Comparison of multiphoton ionization (MPI) fragmentation patterns for the azulene and naphthalene isomers. A test of the maximal-entropy theory

Abstract

We present an experimental test of the Silberstein-Levine maximal-entropy theory of multiphoton ionization-fragmentation using the isomeric pair azulene and naphthalene. According to this theory the fragmentation depends upon the mean energy absorbed and the chemical formula of the parent molecule. The MPI fragmentation pattern of a compound is strongly dependent upon laser power density. However, it is shown experimentally that it is possible to obtain similar fragmentation patterns for the two CioHg compounds, azulene and naphthalene, at different wavelengths by adjusting the laser power so that each system is excited to what we suppose to be the same value of (E).

Mass spectrometry of aromatic molecules with resonance-enhanced multiphoton ionization

“…We have reported an experimental test previously for the case of azulene and naphthalene (29). Although it was shown that the fragmentation patterns of azulene and naphthalene can be made to be the same under the proper conditions, they are actually very different at the same measured input laser power.…”