Technical Report of ISSP Ser. A: Number 3223

Abstract

Beside the now well known self-absorption effect, several phenomena related to the multiplet structure of the intermediate state may occur which will render the X-ray fluorescence different from the true absorption result on 3d transition metals at the L edge and on the M(sub 4, 5) edges of rare earths. Special selection rules of the radiative deexcitation process may play an important role there. The absorption coefficients of thin films of lanthanum, thulium and samarium deposited onto an aluminum foil have been measured at room temperature, through the simultaneous detection of the transmission, 150 eV bandwidth fluorescence yield and total electron yield. While transmission and electron yield results are very similar, as expected for a very thin sample, the fluorescence yield spectrum is definitely different and exhibits polarization effects depending upon the angle between incident and outgoing photon. Theoretically, the resonant X-ray fluorescence spectrum was calculated using an atomic model, and then integrated over the emitted energy to predict the fluorescence yield spectrum. A very good agreement is obtained between the theory and experiment.

現在よく知られている自己吸収効果の他に、希土類のLエッジの3d遷移金属およびM(sub 4, 5)エッジについての真の吸収結果とは異なるX線蛍光を与える、中間状態の多重項構造に関連する幾つかの現象が起こり得る。そこでは放射脱励起プロセスの特殊選択則が重要な役割を演じる。アルミ箔上に蒸着したランタン、ツリウムおよびサマリウムの薄膜の吸収係数を、透過、150eVバンド幅蛍光収量および総電子収量の同時検出により室温で測定した。透過および電子収量の結果は、極薄試料に対して予測していたように、非常に類似していたが、蛍光収量スペクトルは明らかに異なり、入射する光子と飛びだす光子の間の角度次第では偏極効果を呈した。理論的に、共鳴X線蛍光スペクトルを原子模型を用いて計算し、次いで蛍光収量スペクトルを予測するために、放出エネルギーを積分した。理論と実験の間で極めてよい一致を見た。