Valence photoelectron diffraction and direct-transition effects

We have measured the temperature dependence of valence and core x-ray photoelectron intensities for W(110). At 295 K, valence spectra are very sensitive to emission direction due to direct-transition effects, and Ienergy-integratedR valence and core photoelectron diffraction curves are similar in form, but with significant differences in fine structure. At 803 K, valence spectra are by contrast very insensitive to direction due to increased zone averaging, but valence and core diffraction curves retain differences due to the atomic-orbital character of the initial and final states involved.