PHOTOINDUCED CHEMICAL-DYNAMICS OF HIGH-SPIN ALKALI TRIMERS

Nanometer-sized helium droplets, each containing about 10(4) helium at oms, were used as an inert substrate on which to form previously unobs erved, spin-3/2 (quartet state) alkali trimers. Dispersed fluorescence measurements reveal that, upon electronic excitation, the quartet tri mers undergo intersystem crossing to the doublet manifold, followed by dissociation of the doublet trimer into an atom and a covalently boun d singlet dimer. As shown by this work, aggregates of spin-polarized a lkali metals represent ideal species for the optical study of fundamen tal chemical dynamics processes including nonadiabatic spin conversion , change of bonding nature, and unimolecular dissociation.