ROTATIONAL SPECTRUM AND DIPOLE-MOMENT OF THE BENZENE-ARGON VANDERWAALS COMPLEX

Pure rotational transitions of the benzene-h6-argon and benzene-d6-argon complexes have been measured between 9 and 18 GHz with a pulsed nozzle-beam, Fabry-Perot cavity, Fourier-transform microwave spectrometer. The assigned transitions were typical for a symmetric top with fully resolved K splitting. For the benzene-h6-argon complex, the rotational constant B = 1181.25953 (14) MHz and two centrifugal distortion constants DJ=3.2577 (17) kHz and DJK=17.8011 (76) kHz have been determined from the measured transition frequencies. The corresponding constants for the benzene-d6-argon complex are B = 1112.4412 (6) MHz, DJ=2.673 (6) kHz and DJK=14.53 (4) kHz. The permanent electric dipole moment of the weakly polar complex has been estimated from the Stark effect of the benzene-h6-argon complex. The experimental value of 0.12 (4) D is compared with results from preliminary ab initio calculations. © 1990.