ABINITIO SPECTROSCOPIC CONSTANTS AND THE EQUILIBRIUM GEOMETRY OF HCCF

An accurate equilibrium geometry has been obtained for HCCF by combina tion of experimental and ab initio data at the CCSD(T) level: r(e)(CH) = 1.0591 angstrom, R1e(CC) = 1.1961 angstrom and R2e(CF) = 1.2765 ang strom. Calculated and experimental spectroscopic constants for various isotopomers of monofluoroacetylene compare well with each other and m any predictions are made. The performance of CCSD(T) for the equilibri um geometries of ten different molecules is examined and excellent agr eement with the best available equilibrium structures is found.