
^{8}Li (1959AJ76)(See the Energy Level Diagram for ^{8}Li) GENERAL: See also Table 8.1 [Table of Energy Levels] (in PDF or PS). Theory: See (1955LA1D, 1956KU1A, 1957FR1B, 1957KU1B).
The weighted mean of halflives reported in (1955AJ61) is 0.848 ± 0.004 sec. A value of 0.873 ± 0.013 sec is given by (1958VE20). See also (1958IM1A). The decay is complex: see ^{8}Be.
The ground state reaction has been observed by (1952MO19, 1952PE02, 1954AL35, 1955CU17). (1955CU17) also reports one event corresponding to the transition to an excited state at 0.7 ± 0.2 MeV.
The thermal capture cross section is 33 ± 5 mb (1947HU06), 42 ± 10 mb (1956KO1C). At E_{n} = 275 keV, neutron capture is not observed: σ < 0.25 mb (1956KO1C). Polarization of ^{8}Li produced by polarized thermal neutrons has been detected by (1957BU44). See also (1957KU1B, 1958IM1A, 1958SH1A).
Cross sections for Li metal and for ^{7}Li are reported in (1958HU18: see also (1956GO62, 1957KA1B, 1958BR16)). The thermal cross section is 1.07 ± 0.04 b (C. Hibdon: see (1955HU1B, 1956TH06)). A pronounced resonance occurs at E_{n} = 258 keV (see Table 8.2 (in PDF or PS)). Total cross sections and angular distributions establish that the state has J = 3^{+}, formed by pwaves (1956WI04). A further, broad peak centering at E_{n} ≈ 5 MeV may indicate a broad level of ^{8}Li at ≈ 6.5 MeV (1958HU18: see also (1956GO62)). Data on coherent scattering and total cross section for zeroenergy neutrons permit two solutions for the two swave scattering lengths corresponding to antiparallel (J = 1^{}) and parallel (J = 2^{}) interactions; for the first solution, the interaction is essentially pure J = 1^{}, for the other, pure J = 2^{}. Measurement of the interference between the swave background and the pwave (channel spin 2) resonance indicate that the second solution is the correct one, and it is concluded that the splitting between parallel and antiparallel interactions is about 1.5 MeV (1956TH06). (1956WI04) find, on the other hand, that the observed asymmetries in the angular distributions indicate a nearly statistical (5/3) mixture of J = 1^{} and 2^{} background. Use of scattering in ^{7}Li as a polarization analyzer is discussed by (1956WI1E). See also (1956BE98, 1957KH1A).
The excitation function for 0.48MeV γrays shows an abrupt rise from threshold (indicating swave formation and emission) and a broad maximum (Γ ≈ 1 MeV) at E_{n} = 1.35 MeV. The rise above threshold indicates the existence of a J = 1^{} level, which may be identified with the 1.35MeV resonance (if a strong dwave contribution is included). On the other hand, the latter resonance appears to be better described as a J = 1^{+} level, formed by pwaves. Under this assumption, E_{r}(lab) = 1.45 MeV, Γ = 1.14 MeV, with the sum of reduced widths θ^{2}_{in} + θ^{2}_{out} ≈ 0.5 × (3ℏ^{2}/2MR^{2}). The ratio θ^{2}_{in}/θ^{2}_{out} = 0.1 to 0.4 or 1.0 to 3.0 (1955FR10).
Not observed: see ^{7}He.
At E_{n} = 14 MeV, the cross section is 9.8 ± 1.1 mb (1953BA04). See also (1954FR03).
The cross section for reaction (a) is 55 ± 8 mb at E_{n} = 14 MeV (1954FR03). See also (1954MA1E) and (1954BA1B).
Three proton groups are observed, corresponding to the ground state and to levels at 0.974 ± 0.015 (1955LE24), 0.977 ± 0.02 MeV (1955KH31, 1955KH35) and 2.28 MeV (1955LE24). A search for further levels in the range E_{x} = 2.28 to 8 MeV revealed no levels with Γ < 80 keV (1958HA10, 1958HA1G). At E_{d} = 14 MeV, the angular distributions of the protons, analyzed by stripping theory, indicate l_{n} = 1 and therefore even parity, J ≤ 3, for the ground state and the 0.98MeV level (1955LE24). On the assumption that J = 2^{+} and 1^{+} for the ground state and 0.98MeV level, respectively, (1957FR1B) calculate θ^{2} = 0.054 and 0.028 from the data of (1955LE24). These two levels are presumed to arise from a ^{33}P term, with a third component of J = 0^{+} expected at higher energy (1957FR1B). See also (1955GI1A).
Not observed.
Not observed.
Not observed.
Production of ^{8}Li at E_{p} = 20 MeV is reported by (1956LE46). At E_{p} = 185 MeV, the summed proton spectrum shows two peaks, corresponding to pickup of protons with binding energies of ≈ 18 and ≈ 26 MeV, respectively. There is some indication of αparticle structure (1958MA1B, 1958TY49).
See (1954WI25).
Not observed.
Not observed.
See ^{12}B.
