= NEXAFS orientation dependence of a diatomic molecule
{c}
{title2=$I_{\sigma^*}\propto|\mathbf e\cdot\mathbf n|^2,\quad I_{\pi^*}\propto1-|\mathbf e\cdot\mathbf n|^2$}
For a diatomic molecular axis $\mathbf n$ and unit electric-field polarization $\mathbf e$, the axial and summed two transverse dipole transition directions have the displayed geometrical factors. Radial matrix elements differ between resonances. If axes have polar tilt $\beta$ and random azimuth, with electric-field angle $\alpha$ to the surface normal, the mean axial factor is $\cos^2\beta\cos^2\alpha+\tfrac12\sin^2\beta\sin^2\alpha$. Polarization-dependent near-edge absorption therefore constrains an orientation distribution, subject to substrate hybridization and instrumental normalization.
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