Complex sentence: By altering the reflection angle, or the photon energy the beam is scanned through the Bragg condition and the phase of the interference field changes by\\ pi Consequently, the nodal planes of the XSW field shift by half a lattice constant.
Split into simpler sentences: By altering the reflection angle or the photon energy the beam is scanned through the Bragg condition and the phase of the interference field changes by\\ pi. As a consequence the nodal planes of the XSW field shift by half a lattice constant.