AbstractThe dynamics in photoexcited Na(NH3)n clusters up to n = 20 using femtosecond laser pump and probe techniques are investigated. It is found that electronic excitation energy of the metal atom chromophore is transferred to internal vibrations of the surrounding ammonia solvent molecules. The transfer time strongly depends on the number of ammonia molecules bound to the sodium atom, decreasing from 2000 ps when only one ammonia molecules is attached to the metal atom down to a limiting value of about 100 fs for Na(NH3)10. These results can be understood in terms of an internal energy transfer where the rates are governed by the density of states and the Franck‐Condon overlap of the acceptor modes.