Microwave spectral study of 3-fluorobenzonitrile

Abstract

The microwave spectrum of 3-fluorobenzonitrile has been observed and analyzed in the KU (12.5–18.0 GHz) and the K (22.0–26.0 GHz) bands. Both Stark and radio frequency-microwave double resonance spectroscopy have been used in the observation and assignments. Analysis of the spectrum yields three rotational constants (all in MHz), A = 3388.59 ± 0.02, B = 1186.64 ± 0.01, C = 878.72 ± 0.01, and five quartic centrifugal distortion terms (all in MHz), d J = (1.7 ± 0.6) × 10 −4 , d JK = (−4.9 ± 1.1) × 10 −3 , d K = (−10.5 ± 2.4) × 10 −3 , d WJ = (−1.0 ± 1.0) × 10 −7 , d WK = (4.8 ± 1.1) × 10 −6 , for the molecule. An r 0 structure has been proposed which does not suggest serious distortion of the benzene ring. The inertia defect of the molecule is 0.1 amu A ̊ 2 .