I was wondering why sulfur is Raman active but other elements (e.g. carbon) are not.
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1$\begingroup$ Raman activity is a property of compounds, not elements. $\endgroup$ – Ivan Neretin Aug 4 '17 at 6:21
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$\begingroup$ Be aware that C is a very bad counterexample. For single atom there cannot be vibrational spectroscopy. But in principle a pure element that exists in a specific bound forn can have Raman active modes of vibration. C is famous for its allotrooes, diamond graphite fullerenes-nanotubes.... $\endgroup$ – Alchimista Aug 4 '17 at 11:44
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In a review (PDF, CalTech) of the properties of elemental sulfur, the author notes that the most stable form of sulfur at STP is in fact cycloocta-sulfur, $\ce{S8}$, with other polyatomic species also found. Elemental sulfur is commonly formed as a molecular solid, with arrangements of $\ce{S_n}$ rings or chains, and the S-S bonds can be Raman active.
The paper offers depictions of some of those structures, and also tabulates the principal Raman bands for selected allotropes of elemental sulfur.
