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2013

ISM: molecules

Articles 1 - 7 of 7

Full-Text Articles in Physical Sciences and Mathematics

The Carriers Of The Interstellar Unidentified Infrared Emission Features: Constraints From The Interstellar C-H Stretching Features At 3.2-3.5 Μm, Xuejuan Yang, Rainer Glaser, Aigen Li, Jianxin Zhong Oct 2013

The Carriers Of The Interstellar Unidentified Infrared Emission Features: Constraints From The Interstellar C-H Stretching Features At 3.2-3.5 Μm, Xuejuan Yang, Rainer Glaser, Aigen Li, Jianxin Zhong

Chemistry Faculty Research & Creative Works

The unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm, commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules, have recently been ascribed to mixed aromatic/aliphatic organic nanoparticles. More recently, an upper limit of <9% was placed on the aliphatic fraction (i.e., the fraction of carbon atoms in aliphatic form) of the UIE carriers based on the observed intensities of the 3.4 μm and 3.3 μm emission features by attributing them to aliphatic and aromatic C-H stretching modes, respectively, and assuming A 3.4/A 3.3 ≈ 0.68 derived from a small set of aliphatic and aromatic compounds, where A 3.4 and A 3.3 are, respectively, the band strengths of the 3.4 μm aliphatic and 3.3 μm aromatic C-H bonds. To improve the estimate of the aliphatic fraction of the UIE carriers, here we analyze 35 UIE sources exhibiting both the 3.3 μm and …

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Basecol2012: A Collisional Database Repository And Web Service Within The Virtual Atomic And Molecular Data Centre (Vamdc), M.-L Duberne, M. H. Alexander, Y. A. Ba, N. Balakrishnan, C. Balança, C. Ceccarelli, J. Cernicharo, F. Daniel, F. Dayou, M. Doronin, F. Dumouchel, A. Faure, N. Feautrier, D. R. Flower, A. Grosjean, P. Halvick, J. Kłos, F. Lique, G. C. Mcbane, S. Marinakis, N. Moreau, R. Moszynsk, D. A. Neufeld, E. Roueff, P Schilke, A. Spielfiedel, P. C. Stancil, T. Stoecklin, J. Tennyson, B. Yang, A.-M. Vasserot, L. Wiesenfeld May 2013

Basecol2012: A Collisional Database Repository And Web Service Within The Virtual Atomic And Molecular Data Centre (Vamdc), M.-L Duberne, M. H. Alexander, Y. A. Ba, N. Balakrishnan, C. Balança, C. Ceccarelli, J. Cernicharo, F. Daniel, F. Dayou, M. Doronin, F. Dumouchel, A. Faure, N. Feautrier, D. R. Flower, A. Grosjean, P. Halvick, J. Kłos, F. Lique, G. C. Mcbane, S. Marinakis, N. Moreau, R. Moszynsk, D. A. Neufeld, E. Roueff, P Schilke, A. Spielfiedel, P. C. Stancil, T. Stoecklin, J. Tennyson, B. Yang, A.-M. Vasserot, L. Wiesenfeld

Peer Reviewed Articles

The BASECOL2012 database is a repository of collisional data and a web service within the Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu). It contains rate coefficients for the collisional excitation of rotational, ro-vibrational, vibrational, fine, and hyperfine levels of molecules by atoms, molecules, and electrons, as well as fine-structure excitation of some atoms that are relevant to interstellar and circumstellar astrophysical applications. Submissions of new published collisional rate coefficients sets are welcome, and they will be critically evaluated before inclusion in the database. In addition, BASECOL2012 provides spectroscopic data queried dynamically from various spectroscopic databases using the VAMDC technology. …

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The Nature Of The H2-Emitting Gas In The Crab Nebula, C. T. Richardson, J. A. Baldwin, Gary J. Ferland, E. D. Loh, C. A. Kuehn, A. C. Fabian, Philippe Salomé Apr 2013

The Nature Of The H2-Emitting Gas In The Crab Nebula, C. T. Richardson, J. A. Baldwin, Gary J. Ferland, E. D. Loh, C. A. Kuehn, A. C. Fabian, Philippe Salomé

Physics and Astronomy Faculty Publications

Understanding how molecules and dust might have formed within a rapidly expanding young supernova remnant is important because of the obvious application to vigorous supernova activity at very high redshift. In previous papers, we have mapped the Crab nebula (the Crab) in a rotovibrational H2emission line, and then measured the molecular excitation temperature for a few of the brighter H2-emitting knots that we have found to be scattered throughout the Crab's filaments. We found that H2 emission is often quite strong, correlates with optical low-ionization emission lines and has a surprisingly high excitation temperature. Here, …

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High­- Accuracy Quartic Force Field Calculations For The Spectroscopic Constants And Vibrational Frequencies Of 11A′ L-­C3H-­: A Possible Link To Lines Observed In The Horsehead Nebula Pdr, Ryan C. Fortenberry, Xinchuan Huang, T. D. Crawford, Timothy J. Lee Jan 2013

High­- Accuracy Quartic Force Field Calculations For The Spectroscopic Constants And Vibrational Frequencies Of 11A′ L-­C3H-­: A Possible Link To Lines Observed In The Horsehead Nebula Pdr, Ryan C. Fortenberry, Xinchuan Huang, T. D. Crawford, Timothy J. Lee

Ryan C. Fortenberry

It has been shown that rotational lines observed in the Horsehead nebula photodissociation region (PDR) are probably not caused by l-C3H+, as was originally suggested. In the search for viable alternative candidate carriers, quartic force fields are employed here to provide highly accurate rotational constants, as well as fundamental vibrational frequencies, for another candidate carrier: 11 A' C3H–. The ab initio computed spectroscopic constants provided in this work are, compared to those necessary to define the observed lines, as accurate as the computed spectroscopic constants for many of the known interstellar …

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Spectroscopic Constants And Vibrational Frequencies For L­-C3H+ And Isotopologues From Highly­Accurate Quartic Force Fields: The Detection Of L­-C3H+ In The Horsehead Nebula Pdr Questione, Xinchuan Huang, Ryan C. Fortenberry, Timothy J. Lee Jan 2013

Spectroscopic Constants And Vibrational Frequencies For L­-C3H+ And Isotopologues From Highly­Accurate Quartic Force Fields: The Detection Of L­-C3H+ In The Horsehead Nebula Pdr Questione, Xinchuan Huang, Ryan C. Fortenberry, Timothy J. Lee

Ryan C. Fortenberry

Very recently, molecular rotational transitions observed in the photon-dominated region of the Horsehead nebula have been attributed to l-C3H+. In an effort to corroborate this finding, we employed state-of-the-art and proven high-accuracy quantum chemical techniques to compute spectroscopic constants for this cation and its isotopologues. Even though the B rotational constant from the fit of the observed spectrum and our computations agree to within 20 MHz, a typical level of accuracy, the D rotational constant differs by more than 40%, while the H rotational constant differs by three orders of magnitude. With the likely errors in …

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Co Abundance Variations In The Orion Molecular Cloud, F. Ripple, M.H. Heyer, R. A. Gutermuth, R.L. Snell, C.M. Brunt Jan 2013

Co Abundance Variations In The Orion Molecular Cloud, F. Ripple, M.H. Heyer, R. A. Gutermuth, R.L. Snell, C.M. Brunt

Robert A. Gutermuth

Infrared stellar photometry from the Two Micron All-Sky Survey (2MASS) and spectral line imaging observations of 12CO and 13CO J = 1–0 line emission from the Five College Radio Astronomy Observatory (FCRAO) 14-m telescope are analysed to assess the variation of the CO abundance with physical conditions throughout the Orion A and Orion B molecular clouds. Three distinct Av regimes are identified in which the ratio between the 13CO column density and visual extinction changes corresponding to the photon-dominated envelope, the strongly self-shielded interior, and the cold, dense volumes of the clouds. Within the strongly self-shielded interior of the Orion …

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Theoretical Electronic And Rovibrational Studies For Anions Of Interest To The Dibs, Ryan C. Fortenberry Jan 2013

Theoretical Electronic And Rovibrational Studies For Anions Of Interest To The Dibs, Ryan C. Fortenberry

Ryan C. Fortenberry

The dipole-bound excited state of the methylene nitrile anion (CH2CN−) has been suggested as a candidate carrier for a diffuse interstellar band (DIB) at 803.8 nm. Its corresponding radical has been detected in the interstellar medium (ISM), making the existence for the anion possible. This work applies state-of-the-art ab initio methods such as coupled cluster theory to reproduce accurately the electronic excitations for CH2CN− and the similar methylene enolate anion, CH2CHO−. This same approach has been employed to indicate that 19 other anions may possess electronically excited states, five of which are valence in nature. Concurrently, in order to assist …

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