It is shown that the observed sharp peaks in the photodetachment spectra of Li-4(-) can be understood by including the effect of cluster dynamics, Theoretical electronic structure studies show that Li-4(-) is marked by doublet rhombus and quartet distorted tetrahedral isomers. By including dynamical effects within a classical picture, it is shown that the observed spectrum can be explained in terms of transitions from rhombus ground state to the singlet neutral configurations. A vibrational analysis is used to identify the modes leading to the observed peaks. Our studies underscore the importance of dynamical effects on the photodetachment spectra. (C) 2002 Published by Elsevier Science B.V.