Vibronic structure of the2Πuground electronic state of dicyanoacetylene cation revisited by PFI-ZEKE photoelectron spectroscopy andab initiocalculations

Pulsed-ramped-field-ionization zero-kinetic-energy photoelectron spectroscopy: a methodological advance

A new experimental method has been developed to record photoelectron spectra based on the well-established pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy technique and inspired by the data treatment employed in slow photoelectron spectroscopy. This method has been successfully applied to two well-known systems: the X⁺²Π_g,1/2(v⁺ = 0) ← X¹Σ+g(v = 0) and the X⁺¹Σ⁺(v⁺ = 2) ← X²Π_1/2(v = 0) ionizing transitions of CO₂ and NO, respectively. The first results highlight several advantages of our technique such as an improved signal-to-noise ratio without degrading the spectral resolution and a direct field-free energy determination. The data obtained for NO indicate that this method might be useful for studying field-induced autoionization processes.