Nuclear Structure from Decay Spectroscopy

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Hilary Eaton
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1 Nuclear Structure from Decay Spectroscopy Most nuclei decay. Provides complementary information to reaction studies. Studies can be done at the lowest count rates access furthest from stability. Alpha, proton, beta, gamma.

2 Decay spectroscopy vs Reactions Decay Spectroscopy Production and observation widely separated in time. Difficult to change decays (not impossible) Relatively few channels available. Studies possible at rates lower than 1/day. Reactions Production and observation close in time. Reaction mechanism provides some flexibility Many channels typically open. Typically requires 100 particles/second.

3 Decay Spectroscopy Production Separation Experiment High energy Fragmentation Medium energy ISOL Low-energy Multi-nucleon transfer Mass separator Laser spectroscopy Chemistry Energy Loss Semiconductor Moving tape Gas Detectors Passive material

4 Experimental Setups Active detector correlation Beta-delayed gamma Moving Tape Collector Ion implantation Passive Detectors

5 A Sample of Experimental Setups Active detector correlation Wasabi (RIKEN) BCS (MSU) Astrobox (TAMU) Saturn/Tape (ANL) Rising (GSI) Leribss (ORNL) Tape (TRIUMF)

6 What decays? p + 4n 3n 2n n - Proton number 2p p 2p n t d n p 3p Neutron number

7 Experimental Observables Many different types of decay spectroscopy. Beta-decay Alpha decay Proton decay Isomeric decays Widely varying timescales nanoseconds age of universe Widely varying energies ev to 10 MeV Measure three important quantities energy Where is the state? half-lives What is the time difference between creation and destruction? branching ratios Where does the decay go, what gets emitted? Selection rules Connect to underlying structure

8 Question 212 Bi is a member of a naturally occurring 232 Th radioactive decay series The half-life of 212 Bi is 61 minutes. The decay braches at 212 Bi 35.94%, t 1/2, = 168 min % -, t 1/2, = 94 min. If your experimental setup is only sensitive to - what halflife do you measure? 212 Po 212 Bi 208 Tl A 61 min B 94 min C 168 min D 262 min E not enough information

9 Relationships Measure time distribution. Determine t 1/2 // T 1/2 Correct for Q branching ratios. X S Y Y t / = ln 2 λ λ = 1 τ λ = Σ λ t /, = ln 2 λ

10 Particle Emission Competition between decays Beta decay λ ~ Q Charged particle λ ~ e ħ [ Adapted from M. Pfützner

11 Alpha Decay X Y + α + Q Two body decay. Energy split between participants. Q influenced by shell closure. Gieger-Nuttal relationship between Q and t 1/2 W. Loveland, D.J. Morrissey, and G.T. Seaborg. Modern Nuclear Chemistry H. Geiger and J.M. Nuttal, Philos. Mag. 22, 613 (1911)

12 Alpha Decay Difference between theory and experiment contains nuclear structure. Pre-formation factor, RF C (R) 2 C. Qi et al., Phys. Rev. Lett. 103, (2009) A. N. Andreyev et al., Phys. Rev. Lett., 110, (2014)

13 f (< f f f f f f f f f f f f f f f f f 440 ms 8.28 f f f 1.7 s 17 s 3.8 ms Superheavy Elements Recall talk by M. Stoyer See talk tomorrow by J. Gates Location of the island of (enhanced) stability. Proton number Db Rf Lr No Md Fm Es Cf 150 Sg Db s Rf s Lr s No m Md m Fm h Es h 8.6 h Cf y Bh Sg ms Db s 1.5 s Rf ms f Sg s Rf s 4.0 s Lr 255 Lr s 2.1 s 27 s No s Md m (<.50 Fm h Es h Cf y No m Md m 28 m Fm d Es d Hs Db 258 Db s 0.51 s Rf ms Lr s No s Md m Fm h Es d Cf 251 Cf y 2.64 y Rg Ds Mt Bh 261 Bh ms 8.0 ms 102 ms Sg s Db s Rf s Lr s No s Md m Fm h 21 ms Ds ms? Mt ms Bh 264 Sg s 0.9 s Db 262 Db s 27 s Rf s 68 s Rf s? s 1.2 ms 5.52 h Es h 276 d 39.8 d Cf d Hs ms 70 ns Sg ms 60.5 d Db s h f Lr m No m Md m 51 d Fm d Es h 25.4 m Cf h Hs ms Lr 261 Lr m 3.6 h No ms Md 259 Md m 31.8 d Fm 258 Fm ms 1.5 s Cf m Sg ms Es d Ds ms Hs s 52 ms Ds ms 0.1 ms Bh 266 Bh 267 Sg 265 Sg s 0.3 s Rf s No ms Rg 272 Ds ms 1.6 ms Mt ms Hs s Sg s Hs s 20 m 1.2 h Rg ms Ds ms Hs s 1 m 29 h 1.3 h / ms 112/ ms 0.4 s 9.8 s 1.9 m 23 h 9.7 ms 4 ms 0.72 s 0.19 s 50 s 0.17 s 0.07 s 3.6 s 0.20 s 8 s 0.10 s 0.48 s 0.82 ms 3.8 s 11 s E sh =-3 32 ms 87 ms 0.13 s 97 ms Z = Neutron number 26 s 0.5 s 5.5 s 20 s 29 s 7.1 ms 0.48 s 0.80 s ms 220 ms 16 ms 2.6 s ms 80 ms 18 s 61 ms Ca + U... Cf -7 T 1/2 A/Z 29 s E (MeV) EC - SF

14 Proton Emission X Y + p + Q Protons can also be emitted from nucleus. Conserve angular momentum and parity. Strong dependency between l, t 1/2, and Q p. M. Pfutzner et al., Rev. Mod. Phys., 84, 567 (2012)

15 Two Proton Emission Two protons can also be emitted from nucleus. Strong dependency between l, t 1/2, and Q p. X Y + 2p + Q M. Pfutzner et al., Rev. Mod. Phys., 84, 567 (2012)

16 Two Proton Emission Angle and energy dependence between two protons.

17 Optical Time Projection Chamber Courtesy M. Pfützner M. Ćwiok et al., IEEE TNS, 52, 2895 (2005) K. Miernik et al., Nucl. Instrum. Methods. Phys. Res. A 581, 194 (2007)

18 Analysis Courtesy M. Pfützner M. Ćwiok et al., IEEE TNS, 52, 2895 (2005) K. Miernik et al., Nucl. Instrum. Methods. Phys. Res. A 581, 194 (2007)

19 45 Fe 2p xp Courtesy M. Pfützner

20 45 Fe Courtesy M. Pfützner K. Miernik et al., Phys. Rev. Lett. 99, (2007)

21 45 Fe Courtesy M. Pfützner K. Miernik et al., Phys. Rev. Lett. 99, (2007)

22 Outlook Courtesy M. Pfützner M. Pfutzner et al., Rev. Mod. Phys., 84, 567 (2012)

23 What is beta decay? Mediated by the weak interaction. Conversion of neutron into proton or vice versa Three different forms B- decay B+ decay Electron Capture 63 Zn 64 Zn 65 Zn 66 Zn 67 Zn 62 Cu 63 Cu 64 Cu 65 Cu 66 Cu 61 Ni 62 Ni 63 Ni 64 Ni 65 Ni p n + e + v 60 Co 61 Co 62 Co 63 Co 64 Co n p + e + v p + e n + v

24 Question Order the fundamental forces in order of increasing strength. A weak, strong, electromagnetic, gravitational B gravitational, weak, strong, electromagnetic C strong, weak, electromagnetic, gravitational D weak, gravitational, electromagnetic, strong E gravitational, weak, electromagnetic, strong

25 Q values BE/A (MeV) 63 Cr A = 63 Z p n + e + v n p + e + 63 Ni v p + e n + v 63 Ge Three body process Beta-decay Q-value determined from masses. Q - : Mass [ A Z] Mass [ A (Z+1)] Q + : Mass [ A Z] Mass [ A (Z+1)] 2m e c 2 Q EC : Mass [ A Z] Mass [ A (Z-1)] Q values can range up to many MeV 60 Fe MeV 63 Co 11.2 MeV

26 Selection Rules Beta decay follows selection rules. Electron, neutrino are spin ½ particles. S = 1 - parallel S = 0 - antiparallel Allowed approximation Relative angular momentum of electron/neutrino is 0 Fermi S = 0 J = J i J f = 0 Gamow-Teller S = 1 J = J i J f = 1 A X A Y + e + v Parent Daughter Character 6 He (0 + ) 6 Li (1 + ) Gamow- Teller 14 0 (0 + ) 14 N (0 +,2.313 MeV) Fermi n ( 1/2 + ) p (1/2 + ) mixed

27 Decay Rate Beta decay rate depends on three factors Matrix element (nuclear structure) Density of final states Coulomb field from nucleus Fermi integral, f, is tabulated depends on Daughter Z End point Forbidden decays ~ x10-4 per degree of forbiddeness λ = 2π ħ M = M ρ(e ) φ V φ λ = g M f(z E C )

28 Matrix Elements f Z E t = K g M f Z E t = B(F) C + B(GT) Isospin raising/lowering operator Isospin and spin operators B F φ τ φ B(GT) φ στ φ Can be calculated

29 f Behavior of f as a function of Q value. Half-life energy dependence ~E 5 All things being equal Empirical functions can also be used. Z= 82 Z= 8 S.A. Moszkowski, Phys. Rev. 82, 35 (1951)

30 Log ft ~ 4000 beta decays Known initial and final spin and parity Empirical classification useful as a guide λ = g M f(z E C ) f(z K E )t / = g M Log ft Log ft B. Singh, J.L.Rodriguez, S.S.M. Wong, J.K. Tuli, NDS, 84, 487 (1998)

31 Simple Example odd-a Co Odd-A 63,65,67,69 Co isotopes. Known half-lives and branching ratios. Dominated by simple f 5/2 to f 7/2 transition. 0.5 d 5/2 g 9/2 0 p 3/2 N = 40 p 1/2 f 5/2 p 3/2 Log t 1/ Z = 28 N = f 7/2 f 7/2 Q (kev)

32 Beta-decay strength 1 = S t (E )f(z, E ) / Courtesy R. Grzywacz P = Σ S (E )f(z, E ) Σ S (E )f(z, E )

106, 052502 (2012). I. Morales et al., Phys. Rev.

33 Half-lives A ~ 70 A ~ 200 A ~ 110 S. Nishimura et al., Phys. Rev. Lett. 106, (2012). I. Morales et al., Phys. Rev. Lett. 113, (2014). C. Mazzocchi et al., Phys. Rev. C 88, (2013).

34 Connection to Astrophysics: xn Courtesy M. Mumpower

35 xn Courtesy K. Miernik

36 xn Courtesy K. Miernik K. Miernik et al., Phys. Rev. Lett. 111, (2013)

37 xn Courtesy K. Miernik K. Miernik et al., Phys. Rev. Lett. 111, (2013)

38 Outcomes Courtesy K. Miernik K. Miernik et al., Phys. Rev. Lett. 111, (2013) I.N. Borzov, Phhys. Rev. C, 67, (2003) P. Möller et al., Phys. Rev. C, 67, (2003)

39 Pandemonium Courtesy K. Rykaczewski K. Rykaczewski, Physics, 3, 94 (2010). J. Hardy et al., Phys. Lett. B, (1977)

40 Solution: Total Absorption Spectroscopy Measure entire distribution Ideal TAS OSIRIS LNPS LBNL-GSI Lucrecia Adapted J.L. Tain INL SuN Don t worry Krzysztof Duke et al., Nucl. Phys. A, 151, 609 (1970). Bykov et al., IAN SSSR 44, 918 (1980) Greenwood et al., NIMA 314, 514 (1992) Rubio et al., JPG 31, S1477 (2005) Karny et al., NIMB, 126, 211 (1997)

41 Nuclear Structure from Beta Decay: Experiment Shape determination 76 Sr E. Nacher et al., Phys. Rev. Lett. 92, (2004).

42 Total Absorption Spectroscopy Modular Total Absorption Spectroscopy Courtesy K. Rykaczewski

43 Nuclear Reactors Following the shutdown of a nuclear reactor the core is still warm. Why? A Heat from gravitational energy release following core collapse. B Heat from thermal neutron induced fission. C Heat from gamma ray emission. D Heat from neutrino induced interactions. E Heat from radioactive decay. A. Algora et al., Phys. Rev. Lett. 105, (2010).

44 Connections: Decay Heat Priority 1 decay heat: 139 Xe 139 Cs 5% cumulative yield in n th U fission 7 th in direct production per 235 U fission Average gamma-ray energy increase of 47% MTAS 240 -lines populating 63 levels known from 139 Xe decay 18 new s and 11 new β-fed levels added to 139 Xe decay scheme Courtesy K. Rykaczewski

-Strength Determination Using Total Absorption -Ray Spectroscopy

-Strength Determination Using Total Absorption -Ray Spectroscopy J.L. Tain Jose.Luis.Tain@ific.uv.es http://ific.uv.es/gamma/ Instituto de Física Corpuscular C.S.I.C - Univ. Valencia Existing TAS data