DEVELOPMENT OF A SURFACE-IONIZATION TYPE DUAL-ION SOURCE APPLICABLE TO IONIC CRYSTALLINE SAMPLES

A surface ionization type dual-ion source (DIS) developed for ionic cr ystalline samples such as alkali halides (MX) consists of (1) a sample plate (F-1, similar to 0.02 cm(2)) heated up to similar to 1000 K to produce primary ion (M(+) or X(-)) by dissociative self-surface ioniza tion of MX deposited on F-1, (2) a second filament (F-2) kept at 1260 K to produce secondary ion (M(+)) by molecular beam surface ionization of the neutral molecule (MX(0)) desorbing from F-1 and (3) a grid (G) mounted between F-1 and F-2 to retard the primary and secondary ions. These ions are independently extracted efficiently and collected sepa rately without using any separator other than G. Our DIS is free from background ions due to residual gases, easy in operation, simple in st ructure and small in size (similar to 2 cm(3)) but quite useful for ki netic studies of ionic and neutral desorption from MX and also for gen erating monochromatic and stable dual-ion beams (similar to 1 pA) from MX (similar to 1 mu g) deposited on F-1. (C) 1996 American Institute of Physics.