Substituent Effects on The Mechanisms and Dynamics of H$_{\mathrm{3}}^{\mathrm{+}}$ Formation from Organic Molecules In Strong Fields

Recent studies from our groups combining femtosecond time-resolved dynamics, photoion-photoion coincidence measurements, and theory have provided evidence for the existence of two reaction pathways for the formation of H$_{\mathrm{3}}^{\mathrm{+}}$ from methanol under strong-field ionization. Both reaction pathways are initiated by the ultrafast double ionization of the parent molecule and proceed through prompt formation of a roaming neutral H$_{\mathrm{2}}$ molecule. The roaming H$_{\mathrm{2}}$ fragment abstracts a third proton from the methyl carbon or from the hydroxyl oxygen leading to the formation of H$_{\mathrm{3}}^{\mathrm{+}}$. We have extended the study to a series of alcohols presenting an increased number of hydrogen atoms and thus H$_{\mathrm{3}}^{\mathrm{+}}$ formation pathways: methanol (CH$_{\mathrm{3}}$OH), ethanol (CH$_{\mathrm{3}}$CH$_{\mathrm{2}}$OH), 1-propanol (CH$_{\mathrm{3}}$CH$_{\mathrm{2}}$CH$_{\mathrm{2}}$OH), 2-propanol (CH$_{\mathrm{3}}$CH(OH)CH$_{\mathrm{3}})$, and tert-butanol ((CH$_{\mathrm{3}})_{\mathrm{3}}$COH). Similarly, we have studied the substitution of oxygen with sulfur, comparing ethanol and ethanethiol. We will discuss the new pathways found and their relative yields.