Ionization of some aliphatic alcohol molecules with kinetic energy on various surfaces

This paper describes an experimental study on the influence of kinetic energy of fast aliphatic alcohol molecules on surface ionization (SI), using various refractory metal (Re, Pt, Ir) surfaces. Mass spectrometric measurements were done for various incident kinetic energies, surface materials, and surface temperatures. The SI mass spectra were interpreted in a purely empirical way by means of evidence from previous investigations and then compared to conventional EI techniques. Ionization efficiency (beta) was also studied. We conclude that under hyperthermal surface ionization (HSI) conditions that (a) these alcohol compounds with kinetic energy are efficiently surface-ionized, confirming the HSI mechanism, (b) in general, soft ionization can be obtained where the strong molecular ion (M-H)(+) and a few fragments are generated, (c) the ionization efficiency and mass spectral pattern depend on both surface temperature and the surface material in a complex way, and (d) in the case of n-pentanol, beta reaches the level of 10(-4) under the most favorable conditions.