Schreck, S.; Pietzsch, A.; Kunnus, K.; Kennedy, B.; Quevedo, W.; Miedema, P.S.; Wernet, P.; Föhlisch, A.: Dynamics of the OH group and the electronic structure of liquid alcohols. Structural Dynamics 1 (2014), p. 054901/1-14
10.1063/1.4897981
Open Access Version (externer Anbieter)
Abstract:
In resonant inelastic soft x-ray scattering (RIXS) from molecular and liquid sys- tems, the interplay of ground state structural and core-excited state dynamical con- tributions leads to complex spectral shapes that partially allow for ambiguous interpretations. In this work, we dissect these contributions in oxygen K-edge RIXS from liquid alcohols. We use the scattering into the electronic ground state as an accurate measure of nuclear dynamics in the intermediate core-excited state of the RIXS process. We determine the characteristic time in the core-excited state until nuclear dynamics give a measurable contribution to the RIXS spectral profiles to sdyn 1⁄4 1.2 6 0.8 fs. By detuning the excitation energy below the absorption reso- nance we reduce the effective scattering time below sdyn, and hence suppress these dynamical contributions to a minimum. From the corresponding RIXS spectra of liquid methanol, we retrieve the “dynamic-free” density of states and find that it is described solely by the electronic states of the free methanol molecule. From this and from the comparison of normal and deuterated methanol, we conclude that the split peak structure found in the lone-pair emission region at non-resonant excita- tion originates from dynamics in the O–H bond in the core-excited state. We find no evidence that this split peak feature is a signature of distinct ground state struc- tural complexes in liquid methanol. However, we demonstrate how changes in the hydrogen bond coordination within the series of linear alcohols from methanol to hexanol affect the split peak structure in the liquid alcohols.