Survey of Ar-tagged predissociation and vibrationally mediated photodetachment spectroscopies of the vinylidene anion, c₂h ₂^-

We report predissociation spectra of Ar-tagged C₂H ₂^- and C₂D₂^- anions, and explore vibrationally mediated photodetachment from various vibrational levels of the bare C₂H₂^- ion using velocity-map imaging. Intense photodetachment resonances are observed in the C - H stretching region that are strongly correlated with vibrational hot bands in the anion photoelectron spectra, indicating that one-color, resonant two-photon photodetachment (R2PD) is complicated by excitation of vibrationally excited states with autodetaching upper levels embedded in the continuum. Isolation of the R2PD spectrum was achieved using a two-color, IR-IR scheme in which vibrational excitation and photodetachment were carried out in two separate laser interaction regions.