Dissociation of the benzene molecule by UV and soft X-rays in circumstellar environment

Abstract

Benzene molecules, present in the proto-planetary nebula CRL 618, are ionized and dissociated by UV and X-ray photons originated from the hot central star and by its fast wind. Ionic species and free radicals produced by these processes can lead to the formation of new organic molecules. The aim of this work is to study the photoionization and photodissociation processes of the benzene molecule, using synchrotron radiation and time of flight mass spectrometry. Mass spectra were recorded at different energies corresponding to the vacuum ultraviolet (21.21 eV) and soft X-ray (282-310 eV) spectral regions. The production of ions from the benzene dissociative photoionization is here quantified, indicating that C6H6 is more efficiently fragmented by soft X-ray than UV radiation, where 50% of the ionized benzene molecules survive to UV dissociation while only about 4% resist to X-rays. Partial ion yields of H+ and small hydrocarbons such as C2H2+, C3H3+ and C4H2+ are determined as a function of photon energy. Absolute photoionization and dissociative photoionization cross sections have also been determined. From these values, half-life of benzene molecule due to UV and X-ray photon fluxes in CRL 618 were obtained.

arXiv commentThe paper contains 8 pages, 9 figures and 4 tables. Accepted to be published on MNRAS on 2008 November 26

References in corpus (13)

• ISO spectroscopy of disks around Herbig Ae/Be stars
• Are PAHs precursors of small hydrocarbons in Photo--Dissociation Regions? The Horsehead case
• X-ray chemistry in envelopes around young stellar objects
• Spitzer-IRS spectra of disks around T Tauri stars II. PAH emission features
• Discovery of Blue Luminescence in the Red Rectangle: Possible Fluorescence from Neutral Polycyclic Aromatic Hydrocarbon Molecules?
• Shaping Proto-Planetary and Young Planetary Nebulae with Collimated Fast Winds
• A Compact X-ray Source and Possible X-ray Jets within the Planetary Nebula Menzel 3
• ROSAT observations of X-ray emission from planetary nebulae
• O-bearing Molecules in Carbon-rich Proto-Planetary Objects
• Destruction of formic acid by soft X-rays in star-forming regions
• Benzene formation in the inner regions of protostellar disks
• Production of H${}_3^{+}$ via photodissociation of organic molecules in interstellar clouds
• Photodissociation of organic molecules in star-forming regions II: Acetic acid

Cited by in corpus (4)

• Photostability of gas- and solid-phase biomolecules within dense molecular clouds due to soft X-rays
• Destruction and multiple ionization of PAHs by X-rays in circumnuclear regions of AGNs
• Single and Double Photoionization and Photodissociation of Toluene by Soft X-rays in Circumstellar Environment
• Molecular formation along the atmospheric mass loss of HD 209458 b and similar Hot Jupiters