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| documentation:tutorials:small_programs_a_quick_start:xas [2017/01/10 17:55] – Correct page formatting for larger screens Marius Retegan | documentation:tutorials:small_programs_a_quick_start:xas [2025/11/20 03:29] (current) – external edit 127.0.0.1 | ||
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| - | In principle one can calculate the spectra for any magnetic field direction, but also for any polarization direction. The Poyinting vector must not be in the $z$ direction and there are thus infinite possibilities to define left circular polarized light. In optics this is solved by calculating the optical conductivity tensor. This is a three by three matrix that describes the optical properties of the material for any posible polarization. If $\sigma(\omega)$ is the energy dependent conductivity tensor (three by three matrix) and $\varepsilon$ the polarization (a vector of length three) then the absorption is give as: $I_{XAS} = -\mathrm{Im}[\varepsilon^* \cdot \sigma(\omega) \cdot \varepsilon$. The conductivity tensor for Ni$^{2+}$ with a field in the $(102)$ direction is shown in the figure above. | + | In principle one can calculate the spectra for any magnetic field direction, but also for any polarization direction. The Poyinting vector must not be in the $z$ direction and there are thus infinite possibilities to define left circular polarized light. In optics this is solved by calculating the optical conductivity tensor. This is a three by three matrix that describes the optical properties of the material for any posible polarization. If $\sigma(\omega)$ is the energy dependent conductivity tensor (three by three matrix) and $\varepsilon$ the polarization (a vector of length three) then the absorption is give as: $I_{XAS} = -\mathrm{Im}[\varepsilon^* \cdot \sigma(\omega) \cdot \varepsilon$]. The conductivity tensor for Ni$^{2+}$ with a field in the $(102)$ direction is shown in the figure above. |
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