THE ROTATIONAL SPECTRUM OF THE BENZONITRILE-ARGON VAN-DER-WAALS COMPLEX

The microwave spectra of N-14- and N-15-benzonitrile-argon have been recorded using a pulsed molecular beam Fourier transform microwave spectrometer. In the case of N-14-benzonitrile-argon, the rotational constants were determined to be A = 1347.7899(12) MHz, B = 1006.02030(94) MHz, C = 719.81749(24) MHz. The quartic centrifugal distortion constants (van Eijck) are D(J)' = 3.9982(14) kHz, D(JK)' = -15.3062(79) kHz. D(K) = 21.8510(92) kHz, d(J)' = 1.65065(83) kHz, R6' = 0.03043(38) kHz, and the N-14-nuclear quadrupole coupling constants are chi(aa) = -0.4479(17) MHz, chi(bb) - chi(cc) = -4.1255(17) MHz. For N-15-benzonitrile-argon the rotational constants were found to be A = 1335.09150(30) MHz, B = 989.86421(15) MHz, and C = 707.91548(07) MHz. The centrifugal distortion constants are of the same magnitude as for the N-14-isotopomer. The argon atom is placed 3.545 angstrom above the center of the ring plane. In addition, the spectra of benzonitrile and six isotopic species have been reinvestigated; the derived constants and the resulting structure are of higher accuracy than in earlier work.