Knowledge Bank

Wavelength dependent multiphoton photoionization with time of flight mass resolution has been recorded for areas of the spectra of aniline, naphthalene, and benzene. The experiments use either on one two Nd:YAG pumped dye lasers crossing a skimmed supersonic molecular beam in the ion source of a homemade time of flight mass spectrometer. For these molecules, whose first excited singlet state is more that half way to the ionization potential, the one laser, two photon ionization is an efficient way to observe the spectrum. Two laser experiments have also been done with a ""pump"" laser exciting an $S1$ vibration followed by an ""ionzing"" laser scanned to observe the ionization potential or structure in highly excited states. Various examples from the spectra of these molecules, some of which can be compared to fluorescence excitation under equivalent conditions done recently ion our lab, show that multiphoton ionization is an efficient and powerful technique for spectroscopy in molecular beams.