Resonant photodissociation in substituted benzenes

Cyclic aromatic molecules are abundant in organic chemistry, with a wide variety of applications, including pharmacology, pollution studies and genetic research. Among the simplest of these molecules is benzene (C$_{6}$H$_{6})$, with many relevant molecules being benzene-like with a single atomic substitution. In such a substitution, the substituent determines a characteristic perturbation of the electronic structure of the molecule. We discuss the substitution of halogens into the ring (C$_{6}$H$_{5}$X), and its effects on the dynamics of ionization and dissociation of the molecule without the focal volume effect [1]. In particular, using 800-nm, 50-fs laser pulses, we present results in the dissociation of fluorobenzene, chlorobenzene, bromobenzene and iodobenzene into the phenyl ring (C$_{6}$H$_{5})$ and the atomic halogen, and the subsequent ionization of these fragments. The impact of the ``heavy atom effect'' on a $^{1}(\pi $,$\pi $*) $\to \quad ^{3}(n$,$\sigma $*) singlet-triplet intersystem crossing will be emphasized. Currently under investigation is whether such a dissociation can be treated as an effective source of the neutral substituent.\\[4pt] [1] J. Strohaber and C. Uiterwaal, Phys. Rev. Lett. \textbf{100} 023002 (2008).