Theoretical simulations on photoexcitation dynamics of the silver atom embedded in helium clusters

Quantum molecular dynamics simulations have been performed to study the photoexcitation Ag(5p P-2(J))<--Ag(5s S-2(1/2)) in size-selected helium clusters considering electronically nonadiabatic transitions. We employed the hybrid method in which the electronic degree of freedom of Ag(P-2) was treated quantum mechanically while the motions of helium atoms were described by the semiclassical path integral centroid molecular dynamics method in order to take the quantum fluctuation effect into account. It has been found that the dynamics after photoexcitation is dominantly nonadiabatic in all cluster sizes studied, and that nonadiabatic transitions are enhanced by quantum fluctuation of helium motions. Most of the photoexcited AgHen clusters decompose into an isolated Ag atom and free helium atoms within several picoseconds. However, Ag*He-n (n=1-5) exciplex formation was also found to occur for all helium cluster sizes studied, although this process is found to be minor. (C) 2003 American Institute of Physics.