IDENTIFICATION OF 2 (3)PI(U)[-X(3)SIGMA(-)(G) TRANSITIONS OF O-16(2) NEAR 93,850 AND 95,360 CM(-1)

The one-photon absorption spectrum of molecular oxygen in the photoion ization threshold region has been recorded at high resolution (lambda/ Delta lambda = 2 X 10(5)) against the background continuum of a synchr otron radiation source. The room temperature spectrum as well as the r otationally cold absorption of a supersonically expanding jet (T-rot a pproximate to 20 K) have been registered on photographic plates. The d rastically reduced complexity of the jet spectra has led to the unambi guous identification of two (3) Pi(u) vibronic levels of O-16(2) at 93 850 and 95 360 cm(-1); rotational and Lambda-type doubling parameters have been determined. In addition, the upper state of a previously re ported strong band of O-16(2) (O-18(2)) at 86 733 (86 697) cm(-1) (Oga wa et al., J. Mol. Spectrosc. 55, 425-429, 1975) has tentatively been attributed to upsilon = 0 of the bound second adiabatic (3) Pi(u) pote ntial arising from the strong interaction of the ...pi(u)(4) pi(g) . 3 p sigma(u) Rydberg with the ...pi(u)(4) pi(g) sigma(u) valence configu ration (Buenker et al., Chem. Phys. Lett. 34, 225-231, 1975; 42, 383-3 89, 1976). (C) 1995 Academic Press, Inc.