Can super-excited molecules survive fragmentation?

An Auger event triggered by electron-capture (EC) decay of Co-57 incorporat ed in a chelate molecule results in the loss of an average of 5 electrons. During subsequent charge neutralization, the molecule acquires >50 eV of ex citation energy. Only molecules having a large pi -electron system were fou nd to escape fragmentation. The fate of the molecule was followed by the 14 .4 keV Mossbauer emission which occurs 10(-7) second after the EC event. Fo r a conjugated molecule to survive fragmentation, it should be able to disp erse its energy in a time interval shorter than the period of atomic vibrat ions. We had proposed earlier that p-electrons undergo collective excitatio n and that the plasmon decays in <10(-14) second accompanied by ejection of an electron leaving the molecule unscathed. Intermolecular energy transfer is not important and even an isolated molecule of Co-57(II) phthalocyanine encapsulated in a zeolite supercage escapes fragmentation following an Aug er event. Our model for rapid disposal of large excitation energy receives additional support from recent reports of single or mulitphoton plasmon exc itation (<similar to>20 eV) in an isolated C-60 and C-70 fullerene molecule followed by ejection of a single energetic electron leaving the molecule i ntact.