Laser produced TMAE plasma in nitrogen, oxygen, and air

Summary form only given. Reducing the power to produce a plasma requires both efficient creation and small electron loss rates. Our 193 nm laser is very efficient in ionizing tetrakis(dimethyl-amino)ethylene (TMAE), since the photon ionization quantum yield is 30%, and the vertical ionization potential of TMAE is 6.1 eV. Thus, one pulse from our laser (300 mJ/pulse) can produce nearly 10/sup 17/ electrons. To reduce the electron loss rate of a TMAE plasma, we use a chemical method. We find that the electron loss rate of a TMAE plasma can be reduced if it is mixed with nitrogen or air. The effect is larger if the laser energy or the mixed gas pressure is higher. This result involves complex processes. We discuss: (1) TMAE/sup +/ which can be changed into another molecule or radical ion, and these ions show significantly different plasma decay processes from those in pure TMAE. (2) Many metastable atoms, molecules or radicals can be created which are involved in many new ionization processes. (3) TMAE can react with oxygen. This consumes TMAE molecules, but it also produces many excited molecules or radicals, which favors the remaining plasma. Experimental observations involving these processes to increase plasma lifetime will be discussed.