Dynamics of the state of on helium nanodroplets 1 3 P g K 2

Fluorescence following optical excitation of the state of prepared on helium 1 3&u` 2 nanodroplets to the predissociative state yields molecular emission from both the 1 3%g and states as well as atomic emission from the expected (B)1 1%u (A)1 1&u` 2 dissociation channel. A D12 cm~1 red shift is observed in the 4 2P3@2, 1@2 4 2S1@2 molecular emission excitation spectrum compared to the atomic emission excitation spectrum. Time-correlated photon counting measurements demonstrate the rise time for both atomic and molecular products to be \80 ps, independent of vibrational level excited. This lifetime is interpreted as the total depopulation time for the optically excited state, which is dominated by intersystem crossing at low vibrational energy and by 1 3%g predissociation at the highest vibrational level. It is deduced that the timescale for intersystem crossing must be of the order of 10 ps. Symmetry restrictions for the isolated imply that the intersystem crossing from the state to the and 2 1 3%g (B)1 1%u (A)1 1&u` states must be induced by interaction with the helium nanodroplet.