Near threshold three-body final states in7Li+7Lireactions at

Molecular structures inT=1states of10B

“…Based on the reduced widths amplitudes from our R-matrix fit and taking into account isospin Clebsch-Gordon coefficients we estimated the total width of this 2 + state in 10 Be to be ≈ 330 keV. This value seems to be more consistent with the 9 Be(d,p) data [26] that reports a width of 291±20 keV for this state rather than with the 141±10 keV value from the 7 Li( 7 Li,α) data [27].…”

“…Taking into account the difference in penetrability factors between 10 B and 10 Be we estimate the branching ratio for α decay of the 2 + state in 10 Be to be Γ α /Γ = 1.3 ± 0.3 × 10 −4 . This value (that already corresponds to the α single particle limit) is a factor of 30 smaller than the Γ α /Γ = (3.5 ± 1.2) × 10 −3 reported for this state in [27].…”

Observation ofαdecay from a state in10B at 11.48 MeV

“…A slope parameter ofh 2 /2I = 0.19 MeV is deduced from the energy separation of the band members, which nearly equals the slope parameter of 0.20 MeV of the analog band in 10 Be. This may be compared to the ground-state bands in 8,9,10 Be, which have slope parameters of 0.57, 0.53, and 0.56 MeV, respectively. The small slope parameter (large moment of inertia) implies a pronounced molecular structure and a greatly enhanced separation of the two α clusters.…”

“…The second and third members of the band, the 2 + and 4 + excitations, are located at 7.54 and 10.15 MeV, respectively. The moment of inertia deduced from the energy separation of the band members is roughly 2.5 times larger than the moment of inertia of the 8,9,10 Be ground-state bands, indicating pronounced molecular structure and a greatly enhanced separation of the two α clusters. We note that the spin-parity of the 10.15-MeV state remains somewhat controversial.…”

“…Related to this is the unusually large α width of the 7.54-MeV state [6,8], which exceeds the Wigner limit [9] by a factor of ∼50. 1 The enhanced separation of the two α clusters may partially explain the large α width since it results in a lowering of the centrifugal and Coulomb barriers, which inhibit the decay very strongly because the 7.54-MeV state is located only 129 keV above the α + 6 He threshold; see, e.g., the analysis of Ref.…”