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8Li (1984AJ01)


(See Energy Level Diagrams for 8Li)

GENERAL: See also (1979AJ01) and Table 8.2 [Table of Energy Levels] (in PDF or PS).

Special states: (1980OK01).

Complex reactions involving 8Li: (1978BO1B, 1978DU1B, 1979BO22, 1979IV1A, 1980AN1T, 1980BO31, 1980GR10, 1980WI1L, 1981BO1X, 1981MO20, 1982BO35, 1982BO1Y, 1982GO1E, 1982GU1H, 1982MO1N).

Muon and neutrino interactions: (1978BA1G).

Reactions involving pions and other mesons: (1977VE1C, 1979BA16, 1980HA29, 1981JU1A, 1981NI03, 1982HA57).

Hypernuclei: (1978PO1A, 1979BU1C, 1980BE30, 1980DO1A, 1980IW1A, 1980MA1Z, 1982PI1J, 1982RA1L, 1981ST1G, 1981WA1J, 1982KO11).

Other topics:(1978SO1A, 1979BE1H, 1982NG01).

Ground state of 8Li:(1981AV02, 1982NG01).

J = 2: see (1974AJ01)

μ = +1.65335 ± 0.00035 nm: see (1978LEZA)

Q = 24 ± 2 mb: see also (1979AJ01)

1. 8Li(β-)8Be Qm = 16.0037

The β- decay leads mainly to 8Be*(2.9): see 8Be, reaction 27. A recent measurement of the half-life is 836 ± 3 msec (1979MI1E). The value derived from a weighted means calculation using the earlier measurements (± 4 - 8 msec) quoted in (1974AJ01) and this recent value gives 840 ± 2 msec. We adopt 836 ± 6 msec, the value measured by (1971WI05). Log ft = 5.60 (M.J. Martin, private communication). See also (1981KO1D) and reaction 27 in 8Be.

2. 6Li(t, p)8Li Qm = 0.801

Angular distributions have been obtained at Et = 23 MeV for the proton groups to 8Li*(0, 0.98, 2.26, 6.54 ± 0.03); Γc.m. for 8Li*(2.26, 6.54) = 35 ± 10 and 35 ± 15 keV, respectively; J for the latter is ≥ 4 (1978AJ02). See also (1983AB1A).

3. 7Li(n, γ)8Li Qm = 2.033

The cross section for capture radiation has been measured for En = 40 to 1000 keV; it decreases from 50 μb to 5 μb over that interval. The cross section shows the resonance corresponding to 8Li*(2.26): Eres = 254 ± 3 keV, Γn = 31 ± 7 keV, Γγ = 0.07 ± 0.03 eV: see Table 8.3 (in PDF or PS) and (1974AJ01). See also (1981MUZQ).

4. 7Li(n, n)7Li Eb = 2.033

The thermal cross section is 0.97 ± 0.04 b, σfree = 0.97 ± 0.04 b (1981MUZQ), 1.06 ± 0.03 b (1982AL16), the scattering amplitude (bound) = -2.29 ± 0.02 fm (1981MUZQ). Total cross-section measurements have been reported for En = 5 eV to 30 MeV [see (1974AJ01, 1979AJ01)] and at En = 2 to 100 keV (1982AL16; ± 3%), and at En = 2.99 to 49.64 MeV (1979LA1D, 1980KE1L) and 0.1 to 49.6 MeV [J.A. Harvey, private communication]. Elastic cross sections are also reported at En = 4.0 to 7.5 MeV (1979KN01; also n0+1) and 7.47 to 13.94 MeV (1979HO11). See also (1977BI12, 1980BA2Q, 1980MI02, 1981KN03) and 7Li. For polarization measurements see (1974AJ01) and (1982AL16).

A pronounced resonance is observed at En = 254 keV with Jπ = 3+, formed by p-waves: see Table 8.3 (in PDF or PS). A good account of the polarization is given by the assumption of levels at En = 0.25 and 3.4 MeV, with Jπ = 3+ and 2-, together with a broad Jπ = 3- level at higher energy. [However, the 2- state is in contradiction with the work of (1982AL16).] Broad peaks are reported at En = 4.6 and 5.8 MeV (± 0.1 MeV) [8Li*(6.1, 7.1)] with Γ ≈ 1.0 and 0.4 MeV, respectively, and there is indication of a narrow peak at En = 5.1 MeV [8Li*(6.5)] with Γ ≪ 80 keV and of a weak, broad peak at En = 3.7 MeV: see (1974AJ01) and (1980KE1L). See also reaction 5.

5. (a) 7Li(n, n')7Li Eb = 2.033
(b) 7Li(n, n')3H + 4He Qm = -2.4681

The excitation function for 0.48 MeV γ-rays shows an abrupt rise from threshold (indicating s-wave formation and emission) and a broad maximum (Γ ≈ 1 MeV) at En = 1.35 MeV. A good fit is obtained with either Jπ = 1- or 1+ (2+ not excluded), Γlab = 1.14 MeV. At higher energies a prominent peak is observed at En = 3.8 MeV (Γlab = 0.75 MeV) and there is some indication of a broad resonance (Γlab = 1.30 MeV) at En = 5.0 MeV: see (1974AJ01). [(1980OL06) do observe the onset of a resonance at 5 MeV.] The En = 3.8 and 5.0 MeV resonances are attributed to (2+, 3+) and (3+, 3-) states at 8Li*(5.4, 6.4): see however reaction 1 here and (1978ST20). At higher energies there is some evidence for structures at En = 6.8 and 8 MeV followed by a decrease in the cross section to 20 MeV: see (1979AJ01). For other cross-section measurements see (1979AJ01), (1980OL06; En = 0.48 → 5.0 MeV; 0.48 γ) and (1979HO11; En = 8.0 → 13.9 MeV; n0+1, n2). See also (1977BI12, 1980MI02). The cross section for reaction (b) rises to 450 mb at En ≈ 8 MeV and thereafter decreases slowly to 300 mb at En = 15 MeV (1976GAYV). In the range En = 6.89 to 8.96 MeV σave = 372 mb (± 4%) (1981SM04). Measurements are also reported for En = 6.0 to 9.97 MeV by (1981LI22). See also (1977BI12), (1980KA1R, 1982SH1K; applied) and (1979BE1K; theor.).

A multilevel multichannel R-matrix analysis of 7Li + n, including all available elastic and inelastic scattering data, has recently been presented by (1981KN03). Six additional states of 8Li are derived from the analysis at Ex = 2.83 [1-], 3.91 [0+], 4.20 [0-], 4.57 [2-], 4.73 [1-] and 7.81 [2-] MeV [Jπ]. The states shown in Table 8.2 (in PDF or PS) at 3.21, 5.4, 6.1, 7.1 and (9) MeV are located by (1981KN03) at 3.17 [1+], 5.45 [3-], 5.94 [4-], 6.61 [1-] and 8.63 [2+, 3+] MeV [Jπ]. The sharp state 8Li*(6.53) was not included in the analysis.

6. (a) 7Li(n, 2n)6Li Qm = -7.2501 Eb = 2.033
(b) 7Li(n, p)7He Qm = -10.42
(c) 7Li(n, d)6He Qm = -7.750

For reactions (a) and (c) see (1980MI02). See also 6He and 6Li and (1979AJ01).

7. 7Li(d, p)8Li Qm = -0.192

Angular distributions of the p0 and p1 groups [ln = 1] at Ed = 12 MeV have been analyzed by DWBA: Sexp = 0.87 and 0.48 respectively for 8Li*(0, 0.98). Angular distributions have also been measured at several energies in the range of Ed = 0.49 → 3.44 MeV (p0) and 0.95 to 2.94 MeV (p1). The lifetime of 8Li*(0.98) is 10.1 ± 4.5 fsec: see (1979AJ01). See also (1981HU1G, 1982EL03, 1982WAZS) and 9Be.

8. 8He(β-)8Li Qm = 10.653

See 8He.

9. 9Be(γ, p)8Li Qm = -16.887

See (1976MA34).

10. 9Be(e, ep)8Li Qm = -16.887

At Ee = 500 MeV, 8Li*(0, 0.98, 2.26) are populated (1977TU1C, 1979BA1U; prelim.): a large structure at Ex ≈ 25 MeV, mostly of 1s strength, is also reported. See also (1979AJ01, 1979MO1G) and 9Be.

11. 9Be(π+, π+p)8Li Qm = -16.887

The population of 8Li*(0.98) and its subsequent γ-decay are reported by (1978MO01).

12. 9Be(p, 2p)8Li Qm = -16.887

The summed proton spectrum at Ep = 156 MeV shows peaks corresponding to 8Li(0) and 8Li*(0.98 + 2.26) [unresolved]. In addition s-states [Jπ = 1-, 2-] are suggested at Ex = 9 and 16 MeV, with Γc.m. ≈ 6 and 8 MeV; the latter may actually be due to continuum protons: see (1974AJ01). See also (1979JA1C) and (1980CA1A).

13. 9Be(d, 3He)8Li Qm = -11.393

Angular distributions have been reported for the 3He ions to 8Li*(0, 0.98, 2.26, 6.53) at Ed = 28 MeV [C2S (abs) = 1.63, 0.61, 0.48, 0.092] and 52 MeV. The distributions to 8Li*(6.53) [Γ < 100 keV] are featureless: see (1979AJ01).

14. 9Be(t, α)8Li Qm = 2.927

At Et = 12.98 MeV, angular distributions of the α-particles to 8Li*(0, 0.98, 2.26, 6.53 ± 0.02 [Γc.m. < 40 keV] have been measured: see (1974AJ01). At Epol. t = 17 MeV, σ(θ) and Ay measurements, analyzed by CCBA, lead to Jπ = 4+ for 8Li*(6.53) (1981AR19). For 8Li*(0.98), τm = 14 ± 5 fsec, Ex = 980.80 ± 0.10 keV: see (1974AJ01).

15. 9Be(α, 5Li)8Li Qm = -18.85

See 5Li (1981DA03).

16. 9Be(7Li, 8Be)8Li Qm = 0.367

The production of vector polarized 8Li ions has been studied by (1981KO1D) in this reaction as well as in the 7Li(pol. 7Li, 6Li)8Li reaction. See also (1979AJ01).

17. 10Be(p, 3He)8Li Qm = -15.981

At Ep = 45 MeV, 3He ions are observed to a state at Ex = 10.8222 ± 0.0055 MeV (Γc.m. < 12 keV): the angular distributions for the transition to this state, and to its analog (8Be*(27.49)), measured in the mirror reaction [10Be(p, t)8Be] are very similar. They are both consistent with L = 0 using a DWBA (LZR) analysis: see (1979AJ01).

18. 10B(6Li, 8B)8Li Qm = -17.730

See (1979AJ01).

19. 11B(n, α)8Li Qm = -6.632

Angular distributions for the α0 and α1 groups have been measured at En = 14.1 MeV [see (1974AJ01)] and 14.4 MeV (1979AN18). See also 12B in (1980AJ01).

20. 12C(α, 8B)8Li Qm = -41.440

See (1974AJ01).