N(+)分子的半经验击穿曲线应用于产品分支比，预测涉及这些加合物的物理和化学过程

Molecular Astrophysics Pub Date : 2018-09-01 DOI: 10.1016/j.molap.2018.06.003

Tijani IdBarkach , Thejus Mahajan , Marin Chabot , Karine Béroff , Néstor F. Aguirre , Sergio Diaz-Tendero , Thibaut Launoy , Arnaud Le Padellec , Luc Perrot , Maëlle A. Bonnin , Kim Cuong Le , Florian Geslin , Nicolas de Séréville , Fairouz Hammache , Aurélie Jallat , Anne Meyer , Emeline Charon , Thomas Pino , Thibault Hamelin , Valentine Wakelam

{"title":"Semiempirical breakdown curves of C2N(+) and C3N(+) molecules; application to products branching ratios predictions of physical and chemical processes involving these adducts","authors":"Tijani IdBarkach , Thejus Mahajan , Marin Chabot , Karine Béroff , Néstor F. Aguirre , Sergio Diaz-Tendero , Thibaut Launoy , Arnaud Le Padellec , Luc Perrot , Maëlle A. Bonnin , Kim Cuong Le , Florian Geslin , Nicolas de Séréville , Fairouz Hammache , Aurélie Jallat , Anne Meyer , Emeline Charon , Thomas Pino , Thibault Hamelin , Valentine Wakelam","doi":"10.1016/j.molap.2018.06.003","DOIUrl":"10.1016/j.molap.2018.06.003","url":null,"abstract":"<div>We constructed semiempirical breakdown curves (BDC) for C2N, C3N, C2N+ and C3N+ molecules. These BDC, which are energy dependent dissociation branching ratios (BR) curves, were used to predict products branching ratios for various processes leading to the formation of C2N(+) and C3N(+) excited adducts. These processes, of astrochemical interest, are neutral-neutral and ion-molecule reactions, dissociative recombination and charge transfer reactions with He+. Model predictions of BR are compared to the literature data and to reported values in the kinetic database for astrochemistry KIDA. With the new BR values, the CnN abundances in cold cores were simulated.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"12 ","pages":"Pages 25-32"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2018.06.003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85295375","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}

引用次数: 4