(from Rene Reifarth) ss the s-process s-only Zr Y Ni Co Fe rpr oc e ss proton number
ppr oc e Br, t1/2=17 min, 92 % (), 8 % () Sr (n,) Rb p-only Kr Br () Se 85 As () Kr, t1/2=11 a Ge 79 Se, t1/2=65 ka Ga Zn
r-only Cu 80 Cu, t1/2=12 h, 40 % (), 60 % () 63 Ni,neutron t1/2=100number a 64 The sites of the s-process weak s-process: core He/ shell C burning in massive stars main s-process: He shell flashes in low mass TP-AGB stars approx. steady flow Y Y ( n , ) const can easily interpolate s-contribution for s+r-nuclei if neutron capture cross
sections are known The weak s-process Site: Core He burning (and shell C-burning) in massive stars (e.g. 25 solar masses) 14 N is rapidly converted to 22Ne 22Ne 18O He burning core contains initially 14N capture capture 18O 14N
Towards the end of He burning T~3e8 K: 22Ne(,n) n) provides a neutron source preexisting Fe (and other nuclei) serve as seed for a (secondary) s-process Typical conditions (Raiteri et al. ApJ367 (1991) 228 and ApJ371(1991)665: Temperature 2.2 - 3.5 e8 K Density 1 - 3e3 g/cm3 Average neutron density 7e5 cm-3 Peak neutron density 2e7 cm-3 Neutron exposure
0.206 / mb ) time integrated neutron flux * produced abundance/solar Results: jn (t )dt The main s-process Site: low mass TP-AGB stars ( thermally pulsing stars on the asymptotic giant branch in the HR diagram, 1.5 - 3 solar masses ) H-burning shell CO core He-burning shell
unstable - burns in flashes (thin shell instability) H/He burning in a TP-AGB star number of He flashes in stars life: few 100 period of flashes: 1000 100,000 years H burning shell s-process in: He flash via 22Ne(,n) n) He flash (thermal pulse) 13C pocket 40 yr (Lugaro et al. ApJ586(2003)1305) 160 yr
52,n) 000 yr 13C pocket via 13C(,n) n) Conditions during the main s-process 13 C(,n) in pocket 22 Ne(,n) in He flash Temperature 0.9 x 108 K 2.7 x 108 K Neutron density
7 x 107 cm-3 1010 cm-3 Duration 20,000 yr few years Neutron exposure 0.1 / mb 0.01 / mb weaker but longer main contribution (90% of exposure) short, intense burst slight modification of abundances
(branchings !) Results for main s-process model = s-only (Arlandini et al. ApJ525 (1999) 886) The p-process produces p-rich, usually rare (0.1-1% isotopic fraction), stable isotopes Site: Supernova shock passing through O-Ne layers of progenitor star Conditions at different locations in O/Ne layers during a Supernova: (Rayet et al. A&A298 (1995) 517) p-process mechanism Secondary process. Seed: previous s-process in low mass star) Series of (,n) (,p) (,) photodisintegration reactions (also called -process)
produced by disintegration of heavier nuclei (,n) (,p) produces eventually lighter p-nuclei (,n) (,n) p nucleus (,n) s nucleus p-process path Rayet et al. A&A227(1990)271
p-nuclei (,n) flow stopped by (n,) flow proceeds via (,p) or (,) p-process model results Mo-Ru underproduction problem (1-10% isotopic fraction !) (Rayet et al. A&A298 (1995) 517)
Disclaimer. Opinions Expressed Herein or Otherwise are those of the Speaker and do not Necessarily Reflect the Views of the United States Department of Justice. Overview. Background on ADA and Rehab Act. Barrier-Free Health Care Initiative.
* Centre for Evidence-Based Medicine Cochrane Systematic Reviews (522; another 500 in preparation) Database of Abstracts of Reviews of Effectiveness (1895) Registry of Randomised Controlled Trials (218,355) * * * * * Centre for Evidence-Based Medicine * * Centre for...
By: Ms. Susan M. Pojer Horace Greeley HS Chappaqua, NY Christófo Colón [1451-1506] Columbus' Four Voyages Ferdinand Magellan & the First Circumnavigation of the World: Early 16c European Explorations Looking for "El Dorado" Fernando Cortés The First Spanish Conquests: The...
COMPASSis Produced and edited by: Stacy Callaghan and Kelly L Lewis - For comments or suggestions - e-mail to [email protected] WHEELCHAIR PROGRAM RAFFLE! The lucky member or guest whose ticket is pulled, gets a chance at winning ½ the Pot...
Through one easy to use interface, JANET txt allows the UK's educational and research organisations to distribute individual or group messaging via mobiles, landlines, email or pagers. JANET txt service supports both manual messaging from the desktop, as well as...
Domestic abuse contributes directly to the breakdown of mental health, and parent's experiencing domestic abuse are very likely to suffer from depression and other mental health difficulties leading to self-harm, attempted suicide and/or substance misuse.
Ready to download the document? Go ahead and hit continue!