励起誤差

excitation error

[目次：理論(電子の散乱／回折／結像)]

ある反射gのブラッグ条件からのはずれを表すパラメータs_gのことで、逆格子点gから、試料の上表面と垂直な方向に測った、エワルド球までの距離。ブラッグ条件が正確に満たされている場合、s_g = 0。逆格子点がエワルド球の外にあるとき、s_g＞0, エワルド球の内側にあるときs_g＜0。s_g は[長さ]^-1の次元をもち観測可能な量である。s_g に消衰距離ξ_gを乗じたw = s_g・ξ_gという無次元の量（tilt parameter）が、回折強度の角度変化を理論的に扱うときに便利な量として、s_gの代わりに使われる。ただしwは観測される量ではないことに注意する。

"Excitation error," expressed as s_g, means a deviation from a Bragg condition for a certain reflection g. The excitation error is defined as the distance from the reciprocal lattice point g to a point on the Ewald sphere measured along the vertical direction to the upper surface of the specimen. When the Bragg condition is accurately satisfied, s_g = 0. When the reciprocal lattice point is located outside the Ewald sphere, s_g>0, whereas the reciprocal lattice point is located inside the Ewald sphere, s_g<0. s_g is an observable quantity with dimension of [length]^-1. A dimensionless parameter (tilt parameter) "w = s_g ・ξ_g," whereξ_g is the extinction distance, is used instead of s_g as a useful parameter in the theoretical treatment. However, it should be noted that w is a non-observable quantity.

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