Photoelectron and photodetachment spectroscopy of cryogenically cooled 2-anthrolate anion

Polycyclic aromatic hydrocarbon (PAH) molecules and radicals play important roles in astrochemistry and atmospheric chemistry. These species exhibit complicated electronic structures and photophysics, making them challenging to study both experimentally and computationally. Here, we report an investigation of the cryogenically cooled 2-anthrolate anion (2-AT-) using photoelectron imaging and photodetachment spectroscopy. High-resolution photoelectron spectroscopy (PES) yields an electron affinity of 2.440(1) eV for the 2-AT radical while also resolving several vibrational frequencies for its ground electronic state and complex autodetachment features. Photodetachment spectroscopy further identifies both bound and unbound valence-excited states of the 2-AT- anion with rich vibronic features. Single-color resonant two-photon PES via these bound excited states reveals different photophysical processes, including resonant two-photon detachment via S1 and autodetaching resonances above the detachment threshold. The current work uncovers the second PAH anion with bound electronic excited states and provides valuable experimental information about the electronic structure and photophysics of the 2-AT- anion and the 2-AT radical.