Generation of lithium negative ions in a volume source with optical pumping

An experiment is described in which a high density of lithium negative ions (1×1010 cm−3) is generated by dissociative attachment of electrons to optically pumped lithium molecules in a supersonic expansion. During a 3-μs period up to 7% of electrons are attached. A measurement of the lithium vibrational temperature is also reported. Theoretical aspects of Li− production in both a static multicusp source and a supersonic beam source are discussed. The optical pumping requirements for a continuous Li− supersonic beam source are derived.