Structure and rovibrational analysis of the ÜO 2 Ñ 1 D g Ö v˜0 á 2 )ÜO 2 Ñ 3 S g Ö v˜0 á 2 transition of the O 2 dimer

slightly asymmetric prolate top. The rotational analysis of the two K50 subbands leads to very close values of the effective rotational constant, Bp5(B1C)/2, for both A 1 and B 1 levels: 0.095 cm 21 for the @O2( 3 S g ) v50# 2 lower states and 0.063 cm 21 for the @O2( 1 D g) v50# 2 excited states, in close agreement with theoretical values. The H geometry is confirmed as the most stable for the ground electronic singlet state. A distance between the two monomers of 6.1 a0 and 7.5 a0 is derived for the ground and excited singlet states. Similar results are obtained from the two K 52 subbands. A vibrational assignment is given for the two rotationally analyzed subbands ( K 50) and proposed for the main features of the whole band. © 2000 American Institute of Physics. @S0021-9606~00!01614-7#