
^{8}Li (1974AJ01)(See Energy Level Diagrams for ^{8}Li) GENERAL: See also (1966LA04) and Table 8.1 [Table of Energy Levels] (in PDF or PS). Shell model: (1966BA26, 1973HA49). Special levels: (1966BA26, 1970FR1C). Electromagnetic transitions: (1966BA26, 1972EV03, 1973HA49). Special reactions: (1965AF1A, 1966BA1R, 1966KL1C, 1967AU1B, 1967GO1F, 1968GR1E, 1970AZ1A, 1971AG01, 1971DH1A, 1971KA1K, 1972VO06, 1973KO1D, 1973WI15). Pion and kaon reactions: (1967ZE1A, 1968BA1M, 1968BE1R, 1968BH1A, 1969BA1L, 1970AG1B, 1970BA44, 1971DH1A, 1971VA1E, 1971VA19, 1972WE20, 1972BA1C, 1973GE1K). Astrophysical questions: (1967MI1C, 1970BA1M). Other topics: (1966TO04, 1967DI1B, 1971BA2Y, 1972AN05, 1972GA1L, 1972PN1A, 1973JU2A). Ground state properties: (1966BA26, 1969PE1D, 1972VA36, 1973EN1B, 1973MA1K, 1973SU1B).
μ = +1.65335 ± 0.00035 nm (1973HA12); μ = +1.6532 ± 0.0008 nm (1959CO68, 1962CO08); μ = +1.6530 ± 0.0008 nm (1967GU14). See also (1967SH14, 1969FU11, 1971SH26).
The βdecay leads mainly to ^{8}Be*(2.9): see ^{8}Be. Measurements of the halflife of ^{8}Li 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 ^{8}Be). The coefficient for the angular correlation between β^{}, (νbar)_{e} and αparticles, 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 ^{8}Be.
Transitions to ^{8}Li*(0, 0.98) have been observed: see (1966LA04). See also (1968CO1H).
The thermal capture cross section is 45.4 ± 3 mb. Neutron capture γrays 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 ^{8}Li*(2.26): Γ_{γ} = 0.07 ± 0.03 eV (1959IM04). See also (1967GU14), (1966LA04) and (1970AU1B; astrophys. calculations).
The thermal cross section is 1.07 ± 0.04 b (1960HU1A); the coherent scattering length (thermal, bound) is 2.1 ± 0.1 fm (1969BA1P, 1973MU14). Total crosssection 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 (1971FO1A), 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; n_{0}). For earlier references see (1966LA04). See also (1966DA1B, 1972LA1F) and (1966AG1A, 1966SE1E, 1967BE1F, 1967HO1F; theor.). For angular distribution measurements see ^{7}Li and (1970GA1A). A pronounced resonance is observed at E_{n} = 261 keV with J^{π} = 3^{+}, formed by pwaves (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) [^{8}Li*(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 [^{8}Li*(6.5)] with Γ ≪ 80 keV and of a weak, broad peak at E_{n} = 3.7 MeV (1971FO1A: D.G. Foster and C.A. Goulding, private communications). See also reaction 5.
The excitation function for 0.48 MeV 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. 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^{+} [^{8}Li*(5.4)] and J^{π} = 3^{+} or 3^{} [^{8}Li*(6.4)] [(1972PR03: Γ_{λ}, γ^{2}_{λ} and θ^{2}_{λ} are listed for these two states under various assumptions)]. Crosssection measurements have also recently been reported for E_{n} = 3.35, 4.83, 5.74 and 7.5 MeV (1968HO03; n_{1}, n_{2}), 10 MeV (1967CO01; n_{2}) and 19.0 to 21.0 MeV (1972PR03; γ_{1}). See also (1965DE1G, 1972CO1K), and (1966LA04) for a listing of earlier references.
At E_{n} = 19 MeV, the upper limit for reaction (b) is 10 mb (1971KO24). See also ^{7}He and (1973LI02).
See (1967VA12, 1973LI02) and (1966LA04).
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 ^{7}Li (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 ^{5}He, and (1966JE1B).
Proton groups have been observed to ^{8}Li*(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 p_{0} and p_{1} groups [l_{n} = 1] at E_{d} = 12 MeV have been analyzed by DWBA: S_{exp.} = 0.87 and 0.48, respectively for ^{8}Li*(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 γray. The transition is M1 (1962CH14). The lifetime of ^{8}Li*(0.98) is 10.1 ± 4.5 fsec (1971TH02). See also (1966TH1B, 1968FI1F).
See (1970CH1Q) and ^{10}Be. See also (1970JA1J; theor.).
Not reported.
^{8}He decays with τ_{1/2} = 122 ± 2 msec to ^{8}Li*(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 ^{8}Li*(0.98) (1965PO06).
See (1962CU05, 1966DE13, 1968AD09). See also (1966LA04).
See (1969BA1F; theor.). See also ^{9}Be.
The summed proton spectrum at E_{p} = 156 MeV shows peaks corresponding to ^{8}Li(0) and ^{8}Li*(0.98 + 2.26) [unresolved]. In addition sstates [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 ^{9}Be and (1966LA04) [(1965TY1A) has now been published as (1966TY01)]. See also (1971GR1K), (1965CO1E) and (1967KO1B, 1968JA1D, 1973AS02; theor.).
At E_{d} = 38 MeV, differential cross sections have been obtained for the ^{3}He groups corresponding to ^{8}Li*(0, 0.98, 2.26) (1966GA21: see ^{9}Be(d, t)^{8}Be).
At E_{t} = 12.98 MeV, αparticle groups are observed to ^{8}Li*(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 αparticles to ^{8}Li*(6.53) is rather featureless and does not involve a forward maximum, suggesting l > 1. A large ltransfer is consistent with the narrow width of this unbound state (1968AJ01). At E_{t} = 20 MeV these four ^{8}Li states were also observed. ^{8}Li*(6.53) was found to have Γ_{c.m.} = 40 ± 10 keV. No other groups corresponding to sharp states of ^{8}Li (Γ ≲ 100 keV) with E_{x} ≲ 16 MeV were observed at θ = 15°, 25° and 35° (F. AjzenbergSelove and O. Hansen, private communication). The α_{0} angular distribution has also been measured at E_{t} = 2.10 MeV (1970CO04) and 0.52 to 1.31 MeV (1969NA04; also α_{1} at E_{t} = 0.52 to 1.67 MeV). The mean lifetime, τ_{m} = 14 ± 5 fsec for ^{8}Li*(0.98): E_{x} = 980.80 ± 0.10 keV (1972CO09). See also ^{12}B in (1975AJ02).
See (1966LE10) and (1968TO1C; theor.).
This reaction has been observed for E_{d} = 0.7 to 3.0 MeV: see ^{12}B (1970GO11, 1973GO09).
Not reported.
See (1963NE07).
Angular distributions have been obtained at E_{n} = 14.1 MeV for the α_{0} and α_{1} groups (1973BO26). See also (1966JA1C) and ^{12}B in (1975AJ02).
At E_{α} = 129 MeV, ^{8}B groups are observed to ^{8}Li*(0, 0.98, 2.26) (1968MC02).
At E(^{7}Li) = 34 MeV angular distributions have been measured for the transitions to ^{8}Li_{g.s.} + ^{12}C_{g.s.}, ^{8}Li^{*}_{0.98} + ^{12}C_{g.s.}, ^{8}Li_{g.s.} + ^{12}C^{*}_{4.4} and ^{8}Li^{*}_{0.98} + ^{12}C^{*}_{4.4} (1973SC26).
See (1969NE1E).
