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

A new spectrometer is described which combines electron impact excitation a nd deflection studies of atoms and molecules with laser spectroscopy. The s pectrometer initially excites ground state atomic or molecular targets to a metastable state by employing an electron beam well defined in direction a nd energy. These metastable targets are then further excited to high Rydber g states (n greater than or equal to 20) by employing resonant laser radiat ion derived from a frequency doubled pulsed dye laser. The high-n Rydberg t argets are subsequently field ionized by a pulsed electric field and are de tected as a function of both laser wavelength and electron impact energy, a llowing state selected differential cross section measurements to be ascert ained. 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. (C) 1999 American Institute of Physics. [ S0034-6748(99)02904-4].