ROTATIONAL SPECTRA OF THE ISOTOPIC-SPECIES OF CHLOROFORM - EXPERIMENTAL AND AB-INITIO STRUCTURES

The millimeter-wave spectra of three different samples of chloroform ( CHCl3, CDCl3, and (CHCl3)-C-13) have been measured between 145 and 470 GHz which corresponds to J values between 22 and 70. We report accura te rotational and centrifugal distortion constants for the ground vibr ational states of 11 isotopic species. The experimental r(o), r(s), r( le), r(m)(o), and r(z) structures have been determined using the deter mined rotational constants. The structure has also been calculated ab initio at the SCF, MP2, RQCISD, and B3LYP levels using triple zeta pol arized basis sets. The experimental results are found in excellent agr eement with the ab initio predictions. An approximate equilibrium stru cture has been obtained by combining the experimental results and the ab initio calculations: r(e)(C-H) = 1.080 (2) Angstrom, r(e)(C-Cl) = 1 .760 (2) Angstrom, and angle(e)(HCCl) = 108.23 (2)degrees. (C) 1998 Ac ademic Press.