TUNNELING SPLITTINGS IN C2H3+

The occurrence of internal-rotation-like motion of the three protons around the CC core in C2H3+ was discovered by ab initio calculation some time ago, and using an ab initio potential we have previously calculated the splittings of the rotational levels that result from the tunneling between the six identical minima in the potential. Recently the splittings in a CH stretching fundamental band have been measured by Crofton, Tagod, Rehfuss and Oka. In the present paper we attempt to determine an effective tunneling potential in the excited CH stretching state by fitting to the observed splittings. We discuss possible perturbations to the splittings that appear to spoil any attempt at a simple analysis. © 1990.