{"id":102,"date":"2023-07-27T14:26:40","date_gmt":"2023-07-27T14:26:40","guid":{"rendered":"http:\/\/physicsinstruments.de\/?page_id=102"},"modified":"2023-07-28T09:16:34","modified_gmt":"2023-07-28T09:16:34","slug":"22na-decay-scheme","status":"publish","type":"page","link":"http:\/\/physicsinstruments.de\/?page_id=102","title":{"rendered":"Na-22 decay scheme"},"content":{"rendered":"\n<p>The radioactive isotope <sup>22<\/sup>Na decays into the stable <sup>22<\/sup>Ne isotope either via direct positron emission (0.055% probability, end point energy 1821.2 keV, average energy 835 keV) or via positron emission (89.9 % probability, end point energy 546.67 keV, average energy 216 keV) into the first excited 2<sup>+<\/sup> state in <sup>22<\/sup>Ne. The excited state (promptly) decays by emitting a 1274 keV gamma-ray which can be used as a start signal for positron annihilation lifetime studies. Electron capture competes with the \u03b2+ decay and it has a 10.1 % probability. <\/p>\n\n\n\n<p>The decay from the 3<sup>+<\/sup> ground state of <sup>22<\/sup>Na to the 2<sup>+<\/sup> excited state in <sup>22<\/sup>Ne is an allowed Gamow-Teller transition with \u03c0<sub>i<\/sub>\u03c0<sub>f<\/sub> = 1, while the  <sup>22<\/sup>Na 3<sup>+<\/sup> to  <sup>22<\/sup>Ne 0<sup>+<\/sup> ground state transition is twice forbidden. <\/p>\n\n\n\n<p>Widely used nuclear data bases such as  <a href=\"https:\/\/www.nndc.bnl.gov\/nudat3\/DecayRadiationServlet?nuc=22Na&amp;unc=NDS\">NNDC<\/a> state an annihilation radiation probability of 179.91 % (2*89.9 % + 2*0.055 %) for 511 keV photons. However, a non-zero contribution from 3-gamma decays of ortho-Positronium (o-Ps) reduces this fraction.  o-Ps forms in porous media or at the surface of materials in contact with the radioisotope leading to a gamma-ray energy distribution which is continuous with a maximum at 511 keV energy. The 3-gamma to 2-gamma ratio can be used to quantify the porosity of the materials.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"377\" height=\"362\" src=\"http:\/\/physicsinstruments.de\/wp-content\/uploads\/2023\/07\/Na22-decay-scheme.png\" alt=\"\" class=\"wp-image-103\" srcset=\"http:\/\/physicsinstruments.de\/wp-content\/uploads\/2023\/07\/Na22-decay-scheme.png 377w, http:\/\/physicsinstruments.de\/wp-content\/uploads\/2023\/07\/Na22-decay-scheme-300x288.png 300w\" sizes=\"(max-width: 377px) 100vw, 377px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>The radioactive isotope 22Na decays into the stable 22Ne isotope either via direct positron emission (0.055% probability, end point energy&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"_links":{"self":[{"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=\/wp\/v2\/pages\/102"}],"collection":[{"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=102"}],"version-history":[{"count":9,"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=\/wp\/v2\/pages\/102\/revisions"}],"predecessor-version":[{"id":116,"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=\/wp\/v2\/pages\/102\/revisions\/116"}],"wp:attachment":[{"href":"http:\/\/physicsinstruments.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=102"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}