Photoelectron spectroscopy of 1-nitropropane and 1-nitrobutane anions.

We present low-energy velocity map photoelectron imaging results for bare and Ar-solvated 1-nitropropane and 1-nitrobutane anions. We report the adiabatic electron affinity of 1-nitropropane as (223 ± 6) meV and that of 1-nitrobutane as (240 ± 6 meV). The vertical detachment energies of these two species are found to be (0.92 ± 0.05) and (0.88 ± 0.05) eV, respectively. The photoelectron spectra are discussed in the framework of Franck-Condon simulations based on density functional theory. We observe unusual resonances in the photoelectron spectra of both ions under study, whose kinetic energy is independent of the photon energy of the detaching radiation. We discuss possible origins of these resonances as rescattering phenomena, consistent with the experimental photoelectron angular distributions.