Figure 2 shows the mass distribution for each sample with respect to velocity. The horizontal lines represent the mean sample mass, where the range of values for pure PPY is indicated with a maximum and minimum line. Iron has no clearly defined mean mass and this i o is reflected in the plot with the mass ranging 2.5 - 24.7x10" kg. The PEDOT latex sample predominately falls close to the measured sample grain mass. However, the PPY latex and pure PPY samples appear to give a range of values with typically a larger mass than expected. It is possible these are multiple grains clustered together.

The spectra obtained from the low-density particles display a complex response, completely contrasting with the clean elemental spectra obtained from iron. There are many features of mass ranging 1 - 200amu consisting of both elemental components and molecularly bonded fragments. The spectra obtained within each sample type display consistent peak responses for similar velocities. However, there are variations in peak intensities. This is possibly due to slight variations in event conditions, e.g. target morphology. Also there seem to be different peak formations with different velocities, which needs further investigation. The spectra from those events with a high speed of impact reflect a greater abundance of peaks with lower mass and lower abundance of large molecular groups. The sample with most events, PEDOT, has a strictly constrained velocity response.

Figure 3 shows a representative spectrum. System contaminants sodium (Na, 23 amu) and potassium (K, 39 amu) are clearly identifiable and labelled, and there are many higher peaks, one of which may be the target material, rhodium (although this is not expected at such low velocities). A very strong signal is evident at 91 amu. The core material, polystyrene latex, produces a strong response at 91 amu under thermal decomposition [10] and interestingly theis isn't evident in the pure PPY spectra, although the different velocity regimes could account for this.

1 10 20 30 40 50 60 80 100 200 amu

1 10 20 30 40 50 60 80 100 200 amu

Figure 3. Typical mass spectrum for PEDOT-PS event, velocity 3.25km s"1. Mass scale calibrated using Sodium (23amu) and Potassium (39amu)
Table 1. Summary of Sample Characteristics

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