Refractive index spectral dependence, Raman and transmission spectra of high-purity $^{28}$Si, $^{29}$Si, $^{30}$Si, and $^{nat}$Si single crystals · HackerPapers discussionshttps://hackerpaper.kaipfister.de/p/1105.0822/Collected HN comments and submissions linking this paper.enMon, 02 Nov 2026 11:16:22 GMTRefractive index spectral dependence, Raman and transmission spectra of high-purity $^{28}$Si, $^{29}$Si, $^{30}$Si, and $^{nat}$Si single crystals — mentioned by xmcqdpt2https://news.ycombinator.com/item?id=36675605urn:hackerpapers:mention:1105.0822:36675605Tue, 11 Jul 2023 02:02:51 GMT<p>Isotopes are not 100% chemically equivalent and they form chemical bonds with different vibrational resonances because the vibrating masses are different. You can see those differences in spectroscopic line shapes including in refraction (which is related to absorption by the Kramers-Kronig relation). My guess is that those effects would swamp out any relativistic ones by a lot, and because you can&#x27;t tune the isotopic mass you wouldn&#x27;t be able to isolate a gravitational effect. In fact it appears that the isotopic dependence for silicon isotopes is known, https://arxiv.org/abs/1105.0822 and…</p><p><a href="https://hackerpaper.kaipfister.de/p/1105.0822/">Paper and discussion history</a>. A mention is not an endorsement.</p>physics.optics