Photodetachment Spectroscopy of Highly Excited C−2 and Their Temporal Evolution in the Ion Storage Ring RICE

We performed laser-induced electron detachment spectroscopy of C−2 ions, produced by a cesium-sputter ion source and stored in the electrostatic ion storage ring RICE, to study highly excited states and their temporal evolution. From the observed peaks originating in the doublet–doublet transition X 2Σ+g–B 2Σ+u, we determined the spectroscopic constants for B 2Σ+u v′ = 5–8 by applying the Δv = −1 transition. Moreover, we found that the overall spectra showed a striking difference from previously reported spectroscopic measurements. The majority of the observed peaks could not be ascribed to doublet–doublet transitions. We studied the lifetimes of these unassigned peaks by varying the ion storage time prior to pulsed laser irradiation and discovered shorter- and longer-lived components of 1.5–3 ms and more than 10 ms, respectively. The former lifetime is in good agreement with the autodetachment component observed without laser irradiation, suggesting a possible detachment channel from a metastable quartet state.