Magnetic-Bottle and velocity-map imaging photoelectron spectroscopy of APS− (A=C14H10 or anthracene): Electron structure, spin-orbit coupling of APS•, and dipole-bound state of APS−

Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS - (A=C 14 H 10 or anthracene) were generated via electrospray ionization, and characterized by magnetic-bottle photoelectron spectroscopy, velocity-map imaging (VMI) photoelectron spectroscopy, and quantum chemical calculations. The electron affinity (EA) and spin-orbit (SO) splitting of the APS · radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA=(2.62±0.05) eV and SO splitting=(43±7) meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy (eKE) of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31++G(d, p) calculations indicate APS · has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron.