Molecular Astrophysics最新文献_第7页

High resolution absorption cross sections for propylene in the 3 µm region at high temperatures 高温下丙烯在3µm区域的高分辨率吸收截面

Molecular Astrophysics Pub Date : 2016-04-01 DOI: 10.1016/j.molap.2016.06.001

Eric M. Buzan, Robert J. Hargreaves , Peter F. Bernath

引用次数: 6

Statistical model for the abundance of deuterated ammonia in interstellar space 星际空间中氘化氨丰度的统计模型

Molecular Astrophysics Pub Date : 2016-04-01 DOI: 10.1016/j.molap.2016.04.001

Gunnar Nyman

{"title":"Statistical model for the abundance of deuterated ammonia in interstellar space","authors":"Gunnar Nyman","doi":"10.1016/j.molap.2016.04.001","DOIUrl":"10.1016/j.molap.2016.04.001","url":null,"abstract":"<div>The elemental abundance of deuterium to normal hydrogen in the universe is on the order of 10−5. A random distribution would therefore give a ratio of triply deuterated ammonia, ND3, to NH3 of <math><msup><mn>10</mn><mrow><mo>−</mo><mn>15</mn></mrow></msup></math>. Observations indicate an ND3 to NH3 ratio of roughly <math><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math>, implying enrichment of triply deuterated ammonia by about twelve orders of magnitude. A simple model, based on the elemental abundances of N, D and H, is developed and solved analytically. At zero temperature the expressions are particularly simple. Effects of finite temperature are included through the partition functions of the isotopologues. It is found that the effect of finite temperature is modest in the temperature range 10–100 <!-->K. The results of the model are in good agreement with the observed abundances so local thermal equilibrium may therefore be a reasonable approximation and thus also be an explanation for the apparent enrichment of deuterated isotopologues.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"3 ","pages":"Pages 10-15"},"PeriodicalIF":0.0,"publicationDate":"2016-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2016.04.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88096698","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

An optical spectrum of a large isolated gas-phase PAH cation: C78H26+ 大分离气相多环芳烃阳离子C78H26+的光谱

Molecular Astrophysics Pub Date : 2016-03-01 DOI: 10.1016/j.molap.2015.11.001

Junfeng Zhen , Giacomo Mulas , Anthony Bonnamy , Christine Joblin

{"title":"An optical spectrum of a large isolated gas-phase PAH cation: C78H26+","authors":"Junfeng Zhen , Giacomo Mulas , Anthony Bonnamy , Christine Joblin","doi":"10.1016/j.molap.2015.11.001","DOIUrl":"10.1016/j.molap.2015.11.001","url":null,"abstract":"<div>A gas-phase optical spectrum of a large polycyclic aromatic hydrocarbon (PAH) cation - C78H<math><msubsup><mrow></mrow><mrow><mn>26</mn></mrow><mo>+</mo></msubsup></math><math><mo>−</mo></math> in the 410<math><mo>−</mo></math>610 nm range is presented. This large all-benzenoid PAH should be large enough to be stable with respect to photodissociation in the harsh conditions prevailing in the interstellar medium (ISM). The spectrum is obtained via multi-photon dissociation (MPD) spectroscopy of cationic C78H26 stored in the Fourier Transform Ion Cyclotron Resonance (FT-ICR) cell of the PIRENEA setup using the radiation from a mid-band optical parametric oscillator (OPO) laser.The experimental spectrum shows two main absorption peaks at 431 nm and 516 nm, in good agreement with a theoretical spectrum computed via time-dependent density functional theory (TD-DFT). DFT calculations indicate that the equilibrium geometry, with the absolute minimum energy, is of lowered, nonplanar C2 symmetry instead of the more symmetric planar D2h symmetry that is usually the minimum for similar PAHs of smaller size. This kind of slightly broken symmetry could produce some of the fine structure observed in some diffuse interstellar bands (DIBs). It can also favor the folding of C78H<math><msubsup><mrow></mrow><mrow><mn>26</mn></mrow><mo>+</mo></msubsup></math> fragments and ultimately the formation of fullerenes.This study opens up the possibility to identify the most promising candidates for DIBs amongst large cationic PAHs.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"2 ","pages":"Pages 12-17"},"PeriodicalIF":0.0,"publicationDate":"2016-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2015.11.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78030211","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

Potential interstellar noble gas molecules: ArOH+ and NeOH+ rovibrational analysis from quantum chemical quartic force fields 潜在的星际惰性气体分子:ArOH+和NeOH+量子化学四次力场的旋转振动分析

Molecular Astrophysics Pub Date : 2016-03-01 DOI: 10.1016/j.molap.2015.12.001

Riley A. Theis, Ryan C. Fortenberry

{"title":"Potential interstellar noble gas molecules: ArOH+ and NeOH+ rovibrational analysis from quantum chemical quartic force fields","authors":"Riley A. Theis, Ryan C. Fortenberry","doi":"10.1016/j.molap.2015.12.001","DOIUrl":"10.1016/j.molap.2015.12.001","url":null,"abstract":"<div>The discovery of ArH<math><msup><mrow></mrow><mo>+</mo></msup></math> in the interstellar medium has shown that noble gas chemistry may be of more chemical significance than previously believed. The present work extends the known chemistry of small noble gas molecules to NeOH<math><msup><mrow></mrow><mo>+</mo></msup></math> and ArOH<math><msup><mrow></mrow><mo>+</mo></msup></math>. Besides their respective neonium and argonium diatomic cation cousins, these hydroxyl cation molecules are the most stable small noble gas molecules analyzed of late. ArOH<math><msup><mrow></mrow><mo>+</mo></msup></math> is once again more stable than the neon cation, but both are well-behaved enough for a complete quartic force field analysis of their rovibrational properties. The Ar–O bond in ArOH<math><mrow><msup><mrow></mrow><mo>+</mo></msup><mo>,</mo></mrow></math> for instance, is roughly three-quarters of the strength of the Ar–H bond in ArH<math><msup><mrow></mrow><mo>+</mo></msup></math> highlighting the rigidity of this system. The rotational constants, geometries, and vibrational frequencies for both molecules and their various isotopologues are computed from ab initio quantum chemical theory at high-level, and it is shown that these cations may form in regions where peroxy or weakly-bound alcohols may be present. The resulting data should be of significant assistance for the laboratory or observational analysis of these potential interstellar molecules.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"2 ","pages":"Pages 18-24"},"PeriodicalIF":0.0,"publicationDate":"2016-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2015.12.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89029131","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: 31

Ion-neutral reaction of the C2H2N+ cation with C2H2: An experimental and theoretical study C2H2N+阳离子与C2H2离子中性反应的实验与理论研究

Molecular Astrophysics Pub Date : 2016-03-01 DOI: 10.1016/j.molap.2015.09.002

P. Fathi , W.D. Geppert , A. Kaiser , D. Ascenzi

引用次数: 9

Excited vibrational level rotational constants for SiC2: A sensitive molecular diagnostic for astrophysical conditions SiC2的激发态振动能级旋转常数:天体物理条件的敏感分子诊断

Molecular Astrophysics Pub Date : 2015-11-01 DOI: 10.1016/j.molap.2015.07.001

Ryan C. Fortenberry , Timothy J. Lee , Holger S.P. Müller

{"title":"Excited vibrational level rotational constants for SiC2: A sensitive molecular diagnostic for astrophysical conditions","authors":"Ryan C. Fortenberry , Timothy J. Lee , Holger S.P. Müller","doi":"10.1016/j.molap.2015.07.001","DOIUrl":"10.1016/j.molap.2015.07.001","url":null,"abstract":"<div>Silacyclopropynylidene, SiC2, is a known and highly abundant circumstellar molecule. Its spectrum has been established as a major component of lines observed toward the carbon-rich star IRC +10216 (CW Leonis). It has been detected in its low-lying <math><mrow><msub><mi>v</mi><mn>3</mn></msub><mo>=</mo><mn>1</mn></mrow></math> and 2 vibrational states as well as in various isotopic compositions. Increasing sensitivity and spatial resolution will enable many more emission or absorption lines to be detected. In order to detect new molecular species, unassigned lines of known species must be identified. This work uses established ab initio quartic force fields to produce data necessary for this classification of lines related to SiC2. Agreement between the theoretical vibrational frequencies and known rotational and spectroscopic constants is quite good, as good as 5 cm<math><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> and 3 MHz, respectively in some cases. In addition, experimentally unknown vibrational frequencies and rotational constants are provided for the first overtones and combination bands in addition to 3ν3, the second overtone of the low-lying antisymmetric stretch/carbide rotation mode. Frequencies of <math><mrow><msub><mi>v</mi><mn>3</mn></msub><mo>=</mo><mn>3</mn></mrow></math> low-J rotational transitions of the main isotopic species are also estimated from published data for v3 ≤ 2. Further, we determine rotational and centrifugal distortion parameters for which in most cases vibrational effects due to the ν3 mode were reduced to first, and in several cases also to second order. These values may approximate equilibrium values better than the ground state values. The data produced herein will aid in the experimental and observational characterization of this known astromolecule in order to identify some of the unassigned lines for a known entity.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"1 ","pages":"Pages 13-19"},"PeriodicalIF":0.0,"publicationDate":"2015-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2015.07.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77213879","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: 52

Thermal formation of hydroxynitriles, precursors of hydroxyacids in astrophysical ice analogs: Acetone ((CH3)2CO) and hydrogen cyanide (HCN) reactivity 天体物理冰类似物中羟基酸前体羟基腈的热形成:丙酮((CH3)2CO)和氰化氢(HCN)的反应性

Molecular Astrophysics Pub Date : 2015-11-01 DOI: 10.1016/j.molap.2015.10.001

Aurélien Fresneau , Grégoire Danger , Albert Rimola , Fabrice Duvernay , Patrice Theulé , Thierry Chiavassa

{"title":"Thermal formation of hydroxynitriles, precursors of hydroxyacids in astrophysical ice analogs: Acetone ((CH3)2CO) and hydrogen cyanide (HCN) reactivity","authors":"Aurélien Fresneau , Grégoire Danger , Albert Rimola , Fabrice Duvernay , Patrice Theulé , Thierry Chiavassa","doi":"10.1016/j.molap.2015.10.001","DOIUrl":"10.1016/j.molap.2015.10.001","url":null,"abstract":"<div>Reactivity in astrophysical environments is still poorly understood. In this contribution, we investigate the thermal reactivity of interstellar ice analogs containing acetone ((CH3)2CO), ammonia (NH3), hydrogen cyanide (HCN) and water (H2O) by means of infrared spectroscopy and mass spectrometry techniques, complemented by quantum chemical calculations. We show that no reaction occurs in H2O:HCN:(CH3)2CO ices. Nevertheless, HCN does indeed react with acetone once activated by NH3 into CN− to form 2-hydroxy-2-methylpropanenitrile (HO<img>C(CH3)2<img>CN), with a calculated activation energy associated with the rate determining step of about 51 kJ mol−1. This reaction inhibits the formation of 2-aminopropan-2-ol (HO<img>C(CH3)2<img>NH2) from acetone and NH3, even in the presence of water, which is the first step of the Strecker synthesis to form 2-aminoisobutyric acid (NH2C(CH3)2COOH). However, HO<img>C(CH3)2<img>CN formation could be part of an alternative chemical pathway leading to 2-hydroxy-2-methyl-propanoic acid (HOC(CH3)2COOH), which could explain the presence of hydroxy acids in some meteorites.</div>","PeriodicalId":44164,"journal":{"name":"Molecular Astrophysics","volume":"1 ","pages":"Pages 1-12"},"PeriodicalIF":0.0,"publicationDate":"2015-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molap.2015.10.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78298017","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

High-resolution absorption cross sections of C2H6 at elevated temperatures C2H6在高温下的高分辨率吸收截面

Molecular Astrophysics Pub Date : 2015-11-01 DOI: 10.1016/j.molap.2015.09.001

Robert J. Hargreaves, Eric Buzan, Michael Dulick, Peter F. Bernath

引用次数: 15

Molecular astrophysics: Molecular clouds in the Milky Way 分子天体物理学:银河系中的分子云

Molecular Astrophysics Pub Date : 1990-01-01 DOI: 10.1017/CBO9780511564680.003

P. Friberg, Å. Hjalmarson

引用次数: 7

Molecular astrophysics: Interstellar grain chemistry 分子天体物理学:星际颗粒化学

Molecular Astrophysics Pub Date : 1990-01-01 DOI: 10.1017/CBO9780511564680.009

V. Buch

引用次数: 2