Jahn–Teller distortion in CD2H2+ from a rotationally resolved photoelectron spectrum

High-resolution pulsed-field-ionization (PFI) zero-kinetic-energy (ZEKE) photoelectron spectroscopy has been used to study the Jahn–Teller distortion in the ground state of CD2H2+. Analysis of the rotationally resolved spectrum clearly supports a C2v symmetrical equilibrium structure for the methane cation as previously predicted by ab initio calculations. On the basis of these data, an experimental r0 structure for CD2H2+ as well as the first adiabatic ionization potential of CD2H2 (IP=(101 852.3±1.4) cm−1) have been determined.