the electrode surfaces, and by hybrid mode operation. Similarly, improvements via use of oxygen-containing electrodes have been demonstrated in Russia along with design studies of systems employing the advanced thermionic converter performance. Recent studies have shown that excited Cs-atoms in thermionic converters form clusters of Cs-Rydberg matter which yield a decrease of collector emitting work function from 1.5 eV to 1.0 – 0.7 eV. Due to long-lived nature of Rydberg matter this low work function remains low for a long time which essentially increases the low-temperature converter’s efficiency. See also Atomic battery Betavoltaics Optoelectric nuclear battery Magnetohydrodynamic generator Radioisotope piezoelectric generator Radioisotope thermoelectric generator Thermocouple Thermoelectric generator Belousov–Zhabotinsky reaction References Battery types Electric power Electrical generators Nuclear power in space Nuclear technology