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Chemistry

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ISM: molecules

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Full-Text Articles in Physical Sciences and Mathematics

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 …


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 …


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 …