2-COLOR ZERO KINETIC ENERGY-PULSED FIELD-IONIZATION SPECTROSCOPY OF THE ACETONE N-RADICAL CATION - THE A(2) TORSIONAL VIBRATION

Two-color, (2 + 1') resonance multiphoton ionization via the (1)A(2) 3 p(x) Rydberg state is used in combination with high-resolution thresho ld photoelectron spectroscopy (ZEKE-PFI) to measure the a(2)(nu(12)) a nti-gearing torsional frequencies in the n-radical cation of acetone ( -h(6) and -d(6)). The photoelectron band intensities and measured tors ional frequencies show that the anti-gearing torsional potentials for the cation and the 3p(x) Rydberg state are very similar. The cation to rsional frequencies also indicate that, despite the localization of po sitive charge in the carbonyl group, the barrier for synchronous methy l rotation in the cation is higher than that for the neutral acetone g round state. (C) 1998 Elsevier Science B.V. All rights reserved.