Energy levels of 36Ar and 38Ar from alpha capture in sulphur and proton capture in chlorine

Abstract

Abstract:The reactions ssS(~, 7,)SeAr and e~S(~, 7)~Ar were investigated in the energy range E~ = 2.2-3.2 MeV. Five resonance states in SeAr (Ex = 8.9-9.5 MeV) and six in eSAr(Ex = 9.6-10.1 MeV) were found. The excitation energies and resonance strengths are reported. The spins and parities of most resonances showing a ground-state transition were determined from angular distribution measurements. The relative strengths of the J~ = 1-resonances in neAr and 8nAr indicate that the isobaric-spin selection rule for electric dipole transitions in self-conjugate nuclei is still effective in this mass region. The slowing-down factor for these transitions amounts to about ten. The seCl(p, 7)nnAr reaction for F~ = 0.4-1.0 MeV, leads to twenty SeAr levels in the excitation range covered in the s~S(u, 7')SeAr experiment. The yield curves of the two reactions are compared. Three s6Ar resonance levels are excited in both the (13, 7') and the (u, 7) reaction.

Direct measurement of resonance strengths inS34(α,γ)Ar38at astrophysically relevant energies using the DRAGO

“…The canonical [16] uncertainty of ±3keV assigned to this excitation energy is likely misattributed to this state, and more appropriately belongs to the high-spin state of tentative J π = (8 + ) at 9537.2(4) keV observed in 35 Cl(α,pγ ) 38 Ar [15]. Because of the large uncertainty in the canonical value for this state, the excitation energy of [9,10]. Gray bars indicate the energy thickness (55-75 keV in the CM system) of the gas target during the yield measurement.…”

“…When comparing the published results from past 34 S(α,γ ) 38 Ar experiments [3,[9][10][11]13,14], one observes a discrepancy of about a factor of 2 in the literature for the nominal value of the strength of three resonances in 34 S(α,γ ) 38 Ar within the astrophysically relevant energy range for oxygen-burning temperatures (see Table I). The resulting uncertainty in these resonance strengths leads to a significant uncertainty in the narrow resonance reaction rate in this energy range.…”

“…There are several states above the α separation energy (Q = 7.208 MeV [19]) that are known from previous 34 S(α,γ ) 38 Ar measurements [9,10,20]( s e eF i g .1). The states at E x = 9917(5) keV and E x = 9597(5) keV are those for which there exists broad uncertainty in the literature for the measured resonance strength, and the minimum energy to which prior 34 S(α,γ ) measurements probed is E x = 9597 keV.…”

“…Sinha et al [9] Erne and Van Der Leun [10] Clarke et al [ 34 S and subsequently 38 Ar are synthesized mainly through α capture on 30 Si, a product of the heavy-ion reactions ( 16 O + 16 O) that occur during oxygen burning. Oxygen burning occurs in M>8 M ⊙ stars near the end of their evolution during the blue supergiant phase.…”

High-resolution investigation of the reaction 35Cl(p, α0)32S

“…Resonance states of 36Ar have been investigated through the 32S(~, y)a6Ar and the asCl(p,-/)36Ar reactions by Ern6 et al [1][2][3]. They were also studied with lower energy resolution in the reaction 35C1(p, ~o)32S by Clarke et al 4) and by Karad'2ev et al 5).…”