{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"2b91a61033e7b26a71ec64fa4753baa5b34d3086cdcd64da04c8215417891147","created":"2026-10-03T07:17:58Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"0600d492c26020f95610b6ec8ed0e019954ae76c6fdb9833fca3662e41c89169","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"chem.excited-states.carotenoid-dark-states","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Carotenoids, the orange pigments in carrots and plant leaves, have excited states that do not absorb light directly but appear in fast laser experiments. One of them, called S*, has been assigned to at least four different origins.","posed_since":"","precise":"In ultrafast transient absorption of carotenoids (beta-carotene, lycopene, spirilloxanthin) in solution and in light-harvesting complexes, the $S*$ signal has been assigned to a vibrationally hot $S1$ ($2\\mathrm{Ag}-$) state, a distinct electronic state ($1\\mathrm{Bu}-$ or triplet-pair character), a twisted conformer, or ground-state population. Identify the electronic and vibrational character of $S*$, its formation path from $S2$ ($1\\mathrm{Bu}+$), and its role in carotenoid-to-chlorophyll energy transfer. An answer is an assignment consistent with transient absorption and 2D spectra and with multireference calculations on polyenes of 9 to 13 conjugated double bonds.","problem_ref":null,"references":"","settled_by":"Multireference excited-state dynamics on full-length carotenoids compared with two-dimensional electronic and vibrational spectra in solution and in protein.","status_note":"","title":"Nature of the dark $S*$ state in carotenoids","topic_ref":"0739ba72a9006ef026985ebb675d97cf7cac60e63cac01f5b754f9a8beff9516"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"eec23f25914b7679cb32ce67a1273fe93525107171e914a44eb272bfc4594393","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"cb2dbff79c090db51df39de17e6fddb6e1fb24dfde0646e9697917d33e98eb78","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"AWgNsQOdMkmmquiVk3myx2ElkMq8pEFkNR-4TqX8d82jfRclg4gZxlpaKfZwSCPXmW6nnfgGut2yahtjzZSnCA"},"schema":"pubphys.envelope/1"},"record_hash":"eec23f25914b7679cb32ce67a1273fe93525107171e914a44eb272bfc4594393","leaf_index":866}