THE CENTRIFUGALLY INDUCED PURE ROTATIONAL SPECTRUM AND THE STRUCTURE OF SULFUR-TRIOXIDE - A MICROWAVE FOURIER-TRANSFORM STUDY OF A NONPOLAR MOLECULE

The pure rotational spectrum of sulfur trioxide has been observed for the first time. A total of 25 high-J transitions could be assigned. The rotational constants, two quartic centrifugal distortion constants, and three sextic centrifugal distortion constants were determined as: B = 10 449.0667(23) MHz, C = 5216.0330(12) MHz, D(J) = 9.2651 (18) kHz, D(JK) = -16.3922(18) kHz, H(J) = -8.8(34) . 10(-3) Hz, H(JK) = -15.8(73) . 10(-3) Hz, and H(KJ) = 34.2(73) . 10(-3) Hz. An r(o)- and an r(e)-structure are presented: r(o) = 1.4198(7) angstrom (calculated from B), r(o) = 1.4210(7) angstrom (calculated from C), and r(e) = 1.4175 angstrom.