Fragmentation Pathways in a Series of CH₃COX Molecules in the Strong Field Regime

Abstract

In intense laser fields, fragment ions can be produced from CH3COX (X = CH3, CF3, and C6H5) either by absorption and dissociation followed by ionization (ADI) or absorption and ionization followed by dissociation (AID). Electronic structure calculations were carried out using Hartree−Fock, density functional, and correlated levels of theory to understand the possible fragmentation pathways. The calculated ionization potentials are in very good agreement with the available experimental data. For acetone, the acetyl ion is predicted to be the most preferred dissociation product and can be produced by either mechanism. The very low C−CF3 bond energy in the parent ion of trifluoroacetone provides a clear reason for the absence of CF3COCH3+ and CF3CO+ ion peaks from the mass spectrum of CF3COCH3 after intense laser excitation and indicates that fragmentation occurs by AID. For acetophenone, both CH3CO+ and C6H5CO+ are stable fragments, with the latter being produced by an AID mechanism.