Electrostatic space focusing of molecular beams: some methods and applications

Abstract

Electrostatic space focusing of molecular beams has been introduced by means of a brief review of some methods which have been employed in the development of microwave spectroscopy of molecules.
Some electrostatic focuser configurations suitable for space focusing molecules that decrease in energy in an applied eleotric field have been experimentally investigated. These designs include the coaxial, single-wire and a new configuration, the crossed-wire focuser. Characteristic results which have been obtained indicate the crossed-wire focuser to be the most efficient for focusing molecules in the lower inversion states of the rotational energy levels of ammonia.
For the first time, the operation of electrostatic focusers has been achieved in a beam maser without recourse to the continual use of external BET supplies. This development involved the employment of electret focusers. In particular, solid ammonia electrets have been formed and the time dependence of their external electric field has been monitored in a beam maser. The method employed here of monitoring the external electret electric field by probing with a neutral molecular beam, has not previously been utilised.
A space focused ammonia molecular beam has been used to observe electric resonance "beating of beats". This effect, which is analogous to a similar effect observed in nuclear magnetic resonance, followed the rapid passage of an exciting signal through the resolved components of the naturally split main line of the J - 1, K - 1 inversion transition.