Negative hydride ion production by low energy electron impact of alkali metal hydride powder

Abstract

A compact ion source (about 1 cm 3 in size) designed by the author was used to measure the ion current ( I −) of H − or D − produced by electron impact of powdered LiH, NaH, CaH 2 or LiD (about 10 mg) deposited on a fine stainless steel gauze of area S G about 0.1 cm 2 as a function of the energy (20–250 eV) or of the electron current ( J − ≈ 0.01–15 mA) of bombarding electrons emitted from a coiled tungsten filament mounted beneath the gauze. NaH produced the largest I − (about 50 μA), I −/ S G (about 0.5 mA cm −2) and I −/ J − (about 2%). Production of D − from LiD resulted in I −/ S G ≈ 0.002%, nearly the same as for H − production from LiH but about three times larger than results for CaH 2. Possible mechanisms for producing these ions are examined and briefly discussed.