二重回折

double diffraction

[目次：理論(電子の散乱／回折／結像)]

格子定数がわずかに異なる二つの結晶が上下に重なっている場合、上側の結晶で回折された波が下の結晶でさらに回折される現象。二重回折効果のために、上下の結晶からの回折斑点以外に(偽の)斑点が現れるので、試料の物質同定には気をつけなければならない。上下の結晶が相対的に僅かに回転している場合や双晶になっている場合も、二重回折によって多くの偽の斑点が現れる。

When two crystals overlap, which have slightly different lattice parameters to each other, a wave diffracted by the upper crystal is further diffracted by the lower crystal. This phenomenon is called "double diffraction." In addition to the diffraction spots from the upper and lower crystals, spurious spots due to double diffraction appear. Thus, care must be taken to identify a specimen substance. When the upper crystal rotates slightly with respect to the lower crystal (or vice versa) or when the two crystals form twins, many spurious spots also appear due to double diffraction.