UV photolysis of polyynes at λ=254 nm and at λ&gt;222 nm

Cataldo, Franco; Strazzulla, G.; Iglesias‐Groth, Susana

doi:10.1017/s147355040800414x

Cited by 9 publications

(3 citation statements)

References 30 publications

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“…Polyynes have been observed as intermediates in the production of fullerenes and nanotubes and have been synthesized through physical methods, namely arc‐discharge and pulsed laser ablation that are also used to produce fullerenes. Polyynes are also relevant in astrophysics, and their presence in outer space and Saturn moon Titan is being considered. Many natural products have been found containing polyyne moieties with chain lengths in the range of two to four conjugated triple bonds .…”

Section: Introductionmentioning

confidence: 99%

Structure and chain polarization of long polyynes investigated with infrared and Raman spectroscopy

Agarwal

Lucotti

Fazzi

et al. 2013

J Raman Spectroscopy

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Symmetrically and unsymmetrically endcapped polyynes (triisopropylsilyl - TIPS - and super trityl endcapping groups) have been studied with density functional theory calculations and Raman and infrared spectroscopy. This spectroscopic investigation provides general guidelines for studying the vibrational and structural features of sp-carbon-based materials, which nowadays are at the center of growing interest for the potential applications of nanostructured carbon materials in molecular electronics. On the basis of the description of CC stretching modes of polyynes in terms of longitudinal optical phonons of the parent infinite sp-carbon chain, we have carried out the complete assignment of the observed infrared and Raman features in the 2300-1900 cm-1 range, for chain lengths in the range 4-20 triple bonds. This allows demonstration of polarization effects induced by an unsymmetric structure and deviations from chain linearity in long polyynes

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Section: Introductionmentioning

confidence: 99%

Structure and chain polarization of long polyynes investigated with infrared and Raman spectroscopy

Agarwal

Lucotti

Fazzi

et al. 2013

J Raman Spectroscopy

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“…A multitude of polyyne species are therefore the most probable explanation for the absorption features observed. Moreover, it has been found by Cataldo et al (2008) that polyynes are the dominant product of the UV photochemistry of C 2 H 2 suspended in liquid at room temperature.…”

Section: Polymerizationmentioning

confidence: 99%

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

Cuylle

Zhao

Strazzulla

et al. 2014

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Aims. Gas phase acetylene (C 2 H 2 ) and polyynes (H(-C≡C-) m H) are ubiquitous in the interstellar medium. However, astrochemical models systematically underestimate the observed abundances, supporting the idea that enrichment from the solid state takes place. In this laboratory-based study, we investigate the role C 2 H 2 plays in interstellar ice chemistry and we discuss the way its photoproducts may affect gas phase compositions. Methods. C 2 H 2 ice is investigated under vacuum ultraviolet (VUV) irradiation in its pure form as present in the atmosphere of Titan and in a water-dominated ice as present on grain mantles in molecular clouds and on comets. To disentangle the photochemical network, a unique, complementary combination of infrared and ultraviolet-visible (UV-VIS) spectroscopy is used. Results. From the experimental results, it can be concluded that the VUV-induced solid state C 2 H 2 reaction network is dominated by polymerization resulting in the formation of polyynes at least up to C 20 H 2 and larger polyyne-like molecules. At low temperatures, this process takes place very efficiently and suggests low barriers. When extending this reaction scheme to a water-rich environment, the dominant reaction products are CO and CO 2 but the simultaneous detection of polyyne like molecules is evidence that the reactions as observed in pure C 2 H 2 ice persist. Conclusions. From the spectroscopic evidence as presented in this laboratory study, it is concluded that the formation of polyynes upon VUV irradiation of interstellar ices is a process that may contribute to at least part of the observed gas phase enrichment in space.

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“…It is important to note that polyynes, C n H 2 , also absorb strongly in the UV, and there is evidence that these groups are present under certain conditions ). For example, C 8 H 2 produces three intense absorption features near 5.6 eV (Cataldo et al 2008). Individual deposits will contain a range of sp 2 -and sp 3 -bonded carbon components producing absorption at photon energies >E g .…”

Section: Sample Propertiesmentioning

confidence: 99%

THE 217.5 nm BAND, INFRARED ABSORPTION, AND INFRARED EMISSION FEATURES IN HYDROGENATED AMORPHOUS CARBON NANOPARTICLES

Duley

2012

ApJ

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We report on the preparation of hydrogenated amorphous carbon nanoparticles whose spectral characteristics include an absorption band at 217.5 nm with the profile and characteristics of the interstellar 217.5 nm feature. Vibrational spectra of these particles also contain the features commonly observed in absorption and emission from dust in the diffuse interstellar medium. These materials are produced under "slow" deposition conditions by minimizing the flux of incident carbon atoms and by reducing surface mobility. The initial chemistry leads to the formation of carbon chains, together with a limited range of small aromatic ring molecules, and eventually results in carbon nanoparticles having an sp 2 /sp 3 ratio ≈ 0.4. Spectroscopic analysis of particle composition indicates that naphthalene and naphthalene derivatives are important constituents of this material. We suggest that carbon nanoparticles with similar composition are responsible for the appearance of the interstellar 217.5 nm band and outline how these particles can form in situ under diffuse cloud conditions by deposition of carbon on the surface of silicate grains. Spectral data from carbon nanoparticles formed under these conditions accurately reproduce IR emission spectra from a number of Galactic sources. We provide the first detailed fits to observational spectra of Type A and B emission sources based entirely on measured spectra of a carbonaceous material that can be produced in the laboratory.

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UV photolysis of polyynes at λ=254 nm and at λ>222 nm

Cited by 9 publications

References 30 publications

Structure and chain polarization of long polyynes investigated with infrared and Raman spectroscopy

Structure and chain polarization of long polyynes investigated with infrared and Raman spectroscopy

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach

THE 217.5 nm BAND, INFRARED ABSORPTION, AND INFRARED EMISSION FEATURES IN HYDROGENATED AMORPHOUS CARBON NANOPARTICLES

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