Kinetic Energies of Secondary Ions in MeV and keV Particle-induced Desorption

✍ Scribed by R. A. Zubarev; U. Abeywarna; P. Håkansson; P. Demirev; B. U. R. Sundqvist

• Book ID: 102650870
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 929 KB
• Volume: 10
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(199612)10:15<1966::aid-rcm783>3.0.co;2-3

✦ Synopsis

Kinetic energy distributions of secondary ions produced by MeV or keV primary-ion bombardment of molecular solids were measured in a reflectron time-of-flight mass spectrometer. It was found that the energy distributions of many ions exhibit tails extending towards energies lower than the accelerating potential. The degree of tailing depends upon the nature of the desorbed ion and the conditions of the target surface. Some light ions (H' and C' ), ions from inorganic (alkali halide) samples, radical molecular ions (Cg) and pre-formed molecuiar ions (e.g. complexes of valinomycin with alkali metal ions) exhibit almost no tailing. For positive adduct-type molecular ions, such as MH', more extensive tailing was observed for MeV compared with keV primary ions. The origin of the energy tailing is attributed to gas-phase formation of a fraction of the secondary ions. For molecular ions of peptides, the characteristic time of formation of that fraction of ions (*lo% of the whole molecular-ion population) was estimated to be of the order of 10 ns, while the characteristic distance from the target surface was of the order of 10 pm.