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The results indicate that, under confinement, the 3He atoms behave collectively as an oblate symmetric rotor consistent with the global Ih symmetry of the 3He3@C60 endohedral fullerene. The NC-NOCI calculations show that the doublet state lies lower in energy than the quartet; moreover, the effect of the C60 cage is not strong enough to force the fermionic helium atoms to form a shell structure. This can be attributed to the very small energy differences between spin-isomer states, on the order of 2\u00a0cm\u22121.<\/jats:p>","DOI":"10.1063\/5.0336539","type":"journal-article","created":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T10:36:56Z","timestamp":1788345416000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Quantum states of three 3He atoms confined in a C60 fullerene"],"prefix":"10.1063","volume":"165","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-3435-3161","authenticated-orcid":false,"given":"Pohl","family":"Moreno-Roncancio","sequence":"first","affiliation":[{"name":"Department of Physics, Universidad Nacional de Colombia 1 , Av. 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