Electromagnetic Pulse Produced by Obliquely Incident X Rays

In experiments involving the exposure of targets to X-ray pulses, it commonly happens that illuminated surfaces are slanted to the incident beam, so that the arriving X rays strike the surface at an angle ¿ ¿ ¿ with respect to the surface normal. When this situation occurs, we show that there is generated an electromagnetic pulse emanating from the surface predominantly in the direction corresponding to specular reflection of the incident X rays. We present the theory of the generation of this EMP. With approximations that are valid in many experimental situations, we find that the radiated field amplitude is proportional to tane and to the normal spatial integral of the electron current density. We discuss the differences of conducting or dielectric targets, and give qualitative formulae for finite-size target corrections to our large target equations.