On the Problem of Observing the Maximum of a Superposition Wave Field.

The well-known Laue condition determining the intensity maximums of diffracted on an ideal crystal structure plane wave is discussed. It is proved that the Laue conditions, which are restrictions imposed on the values of the scattering wave vector, is more correctly to be considered as a pair of two conditions. The first conditions relate to the wave vector of an incident wave and the second conditions relate to the wave vector of an observation direction. In other words, to observe the maximums, it is not enough that only the difference (the scattering wave vector) of these two vectors satisfies the Laue condition. To observe the maximums, it is necessary that each of these vectors separately, i.e. the wave vector of the incident wave and the wave vector of the observation direction, satisfy the Laue condition. It is shown that such a doubling of the maximums conditions leads to a decrease in the number of observed maximums compared to the condition imposed only on the scattering wave vector. [ABSTRACT FROM AUTHOR]