Distinguishing geometrical conformers using Coulomb Explosion Imaging*

We report the results of an experimental study on distinguishing molecular conformers using coincident ion momentum imaging. This work extends our earlier study on identifying \textit{cis }and \textit{trans} isomers of 1,2-dibromoethene (C$_{\mathrm{2}}$H$_{2}$Br$_{2})$ using Coulomb explosion imaging (CEI). The experiment was performed on 1,2-dibromoethane (C$_{\mathrm{2}}$H$_{4}$Br$_{2})$ using 140 eV photons at the Advanced Light Source (ALS). Our results suggest that CEI can distinguish between anti and gauche conformal isomers, which are only distinguished by rotation around single bond. Moreover, we can observe a change in the ratio between \textit{anti }and\textit{ gauche }conformers as a function of temperature. The observed breakup patterns show similarities to the related cis-trans isomers but indicate a higher fraction of sequential breakup.