Strong-field laser induced H$_{\mathrm{2}}$ roaming reactions and the formation of H$_{\mathrm{3}}^{\mathrm{+}}$ from organic molecules*

Roaming chemical reactions are a novel chapter in our understanding of certain exotic reactions relevant to molecular physics, photochemistry, and combustion chemistry. A recent finding indicating the involvement of H$_{\mathrm{2}}$ roaming for the formation of H$_{\mathrm{3}}^{\mathrm{+}}$ under strong-field photodissociation [Ekanayake, N. \textit{et al}. \textit{Sci. Rep.} \textbf{7}, 4703 (2017)] inspired a series of experiments aimed at elucidating aspects of its mechanisms of formation. In the present study, site-specific details and femtosecond time-resolved dynamics of H$_{\mathrm{3}}^{\mathrm{+}}$ formation were obtained through a combination of strong-field laser excitation studies and \textit{ab initio} calculations on a series of alcohols. Our findings confirm the mechanisms of this intriguing chemical process involving the cleavage and formation of three chemical bonds and reveal that H$_{\mathrm{3}}^{\mathrm{+}}$ yields decrease as the alkane chain length increases. This new understanding will aid in the prediction of expected yields and formation times of H$_{\mathrm{3}}^{\mathrm{+}}$ from different organic molecules.