SEARCH Articles Figures Tables Collision cross-sections Penning ionization Collision effects Penning ionization collisions Dissociative Penning ionization Ionization, associative Penning PEN Pen, pens Penning Penning and Associative Ionization of Atoms Penning ionization collisional Penning ionization collisions Penning ionization electron spectra Penning ionization electron spectroscopy Penning ionization electron spectroscopy PIES) Penning ionization impact Penning ionization processes Penning systems ionization cross sections Pressure cold-cathode Penning ionization SPI (Surface Penning Ionization) Surface penning ionization