Rotational Spectrum of Dichloromethane-Ne: Internal Dynamics and CI Quadrupolar Hyperfine Effects

The rotational spectra of three isotopologues, (CH2Cl2)-Cl-35 center dot center dot center dot Ne-20, (CH2ClCl)-Cl-35-Cl-37 center dot center dot center dot Ne-20, and (CH2Cl2)-Cl-35 center dot center dot center dot Ne-22, of the complex dichloromethane-neon have been assigned and measured by molecular beam Fourier transform microwave spectroscopy. The corresponding tunnelling splittings-due to the motion of Ne from above to below the ClCCl plane-have been determined as Delta E0+0-= 6.8900(5), 6.6630(4), and 6.3724(7) MHz, respectively. From these data the barrier to planarity has been obtained, B-2 = 68.7 cm(-1). In addition, the structure and the Cl-35 (or Cl-37) quadrupole coupling constants have been determined.