Impact ionisation spectra from hypervelocity impacts using aliphatic poly(methyl methacrylate) microparticle projectiles

Burchell, Mark J. and Armes, Steven P. (2011) Impact ionisation spectra from hypervelocity impacts using aliphatic poly(methyl methacrylate) microparticle projectiles. Rapid Communications in Mass Spectrometry, 25 (4). pp. 543-550. ISSN 0951-4198. (doi:https://doi.org/10.1002/rcm.4887) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Official URL
http://dx.doi.org/10.1002/rcm.4887

Abstract

We report impact ionisation spectra from spherical poly(methyl methacrylate) (PMMA) microparticles of 724 nm diameter impacting a rhodium target. These projectiles were coated with an ultrathin (∼11 nm) overlayer of polypyrrole, an electrically conducting organic polymer; this enabled the accumulation of sufficient surface charge to allow electrostatic acceleration up to speeds of 4 to 8 km s−1 using a high-voltage Van de Graaff instrument. A grid above the target (held at 3.33 kV cm−1 with respect to the target) accelerated the cations that were generated during the hypervelocity impacts, and these ions then drifted to a charge detector. By measuring the collected charge vs. time and assuming only single ionisation events, time-of-flight mass spectra were obtained. Strong signals were observed for cationic species with ions of m/z 41, 65 and 115. There were also minor contributions from cations with masses ranging from m/z 29 to 142. The three major signals are assigned to fragment ions (C3Hmath image, C4H5O+/C5Hmath image and C6H11Omath image) which are known to be associated with the decomposition of PMMA. These impact ionisation spectra differ significantly from those reported earlier using polystyrene (PS) microparticles. The aliphatic PMMA microparticles generate small (m/z <100) fragment ions more readily at lower speeds than the predominantly aromatic PS microparticles, where speeds of at least 10 km s−1 are typically required for substantial yields of low-mass fragment ions. This correlates well with the well-known greater chemical and thermal fragility of PMMA compared to PS. The PMMA microparticles should prove useful synthetic mimics for aliphatic carbonaceous micrometeorites.

Item Type: Article
Subjects: Q Science > QB Astronomy
Q Science > QD Chemistry
Divisions: Faculties > Sciences > School of Physical Sciences
Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Mark Burchell
Date Deposited: 05 Dec 2013 13:11 UTC
Last Modified: 05 Jan 2015 13:35 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/37218 (The current URI for this page, for reference purposes)
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