ROTATIONAL STRUCTURE IN THE ABSORPTION-SPECTRA OF O-18(3) AND O-16(3)NEAR 1 MU-M - A COMPARATIVE-STUDY OF THE (3)A(2) AND B-3(2) STATES

Absorption spectra for O-16(3) and O-18(3) near 1 mu have been recorde d to explore the rotational structure associated with the (3)A(2) and B-3(2) electronic states of ozone. Rotational features within the (3)A (2)<--(1)A(1) 1-0 band respond predictably to isotopic substitution, e nabling determination of the upper state adiabatic electronic energy a nd asymmetric stretching frequency via isotope shift techniques. We fi nd an adiabatic energy of 9963+/-4 cm(-1), in excellent agreement with that determined earlier from vibronic isotope shifts observed at lowe r resolution, 9990+/-70 cm(-1). We also find an asymmetric stretching frequency of 367+/-17 cm(-1), indicating that the (3)A(2) state potent ial energy surface is bound against dissociation to O+O-2 despite the fact that it lies above the corresponding dissociation limit. Rotation al structure associated with transitions to the B-3(2) state is detect ed for the first time. It responds anomalously to O-18 substitution. T he geometry of the upper state for O-18(3) appears to differ markedly from that for O-16(3) (Delta theta approximate to-4 deg, or Delta r(e) approximate to+0.07A), suggesting that the B-3(2) surface is strongly anharmonic and precluding a straightforward analysis of the isotope s hifts. (C) 1998 American Institute of Physics. [S0021-9606(98)01910-2] .