Understanding Stellar Nucleosynthesis via Multi-isotopic NanoSIMS analyses of Presolar Grains
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In this lecture, I have covered basic introduction to presolar grains and its scope in understanding nucleosynthesis using multi-isotopic analyses NanoSIMS.
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Understanding Stellar Nucleosynthesis via Multi-isotopic NanoSIMS analyses of Presolar Grains
- 1. Understanding Stellar Nucleosynthesis via Multi-isotopic NanoSIMS analyses of Presolar Grains Lalit K Shukla Assistant Professor Faculty of Physical Sciences
- 2. Physical Research Laboratory Udaipur Solar Observatory
- 3. Physical Research Laboratory Science@PRL • Astronomy & Astrophysics • Solar Physics • Space & Atmospheric Sciences • Earth Sciences • Planetary Sciences & Exploration • Gravitation & Cosmology • Particle Physics • Nuclear, Atomic & Molecular Physics • Nonlinear Dynamics • Quantum Optics & Quantum Information Summer Internship @PRL https://www.prl.res.in/prl-eng/ summer_internship Engineering Project Training https://www.prl.res.in/prl- eng/ept
- 4. Plan of the talk • An introduction to Presolar Grains • Approaches to laboratory studies • Analysis tool: NanoSIMS • Stellar nucleosynthesis: neutron capture processes • Multi-isotopic analyses of heavy elements in single Presolar Grains Understanding Stellar Nucleosynthesis via Multi-isotopic NanoSIMS analyses of Presolar Grains
- 5. Presolar Grains: An introduction Tiny grains (few µm or less) condensed in outer envelop of stars during their mass ejection phase and survived in all energetic processes in the interstellar medium & collapse of molecular cloud (that formed our solar system) and remained almost intact. Presolar Grains are found in the matrix of least metamorphosed chondrites ( a class of stony meteorites that have not been modified due to melting or differentiation of the parent body) and interplanetary dust particle (IDPs). Presolar grains are identified from their isotopic anomalies which can not be explained by any process occurring within solar system
- 6. Presolar Grains: Sources stardust.jpl.nasa.gov hayabusa.jaxa.jp/ http://caslabs.case.edu/ansmet/
- 7. Presolar Grains (found in crystalline as well as amorphous phase) Carbide Grains Nitride Grains Oxide Grains Silicate Grains Diamond Silicon Carbide Graphite Silicon Nitride Corundum (Al2O3) Spinel (MgAl2O4) Hibonite Pyroxene Olivine (Size = 0.002µm) (Size = 0.2-50 µm) (Size = 1-20µm) (Size = <1µm) (Size = 0.2-50 µm) (Size = < 0.5 µm) ((Ca,Ce)(Al,Ti,Mg)12O19) SS: Sne? SS: AGB, SNe SS: SNe SS: RGB, AGB, Sne, Novae SS: RGB, AGB, SNe SS: AGB, J star, Sne, Novae SS: Stellar Source, SNe: core-collapsed supernovae, AGB: Asymptotic Branch Star, RGB: Red Giant Branch Star, J star: J-type carbon star Presolar Grains: An introduction
- 8. 8 Data is taken from Washington University Presolar Grain Database Presolar Grains: An introduction ❖ Varies from meteorite to meteorite (Amari et al. 1994, Huss et al. 1997), ❖ Variations in isotopic properties are seen with grain size (Lewis et al. 1994)
- 9. Chemical Separation: Separated from meteorites by progressively harsher acid dissolution. In situ Search: Identified by multi-detection raster ion imaging by NanoSIMS. ❖ Some presolar phases get dissolve (silicates, amorphous grains, less refractory coating around grains etc.). ❖ May alter surfaces of grains chemically and/ or isotopically. ❖ Not great sampling issue (Abundance calculation?) ❖ Time taking sample preparation. But once over, thousands grains are ready for analysis. ❖ No dilution effect. ❖ All phases can be recovered (no chemistry). ❖ Grain morphologies remain unchanged. ❖ S a m p l i n g m a t t e r s ( A b u n d a n c e calculation?) ❖ Finding grains take quite time. ❖ Dilution effect (?) Provide a glimpse into dust population that accumulated in the presolar molecular cloud. Chemical and isotopic signatures record grain formation and n u c l e o s y n t h e t i c processes of various stars. Presolar Grains: Approaches to Study Morphologies and compositions may reflect grain formation conditions in stellar environments.
- 10. In situ search for Presolar Grains Isheyevo Clast 2 BSE Image Total area analyzed: 13400 µm2 (10x10 µm2 raster) Total presolar grains found: 2 (size:~240 nm and ~280nm) Abundance: 8 ppm SE Image (overview of analyses) Supernova(?) Grain Isheyevo Meteorite Work done with PRL NanoSIMS-50 Isheyevo Meteorite Find, 2003, Russia, 16Kg
- 11. Chemical Separation of Presolar Grains Prof. Sachiko Amari Lodders & Fegley 1999
- 12. Decanted & added 30ml of 30% H2O2 slowly 1ml/min (temp < 20oC) Ultrasonic added DD water twice and ultrasonic, centrifuge, decant Colloid Extraction Residue: Wash with 0.1M NH3 (pH~9) (4 times) Wash with DD water (2 times) 50 ml (0.5 N Na2Cr4O7+ 2 N H2SO4) 85oC , 24 hrs., centrifuge Murray PM (17.8 g) PM + HF (10M) + HCl (1M) (5 Changes) HCl(6M) (5 Changes) To dissolve silicates & metals (at room temp.) PM + HF (10M) + HCl (1M) (7 Changes) HCl(6M) (7 Changes) To dissolve silicates & metals (at 60oC) PM + H3BO3 (0.6M) + HCl (6M) (7 Changes) HF(2M) + HCl(6M) (7 Changes) To dissolve fluorides & silicates (at 55oC) Wash with 0.1 M HCl SEM: No Silicates 47ml 6M KOH to make soln. 4M (70oC, 24hrs) To remove sulfur & reactive kerogen After another colloid extraction Residue + HClO4(200oC, 2 hrs.) (2 times) To destroy remaining organic C & graphite Residue + H2SO4(180oC, 4 hrs.) Wash with DD water (6 times alternatively) To destroy oxides Wash with 0.1M NaOH SiC Chemical Separation of Presolar Grains
- 13. Chemical Separation of Presolar Grains NanoSIMS Study of Presolar Corundum grain, Mostefaoui et al., 2002 28Si 48Ti min max 18O/16O17O/16O16O 16O 17O/16O 18O/16O 1 µm Sah-602-4 Standard grain
- 14. Sputtering of a small localized area of solid sample by an energetic primary ion beam under high vacuum conditions to generate energetic secondary ions from sample surface that are mass analyzed. Basic Principle: ❖ Non-destructive technique ❖ Less sample preparation is needed ❖ Element H to U may be detected ❖ Isotopic ratios can be measured precisely in very localised area Advantages: ❖ Matrix Dependent ❖ Sample must be vacuum Compatible Limitations: Ion Probe Technique: Secondary Ion Mass Spectrometer (SIMS)
- 15. Nano – Secondary Ion Mass Spectrometer (NanoSIMS) High spatial resolution: ( ~ 50 nm for Cs+ and ~200 nm for O-) Capable of analyzing sub micrometer-sized presolar grains. High mass resolution: Interferences can be resolved with MRP (m/Δm) = 10,000 to 15,000. High Transmission: ~ 30 x IMS-4f Multi isotope (5) detection facility: Made in-situ search for presolar grains possible. Less destructive technique: Few Å. Really needed for such precious grains!
- 16. Nano – Secondary Ion Mass Spectrometer (NanoSIMS) https://www.cameca.com/products/sims/nanosims PRL NanoSIMS 50 PRL SIMS
- 17. Solar Value (270) Solar Value (92) Data is taken from Washington University Presolar Grain Database Carbon and Nitrogen isotopic data: Why Isotopic Abundances? Formation of 12C: α +α → 8Be + α → 12C Formation of 13C: 12C(p, γ)13N(β+)13C Completely different process!! Formation of 14N: 13C(p,γ)14N Formation of 15N: 14N(p,γ)15O(β+)15N 18O(p,α)15N Oxygen Isotopic Data Formation of 16O: 12C(α,γ)16O Formation of 17O: 16O(p, γ)17F(β+)17O Formation of 18O: 14N(α, γ)18F(β+)18O Data is taken from Washington University Presolar Grain Database Presolar Grains: Classification
- 18. Presolar Grains: Classification Data is taken from Washington University Presolar Grain Database Formation of 28Si: 16O+16O →28Si+ α 24Mg(α, γ) 28Si Formation of 29Si: 28Si(n,γ)29Si 25Mg(α, γ)29Si Formation of 30Si: 28Si(n,γ)29Si(n, γ)30Si 26Mg(α, γ)30Si
- 19. Life of Stars
- 20. Neutron Capture Nucleosynthesis • Creation of elements heavier than Fe through fusion is an endothermic process. • Coulomb repulsion is high for high Z. • Thus, heavy element creation is not favoured by primary fusion or charge particle reaction. • Neutron capture is not hindered by Coulomb repulsion. • Seed nuclei encounters an external neutron flux. • Based on neutron density, slow (s-process) and rapid (r-process) processes have been identified. s- process (slow) r-process (rapid) τ (n capture) >> τ (β- decay) τ (n capture) << τ (β- decay) N Density ~ 108 n/cm3 N Density ~ 1021 n/cm3 Major Sites: AGB stars Major Sites: Core collapse Supernovae
- 21. Major neutron sources for sustaining s- process in AGB stars: 13C(α, n)16O 22Ne(α, n)25Mg T ~ 1×108 K T ~ 2-3×108 K n ~ 107 n/cm3 n ~ 108-11 n/cm3 τ ~ 1000 years τ ~ few years Characterized by an inert carbon- oxygen core, surrounded by two separate nuclear burning layers - an inner layer of Helium and an outer layer of Hydrogen. These layers are in turn surrounded by a strongly convective outer envelope. Asymptotic Giant Branch (AGB) stars
- 22. Presolar Grains: A probe to AGB stars ❖ About 90% Silicon Carbide grains (mainstream) and large fraction of Oxide and Silicate grains show the signature of AGB star origin. ❖ Characterized by lower 12C/13C and higher 14N/15N than solar, enriched in 17O. Hoppe et al, 1994 Lambert et al, 1986 Mass Number 142 144 146 148 150 0 100 200 300 400 Mass Number 130 132 134 136 138 0 100 200 300 400 Neodymium Barium Overabundance(%) Prombo et al. (1993)Richter et al. (1995) From Thermal Ionization Mass Spectrometer (TIMS) measurements on bulk presolar SiC Problems with data from bulk measurements
- 23. Marhas et al. (2007) Before this work: 13C pocket size was almost a free parameter (ST/12 to STx2) After this work: Needed 13C spread reduced from factors ~20 down to 2. Constraining on 13C can help in understanding complex physical process. ST: M(13C) = 3X10−6 Mʘ burnt per pulse Signatures of s-process: Single grain analysis for Barium
- 24. Signatures of s-process: Single grain analysis for Neodymium Branching at 141Ce. Isobaric, Hydride, molecular interference Branching at 147Nd
- 25. Required instrumental condition for measurement Marhas et al. (2007) First of all, we need standards of similar matrix for measurements i.e. synthetic grains rich in trace elements. Detectors arrangements according to our need i.e. resolve interferences with least analysis time. For C, N, and Si isotopic data: Cs+ primary ion beam, ~100 nm , ~1pA For Nd isotopic data: O- primary ion beam, ~300 nm, ~10pA Need to be vary careful about contaminations.