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The structure of 30 S and the 29 P( p ,g ) 30 S reaction rate

The structure of 30 S and the 29 P( p ,g ) 30 S reaction rate. Kiana Setoodehnia. 29 P( p ,g ) 30 S Reaction. P lays an important role in explosive hydrogen burning: At nova temperature regime (0.1 – 0.4 GK) : Influences the abundances of Si isotopes : linked to the

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The structure of 30 S and the 29 P( p ,g ) 30 S reaction rate

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  1. The structure of 30S and the 29P(p,g)30S reaction rate • KianaSetoodehnia

  2. 29P(p,g)30S Reaction Plays an important role in explosive hydrogen burning: • At nova temperature regime (0.1 – 0.4 GK): • Influences the abundances of Si isotopes: linked to the • presolar grains of nova origin. • At X-ray burst temperature regime (0.4 – 1.5 GK): • Influences the energy generation, duration and the light- • curve structure of the burst. C. Iliadiset al., Ap. J. Suppl. Ser. 142(2002)105 J. José et al., Ap. J. 612(2004)414 J. José et al., Ap. J. Suppl. Ser. 189(2010)204

  3. 29P(p,g)30S Reaction Rate • (3-,2+) 5390(4) At the temperature regime of astrophysical interest (0.1 – 1.5 GK),the 29P(p,g)30S reaction rate is dominated by: • A 3+ state near 4.7 MeV and a2+ state • near 4.8 MeV The 29P(p,g)30Sreaction rate is uncertain over the temperaturerange of astrophysical interest by 3 orders of magnitude. Need to study the 29P+p states in 30S 3- 5290(9) 5217.4(7) 0.1 GK≤T≤1.5 GK (4+) 5136(2) (2+) 4888(40) (3+) 4733(40) 29P+p Q = 4399 keV C. Iliadiset al., Ap. J. Suppl. Ser. 134(2001)151 (1+) 3677(3) (0+) 3666(2) 2+ 3404.6(8) 2+ 2210.6(5) 0+ 0 30S

  4. Spectroscopy of 30S In recent years: • Bardayanet al. 2007: 32S(p,t)30S • Galavizet al. 2007: 31S(12C,12Cn)30S*(g)30S • O’Brien et al. 2010: 32S(p,t)30S • Tan et al. 2010: 28Si(3He,n)30S • Some new states were discovered: 4704(5) keV – (3+), • but properties of the key resonances remained poorly • known. PRC 76(2007)045803 J. Phys. Conf. Ser. 202(2010)012009 AIP Conf. Proc. 1090(2009)288 Nucl. Phys. A834(2010)679c

  5. Our Experiments • Westudied 30S via: • The 32S(p,t)30S reaction: • At Wright Nuclear Structure Laboratory using Enge spectrograph • The 28Si(3He,ng)30S reaction: • At University of TsukubaTandem AcceleratorComplex usingGe-detectors • Goals: • Investigating Ex and J of 30S states above the proton threshold (4399 keV) • Determining the 29P(p,g)30S reaction rate with more accuracy

  6. 32S(p,t)30S Measurement at Yale • Beam of protons accelerated with tandem Van de Graaff accelerator: • Target:250 μg/cm2 of CdS evaporated on a 20 μg/cm2 • naturalcarbon backing • Momentum analyzed the reaction products by the Enge magnetic spectrograph at Yale University • Energy = 34.5 MeV • Intensity = 5 – 95 pnA • Tandem Terminal voltage = 17.3 MV

  7. 32S(p,t)30S Measurement at Yale Spectrograph angles: 10˚, 20˚, 22˚ and 62˚ • Detectors: • 1- Gas-filled, position sensitive ionization drift chamber: • Energy loss • momentum • 2- plastic scintillator • Residual energy Target 1H-Beam

  8. 30S Spectrum via 32S(p,t)30S 5393 5225 5136 32S(p,t)30S θlab = 22˚ Target: CdS 3402.6 60 New state 6768 3680 6344 5314 40 4399 5850 6056 Counts 4688 4812 6535 20 0 500 1000 1500 2000 Channel Excitation Energy of 30S Triton Energy

  9. Energy Resolution 60 3402.6 22˚ 5136 5225 6768 5393 50 • Resolution: • 30 keV • Resolution: • 80 – 120 keV 3680 6344 40 5314 5850 6056 4688 30 Counts 4812 6535 Setoodehniaet al. Phys. Rev. C 82(2010)022801(R) 20 10 0 500 1000 1500 2000 Channel (arbitrary unit) 25˚ Bardayan et al. Phys. Rev. C 76(2007)045803

  10. Implanted Target vs. CdS • We fabricated a 32S implanted target to reduce the background: • 10.7 μg/cm2 of 32S implanted into a 60 μg/cm212C backing • Then, repeated the measurement at 22˚, 27.5˚ and 45˚. 10 • 32S(p,t)30STarget: CdS θlab = 22˚ Counts 4812 4688 0 10 • 32S(p,t)30SImplanted θlab = 22˚ target 4688 4812 Counts 0 1000 1500 2000 Channel

  11. Jπ Assignment: 4688 keV Jπ = 3+ Jπ = 2+

  12. Jπ Assignment: 4812 keV Jπ = 3+ Jπ = 2+ Jπ of higher energy states are still under investigation

  13. The29P(p,g)30S Reaction Rate Setoodehniaet al. Phys. Rev. C 82(2010)022801(R) • The rate is substantially larger (4 – 20 times) than the previously • determined rate, and is dominated by the newly observed state from • 0.3 – 1.5 GK

  14. 29P(p,g)30S Rate Uncertainty Iliadis et al. Bardayan et al. New rate uncertainty Setoodehniaet al. Phys. Rev. C 82(2010)022801(R) The uncertainty in the rate is reduced significantly (up to factors of 7 and 17) with respect to the previously determined uncertainties

  15. Summary The existence and the Jπ assignment of the state near 4.7 MeV in 30S was confirmed. A new state was observed in 30S at 4812(2)keV, whose existence was predicted by shell model calculations. Its Jπ assignment has been determined to be most likely 2+. The existence and the energy of the latter state is already confirmed by an in-beam γ-ray spectroscopy experiment via the 28Si(3He,nγ)30S reaction at University of Tsukuba Tandem Accelerator Complex. The 29P(p,γ)30S rate is entirely dominated by these two resonances in the temperature range of 0.1 – 1.5 GK.

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