Strong photoionization spectra have been observed in molecular Iodine following laser excitation in the near ultraviolet. The dependence upon laser power, and the structure of the spectra are consistent with three-photon ionization with resonance in an intermediate state excited by two photons. Vibrational analysis indicates an electronic energy T[sub e] of 53,562.75 ± 1 cm⁻¹, a harmonic vibrational constant we of 241.4 ± 0.4 cm⁻¹, and an anharmonic vibrational constant toexe of 0.58 ± 0.06 cm⁻¹. Rotational analysis done by the Franck-Condon method, whereby the relative experimental band intensities are compared with theoretical values, indicates that the internuclear separation r[sub e] in the resonant electronic state is 2.567 ± 0.002A, corresponding to a rotational constant B of 0.04029 ± 0.00007 cm⁻¹. The new electronic state has, with high probability, the designation 1[sub g] . Several im purity lines were observed at exciting energies 26,297.14 ± 1 cm⁻¹ (half width 8.09 cm⁻¹), at 26,915.22 ± 1 cm⁻¹, and at 27,343.96 ± 1 cm⁻¹. The impurity signal varies as I[sub o][sup 2.02]. The features likely arise from complex molecular species formed in reactions at high temperature with l₂, and have not been identified. The photoionization efficiency of in nonlinear absorption exhibits an apparent resonance in the vicinity of 80,000 cm⁻¹ in terms of total molecular energy. / Science, Faculty of / Physics and Astronomy, Department of / Graduate