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Polycyclic Aromatic Hydrocarbon Ionization Energy Lowering in Water IcesIn studying various interstellar and solar system ice analogs, we have recently found that upon vacuum ultraviolet photolysis, polycyclic aromatic hydrocarbons (PAHs) frozen in water ice at low temperatures are easily ionized and indefinitely stabilized as trapped ions (Gudipati; Gudipati & Allamandola). Here we report the first experimental study that shows that PAH ionization energy is significantly lowered in PAH/H2O ices, in agreement with recent theoretical work (Woon & Park). The ionization energy (IE) of the PAH studied here, quaterrylene (C40H20, IE = 6.11 eV), is lowered by up to 2.11 eV in water ice. PAH ionization energy reduction in low-temperature water ice substantially expands the astronomical regions in which trapped ions and electrons may be important. This reduction in ionization energy should also hold for other types of trapped species in waterrich interstellar, circumstellar, and solar system ices. Subject headings: ISM: clouds - methods: laboratory - molecular processes - radiation mechanisms: nonthermal -ultraviolet: ISM - ultraviolet: solar system
Document ID
20060024654
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Gudipati, Murthy S.
(NASA Ames Research Center Moffett Field, CA, United States)
Allamandola, Louis J.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 23, 2013
Publication Date
October 11, 2004
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 615
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: 344-58-12
CONTRACT_GRANT: 188-02-04
CONTRACT_GRANT: NCC2-1303
CONTRACT_GRANT: 344-53-92
Distribution Limits
Public
Copyright
Other

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