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12Li (2017KE05)

(See Table 12.1 preview 12.1 (in PDF or PS))

1. 1H(14Be, 12Li)3He Qm = -16.6122

The ground state of 12Li was reported in the kinematic reconstruction of 11Li + n events resulting from multi-nucleon knockout reactions of E = 304 MeV/A 14Be ions impinging on a liquid hydrogen target (2008AK03). Analysis of the differential cross section as a function of relative energy indicates the ground state is an unbound "virtual" s-state with a scattering length of -13.7 ± 1.6 fm (Eres = 120 ± 15 keV). Since 11Li has Jπ = 3/2-, the ground state of 12Li must then have either Jπ = (1-, 2-). In (2013KO03), it is suggested that 13Li → 11Li + 2n events contaminated the analysis primarily because the neutron array has a low efficiency for 2n-events with a small relative energy. In (2013KO03) as > -4 fm is deduced. See relevant discussion in reaction 2. See also (2011XU03, 1988POZS).

2. 9Be(14Be, 12Li)11B Qm = -6.2895

The neutron scattering length as > -4 fm was deduced from analysis of n + 11Li pairs produced in the 9Be(14Be, 12Li) reaction at E(14Be) = 53.6 MeV/A (2013KO03). Using this constraint the data of (2008AK03) was reanalyzed; it is suggested that the results were influenced by 13Li → 11Li + 2n events that were not fully excluded from the data due to a low efficiency for 2n-events with a small relative energy. Using the new scattering length, the data of (2010HA04) were reanalysed. See comments in reaction 3.

3. 9Be(14B, 12Li)11C Qm = -24.5579

Excited states in 12Li were observed in the kinematic reconstruction of 11Li + n events produced when a 53.4 MeV/A beam of 14B ions impinged on a thick 9Be target (2010HA04). The 11Li + n relative energy spectrum was reproduced by fitting unbound resonances with Eres(keV) = 120 ± 15 (from (2008AK03)), 250 ± 20 and 555 ± 20; these states are presumably the ground and first two excited states of 12Li. The detector resolution permitted upper limits of Γ = 15 and 80 keV for the first and second excited states, respectively. The 12Li ground state is consistent with an s-wave neutron coupled to the Jπ = 3/2- 11Li ground state; hence Jπ = (1-, 2-). A comparison with shell model predictions suggests Jπ = (2-), (4-) and (1-) for the ground, first and second excited states, respectively.

These data were reanalyzed in (2013KO03). In the scenario where as > -4 fm, slightly lower values of Eres = 210 ± 30 keV and 525 ± 25 keV were deduced for the resonances previously reported at Eres = 250 and 555 keV. However, a more significant impact of this reanalysis is the suggestion that only the two states at 210 and 525 keV should be accepted and that because of the broad width of the s-wave strength this group should not be considered the ground state.

4. 14C(π-, 2p)12Li Qm = 79.0921

The 14C(π-, 2p) missing mass spectrum resulting from the capture of stopped π- on a 76% enriched 14C target (26 mg/cm2) was measured and analyzed in a search for states in 12Li (2010GU04, 2013CH30). Evidence is found for a broad peak with Eres = 4.0 ± 0.2 MeV and Γ = 1.1 ± 0.4 MeV; in addition an excess of counts near Eres = 6 to 7 MeV is present in the measured spectrum.