Laser–ion coaxial beams spectrometer

Abstract

An apparatus has been constructed to provide laser excitation of ion beams in both coaxial and crossed configurations. The coaxial geometry provides very high sensitivity and nearly Doppler-free wavelength resolution for spectroscopic measurements, and allows the use of the Doppler shift to ’’tune’’ the wavelength. A novel transverse quadrupole electric field arrangement is used to deflect the ion beam into and out of the laser beam axis. The ion beam is highly collimated and a high-resolution 180° electrostatic analyzer is used for photofragment energy analysis. The apparatus has demonstrated a resolution of better than 10 meV for normal photofragment spectroscopy and 0.001 meV for coaxial beams photofragment spectroscopy using a single-mode laser. While providing these high resolutions the apparatus has an overall sensitivity several orders of magnitude greater than conventional ones.