Nucleosynthesis of the nuclides

1. Nucleosynthesis of the nuclides

2. Chart

3. 2nd Generation Stars (Our Sun)Fusion by CNO reaction 12C + 1H 13N + g 13N 13C + b+ + v 13C + 1H 14N + g 14N + 1H 15O + g 15O 15N + b+ + v 15N + 1H 12C + 4He 12C + 4 1H 12C + 3 g + 2 b+ + 2 v

4. Then by combustion of 16O ( < 1 yr), a reaction that produces higher mass elements, including Si and Mg 16O + 16O 28Si + 4He + g 12C + 16O 24Mg + 4He + g chart

5. Fusion is limited at mass 56Fe by the diminishing return of energy of fusion and increased energy of nuclear bonds p = proton = 1.007593 u = 1.6726234 E–27 kg n = neutron = 1.008982 u = 1.6749287 E–27 kg u = 1 atomic mass unit = 1/12 12C = 1.660018 E–27 kg 5626Fe30 = 26p + 30n A 56Fe = 56 Mais le poid atomique de 56Fe = 55.934942 (http://csnwww.in2p3.fr/AMDC/web/masseval.html) 26 x 1.007593 = 26.197418 u 30 x 1.008982 = 30.269460 u 56.466878 u 56.466878 – 55.934942 = 0.531936 u = 0.883 E–27 kg = masse perdue Converti en énergie de liason nucléaire: E = mc2

6. Energy of nuclear bonding • maximum at 56Fe • beyond, fusion is an endothermic reaction • nucleosynthesis beyond 56Fe by neutron capture reactions and by fission of the nuclides with Z > 90 (uranium and the transuranics) http://www.chem.uidaho.edu/~honors/nucbind.html

7. End as a red giant and a supernova

8. Supernova remnants Cygnus Loop (HST): green=H, red=S+, blue=O++ Cas A in x-rays (Chandra) Vela Remnant of SN386, with central pulsar (Chandra) SN1998bu

9. Nucleosynthsis in 2nd generation stars:Inventory – 1H, 4He, 12C, 13C, 14N, 15N, 16O, 20Ne, 24Mg, 28Si, 32S,36Ar,40Ca, 44Ca,48Ti,52Cr,56FeProduction of neutrons: 13C + 4He 16O + n

10. Nucleosynthesis by neutron and proton capture Process S – slow neutron capture (2nd generation stars) Production of elements up to Bi Process R – capture of fast neutrons (red giants) Production of heavy elements – to U. After is limited by fission Process P – proton capture (1H) Production of nuclides poor in neutrons s

13. The Stable Environmental Isotopes Isotope Ratio % natural Reference abundance 2H 2H/1H 0.015 VSMOW 3He 3He/4He 0.000138 Atmospheric He 13C 13C/12C 1.11 VPDB 15N 15N/14N 0.366 AIR N2 18O 18O/16O 0.204 VSMOW, VPDB 34S 34S/32S 4.21 CDT 37Cl 37Cl/35Cl 24.23 SMOC

14. Routine and non-routine stable environmental isotopes

15. Delta - permil: d - ‰ ‰ VSMOW

16. What is the relative enrichment or depletion of 18O in crustal rocks (~0.204%) relative to VSMOW = 17.4‰ VSMOW  crustal rocks are enriched in 18O by 17.4‰ or 1.7% relative to the standard VSMOW

17. Isotope Ratio Mass Spectrometry

19. Laser attenuation isotope analyser(Wavelength-Scanned Cavity Ring Down Spectroscopy – WS-CRDS) Laser absorption Reads fraction of heavy isotope bonds Direct reading of BOTH 18O and D ratios Do it in the field! New!

20. Los Gatos – the original black box Laser attenuation isotope analyser(Wavelength-Scanned Cavity Ring Down Spectroscopy – WS-CRDS) and Picarro – nice small footprint

21. Laser attenuation isotope analyser(Wavelength-Scanned Cavity Ring Down Spectroscopy – WS-CRDS) Check out the sample requirements – 2 mL. Fill a tray of 100! – lots of good data.

22. Distribution of isotopes in nature • Isotope fractionation during reaction • Rayleigh distillation during reservoir depletion

23. Isotope fractionation, a

25. Physico-chemical fractionation

26. Isotope partitioning functions  = symmetry value m = mass of isotope E = the energy state summed from the zero-point to the energy of the dissociated molecule (J·mole–1) k = Boltzmann constant (gas constant per molecule) = n · 1.380658 · 10–23 JK–1 T = thermodynamic temperature K

27. Diffusive fractionation v = molecular velocity (cm · s–1) k = Boltzmann constant (gas constant per molecule) = n · 1.380658 · 10–23 JK–1 m = molecular mass (e.g. 7.3665 · 10–26 kg for 12C16O2) T = absolute temperature K

28. Diffusive Fractionation e.g. 13C during CO2 diffusion Diffusion in a vacuum Diffusion in air

29. Metabolic (biologic) Fractionation • 13C during photosynthesis • sulphate reduction • methanogenesis . . .

30. Units Isotope Enrichment (e) • Isotope difference in permil units between two reacting phases at equilibrium • when a is small, then we can use:

31. Units Isotope Separation (D) • Isotope difference in permil units between any two phases

32. For a water – vapor exchange at 25°C what is the d18O of vapor, where: • water d18Ow = 0.0 ‰ VSMOW

33. For a water – vapor exchange at 25°C what is the d18O of vapor, where: • water d18Ow = 0.0 ‰ VSMOW The fractionation factor (a) is: a18Ow-v = 1.0093 The isotopic enrichment (e): e18Ow-v = (a–1) ·103 = 9.3‰ and e18Ov-w = – 9.3‰

34. For a water – vapor exchange at 25°C what is the d18O of vapor, where: • water d18Ow = 0.0 ‰ VSMOW e18Ow-v = (a–1) ·103 = 9.3‰ d18Ovapor = d18Owater – e18Owater-vapor = 0.0 – 9.3‰ = – 9.3‰ • vapor d18Ov = –9.30‰ VSMOW

35. For most reactions in hydrogeology: • d values are typically –50 to +50 ‰ • a values are close to 1 (0.98 to 1.02) • e values are typically –20 to +20 ‰ Except for some extreme reactions and light isotopes . . . e.g. hydrogen gas produced from water is strongly depleted in 2H and has a fractionation factora2HH2O-H2 = 3.76 at 25°C. What will be the d2H value for H2 produced from water with d2HH2O = –75‰ at 25°C?

36. d2HH2 = –754‰ VSMOW (but using e, d2HH2 = –75 – 2760 = –2835‰)

37. So, use the e simplification . . . • when a is close to 1 • when the d-values are not too different from the reference (i.e. within a few tens of permil of 0)

38. Fractionation and Temperature lnaX-Y = aT–2 + bT–1 + c

39. Fractionation and Temperature

40. e D ‰ 60 80 100 120 140 160 40 40 30 30 2 H w-v 20 20 18 O w-v 10 10 T °C T °C 0 0 2 H i-v 18 -10 O -10 i-v -20 -20 8 10 12 14 16 18 18 e O ‰ Fractionation and Temperature

41. Fractionation - Other Systems