{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f1fc5c3a2ef2694486ffe8ae232294e070b8b7767dd87c0ae2c1a0992cbc8111","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["4ea2db8d2c3f108a98346aea06c8b728ceb2fa32cea785043977ab5a8fb15532","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"05afe3fcba8e8ef0e952f075b43026b7dd3ea89f0186124d6fdfb5de41aab66a","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"nuc.stellar-reaction-rates.electron-screening-excess","kind":"phenomenon","literature_status":"open","n":"2","parents":[],"plain":"The electrons around target atoms partly hide the electric repulsion between colliding nuclei, which raises measured low-energy reaction rates. The measured boost is larger than the maximum that atomic physics seems to allow, and nobody knows why.","posed_since":"","precise":"Low-energy measurements of $3\\mathrm{He}(d,p)4\\mathrm{He}$, $6,7\\mathrm{Li}(p,\\alpha)$ and $d(d,p)t$ yield screening potentials $U_e$, defined by $\\sigma_{\\mathrm{screened}}(E)/\\sigma_{\\mathrm{bare}}(E)\\sim \\exp(\\pi \\eta U_e/E)$ with $\\eta$ the Sommerfeld parameter, that exceed the adiabatic limit $U_{\\mathrm{ad}}$ (the difference in electron binding between the separated atoms and the united atom) by up to a factor $\\sim 2$ in gas targets and by an order of magnitude for deuterons in some metal hosts. Explain the excess quantitatively, and determine whether the error lies in the screening physics, in stopping-power corrections, or in the extrapolated bare S-factors.","problem_ref":"4ea2db8d2c3f108a98346aea06c8b728ceb2fa32cea785043977ab5a8fb15532","references":"","settled_by":"A calculation of $U_e$ from atomic and solid-state theory that reproduces gas and metal data for the same reaction, or an independent determination of the bare $S$-factor (for example by the Trojan-horse method) that removes the excess.","status_note":"A 2023 palladium measurement found $U_{e}$ up to ten times model values, and a 2023 analysis argued that resonance strengths need no laboratory screening correction at all.","title":"Why laboratory electron-screening potentials exceed the adiabatic 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