HOT TUNGSTEN CLUSTERS - COMPETITION BETWEEN ATOM EJECTION AND THERMIONIC EMISSION

This is a first report concerning the thermionic emission of electrons from hot metal clusters. Tungsten clusters were exposed to a 10 ns laser pulse, and the delayed emission of electrons from the clusters was recorded as a function of time after the excitation. A large yield of W(n)+ cluster ions, which were born as late as microseconds after the laser pulse, has been detected for n > 4. Tungsten cluster ions created via thermionic emission show no measurable metastable decay during the flight time in the mass spectrometer. This indicates that they are colder than expected, if evaporative cooling after prompt ionization would prevail.