OBSERVATION OF THE NU(1), FUNDAMENTAL-BAND IN SULFUR-TRIOXIDE INDUCEDBY SYMMETRY-BREAKING UPON O-18 SUBSTITUTION

The infrared (IR) absorption spectrum of gaseous SO3 enriched with O-1 8 is studied. The nu(1) band of (SO2O)-O-16-O-18 1040 +/- 2 cm(-1) is observed in the IR spectrum, whereas it is inactive for (SO3)-O-16. Th e isotope shift measured in nu(1) is 28 +/- 2 cm(-1). The integrated i ntensity of this band was measured to 5.7 +/- 1.6 atm (-1) cm(-2). The se results agree with our calculations, carried out within the framewo rk of the valence force model. The opportunity to realize isotopically selective photolysis of (S16O2O)-O-18 molecules with excitation of th e nu(1) mode by combined IR + UV laser radiation is discussed. (C) 199 8 Elsevier Science B.V. All rights reserved.