A=8Li (1974AJ01)

The β-decay leads mainly to ⁸Be*(2.9): see ⁸Be. Measurements of the half-life of ⁸Li include τ_1/2 = 841 ± 4 msec (1954KL36), 848 ± 5 msec (1960JA12), 844.0 ± 0.7 msec (1966CL02), 854 ± 8 msec (1968DA12), 838 ± 6 msec (1971WI05): τ_1/2 = 842 ± 6 msec is adopted. [For other measurements see Table 8.2 (in PDF or PS) in (1966LA04)]. See also (1968BO32). Taking τ_1/2 = 842 msec and Q = 16.006 - 2.94, log ft = 5.61 (B. Zimmerman, private communication). See also (1966BA1A, 1969BA43). The distribution of recoil momenta indicates J^π = 2⁺ (see ⁸Be).

The coefficient for the angular correlation between β^-, (ν-bar)_e and α-particles, b = -0.88 ± 0.08 (1965GR25), -1.01 ± 0.07 (1966EI02), in substantial agreement with b = -1, expected from axial vector coupling.

See also (1970SC34) and ⁸Be.

2. ⁶Li(t, p)⁸Li Q_m = 0.801

Transitions to ⁸Li*(0, 0.98) have been observed: see (1966LA04). See also (1968CO1H).

3. ⁷Li(n, γ)⁸Li Q_m = 2.0327
Q₀ = 2032.78 ± 0.15 keV (E.T. Jurney, private communication);
Q₀ = 2032.8 ± 1 keV (1967RA24).

The thermal capture cross section is 45.4 ± 3 mb. Neutron capture γ-rays are observed with E_γ = 980.6 ± 0.2, 1052.0 ± 0.2 and 2032.5 ± 0.28 keV, with intensities of 10.6 ± 1, 10.6 ± 1 and 89.4 ± 1 γ/100 neutrons: E_x = 980.7 ± 0.2 keV for the first excited state (E.T. Jurney, private communication). The cross section for capture radiation has been measured for E_n = 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): Γ_γ = 0.07 ± 0.03 eV (1959IM04). See also (1967GU14), (1966LA04) and (1970AU1B; astrophys. calculations).

4. ⁷Li(n, n)⁷Li E_b = 2.0327

The thermal cross section is 1.07 ± 0.04 b (1960HU08); the coherent scattering length (thermal, bound) is -2.1 ± 0.1 fm (1969BA1P, 1973MU14). Total cross-section measurements have recently been reported at E_n = 0.010 to 1.236 MeV (1968HI1E), 0.10 to 1.50 MeV (1970ME1C), 1.12 to 2.30 MeV (1968KN1B), 2.5 to 15.0 MeV (1971FO1P, 1971FO24), 3.35, 4.83, 5.74 and 7.5 MeV (1968HO03: also σ_el), 10 MeV (1967CO01) and 0.6 to 30.0 MeV (C.A. Goulding, private communication, and (1973GO2B)). See also (1968EN1A, 1972PR03). Polarization measurements at E_n = 4.4 MeV are reported by (1966ST09; n₀). For earlier references see (1966LA04). See also (1966DA1B, 1972LA1F) and (1966AG1A, 1966SE1E, 1967BE1F, 1967HO1F; theor.). For angular distribution measurements see ⁷Li and (1970GA1A).

A pronounced resonance is observed at E_n = 261 keV with J^π = 3⁺, formed by p-waves (Table 8.2 (in PDF or PS)) (1970ME1C). A good account of the polarization is given by the assumption of levels at E_n = 0.25 and 3.4 MeV, with J^π = 3⁺ and 2^-, together with a broad J^π = 3^- level at higher energy (1964LA19). Broad peaks are reported at E_n = 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 E_n = 5.1 MeV [⁸Li*(6.5)] with Γ ≪ 80 keV and of a weak, broad peak at E_n = 3.7 MeV (1971FO1P, 1971FO24: D.G. Foster and C.A. Goulding, private communications). See also reaction 5.

5. ⁷Li(n, n')⁷Li* E_b = 2.0327

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 E_n = 1.35 MeV. A good fit is obtained with either J^π = 1^- or 1⁺ (2⁺ not excluded), Γ_lab = 1.14 MeV (1955FR10). At higher energies a prominent peak is observed at E_n = 3.8 MeV (Γ_lab = 0.75 MeV) and there is some indication of a broad resonance (Γ_lab = 1.30 MeV) at E_n = 5.0 MeV. Between E_n = 6.0 and 9.0 MeV, the cross section decreases monotonically. The two resonances are interpreted as being due to states with J^π = 2⁺ or 3⁺ [⁸Li*(5.4)] and J^π = 3⁺ or 3^- [⁸Li*(6.4)] [(1972PR03: Γ_λ, γ²_λ and θ²_λ are listed for these two states under various assumptions)]. Cross-section measurements have also recently been reported for E_n = 3.35, 4.83, 5.74 and 7.5 MeV (1968HO03; n₁, n₂), 10 MeV (1967CO01; n₂) and 19.0 to 21.0 MeV (1972PR03; γ₁). See also (1965DE1G, 1972CO1K), and (1966LA04) for a listing of earlier references.

6. ⁷Li(n, 2n)⁶Li Q_m = -7.251 E_b = 2.0327

See (1963AS01, 1964ST25).

7. (a) ⁷Li(n, p)⁷He Q_m = -10.42 E_b = 2.0327
(b) ⁷Li(n, p)⁴He + 3n

At E_n = 19 MeV, the upper limit for reaction (b) is 10 mb (1971KO24). See also ⁷He and (1973LI02).

8. ⁷Li(n, d)⁶He Q_m = -7.753 E_b = 2.0327

See (1967VA12, 1973LI02) and (1966LA04).

9. ⁷Li(n, t)⁴He + n Q_m = 2.4668 E_b = 2.0327

The cross section rises to 450 mb at E_n ≈ 8 MeV and thereafter decreases slowly to 300 mb at E_n = 15 MeV (1964ST25). The large cross section, comparable to the geometric value, is understood in terms of the (α + t) cluster nature of ⁷Li (1962RO12). Cross sections for this reaction have recently been reported at E_n = 3.35, 4.83, 5.74 and 7.5 MeV (1968HO03) and at 10 MeV (1967CO01). See also (1967VA12, 1971AN1M, 1973LI02) and ⁵He, and (1966JE1B).

10. ⁷Li(d, p)⁸Li Q_m = -0.1919
Q₀ = -188 ± 7 keV (1967SP09).

Proton groups have been observed to ⁸Li*(0, 0.98, 2.26): see (1966LA04). At E_d = 15 MeV, no states are observed in the region 2.3 < E_x < 8 MeV: a limit of 0.6 mb/sr is placed on groups with widths ≲ 100 keV (θ = 10°, 14°, 25°) (1960HA14). Angular distributions of the p₀ and p₁ groups [l_n = 1] at E_d = 12 MeV have been analyzed by DWBA: S_exp. = 0.87 and 0.48, respectively for ⁸Li*(0, 0.98) [S_exp./S_theor. = 0.84, 1.09] (1967SC29). For PWBA analyses, see (1966LA04).

The first excited state decays by emitting a 980 ± 10 keV γ-ray. The transition is M1 (1962CH14). The lifetime of ⁸Li*(0.98) is 10.1 ± 4.5 fsec (1971TH02). See also (1966TH1B, 1968FI1F).

11. ⁷Li(t, d)⁸Li Q_m = -4.2249

See (1970CH1Q) and ¹⁰Be. See also (1970JA1J; theor.).

12. ⁷Li(α, ³He)⁸Li Q_m = -18.546

Not reported.

13. ⁸He(β^-)⁸Li Q_m = 10.70

⁸He decays with τ_1/2 = 122 ± 2 msec to ⁸Li*(0.98) with an 88% branch [log ft = 4.20; B. Zimmerman, private communication] and to neutron unstable states with a 12 ± 1% branch. The allowed decay supports the assignment J^π = 1⁺ to ⁸Li*(0.98) (1965PO06).

14. ⁹Be(γ, p)⁸Li Q_m = -16.888

See (1962CU05, 1966DE13, 1968AD09). See also (1966LA04).

15. ⁹Be(e, ep)⁸Li Q_m = -16.888

See (1969BA1F; theor.). See also ⁹Be.

16. ⁹Be(n, d)⁸Li Q_m = -14.664

See (1969SC05) in ¹⁰Be.

17. ⁹Be(p, 2p)⁸Li Q_m = -16.888

The summed proton spectrum at E_p = 156 MeV shows peaks corresponding to ⁸Li(0) and ⁸Li*(0.98 + 2.26) [unresolved]. In addition s-states [J^π = 1^-, 2^-] are suggested at E_x = 9 and 16 MeV, with Γ_c.m. ≈ 6 and 8 MeV: the latter may actually be due to continuum protons (1967RO06). See also ⁹Be and (1966LA04, 1966TY01). See also (1970GR39), (1965CO1E) and (1967KO1B, 1968JA1D, 1973AS02; theor.).

18. ⁹Be(d, ³He)⁸Li Q_m = -11.395

At E_d = 38 MeV, differential cross sections have been obtained for the ³He groups corresponding to ⁸Li*(0, 0.98, 2.26) (1966GA21: see ⁹Be(d, t)⁸Be).

19. ⁹Be(t, α)⁸Li Q_m = 2.926

At E_t = 12.98 MeV, α-particle groups are observed to ⁸Li*(0, 0.98, 2.26) and to a state at E_x = 6.530 ± 0.020 MeV with Γ_c.m. < 40 keV (1965WA12). For angular distributions to these four states, see (1968AJ01): the distribution of the α-particles to ⁸Li*(6.53) is rather featureless and does not involve a forward maximum, suggesting l > 1. A large l-transfer is consistent with the narrow width of this unbound state (1968AJ01). At E_t = 20 MeV these four ⁸Li states were also observed. ⁸Li*(6.53) was found to have Γ_c.m. = 40 ± 10 keV. No other groups corresponding to sharp states of ⁸Li (Γ ≲ 100 keV) with E_x ≲ 16 MeV were observed at θ = 15°, 25° and 35° (F. Ajzenberg-Selove and O. Hansen, private communication). The α₀ angular distribution has also been measured at E_t = 2.10 MeV (1970CO04) and 0.52 to 1.31 MeV (1969NA04; also α₁ at E_t = 0.52 to 1.67 MeV).

The mean lifetime, τ_m = 14 ± 5 fsec for ⁸Li*(0.98): E_x = 980.80 ± 0.10 keV (1972CO09). See also ¹²B in (1975AJ02).

20. ⁹Be(⁷Li, ⁸Be)⁸Li Q_m = 0.368

See (1966LE10) and (1968TO1C; theor.).

21. ¹⁰Be(d, α)⁸Li Q_m = 2.372

This reaction has been observed for E_d = 0.7 to 3.0 MeV: see ¹²B (1970GO11, 1973GO09).

22. ¹⁰B(n, ³He)⁸Li Q_m = -15.755

Not reported.

23. ¹¹B(γ, ³He)⁸Li Q_m = -27.211

See (1963NE07).

24. ¹¹B(n, α)⁸Li Q_m = -6.633

Angular distributions have been obtained at E_n = 14.1 MeV for the α₀ and α₁ groups (1973BO26). See also (1966JA1C) and ¹²B in (1975AJ02).

25. ¹²C(α, ⁸B)⁸Li Q_m = -41.445

At E_α = 129 MeV, ⁸B groups are observed to ⁸Li*(0, 0.98, 2.26) (1968MC02).

26. ¹³C(⁷Li, ¹²C)⁸Li Q_m = -2.914

At E(⁷Li) = 34 MeV angular distributions have been measured for the transitions to ⁸Li_g.s. + ¹²C_g.s., ⁸Li^*_0.98 + ¹²C_g.s., ⁸Li_g.s. + ¹²C^*_4.4 and ⁸Li^*_0.98 + ¹²C^*_4.4 (1973SC26).

27. ¹⁸O(⁷Li, ¹⁷O)⁸Li Q_m = -6.014

See (1969NE1E).