A Plasma Injection Ion Source for Photoelectron Imaging of Metal-Containing Anions

A plasma injection ion source has been developed for the photoelectron velocity imaging studies of metal-containing anions. The source employs a pulse discharge nozzle for generating a plasma beam that perpendicularly crosses the master supersonic jet beam from a home-made pulsed piezo valve. The discharge nozzle is designed for high voltage gas discharge with efficient metal sputtering of the cathode, and thus plays a role in metal atom and ion source. Supersonically jet-cooled anions can be produced in the master gas jet via reactions of the plasma products. The source is integrated into a photoelectron velocity imaging spectrometer. Test mass spectrometry experiments show that the ion source can efficiently produce transition metal containing anions, such as FeO_m^–, CuO_m^–, CuC_n^–, CuC_nO_m^–. The photoelectron imaging results by photodetachment of O^– show that the photoelectron energy resolution of the whole instrument is ΔE/E≈2.3%, and the results of FeO⁻ indicate that internal temperatures of anions from the source could be efficiently cooled down.