A novel spectrometer combining laser and electron excitation and deflection of atoms and molecules

Abstract

A new spectrometer is described which combines electron impact excitation and deflection studies of atoms and molecules with laser spectroscopy. The spectrometer initially excites ground state atomic or molecular targets to a metastable state by employing an electron beam well defined in direction and energy. These metastable targets are then further excited to high Rydberg states (n⩾20) by employing resonant laser radiation derived from a frequency doubled pulsed dye laser. The high-n Rydberg targets are subsequently field ionized by a pulsed electric field and are detected as a function of both laser wavelength and electron impact energy, allowing state selected differential cross section measurements to be ascertained. The momentum transferred to the target by the electron impact can be exploited to provide additional information about the atomic or molecular state excited by electron impact.