Niskanen, J.; Fondell, M.; Sahle, C.J.; Eckert, S.; Jay, R.; Gilmore, K.; Pietzsch, A.; Dantz, M.; Lu, X.; McNally, D.E.; Schmitt, T.; Vaz da Cruz, V.; Kimberg, V.; Gel'mukhanov, F.; Foehlisch, A.: Reply: Why X-ray spectral features are compatible to continuous distribution models in ambient water. Proceedings of the National Academy of Sciences of the United States of America 116 (2019), p. 17159
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Ambient water properties have been shown to require heterogeneity”(1) is the imperative followed by Pettersson et al.(2) to relate X-ray spectroscopic findings to a heterogeneous or 2-phase model of ambient water. In ref. 3 we question this hypothesis based on quantitative X-ray spectroscopic evidence. We come to conclude that X-ray spectroscopies support no observations related to heterogeneous, distinct structural motives in ambient water. The critique of sum rules by Pettersson et al.(2) is unjustified: Through normalization to the asymptotic behavior we avoid sum rule normalization of X-ray absorption spectroscopy (XAS). In liquid water, extended X-ray absorption fine structure oscillations are less than a percent for the used normalization range (4)(digitized), and less than twice that for ice (5). Pettersson et al.(2) point toward well-known discrepancies between XAS calculations and experiments.