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Laser vaporization of a rotating metal target within a pulsed supersonic nozzle has been used to produce ultracold beams of copper clusters. Photoionization with an argon fluoride excimer laser followed by time-of-flight mass spectrometric analysis showed the cold beam to contain clusters in the range from 1 through 13 copper atoms. The ionization potential (IP) of the small clusters was seen to alternate above and below the 6.4-eV laser photon energy depending upon whether the cluster contained an even (high IP) or odd (low IP) number of copper atoms. The absorption spectrum of Cu2 was recorded in the 4480-4660-Å region by using two-color resonant two-photon ionization. The Cu2 cluster beam was found to have translational, rotational, and vibrational temperatures of <5, <10, and 50-100 K, respectively. In addition to the known B 1Σu+ ← X 1Σg+ band system, a new system was found in the same spectral range. Parameters for the new system were Te = 21867 ± 4 cm-1, ωe′ = 226 ± 3 cm-1, ωeXe′ = 3 ± 2 cm-1. The lifetime of the B state was found to be 35 ± 10 ns for the vibrational levels υ′ = 0 and 1, and it is argued this short lifetime is likely due to predissociation. The lifetime of the new C state was found to be 1.0 ± 0.2 μs. © 1982 American Chemical Society.
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