Electron-rotation coupling in UV photodissociation of aligned diatomics

We investigate the effect of electron-rotation coupling ($\mathbf{R}\ensuremath{-}\mathrm{\ensuremath{\Omega}}$ coupling) on fs UV photodissociation dynamics of aligned diatomic molecules. We consider the showcase of ground-state $\mathrm{Mg}{\mathrm{H}}^{+}$ (${}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$) pumped by an fs IR pulse, which initiates rotational dynamics leading to field-free molecular alignment. A time-delayed fs UV pulse probes the degree of alignment of the rotational wave packet in the framework of photodissociation spectroscopy. The molecular alignment correlates directly with the angular distribution of the photofragments in the dissociative ${}^{1}\mathrm{\ensuremath{\Pi}}$ state, as it is shown in our simulations comparing the cases when the $\mathbf{R}\ensuremath{-}\mathrm{\ensuremath{\Omega}}$ coupling is included and ignored. We show how the angular distribution of the photofragment is strongly affected by the $\mathbf{R}\ensuremath{-}\mathrm{\ensuremath{\Omega}}$ coupling at various delay times with specific molecular alignment. It was shown that increases of the fs UV pulse intensity and the degree of alignment enhance the effect of $\mathbf{R}\ensuremath{-}\mathrm{\ensuremath{\Omega}}$ coupling on the angular distribution of the photofragments. On the contrary, an increase of the initial temperature tends to reduce the effect of $\mathbf{R}\ensuremath{-}\mathrm{\ensuremath{\Omega}}$ coupling, which is explained by the fact that such an effect turns smaller as the increasing of magnetic state $|{\mathrm{M}}_{0}|$ for each initial rotational state ${\mathrm{J}}_{0}$; furthermore, higher excited rotational state ${\mathrm{J}}_{0}$ contains more magnetic states ${\mathrm{M}}_{0}$, and the results have been averaged over all degenerated ${\mathrm{M}}_{0}$ states.

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