A COMPARATIVE-ANALYSIS OF COLLECTIVE EXCITATIONS IN MOLECULAR FILMS, ATOMIC CLUSTERS AND NUCLEI

The experimental study of the energy-loss spectra of charged particles penetrating through various kinds of molecular films revealed a unive rsal picture: a broad high peak in the energy region (h) over bar omeg a(r) similar or equal to 21-22 eV with the ratio Delta omega/omega(tau ) similar or equal to 0.15. The laser induced excitations in small met al clusters (Na-n) manifested a broad peak in the energy region (h) ov er bar omega similar or equal to 2.5 eV for Na-n clusters and with a r atio of width to resonance energy Delta omega/omega(tau) similar or eq ual to 0.16. The absorption of gamma rays by nuclei is also characteri zed by a broad resonance peak in the 25-12 MeV region with a ratio Del ta omega/omega(tau) similar or equal to 0.3-0.4 These experimental fin dings are attributed to the collective nature of the states excited in the energy-absorption process. We discuss the striking similarity in the nature of the collective states excited in atomic, molecular and n uclear systems, and also the differences in the possible channels of t heir decay.