Interpretation of photoelectron spectra in clusters including thermal and final-state effects: The case

We introduce an approach to investigate thermal effects on the photoelectron spectra of small clusters. By combining first-principles molecular dynamics and a simplified scheme to account for final-state relaxation effects, we obtain averaged excitation spectra at finite temperature. We apply our approach to the case of (Formula presented), in which two isomers are found very close in energy at T=0 K. At T=400 K, the isomer of (Formula presented) symmetry transforms into one of (Formula presented) symmetry. This behavior is in accord with the observed photoelectron spectra in which the predominant features can be associated with the (Formula presented) isomer. The averaged spectrum at T=400 K for this isomer suggests that the splitting observed in the peak at lowest excitation energies is a thermal effect.