Academia.edu no longer supports Internet Explorer.
To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser.
2013, Monthly Notices of the Royal Astronomical Society
2013 •
The Journal of Physical Chemistry A
Production of Hydronium Ion (H3O)+ and Protonated Water Clusters (H2O)nH+ after Energetic Ion Bombardment of Water Ice in Astrophysical Environments2019 •
Astronomy and Astrophysics
Photodissociation of organic molecules in star-forming regions2015 •
The results of the laboratory study of reaction rate coefficients of several ion-molecule reactions with atomic and molecular hydrogen and molecular deuterium at low temperatures are presented in the thesis. The reaction rate coefficients of the N+ and H+ reaction with H2 were measured with respect to the nuclear spin configuration and rotational excitation of H2. The reactions of anions were a subject of the isotope exchange and isotope effect study. The measurements of the rate coefficients of H2O and D2O formation in the reaction of O– with H2 and D2, isotope exchange reactions OH– + D2 and OD– + H2, and associative detachment and charge transfer channels of D– + H interaction were performed. Experiments were carried out using an AB-22PT instrument with an ion trap. It has producing, guiding, trapping, and detecting systems for ions and a separate source of atomic H. The cooling system allowed to measure the temperature dependencies of the reaction rate coefficients at temperatur...
Astronomy and Astrophysics
Radiolysis of ammonia-containing ices by energetic, heavy, and highly charged ions inside dense astrophysical environments2010 •
Astronomy & Astrophysics
Hydrides in young stellar objects: Radiation tracers in a protostar-disk-outflow system2010 •
Context. Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods: W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (≃2500 s) in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J = 1-0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions: The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation. Herschel is an ESA space observatory with science instruments provided by a European-led Principal Investigator consortia and with important participation from NASA.Appendix (page 5) is only available in electronic form at http://www.aanda.org
The desorption process induced by photons, electrons, or ions onto icy surfaces is an important mechanism for leading neutral or ionized molecular species to the gas phase in interstellar and circumstellar environments. In this work, we report the results of high energy electron impact onto a condensed pyrimidine ice by means of electron-stimulated ion desorption (ESID). Desorbed cations from the icy surface were analyzed by time-of-flight mass spectrometry (TOF-MS). The most abundant desorbed ions are H+ and H2+, although several other fragments, such as C2H2+ , HCN+,C3H3+, CHN2+,C2H2N2H+, and C4H4N2H+, have also been identified. The fragmentation pattern of pyrimidine was found to be characterized by six distinct regions on its desorption spectra, containing ionic fragments bearing one to six members of the original pyrimidine ring. Five-membered fragment ions were observed for the first time in electron impact experiments. Absolute values of desorption yield for several ions were determined. Desorbed ions observed in this experiment are in agreement with observations of the comet Halley coma composition and may act as markers of the presence of pyrimidine in the interstellar medium.
Rendiconti Lincei-Scienze Fisiche E Naturali
Production of ions at high energy and its role in extraterrestrial environmentsMonthly Notices of The Royal Astronomical Society
Production of H+3 via photodissociation of organic molecules in interstellar clouds2007 •
We present experimental results obtained from photoionization and photodissociation processes of abundant interstellar CH3-X type organic molecules like methanol (CH3OH), methylamine (CH3NH2) and acetonitrile (CH3CN) as alternative route for the production of H+3 in interstellar and star-forming environments. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing soft X-ray photons with energies between 200 and 310 eV and time-of-flight (TOF) mass spectrometry. Mass spectra were obtained using the photoelectron-photoion coincidence techniques. Absolute averaged cross-sections for H+3 production by soft X-rays were determined. We have found that, among the channels leading to molecular dissociation, the H+3 yield could reach values up to 0.7 per cent for single photoionization process and up to 4 per cent for process involving double photoionization. The H+3 photoproduction cross-section due to the dissociation of the studied organic molecules by photons over the C1s edge (200-310 eV) were about 0.2-1.4 × 10-18 cm2. Adopting the typical X-ray luminosity LX >~ 1031 erg s-1 which best fit the observational data for AFGL 2591 we derive an estimative for the H+3 photoproduction rate due to methyl compound dissociation process. The highest value for the H+3 column density from methanol dissociation by soft X-rays, assuming a steady state scenario, was about 1011 cm2, which gives the fraction of the photoproduced H+3 of about 0.05 per cent, as in the case of dense molecular cloud AFGL 2591. Despite the extreme small value, this represent a new and alternative source of H+3 into dense molecular clouds and it is not been considered as yet in interstellar chemistry models.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.
Monthly Notices of the Royal Astronomical Society
Radiolysis of NH3:CO ice mixtures – implications for Solar system and interstellar ices2020 •
Proceedings of the International Astronomical Union
Heavy ion irradiation of astrophysical ice analogsMolecular Astrophysics
Studies of Astrophysically Important Molecular Ions with Ultrasensitive Infrared Laser Techniques1985 •
Monthly Notices of the Royal Astronomical Society
The SILCC project – IV. Impact of dissociating and ionizing radiation on the interstellar medium and Hα emission as a tracer of the star formation rate2016 •
Monthly Notices of the Royal Astronomical Society
Cosmic ray-ice interaction studied by radiolysis of 15 K methane ice with MeV O, Fe and Zn ions2013 •
The Astronomical Journal
H ii REGION G46.5-0.2: THE INTERPLAY BETWEEN IONIZING RADIATION, MOLECULAR GAS, AND STAR FORMATION2015 •
Astronomy & Astrophysics
Organic molecules in protoplanetary disks around T Tauri and Herbig Ae stars2004 •
Astronomy & Astrophysics
Cosmic ray impact on astrophysical ices: laboratory studies on heavy ion irradiation of methane2011 •
2011 •
Monthly Notices of the Royal Astronomical Society
The ionizing radiation from massive stars and its impact on H ii regions: results from modern model atmospheres2008 •
The Astrophysical Journal
Kinetics and Mechanisms of the Acid-Base Reaction Between NH3AND Hcooh in Interstellar Ice Analogs2016 •
Monthly Notices of the Royal Astronomical Society
Processing of low carbon content interstellar ice analogues by cosmic rays: implications for the chemistry around oxygen-rich stars2014 •
Surface Science
Frozen methanol bombarded by energetic particles: Relevance to solid state astrochemistry2009 •
Arxiv preprint arXiv:1012.4477
H2 Infrared Line Emission From the Ionized Region of Planetary Nebulae2010 •
Low Temperature Physics
Radiolysis of astrophysical ices by heavy ion irradiation: Destruction cross section measurement2012 •