Design Near-threshold Photoelectron Imaging Spectrometer Based on UV Laser Induced Photoelectron Emission Anion Source

We have developed a compact photoelectron imaging facility, including an anion source with dissociative photoelectron attachment to molecules, a linear time‐of‐flight mass spectrometry (TOFMS), and an orthogonal high‐resolution threshold photoelectron velocity map imaging spectrometer (VMI). Intense and cold cluster anions were prepared in photoelectron‐attachment processes upon pulsed UV laser ablation of metal target. Combining this anion source with TOFMS‐VMI, the achieved mass resolution is about 200, and the electron kinetic energy resolution is better than 3%, i.e., 30 meV for 1 eV electrons. More importantly, low‐energy photoelectron imaging spectra for CH3S− and S2− at 611.46 nm are obtained. In both cases, the refined electron affinities are determined to be 1.8626±0.0020 eV for CH3S and 1.6744±0.0035 eV for S2, respectively. Preliminary results suggest that the apparatus is a powerful tool for estimating precise electron affinities values from threshold photoelectron imaging spectroscopy.