Photoabsorption spectra of Nan+ clusters:: Thermal line-broadening mechanisms -: art. no. 053401

Photoabsorption cross sections of small sodium cluster cations (Na-n(+), n = 3, 5, 7, and 9) were calculated at various temperatures with the time-dependent local-density approximation in conjunction with ab initio molecular dynamics simulations, yielding spectra that agree with measured ones without ad hoc line broadening or renormalization. Three thermal line-broadening mechanisms are revealed: (I) lifting of level degeneracies caused by symmetry-breaking ionic motions, (II) oscillatory shifts of the entire spectrum caused by breathing vibrations. and (III) cluster structural isomerizations.