Chemistry, Light and Dynamics Seminar

The electronically excited states of the tetracene radical anion were probed using photodetachment yield spectroscopy of cryogenically cooled ions and complementary high-level electronic structure methods. The experimental spectrum gives insight into both the position and lifetime of these resonance states, which are embedded in the neutral plus free electron continuum. The resolution of the spectrum is limited by the ∼5 cm–1 line width of the tunable laser and thus provides a stringent benchmark for computations of the energies and autodetachment lifetimes of these resonance states. Using extended multi-configuration quasi-degenerate perturbation theory (XMCQDPT2) and the orbital stabilisation method, the character, energy and lifetimes of these resonance states was modelled. These theoretical results are found to be in near quantitative agreement with the experimental data, highlighting their capability to accurately describe the energies and lifetimes of anion resonances for relatively large molecules.