15min:

S. WILLITSCH, L. IMBACH AND F. MERKT, Physical Chemistry, ETH Zurich, CH-8093 Zurich.

The \textrmX ² \textrmA₁ (0,0,0) ground vibronic state of CH₂ ⁺ has been studied by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy by recording transitions from the \textrmX ³\textrmB₁ (0,0,0) ground vibronic state of CH₂ which has been produced by photolysis of CH₂CO at 351 nm. The rotational energy level structure and the spin-rotation splittings of levels with K_a \geq 1 could be resolved. The rotational structure in the \textrmX ² \textrmA₁ (0,0,0) state deviates strongly from that of a rigid rotor. The adiabatic ionization potential of ³CH₂ has been determined to be (83772\pm3) cm^-1. Analysis of the photoionization selection rules indicates that the photoelectron is ejected as a superposition of \ell even and \ell odd partial waves.