TRIAC Progress Report - KEK

the beta-delayed deuteron emission probabilities [3-27] (Fig. 3-21). This level is also a
candidate of a “halo analog state” of 11 Li, which is populated by a Gamow-Teller (GT)
transition of the two halo neutrons in 11 Li, namely 11 Li ( 9 Li+2n) 11 Be* ( 9 Li+d) [3-28].
20.68
11 Li
β −
18.15
0
11 Be
75
17.916
9 Li+d
8 Li+t, 2α+3n,
6 He+α+n,
9 Be+2n, 10 Be+n
Fig. 3-21. Level diagram of beta-delayed particle-emitting 11 Li.
Clear determination of the energy, width, and spin-parity may be therefore useful for
studying the GT transitions of 11 Li and its halo structure. However the signature of the
level was not so clear in the beta decay experiments; the energy and width of the level
were deduced from the spectrum, which contained unresolved deuterons and tritons
without any well identified peaks, and from an unresolved 4,6 He spectrum in the decay
11 Li (β) 11 Be * 6 He+α+n, which did not show any peak corresponding to the level
because of the three body decay. Moreover, a recent observation of beta delayed
deuterons did not indicate any resonance signature [3-29]. Further experimental
investigation with a different approach is necessary.
Fig. 3-22. Experimental setup for studying 9 Li+d reactions.
In the present experiment we have studied 9 Li+d reactions to search for a
resonance signature attributed to the 18.2-MeV level. We measured deuteron, triton,
alpha spectra from 9 Li+d elastic scattering, 9 Li(d,t), and 9 Li(d,α) reactions, respectively.
The 9 Li+d reaction experiment was performed at the TRIAC. A primary beam of 7 Li at
70 MeV from the JAEA tandem accelerator bombarded an ISOL target of BN.