Adiabatic ionization energies of the overlapped A2A1 and B2E electronic states in CH3Cl+/CH3F+ measured with double imaging electron/ion coincidence

Abstract

Utilizing the vacuum ultraviolet (VUV) synchrotron radiation and a double imaging photoelectron photoion coincidence (i²PEPICO) technique, we have measured the adiabatic ionization energies (AIEs) of the overlapped A²A₁ and B²E electronic states of CH₃Cl⁺ and CH₃F⁺ ions. We show that the two overlapped electronic states can be separated in the electron and ion kinetic energy correlation diagrams based on their state-specific dissociation dynamics, leading to different kinetic energies released in dissociation, along the CH₃⁺ fragmentation channel. Thus the correlation diagrams yielded values of 13.67 ± 0.03 and 14.77 ± 0.03 eV for the AIEs of the A²A₁ and B²E states of CH₃Cl⁺, and 16.08 ± 0.03 and 17.00 ± 0.05 eV for CH₃F⁺, respectively. This method can be generalized to separate ionic states that are otherwise overlapped in normal photoelectron spectra (PES), especially by combining VUV sources and electron/ion coincidence techniques.