Cavity ring-down spectroscopy and vibronic activity of benzo[ghi]perylene

Tan, Xiaofeng; Salama, Farid

doi:10.1063/1.1938907

Cited by 35 publications

(23 citation statements)

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“…The synthetic bands are represented in terms of Lorentzian profiles, where the ratios of their widths and their heights are obtained from the spectrum of hexabenzocoronene measured in the Ne matrix. We have chosen to fix the widths to 5 and 7 cm −1 because these values are typical of the bandwidths observed in the jet-cooled spectrum of the S 2 ← S 0 transition of benzo[ghi]perylene (Tan & Salama 2005). This transition is affected by an interaction between electronic states (Tan & Salama 2005) like the S β ← S 0 transition of hexabenzocoronene (Rouillé et al 2009).…”

Section: Comparison Of Astrophysical and Laboratory Spectramentioning

confidence: 99%

Abundances of PAHs in the ISM: confronting observations with experimental results

Gredel

Carpentier

Rouillé

et al. 2011

A&A

104

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Context. The identification of the carriers of the diffuse interstellar bands (DIBs) is the longest standing problem in the study of the interstellar medium. Here we present recent UV laboratory spectra of various polycyclic aromatic hydrocarbons (PAHs) and explore the potential of these molecules as carriers of the DIBs. Whereas, in the near IR range, the PAHs exhibit vibrational bands that are not molecule-specific, their electronic transitions occurring in the UV/vis provide characteristic fingerprints. The comparison of laboratory spectra calibrated in intensity with high signal-to-noise observational data in the UV enables us to establish new constraints on PAH abundances. Aims. From a detailed comparison of the gas-phase and Ne-matrix absorption spectra of anthracene, phenanthrene, pyrene, 2,3-benzofluorene, benzo[ghi]perylene, and hexabenzocoronene with new interstellar spectra, we aim to infer the abundance of these PAHs in the interstellar medium. Methods. We present spectra of PAHs measured at low temperature in the gas phase and in an Ne matrix, and present methods to derive absolute absorption cross sections for the matrix and gas phase spectra. We have obtained high signal to noise (S/N > 100) absorption spectra toward five lines of sight with reddenings of E B−V = 1−1.6 mag. The spectra cover the 3050−3850 Å wavelength region where the PAHs studied here show prominent absorption features. Results. From the observations, we infer upper limits in the fractional abundances of the PAHs studied here. Upper limits in the column densities of anthracene of 0.8−2.8 × 10 12 cm −2 and of pyrene and 2,3-benzofluorene ranging from 2−8 × 10 12 cm −2 are inferred. Upper limits in the column densities of benzo [ghi]perylene are 0.9−2.4 × 10 13 and 10 14 cm −2 for phenanthrene. The measurements indicate fractional abundances of anthracene, pyrene, and 2,3-benzofluorene of a few times 10 −10 . Upper limits in the fractional abundance of benzo [ghi]perylene of a few times 10 −9 and of phenanthrene of few times 10 −8 are inferred. Toward CPD −32 • 1734, we found near 3584 Å an absorption line of OH + , which was discovered in the interstellar medium only very recently. Conclusions. The fractional abundances of PAHs inferred here are up to two orders of magnitude lower than estimated total PAH abundances in the interstellar medium. This indicates that either neutral PAHs are not abundant in translucent molecular clouds or that a PAH population with a wide variety of molecules is present.

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Section: Comparison Of Astrophysical and Laboratory Spectramentioning

confidence: 99%

Abundances of PAHs in the ISM: confronting observations with experimental results

Gredel

Carpentier

Rouillé

et al. 2011

A&A

104

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“…Neutral PAHs, for example, have been detected and probed with CRDS [7,8]. Hence, the ReTOF-MS is equipped with an electron ionization (EI) source that ionizes the cold neutrals in the extraction region of the ReTOF-MS.…”

Section: Detection Of Neutrals Formed In the Csc With The Retof-msmentioning

confidence: 99%

“…One such experiment is the pulsed discharge nozzle (PDN)-cavity ring-down spectrometer (CRDS) system, a cosmic simulation experiment, which was developed at NASA-Ames to measure the gas phase spectra of neutral and ionized interstellar PAH analogs [5]. The PDN-CRDS has been successfully used to measure the spectra of several PAH species, for example the naphthalene cation (C 10 H 8 + ) and acenaphthene cation (C 12 H 10 + ) [5], pyrene cation (C 16 H 10 + ) [6], neutral perylene (C 20 H 12 ) [7], and benzo(g,h,i)perylene (C 22 H 12 ) [8], under the conditions of the interstellar medium.…”

Section: Introductionmentioning

confidence: 99%

The coupling of a reflectron time-of-flight mass spectrometer with a cosmic simulation chamber: A powerful new tool for laboratory astrophysics

Ricketts

Contreras

Walker

et al. 2011

International Journal of Mass Spectrometry

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a b s t r a c tThe addition of an orthogonal reflectron time-of-flight mass spectrometer (ReTOF-MS) to the NASA Ames cosmic simulation chamber (CSC) experiment is described. The simulation chamber contains the elements that produce the molecular species under astrophysically relevant conditions. A pulsed discharge nozzle (PDN) produces ions, neutrals and radicals in a plasma discharge, which are then expanded and supersonically cooled into the chamber. The coupling of the ReTOF-MS to the CSC provides real-time identification of the species, including cations and neutrals, formed in the plasma, an insight into the chemical pathways of the species reacting in the plasma, and an efficient method for the quick determination of the species present in the plasma, which can then be probed spectroscopically with the cavity ring-down spectrometer (CRDS). The combination of the ReTOF-MS, CRDS and PDN components into a single instrument offers a powerful tool, which can be used to probe a variety of different astrophysical environments such as interstellar clouds and planetary atmospheres. The experimental details and representative mass spectra are presented for plasmas generated in combinations of argon and methane samples. These mass spectra show the unambiguous detection of externally generated ions from the plasma in the simulation chamber. In addition, the various spectra show evidence of fragmentation and bond forming reactivity, illustrating the impact of the composition of the plasma.Published by Elsevier B.V.

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“…In recent years, cavity ring-down spectroscopy (CRDS; Herbelin et al 1980;Anderson et al 1984;O'Keefe & Deacon 1988;Berden et al 2000)-a high sensitivity direct absorption technique-has made it possible to measure the UV/visible absorption spectra of jet-cooled PAHs in the gas phase (Romanini et al 1999;Biennier et al 2003Biennier et al , 2004Sukhorukov et al 2004;Staicu et al 2004;Tan & Salama 2005a, 2005b, 2006Rouillé et al 2004Rouillé et al , 2007. Unlike MIS spectra, CRDS spectra of jet-cooled PAHs in gas phase in the UV/visible range are fully vibronically resolved, and intrinsic band profiles can be derived (Tan & Salama 2005a, 2005bRouillé et al 2007). This point is illustrated in Figure 1, which compares the vibronic spectra of perylene (C 20 H 12 ) measured in an MIS experiment and in a jet-cooled CRDS experiment.…”

Section: Introductionmentioning

confidence: 99%

On Estimating Interstellar Polycyclic Aromatic Hydrocarbon Abundances With Calculated Oscillator Strengths

Tan¹,

Bernstein²,

Cami³

et al. 2011

ApJ

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Vibronic bands of polycyclic aromatic hydrocarbons (PAHs) in the UV/visible range are often used to estimate the abundances of PAHs in the interstellar medium by comparing laboratory-measured spectra with astronomical observations. We investigate the errors introduced by associating theoretical electronic oscillator strengths with individual vibronic bands when estimating the abundances of interstellar PAHs. The vibronic oscillator strengths of the 0-0 bands of nine PAHs with two to seven benzene rings, spanning in the 2800-6700 Å spectral range, have been calculated using the Franck-Condon approximation and compared to their electronic oscillator strengths. It is found that the use of calculated electronic oscillator strengths rather than the more physically relevant vibronic oscillator strengths underestimates interstellar abundances of the nine PAHs under study, on average by a factor of about 2.4. It is recommended that vibronic oscillator strengths should be systematically used to analyze the vibronic spectra of specific PAHs and to estimate their abundances in the interstellar medium. An empirical correcting factor is suggested for the cases where the vibronic oscillator strengths are unknown for more realistic estimation of interstellar PAH abundances.

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Cavity ring-down spectroscopy and vibronic activity of benzo[ghi]perylene

Cited by 35 publications

References 53 publications

Abundances of PAHs in the ISM: confronting observations with experimental results

Abundances of PAHs in the ISM: confronting observations with experimental results

The coupling of a reflectron time-of-flight mass spectrometer with a cosmic simulation chamber: A powerful new tool for laboratory astrophysics

On Estimating Interstellar Polycyclic Aromatic Hydrocarbon Abundances With Calculated Oscillator Strengths

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