{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"7d36cd0fceebf5fec73f560a1bdc206750d71ccbfc51890e39d7ccd050fbd23b","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"265212969f61b1294ed95f59d09f0947a8a3a99dd36569ffa2ceadc2bbce8d4e","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"nuc.fission-theory.fragment-angular-momentum","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Fission fragments spin with several units of angular momentum even when the parent nucleus barely rotates. A 2021 experiment found that the spins of the two fragments are unrelated in size, which challenges the idea that they are set by shared motions before the split.","posed_since":"","precise":"For $252\\mathrm{Cf}(\\mathrm{sf})$, $232\\mathrm{Th}(\\mathrm{n},\\mathrm{f})$, $238\\mathrm{U}(\\mathrm{n},\\mathrm{f})$ and $235\\mathrm{U}(\\mathrm{n}_{\\mathrm{th}},\\mathrm{f})$, determine when (before scission, at scission, or after, during shape relaxation of the deformed fragments) and through which collective modes (bending, wriggling, twisting, tilting) the fragment spins $J_{\\mathrm{L}}$ and $J_{\\mathrm{H}}$ of several $\\hbar$ are generated. An answer is a dynamical calculation that reproduces the measured mean spins versus fragment mass, the observed lack of correlation between $\\mid J_{\\mathrm{L}}\\mid$ and $\\mid J_{\\mathrm{H}}\\mid$, and their dependence on total kinetic energy.","problem_ref":null,"references":"","settled_by":"A microscopic calculation of the joint distribution $P(J_{L}, J_{H})$ that matches gamma-spectroscopy data on spin magnitudes versus fragment mass and total kinetic energy, plus a direct measurement of spin orientation correlations.","status_note":"Since the 2021 measurement of uncorrelated spin magnitudes (Wilson et al., Nature), 2025-2026 microscopic calculations across all fragments and spin versus kinetic energy data have not settled when the spin is generated.","title":"How fission fragments acquire their angular momentum","topic_ref":"4682ec98f6efef769b56a4880afd87dd00cb0bc4ad4f0a7af1b11de1483f7592"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"e1367750436adbfebe455c7676078793766553bf4d1dae6ef5bff09a8b0dd900","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"c7c4e1819fd4b93177be09fcb4ebf08329d8967ce368d634b3aa802a1281ddc4","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"4KQ0Z6ahkO82PkcoewmM8uLhUuvNhndfcPbR4vt_TjGFMna1fpWVD7gokhy4LZ8gaNoNXsTRANSvL2iP67RyCQ"},"schema":"pubphys.envelope/1"},"record_hash":"e1367750436adbfebe455c7676078793766553bf4d1dae6ef5bff09a8b0dd900","leaf_index":1752}