- 學位論文
鍺的共振多光繞射與共振相位之研究
Resonant Multi-wave X-Ray Diffraction and Resonance Phase Researches on Germanium
摘要
共振X光繞射，是利用入射光能量在鍺的K 吸收邊附近時，造成的異常色散 效應來研究電子與原子結構的方式。由於一般在收X光強度時，收到的強度只與 結構因子的絕對值平方有關，因此散失了相位的資訊，而本實驗則是利用X光複 繞射的方法，藉由主繞射(primary)與耦合(coupling)兩道光互相干涉的結果，得到相位的訊息。 而由實驗可看出，當入射光能量接近鍺的K 吸收邊時，繞射峰的圖形產生變 化，這就代表了相位的確有改變。但是由於擬合時所採用的非對稱羅倫茲方程式 是將動力項與靜力項的參數綁在一起，所以當靜力項太大時，即會造成動力項的 效應被蓋掉，導致遠離吸收邊時，擬合出的相位並非接近0 或180 。而後雖然採 用將動力項與靜力項分開的方法，但是由於參數間的自由度太高，導致擬合的結 果太過人為，可信度不足。
並列摘要
If the phase of the structure factor are known, then the crystal structure is known.However the problem is that when we take the two wave diffraction experiments ,we can only receive the intensity of the diffraction wave which is only proportional to the absolute magnitude of structure factors. It is so called X-ray phase problem. As can be seen ,when the incident photon energy is close to absorption edge ,the diffraction profile indeed changed , especially the (222) case . It means that the triplet phase is really changed. But when the incident photon energy was far from the absorption edge , the kinematical term is too strong that the asymmetrical profile of the dynamical term is overlaid by a symmetrical profile. It causes the triplet phase which we get from the fitting parameter approaches Finally , although we try a new method let the parameter “b” decomposed into the dynamical and kinematical term , but we are not sure that how far away from incident photon energy to absorption edge should be called as “non-resonant” .So, at beginning we adjust the parameter artificially , this action makes the result not convincible