Schottky barrier governed injection of solvated ions through track membrane interfaced vacuum inlets

Poly(ethylene terephthalate) track membranes (TM) were recently suggested f or electrostatic injection of charged species into time-of-flight mass spec trometers (TOF-MS). A Schottky-type barrier reduction was investigated usin g a thermally activated extraction regime. A brief description of the physi cal processes involved is given. A wide range of the externally applied ele ctrical potential, Phi, was covered. Collector currents were found to exhib it an activation-like behavior, similar to exp(-Delta F/k(B)T), whereas the free energy difference, Delta F, across the liquid-to-vacuum boundary is s uch that Delta F = Delta F-0(-) Delta F-Phi. An externally controlled term, Delta F-Phi, was also sensitive to the salt concentration for the KCl/glyc erol solutions used. A dramatic decrease of Delta F(Delta(Phi) --> 0) was f ound for an increasing charge carrier concentration. In accordance with the thermionic emission mechanism of ion extraction, the Schottky effect has m anifested itself in Delta F-Phi similar to Phi(1/2). (C) 2000 Elsevier Scie nce B.V.