Is (hν)3 an allotrope of light?

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A little while ago I pondered allotropic bromine, or Br(Br)3. But this is a far wackier report[1] of a molecule of light.

The preparation and detection of dimer and trimer bound photon states is pure physics; probably considered by the physicists themselves as NOT chemistry. It is certainly true, as a chemist,  that I understood only a little of the article. But chemistry uses photons extensively in the area we call photochemistry. We represent photons as hν, and hence (hν)3.

This molecular light has some fascinating properties. One is that it travels around 100,000 times slower than the usual speed of light. Another is the estimate of the photon-photon binding energies, which are ~1010 times smaller than in diatomic molecules such as NaCl and H2. I await with interest to see whether this new state of light will achieve any interesting chemistry.


  1. Q. Liang, A.V. Venkatramani, S.H. Cantu, T.L. Nicholson, M.J. Gullans, A.V. Gorshkov, J.D. Thompson, C. Chin, M.D. Lukin, and V. Vuletić, "Observation of three-photon bound states in a quantum nonlinear medium", Science, vol. 359, pp. 783-786, 2018.

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