Observing the non-adiabatic photodissociation of neutral excited CH$_{\mathrm{3}}$OH with few-femtosecond sensitivity

The ultrafast dissociation dynamics of neutral excited methanol (CH$_{\mathrm{3}}$OH) have been explored using time-resolved photoelectron imaging and excited state potential energy surface calculations. Nuclear motions on the initially populated 2 $^{\mathrm{1}}$A" (S2) state, through a region of strong non-adiabatic coupling, and on a dissociative state are resolved within the first 15 femtoseconds following excitation. A CH$_{\mathrm{3}}$ hydrogen-loss channel is also observed and found to depend more strongly on OH rather than CH$_{\mathrm{3}}$ deuteration. The measurements and calculations indicate that the previously ignored 1 $^{\mathrm{1}}$A' (S3) state, rather than the 1$^{\mathrm{\thinspace 1}}$A" (S1) state, plays an important role in these dynamics.