MeV Electron Diffractive Imaging of Competing Ring-Opening and Photodissociation

Here we present time-resolved MeV electron scattering results of 2-Iodothiophene and 3-Iodothiophene and interrogate the branching ratios between ring-opening and C-I bond cleavage following photoexcitation at 245 nm. After UV excitation, halothiophenes can either undergo ring-opening or prompt bond cleavage. The branching ratio between these processes is dependent on the wavelength, substitution position, and atom identity, as a result of the different substitution effects for the electron-withdrawing halogen. The use of ultrafast electron bunches to study time-resolved dynamics has become a powerful tool for probing transient geometries. Of particular interest is the ability to use this to quantitatively probe reactions that proceed along competing reaction coordinates. This time-resolved geometric comparison further elucidates the direct and indirect C-I cleavage processes identified in a recent coulomb explosion study of these same two isomers [1].

[1] W. Razmus et al. Exploring the Ultrafast and Isomer-Dependent Photodissociation of Iodothiophenes via Site-Selective Ionization (Submitted December 2023).