Identification of two (3)Sigma(u)(-)<-X(3)Sigma(g)(-) transitions of O-16(2) near 88930 and 90780 cm(-1)

New O-16(2) photoabsorption cross-section measurements are presented for two bands near 88930 cm(-1) and 90780 cm(-1). We have assigned these bands as the (0,0) and (1,0) bands of the E'(3) Sigma(u)(-)<--X(3) Sigma(g)(-) system, where the E' state is a mixed state resulting from the coupling of 4p pi(u) and 5p pi(u) (3) Sigma(u)(-) Rydberg states with the lowest (3) Sigma(u)(-) valence state. In contrast to the Sigma(3) Sigma(u)(-)<--X(3) Sigma(g)(-) bands seen at lower energies, these bands show resolved rotational structure. Spectroscopic parameters for the upper levels have been derived using an effective Hamiltonian and cross-section band models. The observed levels are perturbed by spin-orbit interactions with nearby levels (upsilon=1 and 2) of the 4p pi(u) D'(3) Sigma(u)(+) Rydberg state. In addition, transitions to the upsilon=2 level of the perturber state have been observed near 90920 cm(-1). (C) 1996 American Institute of Physics.