Secondary Electron Emission Yields from a CsI Surface Under Impacts of Large Molecules at Low Velocities (5 × 103−7 × 104 ms−1)

The yields of electron emission from a CsI surface bombarded with very heavy molecular ions have been measured by coincidence counting in time-of-flight mass spectrometry. These ions were produced by the matrix-assisted laser desorption/ionization technique. The masses ranged from 700 to 66 000 Da with velocities V between 5 × 103 and 7 × 104 ms−1. An electron emission rate of a few per cent was measured for the smaller impact velocities. The variations of the electron yields with mass and velocity are compared to previous data and analysed by different models. A sublinear mass dependence is observed as well as a V4 dependence at low velocity.