Multiphoton ionization and fragmentation of the hydrogen iodide molecule have been examined at 355 and 532 nm and optical field intensities of 1011minus;5times;1012Wthinsp;cmminus;2by photoelectron spectroscopy and timehyphen;ofhyphen;flight mass spectrometry. At 532 nm, scission of the Hndash;I bond is favored over direct photoionization of the molecule. Three and four photon ionization of HI at 355 nm (planck;ohgr;ape;3.5 eV), however, reveals clear vibrational progressions associated with the HI+2Pgr;3/2and2Pgr;1/2ion product states. Analysis of these spectra yields vibrational frequencies for the2Pgr;3/2and2Pgr;1/2states that agree to better than 8percnt; with those determined by Bouml;weringetal. lsqb;Chem. Phys. Lett.189, 467 (1992)rsqb; from single photon ionization experiments. Above threshold ionization (ATI) of both HI and atomic iodine are also observed.
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