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We have studied the effects of an inert cooling gas on laser vaporization of solid sodium chloride.The unicluster decay cascades that follow the vaporizing laser pulse are rapidly quenched in helium or argon gas, generating cluster ions whose relative populations reflect their high-temperature stabilities against decay. Cluster production and thermalization are shown to occur in less than 15 ns.Abundance measurements of [Na(Nacl)"]+ ions (n = 1-157) confirm that surface steps are the most stable additions to a cuboid base lattice.

The elimination of H2 in the photodissociation of mono- and di-chloroethylenes was studied with a pump-and-probe technique. A 193 nm excimer laser was used to photodissociate the parent molecules, and a tunable dye laser was used to probe the H2 fragment by 2+1 resonance-enhanced multiphoton ionization (REMPI). The nascent rotational state distributions of H2(X 1Σ+g,v″=0–4) were extracted from the REMPI spectra, and were found to have Boltzmann-type distributions. The maximum and average translational energies for some of the rovibrational levels of H2 were measured using magic angle Doppler spectroscopy. The translational energy of the fragments plus the internal energy of H2 was found to exceed the available energy for a three-center elimination mechanism. It is concluded that a migration mechanism plays a significant role in H2 elimination.

Ultraviolet photoelectron spectroscopy (UPS) and photofragmentation data for (KI); , K (KI) ; , and K, (KI); (n up to 13) are presented. The excess electrons in these clusters are all loosely bound with vertical detachment energies below 1.6 eV, and the photofragmentation data correlated well with the UPS results. Our results for the stoichiometric clusters are in good agreement with theoretical predictions, and the ground state geometry of these clusters are discussed. For the excess potassium cluster series, we suggest the possible existence of electron spin pairs in some of these cluster anions.

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