Time-of-flight mass spectrometric analysis of ion formation in hypervelocity impact of organic polymer microspheres: comparison with secondary ion mass spectrometry, (252)Cf mass spectrometry and laser mass spectrometry.

Abstract

Unisized 1.6-microm polystyrene microspheres coated with PEDOT (polyethylene-dioxythiophene) were accelerated to speeds of 6-16 km/s and shot onto a silver target. Either positive or negative ions, both instantaneously formed by the impact process, have been analyzed by time-of-flight mass spectrometry (TOF). Apparently, the processes that control the formation of ions of either polarity depend on the impact velocity. Comparing the results with those of secondary ion mass spectrometry with primary ion energy in both the elastic and the inelastic ((252)Cf-MS) energy loss regimes, some reaction mechanisms of the polymer ions for different energy densities could be elucidated. Some aspects of ion formation are also related to those found in pulsed laser ion generation from these microspheres. This investigation was performed in order to further improve the method of analyzing the organic fraction of interstellar, interplanetary, and cometary dust particles impinging on the targets of the "CIDA" time-of-flight (TOF) mass spectrometers on-board the NASA comet missions "STARDUST" and "CONTOUR".