scholarly journals The Optical Spectroscopy of Extraterrestrial Molecules

2005 ◽  
Vol 58 (2) ◽  
pp. 69 ◽  
Author(s):  
Timothy W. Schmidt ◽  
Robert G. Sharp
Keyword(s):  
Interstellar Medium ◽  
Optical Spectroscopy ◽  
Electronic Spectra ◽  
Visible Region ◽  
Experimental Techniques ◽  
Molecular Absorption ◽  
Molecular Emission ◽  
Diffuse Interstellar Bands

The ongoing quest to identify molecules in the interstellar medium by their electronic spectra in the visible region is reviewed. Identification of molecular absorption is described in the context of the elucidation of the carriers of the unidentified Diffuse Interstellar Bands, and molecular emission is discussed with reference to the unidentified Red Rectangle bands. The experimental techniques employed in undertaking studies on the optical spectroscopy of extraterrestrial molecules are described and critiqued in the context of their application.

The electronic spectra of phenyl radicals

1965 ◽  
Vol 287 (1411) ◽  
pp. 457-470 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Ground State ◽  
Electronic Spectra ◽  
Flash Photolysis ◽  
Visible Region ◽  
Electronic Configuration ◽  
Vibrational Structure ◽  
Fundamental Frequencies

An electronic absorption spectrum, attributed to phenyl, has been observed in the visible region with origin at 18 908 cm -1 after flash photolysis of benzene and halogenobenzenes. Similar spectra of fluoro, chloro and bromo phenyl are observed after flash photolysis of disubstituted benzenes. The vibrational structure of the phenyl spectrum has been analysed in terms of two fundamental frequencies at 571 and 896 cm -1 which correspond to the e 2 g and a 1 g frequencies of the B 2 u state of benzene. The ground state of phenyl has a π 6 n electronic configuration and the observed transition is interpreted as 2 A 1 → 2 B 1 resulting from a π → n excitation.

scholarly journals Diffuse Interstellar Bands – The Unidentified Part of the Interstellar Absorption Spectrum

1989 ◽  
Vol 135 ◽  
pp. 67-86 ◽  
Author(s):  
Jacek Krełowski
Keyword(s):  
Absorption Spectrum ◽  
Line Of Sight ◽  
Optical Parameters ◽  
Interstellar Matter ◽  
Molecular Absorption ◽  
Interstellar Clouds ◽  
Diffuse Interstellar Bands ◽  
Intensity Ratios ◽  
Molecular Abundances

The unidentified (since 1921) diffuse interstellar bands (DIBs) are discussed together with their relations to other interstellar absorptions sucn as: continuous extinction, polarization and atomic or molecular absorption lines. It is shown that DIBs do not form the absorption spectrum of one agent, but probably of several (3 or more). DIBs as well as other interstellar absorptions are usually formed in several clouds along a line-of-sight. Thus, they suffer Doppler splitting; the first high resolution profiles free of the latter effect are described. Since single interstellar clouds may differ not only in radial velocities but also in many physical (optical) parameters, the observed interstellar absorptions are ill-defined averages over all clouds situated along any line-of-sight. It is of basic importance to determine not only the single cloud profiles of diffuse bands, but also their relations to other interstellar absorptions in the same clouds. Intensity ratios of DIBs are shown to be sensitive to the shapes of extinction curves, depletion patterns of elements and molecular abundances in the considered clouds. The sensitivity of the DIBs to the variation in polarization is less documented but probably also present. Thus the diffuse lines are presented as the unidentified part of the absorption spectrum of interstellar matter. Their identification depends on the determination of their relations to other interstellar absorptions which must be determined precisely.

scholarly journals Formation, Evolution and Destruction of Possible DIB Carriers: Dirty Molecular Hydrogen Ice Clusters

2013 ◽  
Vol 9 (S297) ◽  
pp. 381-382
Author(s):  
D. K. Lynch ◽  
L. S. Bernstein ◽  
F. O. Clark
Keyword(s):  
Interstellar Medium ◽  
Single Molecule ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Single Layer ◽  
Molecular Clusters ◽  
Electronic Transitions ◽  
Giant Molecular Clouds ◽  
Diffuse Interstellar Bands ◽  
Optical Photons

AbstractWe suggest that the diffuse interstellar bands (DIBs) are absorption lines arising from electronic transitions in molecular clusters primarily composed of a single molecule, atom, or ion (“seed”), embedded in a single-layer shell of H2 molecules (Bernstein et al. 2013). We refer to these clusters as CHCs (Contaminated H2 Clusters). CHCs arise from cm-sized, dirty H2 ice balls, called CHIMPs (Contaminated H2 Ice Macro-Particles), formed in cold, dense, Giant Molecular Clouds (GMCs), and later released into the interstellar medium (ISM) upon GMC disruption. Absorption by the CHIMP of a UV photon releases CHCs. CHCs produce DIBs when they absorb optical photons. When this occurs, the absorbed photon energy disrupts the CHC.

scholarly journals Atomic data for IR and sub-mm wavelengths

2009 ◽  
Vol 5 (H15) ◽  
pp. 539-540
Author(s):  
Gillian Nave
Keyword(s):  
Interstellar Medium ◽  
Electric Dipole ◽  
Visible Region ◽  
Diagnostic Information ◽  
Atomic Data ◽  
Low Density ◽  
Potential Importance ◽  
Ground Term ◽  
Atomic Spectra

Atomic spectra in the infrared and sub-mm wavelength regions can be divided into two broad categories: electric dipole-allowed transitions, and forbidden lines due to transitions within the ground term or between low-lying levels of the same parity. Both are of potential importance in the interpretation of astrophysical spectra. Allowed transitions can provide diagnostic information for stellar photospheres, particularly for elements that are not accessible in the visible region. Electric-dipole forbidden lines are important diagnostics of low-density plasmas, such as nebulae and the interstellar medium. In order to interpret astrophysical spectra, accurate atomic data are required. This paper summarizes the techniques for measuring atomic data and lists the most important compilations and databases.

scholarly journals Detection of buckminsterfullerene emission in the diffuse interstellar medium

2017 ◽  
Vol 605 ◽  
pp. L1 ◽  
Author(s):  
O. Berné ◽  
N. L. J. Cox ◽  
G. Mulas ◽  
C. Joblin
Keyword(s):  
Interstellar Medium ◽  
Charge State ◽  
Laboratory Data ◽  
Electronic Transitions ◽  
Hot Stars ◽  
Large Molecules ◽  
Diffuse Interstellar Bands ◽  
Classical Models ◽  
Vibrational Bands

Emission of fullerenes in their infrared vibrational bands has been detected in space near hot stars. The proposed attribution of the diffuse interstellar bands at 9577 and 9632 Å to electronic transitions of the buckminsterfullerene cation (i.e. C60+) was recently supported by new laboratory data, confirming the presence of this species in the diffuse interstellar medium (ISM). In this Letter, we present the detection, also in the diffuse ISM, of the 17.4 and 18.9 μm emission bands commonly attributed to vibrational bands of neutral C60 . According to classical models that compute the charge state of large molecules in space, C60 is expected to be mostly neutral in the diffuse ISM. This is in agreement with the abundances of diffuse C60 we derive here from observations.

scholarly journals Detection of the Buckminsterfullerene Cation (C60+) in Space

2013 ◽  
Vol 9 (S297) ◽  
pp. 203-207 ◽  
Author(s):  
O. Berné ◽  
G. Mulas ◽  
C. Joblin
Keyword(s):  
Interstellar Medium ◽  
Gas Phase ◽  
Laboratory Data ◽  
Infrared Emission ◽  
Diffuse Interstellar Bands ◽  
Proposal A ◽  
Significant Step ◽  
Chemistry Calculation ◽  
Vibrational Bands ◽  
Phase Data

AbstractIn the early 90's, C60+ was proposed as the carrier of two diffuse interstellar bands (DIBs) at 9577 and 9632 Å, but a firm identification still awaits gas-phase spectroscopic data. Neutral C60, on the other hand, was recently detected through its infrared emission bands in the interstellar medium and evolved stars. In this contribution, we present the detection of C60+ through its infrared vibrational bands in the NGC 7023 nebula, based on spectroscopic observations with the Spitzer space telescope, quantum chemistry calculation, and laboratory data from the literature. This detection supports the idea that C60+ could be a DIB carrier, and provides robust evidence that fullerenes exist in the gas-phase in the interstellar medium. Modeling efforts to design specific observations, combined with new gas-phase data, will be essential to confirm this proposal. A definitive attribution of the 9577 and 9632 Å DIBs to C60+ would represent a significant step forward in the field.

scholarly journals Putting the Diffuse Interstellar Bands on the Map – Literally!

2013 ◽  
Vol 9 (S297) ◽  
pp. 79-83
Author(s):  
J. Th. van Loon
Keyword(s):  
Interstellar Medium ◽  
Globular Clusters ◽  
Magellanic Clouds ◽  
Hot Stars ◽  
Local Bubble ◽  
Diffuse Interstellar Bands ◽  
Nearby Stars

AbstractIn a quest to further our understanding of the diffuse interstellar medium (ISM) as well as the unidentified carriers of the diffuse interstellar bands (DIBs), we are mapping DIBs across the sky using hundreds of hot stars as background torches – globular clusters (in particular ω Centauri), nearby stars in and around the Local Bubble, and stars within the Magellanic Clouds. I describe the results so far obtained and our current experiments.

scholarly journals Electronic spectra of carbon chains and rings: Astrophysical relevance?

2008 ◽  
Vol 4 (S251) ◽  
pp. 395-402 ◽  
Author(s):  
Evan B. Jochnowitz ◽  
John P. Maier
Keyword(s):  
Laser Ablation ◽  
Gas Phase ◽  
Electronic Spectra ◽  
Supersonic Jets ◽  
Spectroscopic Methods ◽  
Carbon Chains ◽  
Diffuse Interstellar Bands ◽  
Key Species ◽  
Future Search ◽  
Unstable Molecules

AbstractOur research has focused on the measurement of the electronic spectra of unstable molecules which are presumed to be of relevance to astrophysical observations. Among these are the carbon chains and their ions. Thus we have been using and developing a number of spectroscopic methods to determine their spectra in the gas phase, including absorption via cavity ring-down and REMPI methods. The species are produced in supersonic jets coupled with discharge and laser ablation sources. With the successful laboratory detection of the electronic spectra of a number of key species, such as bare carbon chains Cnn=4,5, comparisons with astrophysical data could be made which lead to interesting implications for the future search for the species which could be responsible for the diffuse interstellar bands. Among the recent relevant observations in the laboratory have been the electronic spectra of carbon rings, Cnn=14,18,22, the development of a method to study transitions in mass-selected ions collisionally relaxed to 20 K and held in a 22-pole radiofrequency trap, and the study of metal containing carbon chains.

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