Volume 401, Number 1, April I 2003
|Page(s)||57 - 65|
|Published online||17 March 2003|
Structural processing of enstatite by ion bombardment
Friedrich-Schiller-Universität Jena, Astrophysikalisches Institut and Universitäts-Sternwarte (AIU), Schillergäßchen 2-3, 07745 Jena, Germany
2 Friedrich-Schiller-Universität Jena, Institut für Festkörperphysik, Max-Wien-Platz 1, 07743 Jena, Germany
Corresponding author: C. Jäger, firstname.lastname@example.org
Accepted: 19 December 2002
During their lifetime, cosmic dust silicates suffer from a continuous processing by annealing, cosmic ray and UV irradiation, destruction and possibly also interstellar recondensation. Since the discovery that a significant proportion of stardust silicates leaves their star in crystalline form, the question arose as to why the interstellar silicate dust component does not show any indication of crystallinity. Amorphization due to ion irradiation is one possible explanation for the effect. In this paper, the results of irradiation experiments of submicrometre-sized clinoenstatite (MgSiO3) particles with 400 keV Ar+ and 50 keV He+ ions are presented. The irradiation doses have been varied between 11016 and 11018 ions/cm2 for He+ ions and 11014 up to 51014 ions/cm2 for Ar+ ions. These doses are comparable to those values that an interstellar silicate grain should be exposed to during its average life-time of 4108 years. Threshold values for amorphization have been amounted to 11017 and 31014 ions/cm2 for 50 keV He+ and 400 keV Ar+ ions. Besides the structural changes in the microcrystallites morphological modifications in the grains, but no change of the chemical composition are found. Conclusions of potential astrophysical relevance have been drawn.
Key words: ISM: cosmic rays / ISM: dust, extinction / ISM: general
© ESO, 2003
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.