The Design and Construction of a Nitrogen Laser and Its Use to Pump a Tunable Dye Laser to Measure the Multiphoton Ionization Spectrum of Molecular Iodine

摘要

A nitrogen laser was constructed for use in multiphoton ionization studies. The short pulse duration and highly intense pulse make the nitrogen laser ideal for pumping a dye laser.By using the nitrogen laser to pump a tunable dye laser, the multiphoton ionization spectrum for molecular iodine vapor was obtained for the visible spectrum between 23,188 cm-1 (430 nm) and 16, 304 cm-1 (615 nm) using pulsed electronics and a parallel plate ionization chamber. The ionization occurs in this region upon the absorption of four or five photons. The ionization appears to take place via a three-step process. The first photon excites the molecule to a resonant state which is one of the vibrational states of B3πo+u level. From this level, two photons are absorbed to a higher resonant level, and then ionization takes place when that higher excited state absorbs the one or two photons necessary for ionization.