THE STRUCTURES OF THE CYCLIC C3H RADICAL - AN INTERSTELLAR MOLECULE

The equilibrium structure of the cyclic C3H radical was obtained by ab initio computation. The total energy at a C-s optimum structure is lo wer than that of a C-2v optimum structure by only 10(-4) hartree and t he adiabatic potential surface for the antisymmetric motion is so flat that no locally bound vibrational level exists around the C-s minimum ; the force constant for the CC antisymmetric stretching mode is about one sixth of that for the CC symmetric stretching mode.