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.
References
- 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. http://dx.doi.org/10.1126/science.aao7293