Coaxial ion beam/infrared laser beam spectrometer for investigating infrared spectra of doubly positively charged molecules (molecular dications)

We have constructed an apparatus for studying the infrared spectra of molecules with a doubly positive charge (molecular dications). The spectroscopic transitions were recorded indirectly by means of observing a change in the fragmentation rate of the molecular dication when a transition was in resonance. The design and performance of the spectrometer are described, with particular emphasis on the sensitivity achieved for detecting infrared spectra and Zeeman split infrared spectra. The operation and calibration of the spectrometer are discussed and sample results for DCl2+ are presented. It is shown that we achieve the maximum possible signal/noise ratio that could be achieved in this type of experiment. (C) 2002 American Institute of Physics.