Dynamic effects in VUV- and XUV-Spectroscopy of Organic Molecular Solids

Dynamic effects, i.e., shake up transitions in photoemission of non-polar, polar and, in particular, dipolar organic compounds are reviewed. Gas phase spectra are contrasted with solid phase spectra. For the non-polar molecules a one-to-one correspondence between the two phases is well documented. For polar and dipolar molecules, however, this one-to-one correspondence is lost, i.e., the dynamics of the hole creation process changes. It is shown that intermolecular screening becomes important. We develop simple physical criteria that allow to rationalize and predict under which conditions such effects are to be expected. In general it is concluded, that the interpretation of solid state spectra on the basis of calculations on the free molecule is not necessarily sound. We show, that even in cases where solid and gas phase spectra appear to be similar this similarity may be accidental and that it may be caused by particularly intermolecular interactions in the solid.