Search results for "Photoionization mode"
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Trace detection of plutonium by three-step photoionization with a laser system pumped by a copper vapor laser
1985
Laser photoionization has been used to detect trace amounts of plutonium. A high sensitivity and selectivity has been achieved by applying three-step excitation and ionization of the plutonium atoms with high pulse-repetition rates and additional mass determination by time-of-flight measurements. A laser system was developed which consists of a copper vapor laser pumping three dye lasers simultaneously. Samples containing between 1010 and 1012 atoms of239Pu on Re filaments were measured yielding strong resonance signals with maximum ion count rates of several kHz at a vanishingly low background. A detection efficiency of 10−7 was determined allowing the detection of about 108 plutonium atom…
Photoionization of metal clusters.
1996
The photoionization cross section of metal clusters is studied using simple theoretical models. In the case of small clusters, the plasmon is well below the photoionization threshold and the photoionization is dominated by simple independent-particle processes: One electron absorbs all the energy of the photon and immediately leaves the cluster. For large sodium clusters the photoionization efficiency curve is a result of a two-step process: First, the photon excites a plasmon and then the plasmon decays, either by emitting a photoelectron or by heating the cluster. A simple expression for the photoionization cross section near the threshold is derived. \textcopyright{} 1996 The American Ph…