Impact ionisation mass spectrometry of polypyrrole-coated pyrrhotite microparticles

• Published in: Planetary and space science 2014-07, Vol.97, p.9-22
• Main Authors: Hillier, Jon K., Sternovsky, Zoltan, Armes, Steven P., Fielding, Lee A., Postberg, Frank, Bugiel, Sebastian, Drake, Keith, Srama, Ralf, Kearsley, Anton T., Trieloff, Mario
• Format: Article
• Language: English
• Subjects: Cations; Fragmentation; Impact analysis; Impact velocity; Interplanetary dust; Mass spectrometry; Mineralogy; Organic chemistry; Polypyrroles; Pyrrhotite; Silver; Spectra
• ISSN: 0032-0633; 1873-5088
• DOI: 10.1016/j.pss.2014.04.008

Cation and anion impact ionization mass spectra of polypyrrole-coated pyrrhotite cosmic dust analogue particles are analysed over a range of cosmically relevant impact speeds. Spectra with mass resolutions of 150–300 were generated by hypervelocity impacts of charged particles, accelerated to up to 37kms−1 in a Van de Graaff electrostatic accelerator, onto a silver target plate in the Large Area Mass Analyzer (LAMA) spectrometer. Ions clearly indicative of the polypyrrole overlayer are identified at masses of 93, 105, 117, 128 and 141u. Organic species, predominantly derived from the thin (20nm) polypyrrole layer on the surface of the particles, dominate the anion spectra even at high (>20kms−1) impact velocities and contribute significantly to the cation spectra at velocities lower than this. Atomic species from the pyrrhotite core (Fe and S) are visible in all spectra at impact velocities above 6kms−1 for 56Fe+, 9kms−1 for 32S+ and 16kms−1 for 32S− ions. Species from the pyrrhotite core are also frequently visible in cation spectra at impact speeds at which surface ionisation is believed to dominate (