Study of Correction of X-ray Absorption Near Edge Structure : MgO

• Main Author: 王紹宇
• Other Authors: Chu-Nan Chang
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/29989095133226603937

碩士 === 國立臺灣師範大學 === 物理學系 === 95 === By using the method of the total fluorescence yield, one can obtain the X-ray absorption near-edge spectrum. But the target self-absorption effect will distort the intensity of X-ray absorption near-edge spectrum, especially at the resonance absorption peaks. It is important to correct the target self-absorption effect in the X-ray absorption near-edge spectrum for some experiments in which the information of the absorption intensity is important. The other effect that may make the X-ray absorption near-edge spectrum distorted is the core hole effect. We shall examine it along with the correction of the target self-absorption effect by studying the X-ray absorption spectrum of MgO. We have verified that we can’t correct the intensity of the absorption near-edge spectrum at the resonance peaks by using the absorption coefficient obtained by atoms theoretical calculation. A self-consistent method has been developed to correct target self-absorption effect. This method has been demonstrated that it corrects the target self-absorption effect quite well if the thickness of target is less than half of mean free path. However, for a thicker sample, different iteration loops are needed for different resonance peaks to have a reasonable good target self-absorption correction. In other words, it is hard to correct every resonance peaks by the same number of iteration loops. Nevertheless a certain degree of correction can be made by using only one iteration loop. Both X-ray absorption near-edge spectra of Mg K edge and O K edge show the core hole effect in MgO. MgO is considered as an ionic bond solid and therefore, around oxygen atom in MgO should have greater electron screening and will have less core hole effect. But our data show that there is still quite large core hole effect in the X-ray absorption near-edge spectrum of O K edge