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The $1+1\prime$ two-colour pulsed-field induced zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of $C2H2$ via a single rovibronic level of the $A¯1Au$ state of acetylene were previously reported by Pratt $etalg$. In this work, with similar approach the effects of the pulsed-field strengths and the rovibronic symmetries of the intermediate states of $C2H2$ and $C2D2$ on the PFI-ZEKE photoelectron spectra near the ionization threshold were investigated and will be reported. Although the number of observed transitions was limited, the spectroscopic constants of the zero-point energy levels of $C2H2+$ obtained from the best fit are in good agreement with those reported by Jagod $etalh$: $B=1.098\pm 0.002cm-1,A80$(spin-orbit constant)=$-30.84\pm 0.05cm-1$, and $IP0=91967.06\pm 0.03cm-1$. Those of $C2D2+$ are $B=0.82\pm 0.03cm-1,A80=-31.1\pm 0.3cm-1$, and $IP0=92004.7\pm 0.3cm-1.IP0$ is defined as the energy difference between the zero point levels of the ground states of the neutral and its cation. We propose to use $IP0$ to denote the ionization potential of the molecule, of which the cation belongs to the Hund’s case(b) coupling.