An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can
provide a measure directly proportional to the total x-ray absorption coefficient, $mu(E)$. In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from $mu(E)$ by an unknown and difficult to measure amount. Moreover, our measurement can determine $mu(E)$ in absolute units with no free parameters by scaling to $mu(E)$ at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO$_3$. Determining $mu(E)$ across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO$_3$, we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively.
