The structure of 30 S and the 29 P(p  30 S reaction rate Kiana Setoodehnia

29 P(p  30 S 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. Iliadis et 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

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

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

Our Experiments We studied 30 S via: The 32 S(p,t) 30 S reaction: At Wright Nuclear Structure Laboratory using Enge spectrograph The 28 Si( 3 He,n  ) 30 S reaction: At University of Tsukuba Tandem Accelerator Complex using Ge-detectors Goals: Investigating E x and J  of 30 S states above the proton threshold (4399 keV) Determining the 29 P(p  ) 30 S reaction rate with more accuracy

32 S(p,t) 30 S Measurement at Yale Beam of protons accelerated with tandem Van de Graaff accelerator: Target: 250 μg/cm 2 of CdS evaporated on a 20 μg/cm 2 natural carbon 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

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

30 S Spectrum via 32 S(p,t) 30 S 4399 New state S(p,t) 30 S θ lab = 22˚ Target: CdS Triton EnergyExcitation Energy of 30 S Counts Channel

Energy Resolution 25˚ Resolution: 30 keV Resolution: 80 – 120 keV 22˚ Bardayan et al. Phys. Rev. C 76(2007) Counts Channel (arbitrary unit) Setoodehnia et al. Phys. Rev. C 82(2010)022801(R)

Implanted Target vs. CdS We fabricated a 32 S implanted target to reduce the background: 10.7 μg/cm 2 of 32 S implanted into a 60 μg/cm 2 12 C backing Then, repeated the measurement at 22˚, 27.5˚ and 45˚. Counts Channel Counts 32 S(p,t) 30 S Target: CdS θ lab = 22˚ 32 S(p,t) 30 S Implanted θ lab = 22˚ target

J π Assignment: 4688 keV J π = 3 + J π = 2 +

J π Assignment: 4812 keV J π of higher energy states are still under investigation J π = 3 + J π = 2 +

The 29 P(p  30 S Reaction Rate 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 Setoodehnia et al. Phys. Rev. C 82(2010)022801(R)

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

Summary The existence and the J π assignment of the state near 4.7 MeV in 30 S was confirmed. A new state was observed in 30 S at 4812(2) keV, whose existence was predicted by shell model calculations. Its J π 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 28 Si( 3 He,n γ ) 30 S reaction at University of Tsukuba Tandem Accelerator Complex. The 29 P(p, γ ) 30 S rate is entirely dominated by these two resonances in the temperature range of 0.1 – 1.5 GK.