A detector for state-resolved molecular beam experiments using optical fibres

A detector suitable for state-resolved molecular beam analysis and for the determination of state-to-state differential cross-sections in crossed-beam experiments is described. It detects molecules via laser-induced fluorescence. A single optical fibre and a fibre bundle provide a flexible link between the laser and a photomultiplier outside a vacuum tank. Internal state resolution is achieved by tuning the laser to an appropriate transition frequency. Representative measurements involving a sodium molecular beam are shown.