
^{8}Be (1984AJ01)(See Energy Level Diagrams for ^{8}Be) GENERAL: See also (1979AJ01) and Table 8.4 [Table of Energy Levels] (in PDF or PS). Shell model: (1978RA1B, 1979EL04, 1981BO1Y, 1981RA06, 1981ST22, 1982FI13). Collective, rotational and deformed models: (1978CA1D, 1979EL04, 1979MA1J, 1980FI09, 1981RA06, 1981ST22, 1982FI13). Cluster and αparticle models: (1977WU1A, 1979GO24, 1979GR1F, 1979PA22, 1979ZH1C, 1980FU1G, 1980HA1M, 1980IK1B, 1981GA1J, 1981KA1P, 1981KN12, 1981KR1J, 1981ST22, 1982HA1M, 1982TS1A, 1982VA11, 1983KA1K, 1983RO1G). Special states: (1978CA1D, 1978LA1D, 1978RA1B, 1979AR03, 1979GA1E, 1979HA1E, 1979IN07, 1979KA40, 1980KA28, 1980OK01, 1981BA2P, 1981BO1Y, 1981GA1G, 1981GA1J, 1981KU1H, 1981RA06, 1981SE06, 1981ST22, 1982BI09, 1982FI13, 1982HA1M, 1982OR03, 1983AR07, 1983JO03). Electromagnetic transitions, giant resonances: (1979KA40, 1979PA22, 1981KN12, 1982HA1M). Complex reactions involving ^{8}Be: (1978BE1G, 1978GU16, 1978VO1A, 1979BE1M, 1979BO22, 1979GE05, 1979HA1E, 1979SI09, 1981BL1G, 1981CH18, 1981GU1B, 1981GU1E, 1981WO1A, 1982GU1E, 1982GU1K, 1982KO17, 1982SH01). Reactions involving pions and other mesons: (1978GI14). Hypernuclei: (1978PO1A, 1978SO1A, 1981ST1G, 1981SU1D, 1981WA1J, 1982KO11). Other topics: (1978FI1C, 1978LA1D, 1978RO17, 1978UL02, 1979AR03, 1979BE1H, 1979EL04, 1979GO24, 1979KA40, 1979KA43, 1979VA1A, 1980AM1B, 1980FI09, 1981BA2P, 1981CA1H, 1981KU1H, 1981SE06, 1981SU1D, 1982BE17, 1982BO01, 1982DE1N, 1982NG01, 1982VA1C, 1983AG1C, 1983AR07, 1983BA2F, 1983FI1J, 1983JO03). Groundstate properties of ^{8}Be: (1978FI1C, 1978OV1A, 1978RO17, 1978SM02, 1978UL02, 1979IN07, 1979KA40, 1979PA22, 1981AV02, 1981CH18, 1981ST22, 1982BO01, 1982FI13, 1982HA1M, 1982NG01, 1982TS1A, 1982ZE1A, 1983AR07).
γ_{c.m.} for ^{8}Be_{g.s.} = 6.8 ± 1.7 eV: see (1974AJ01). See, however, (1979FE1C). See also (1980PE1N, 1980RE1C; theor.).
The yield of γ_{1}, has been measured for E_{α} = 32 to 36 MeV. The yield of γ_{0} for E_{α} = 33 to 38 MeV is twenty times lower than for γ_{1}, consistent with E2 decay. An angular correlation measurement at the resonances corresponding to ^{8}Be*(16.6 + 16.9) [2^{+}; T = 0 + 1] gives δ = 0.19 ± 0.03, γ_{γ}(M1) = 6.4 ± 0.5 eV [weighted mean of the two published measurements listed in (1979AJ01)]. See also (1982NA1L). On the basis of these results there is no evidence for violation of CVC or for the existence of SCC. The E_{x} of ^{8}Be*(3.0) is determined in this reaction to be 3.18 ± 0.05 MeV [see also Table 8.4 (in PDF or PS) in (1974AJ01)]. For all references see (1979AJ01). See also (1979AL1F).
The cross sections for formation of ^{7}Li*(0, 0.48) [E_{α} = 39 to 49.5 MeV] and ^{7}Be*(0, 0.43) [39.4 to 47.4 MeV] both show structures at E_{α} ≈ 40.0 and ≈ 44.5 MeV: they are due predominantly to the 2^{+} states ^{8}Be*(20.1, 22.2): see (1979AJ01). The excitation functions for p_{0}, p_{2}, d_{0}, d_{1} for E_{α} = 54.96 to 55.54 MeV have been measured in order to study the decay of the first T = 2 state in ^{8}Be: see Table 8.5 (in PDF or PS). Cross sections for p_{0+1} are also reported at E_{α} = 60.2, 92.4 and 140.0 MeV [see (1979AJ01)] and at E_{α} = 37.5 to 43.0 MeV (1982SL01; p_{0}, p_{1}). The cross section for reaction (c) has been measured at three energies in the range E_{α} = 46.7 to 49.5 MeV: see (1979AJ01). The production of ^{6}Li, ^{7}Li and ^{7}Be [and ^{6}He] has been studied for E_{α} = 61.5 to 158.2 MeV by (1982GL01). The production of ^{7}Li (via reactions (a) and (b)) in the interaction of cosmic rays with the interstellar medium is discussed: it appears that the cross section is too small to account for the observed ^{7}Li abundance and it is suggested that the "missing" ^{7}Li was produced in the Big Bang, thus supporting the theory of an open universe (1978GL03, 1982GL01). Inclusive proton and deuteron spectra have been measured at E_{α} = 110, 130, 158 and 172 MeV (1981PA15). A study of the (α, αp) reaction at E_{α} = 119 MeV is reported by (1981KA1V) [see for excited states of ^{4}He]. See also (1979AL1F), (1979RA1C; astrophysics) and (1978SL02).
The αα scattering reveals the ground state as a resonance with Q_{0} = 92.12 ± 0.05 keV, γ_{c.m.} = 6.8 ± 1.7 eV, [τ = (0.97 ± 0.24) x 10^{16} sec]. For E_{α} = 30 to 70 MeV the l = 0 phase shift shows resonant behavior at E_{α} = 40.7 MeV, corresponding to a 0^{+} state at E_{x} = 20.2 MeV, γ < 1 MeV, γ_{α}/γ < 0.5. No evidence for other 0^{+} states is seen above E_{α} = 43 MeV. The dwave phase shift becomes appreciable for E_{α} > 2.5 MeV and passes through resonance at E_{α} = 6 MeV (E_{x} = 3.18 MeV, γ = 1.5 MeV, J^{π} = 2^{+}): see Table 8.4 (in PDF or PS) in (1974AJ01). Five 2^{+} levels are observed from l = 2 phase shifts measured from E_{α} = 30 to 70 MeV: ^{8}Be*(16.6, 16.9) with γ_{α} = γ [see Table 8.6 (in PDF or PS)], and states with E_{x} = 20.2, 22.2 and 25.2 MeV. The latter has a small γ_{α}. The l = 4 shift rises from E_{α} ≈ 11 MeV and indicates a broad 4^{+} level at E_{x} = 11.5 ± 0.3 MeV [γ = 4.0 ± 0.4 MeV]. A rapid rise of δ_{4} at E_{α} = 40 MeV corresponds to a 4^{+} state at 19.9 MeV with γ_{α}/γ ≈ 0.96; γ < 1 MeV and therefore γ_{α} < 1 MeV, which is < 5% of the Wigner limit. A broad 4^{+} state is also observed near E_{α} = 51.3 MeV (E_{x} = 25.5 MeV). Over the range E_{α} = 30 to 70 MeV a gradual increase in δ_{6} is observed. Some indications of a 6^{+} state at E_{x} ≈ 28 MeV and of an 8^{+} state at ≈ 57 MeV have been reported; γ_{c.m.} ≈ 20 and ≈ 73 MeV, respectively. A resonance is not observed at the first T = 2 state, ^{8}Be*(27.49): see Table 8.5 (in PDF or PS). See (1979AJ01) for references. The elastic scattering has also been studied at E_{α} = 650 and 850 MeV [see (1979AJ01)] and at E_{α} = 158.2 MeV (1978NA16), as well as at 4.32 and 5.07 GeV/c (1980BE14). Total cross sections are reported at 0.87 and 2.1 GeV/c (1978JA16). Inclusive inelastic cross sections have been measured at 4.32 and 5.07 GeV/c (1981BA1Q, 1981DU08). Elastic and quasielastic cross sections are reported at 17.9 GeV/c (1980AB1C). At 31, 44, 88 and 125 GeV elastic (at the two higher energies) and inelastic collisions have been studied by (1982BE1T, 1982BE1X). For a study of excited states of ^{4}He see (1980KA20). The bremstrahlung cross section has been measured for E_{α} = 9.35 to 18.7 MeV: see (1974AJ01). See also (1978BR1A, 1978CH1C, 1981SY1A, 1982FA1B, 1982FA1F, 1982YA1A) and (1978SA24, 1978FI1D, 1978SC1B, 1978TA1A, 1979BA18, 1979DY03, 1979FE1B, 1979GH01, 1979LU1A, 1979SA08, 1979SA1E, 1980CH1R, 1980DY1A, 1980KO1M, 1980LI1K, 1980MA30, 1980RA1D, 1980RE1C, 1980SH1M, 1980SI1M, 1980TO1E, 1980VI01, 1980ZH1B, 1981DY02, 1981ER11, 1981FR1N, 1981KI03, 1981KR15, 1981LI1V, 1981SH1A, 1981SU1D, 1982AO1A, 1982AO06, 1982BA29, 1982DR1C, 1982FI16, 1982HA1M, 1982LE1G, 1982LI1G, 1982OR03, 1982SC16, 1982SH08, 1982TI1A, 1983BA1T, 1983BR1F, 1983FI1K, 1983HO1F, 1983KO14, 1983VI1D; theor.).
The yield of γrays to ^{8}Be*(17.64) [1^{+}; T = 1] has been measured for E_{d} = 6.85 to 7.10 MeV. A resonance is observed at E_{d} = 6962.8 ± 3.0 keV [E_{x} = 27495.8 ± 2.4 keV, γ_{c.m.} = 5.5 ± 2.0 keV]; γ_{γ} = 23 ± 4 eV [1.14 ± 0.20 W.u.] for this M1 transition from the first 0^{+}; T = 2 state in ^{8}Be, in good agreement with the intermediate coupling model: see Table 8.5 (in PDF or PS). See also (1979AJ01). [The energy at resonance, E_{d} is ≈ 6965 keV, based on the new Q_{m}.]
Yield curves and cross sections have been measured for E_{d} = 60 keV to 5.5 MeV and 12 to 17 MeV [see (1979AJ01)], for 48 to 170 keV (1982CE02; n_{1}γ; deduced S(E)), for 0.4 to 1.0 MeV (1979RU07; activation) and 1.3 to 11.9 MeV (1980GU26). Polarization measurements are reported at E_{d} = 0.27 to 3.7 MeV. Comparisons of the populations of ^{7}Be*(0, 0.43) and of ^{7}Li*(0, 0.48) have been made at many energies, to E_{d} = 7.2 MeV. The n/p ratios are closely equal for analog states, as expected from charge symmetry. See (1979AJ01) for references. See also ^{7}Be, (1979EL03) in reaction 10, and (1981HO1E).
Excitation functions have been measured for E_{d} = 30 keV to 5.4 MeV [see (1979AJ01)], for 36 to 170 keV (1981CE04; p_{0}, p_{1} [from 47 keV]) and for 100 to 180 keV (1979BO33; σ_{t}). An anomaly is observed in the p_{1}/p_{0} intensity ratio at E_{d} = 6.945 MeV, corresponding to the first 0^{+}; T = 2 state, γ = 10 ± 3 keV, γ_{p}_{0} « γ_{p}_{1}; γ_{p}_{0} < γ_{d}. Polarization measurements have been reported at E_{d} = 0.6 to 10.9 MeV: see (1979AJ01). See also ^{7}Li, (1974FI1D), (1979EL03, 1981HO1E), (1979SE04; theor.) and reaction 10.
The yield of elastically scattered deuterons has been measured for E_{d} = 2 to 7.14 MeV; no resonances are observed: see (1974AJ01). See also (1974FI1D) and (1979SE04, 1982LE10; theor.).
The cross section for tritium production rises rapidly to 190 mb at 1 MeV, then more slowly to 290 mb near 4 MeV: see (1974AJ01). See also ^{5}Li. For reaction (b) see ^{5}He.
Cross sections and angular distributions (reaction (a)) have been measured at E_{d} = 30 keV to 13.6 MeV [see (1979AJ01)], at 47 to 147 keV (1981GO19; σ_{t}), at 100 to 180 keV (1979BO33; σ_{t}) and at E(^{6}Li) = 10 to 31 MeV (1979WA02: 30° yield of α_{0} and α* to ^{4}He*(20.1)[0^{+}]). A critical analysis of the lowenergy data has led to a calculation of the reaction rate parameters for thermonuclear reactions for plasma temperatures of 2 keV to 1 MeV (1978CL07). See also (1981GO19). Polarization measurements are reported at E_{d} = 0.4 to 11.8 MeV and at E(^{6}Li) = 0.6 MeV [see (1979AJ01)], at E(pol. ^{6}Li) = 0.4 and 0.6 MeV (1981UL1A; TAP), at E_{pol. d} = 5.0 to 6.5 MeV and 8.0 to 10.0 MeV (1979RI03; VAP, TAP) and at E_{pol. d} = 7.92 MeV (1981KA21; analyzing powers at θ_{lab} = 65°). Pronounced variations are observed in the cross sections and in analyzing powers. Maxima are seen at E_{d} = 0.8 MeV, γ_{lab} ≈ 0.8 MeV and E_{d} = 3.75 MeV, γ_{lab} ≈ 1.4 MeV. The 4 MeV peak is also observed in the tensor component coefficients with L = 0, 4 and 8 and in the vector component coefficients: two overlapping resonances are suggested. At higher energies all coefficients show a fairly smooth behavior which suggests that only broad resonances can exist. The results are in agreement with those from reaction 4, that is with two 2^{+} states at E_{x} = 22.2 and 25.2 MeV and a 4^{+} state at 25.5 MeV. See also (1979EL03). A strong resonance is seen in the α* channel [to ^{4}He(20.1), J^{π} = 0^{+}] presumably due to ^{8}Be*(25.2, 25.5). In addition the ratio of the α*/α differential cross sections at 30° show a broad peak centered at E_{x} ≈ 26.5 MeV (which may be due to interference effects) and suggest a resonancelike anomaly at E_{x} ≈ 28 MeV (1979WA02). See also the discussion in (1974AJ01). A_{yy} = 1 points are reported at E_{d} = 5.55 ± 0.12 (θ_{c.m.} = 29.7 ± 1.0°) and 8.80 ± 0.25 MeV (θ_{c.m.} = 90.0 ± 1.0°) [corresponds to E_{x} = 26.44 and 28.87 MeV] (1979RI03). At E_{d} = 6.945 MeV, the α_{0} yield shows an anomaly corresponding to ^{8}Be*(27.49), the 0^{+}; T = 2 analog of ^{8}He_{g.s.}. See also (1979SO1A). An Rmatrix analysis of the very accurate differential and crosssection measurements by (1977EL09) for ^{6}Li(d, n), (d, p) and (d, α) [E_{d} = 0.1 to 1.0 MeV] has been presented by (1979EL03): nonnegligable direct and directcompound interference are present in the (d, n) and (d, p) processes. A kinematically complete study of reaction (b) has been reported at E_{d} = 1.2 to 8.0 MeV: the transition matrix element squared plotted as a function of E_{α}α* (the relative energy in the channel ^{4}He_{g.s.} + ^{4}He*(20.1)[0^{+}]) shows a broad maximum at E_{x} ≈ 25 MeV. Analysis of these results, and of a study of ^{7}Li(p, α)α* [see reaction 19] which shows a peak of different shape at E_{x} ≈ 24 MeV, indicate the formation and decay of overlapping states of high spatial symmetry, if the observed structures are interpreted in terms of ^{8}Be resonances (1978GE12, 1980CA13). Cross sections have been measured for reactions (b) [E_{d} = 117 to 772 keV] and (c) [E_{d} = 204 to 779 keV] (1979HO04). For reaction (d) see (1980LU1C). See also ^{6}Li, (1974AJ01, 1979AJ01) for earlier references, (1983KU1H; applied) and (1978FI1D, 1979SE04, 1980LE07, 1981KU1B; theor.).
Angular distributions have been reported at E(^{3}He) = 1.4 to 17 MeV [see (1974AJ01, 1979AJ01)] and in the range E(^{3}He) = 0.46 to 1.85 MeV (1980EL02; very accurate σ(θ); to ^{8}Be*(0, 3.0, 16.63, 16.92) and for the protons from reaction (b)) and E(pol. ^{6}Li) = 21 MeV (1983KO04; p_{0}). The population of ^{8}Be*(17.64, 18.15, 19.0, 19.4, 19.9) has also been reported: see (1974AJ01). Reaction (b) proceeds via ^{8}Be*(16.63, 16.92): γ = 117 ± 10 and 85 ± 10 keV, respectively. Interference effects are reported: see (1974AJ01). See also ^{9}B, (1978AL37, 1982LA20) and (1981DU1F; theor.).
Deuteron groups have been observed to ^{8}Be*(0, 3.0, 11.3 ± 0.4). Angular distributions have been measured at E_{α} = 15.8 to 48 MeV: see (1974AJ01, 1979AJ01). A study of reaction (b) shows that the peak due to ^{8}Be*(3.0) is best fitted by using γ = 1.2 ± 0.3 MeV. At E_{α} = 42 MeV the αα FSI is dominated by ^{8}Be*(0, 3.0). See also Table 8.4 (in PDF or PS) in (1974AJ01), (1983GO07) and (1978ZE03, 1980ZE05, 1982BE1K, 1982BE17, 1983BE1P; theor.).
At E_{max}(^{6}Li) = 13 MeV reaction (a) proceeds via ^{8}Be*(0, 3.0, 16.6, 16.9, 22.5). The involvement of a state at E_{x} = 19.9 MeV (γ = 1.3 MeV) is suggested. Good agreement with the shapes of the peaks corresponding to ^{8}Be*(16.6, 16.9) is obtained by using a simple twolevel formula with interference, corrected for the effect of finalstate Coulomb interaction, assuming γ(16.6) = 90 keV and γ(16.9) = 70 keV: see also Table 8.6 (in PDF or PS). The ratio of the intensities of the groups corresponding to ^{8}Be*(16.6, 16.9) remains constant for E(^{6}Li) = 4.3 to 5.5 MeV: I(16.6)/I(16.9) = 1.22 ± 0.08. Partial angular distributions for the α_{0} group have been measured at fourteen energies for E(^{6}Li) = 4 to 24 MeV. See (1979AJ01) for the references. At E(^{6}Li) = 36 to 46 MeV sequential decay (reaction (b)) via ^{8}Be states at E_{x} = 11.4, 16.9 and 19.65 MeV, with γ_{lab} = 7.8, 2.4 and 3.7 MeV [(Primarily experimental widths. I am grateful to Prof. F.C. Barker for calling this to my attention.)], and ^{8}Be*(3.0), is reported by (1979WA13). Reaction (c) has been studied at E(^{6}Li) = 36 to 47 MeV: enhancements in the yield have been observed in the yield of dd and αα but not of α  d. These enhancements are due to double spectator poles. Their widths are smaller than predicted from the momentum distribution of α + d clusters in ^{6}Li. The enhancements are not due to phase space, FSI, or the involvement of states in ^{4}He, ^{6}Li or ^{8}Be. The strengths of the DSP peaks suggest qualitatively that quasifree scattering is the basic mechanism producing the dd or αα detected pairs (1980WA10, 1981WA15). See also (1982WA07, 1983LA1J; theor.).
Cross sections and angular distributions have been reporteed from E_{p} = 30 keV to 18 MeV. Gamma rays are observed to the ground (γ_{0}) and the the broad, 2^{+}, excited state at 3.0 MeV (γ_{1}) and to ^{8}Be*(16.6, 16.9) (γ_{3}, γ_{4}). Resonances for both γ_{0} and γ_{1} occur at E_{p} = 0.44 and 1.03 MeV, and for γ_{1} alone at 2, 4.9, 6.0, 7.3, and possibly at 3.1 and 11.1 MeV. In addition broad resonances are reported at E_{p} ≈ 5 MeV (γ_{0}), γ ≈ 4  5 MeV, and at E_{p} ≈ 7.3 MeV (γ_{1}), γ ≈ 8 MeV: see Table 8.7 (in PDF or PS). The E_{p} ≈ 5 MeV resonance (E_{x} ≈ 22 MeV) represents the giant dipole resonance based on ^{8}Be(0) while the γ_{1} resonance, ≈ 2.2 MeV higher, is based on ^{8}Be*(3.0). The γ_{0} and γ_{1} giant resonance peaks each contain about 10% of the dipole sum strength. The main trend between E_{p} = 8 and 17.5 MeV is a decreasing cross section. At the E_{p} = 0.44 MeV resonance (E_{x} = 17.64 MeV) the radiation is nearly isotropic consistent with pwave formation, J^{π} = 1^{+}, with channel spin ratio σ(J_{c} = 2)/σ(J_{c} = 1) = 3.2 ± 0.5. Radiative widths for the γ_{0} and γ_{1} decay are displayed in Table 8.8 (in PDF or PS). A careful study of the αbreakup of ^{8}Be*(16.63, 16.92) [both J^{π} = 2^{+}] for E_{p} = 0.44 to 2.45 MeV shows that the nonresonant part of the cross section for production of ^{8}Be*(16.63) is accounted for by an extranuclear directcapture process. Resonances for production of ^{8}Be*(16.63, 16.92) are observed at E_{p} = 0.44, 1.03 and 1.89 MeV [^{8}Be*(17.64, 18.15, 18.9)]. The results are consistent with the hypothesis of nearly maximal isospin mixing for ^{8}Be*(16.63, 16.92): decay to these states is not observed from the 3^{+} states at E_{x} = 19 MeV, but rather from the 2^{} state at 18.9 MeV excitation. Squared T = 1 components calculated for ^{8}Be*(16.6, 16.9) are 40 and 60%, and 95 and 5% for ^{8}Be*(17.6, 18.2). The cross section for (γ_{3} + γ_{4}) has also been measured for E_{p} = 11.5 to 30 MeV (θ = 90°) by detecting the γrays and for E_{p} = 4 to 13 MeV (at five energies) by detecting the two αparticles from the decay of ^{8}Be*(16.6, 16.9): a broad bump is observed at E_{p} = 8 ± 2 MeV (1981MA33). The angle and energy integrated yield only exhausts 8.6% of the classical dipole sum for E_{p} = 4 to 30 MeV, suggesting that this structure does not represent the GDR built on ^{8}Be*(16.6, 16.9). A weak, very broad [γ ≳ 20 MeV] peak may also be present at E_{x} = 20  30 MeV. A directcapture calculation adequately describes the observed cross section (1981MA33). For earlier references see (1979AJ01). See also (1982SC1H; applications) and (1979BA1V; theor.).
Measurements of cross sections have been reported for E_{p} = 1.9 to 52 MeV [see (1974AJ01, 1979AJ01)] and at 60.1 to 199.1 MeV (1982WA02; activation σ). Polarization measurements have been reported at E_{p} = 2.05 to 5.5 MeV, 30 and 50 MeV: see (1974AJ01). The yield of groundstate neutrons (n_{0}) rises steeply from threshold and shows pronounced resonances at E_{p} = 2.25 and 4.9 MeV. The yield of n_{1} also rises steeply from threshold and exhibits a broad maximum near E_{p} = 3.2 MeV and a broad dip at E_{p} ≈ 5.5 MeV, also observed in the p_{1} yield. Multichannel scattering length approximation analysis of the 2^{} partial wave near the n_{0} threshold indicates that the 2^{} state at E_{x} = 18.9 MeV is virtual relative to the threshold and that its width γ = 50 ± 20 keV. The ratio of the cross section ^{7}Li(p, γ)^{8}Be*(18.9) γ/→ ^{8}Be*(16.6 + 16.9) to the thermalneutroncapture cross section ^{7}Be(n, γ)^{8}Be*(18.9) γ/→ ^{8}Be*(16.6 + 16.9), provides a rough estimate of the isospin impurity of ^{8}Be*(18.9): σ_{p}, γ/σ_{n}, γ ≈ 1.5 x 10^{5} and therefore the T = 1 isospin impurity is < 4% in intensity. See, however, (1979AJ01) and (1977BA62) who finds a 10% impurity. The structure at E_{p} = 2.25 MeV is ascribed to a 3^{+}, T = (1), l = 1 resonance with γ_{n} ≈ γ_{p} and γ^{2}_{n}/γ^{2}_{p} = 3 to 10: see (1966LA04). At higher energies the broad peak in the n_{0} yield at E_{p} = 4.9 MeV can be fitted by J^{π} = 3^{(+)} with γ = 1.1 MeV, γ^{2}_{n} ≈ γ^{2}_{p}. The behavior of the n_{1} cross section can be fitted by assuming a 1^{} state at E_{x} = 19.5 MeV and a J = 0, 1, 2, positiveparity state at 19.9 MeV [presumably the 20.1  20.2 MeV states reported in reaction 4]. In addition the broad dip at E_{p} ≈ 5.5 MeV may be accounted for by the interference of two 2^{+} states. See Table 8.9 (in PDF or PS). The total reaction cross section goes down exponentially from E_{p} = 23 to 199.1 MeV: see (1982WA02). See also ^{7}Be, (1977KO46, 1980AU02, 1982AB1D), (1979AJ01, 1982TA03), and (1979CH1C, 1979DU1A; applications).
Absolute differential cross sections for elastic scattering have been reported for E_{p} = 0.4 to 12 MeV and at 14.5, 20.0 and 31.5 MeV. The yields of inelastically scattered protons (to ^{7}Li*(0.48)) and of 0.48 MeV γrays have been measured for E_{p} = 0.8 to 12 MeV: see (1974AJ01). Polarization measurements have been reported at a number of energies in the range E_{p} = 0.67 to 155 MeV [see (1974AJ01, 1979AJ01)] and at 2.1 GeV/c (1979ZH1A). Anomalies in the elastic scattering appear at E_{p} = 0.44, 1.03, 1.88, 2.1, 2.5, 4.2 and 5.6 MeV. Resonances at E_{p} = 1.03, 3 and 5.5 MeV and an anomaly at E_{p} = 1.88 MeV appear in the inelastic channel. A phaseshift analysis and a review of the exisitng crosssection data show that the 0.44 and 1.03 MeV resonances are due to 1^{+} states which are a mixture of ^{5}P_{1} and ^{3}P_{1} with a mixing parameter of +25°; that the 2^{} state at a neutron threshold (E_{p} = 1.88 MeV) has a width of about 50 keV [see also reaction 16]; and that the E_{p} = 2.05 MeV resonance corresponds to a 3^{+} state. The anomalous behavior of the ^{5}P_{3} phase around E_{p} = 2.2 MeV appears to result from the coupling of the two 3^{+} states [resonances at E_{p} = 2.05 and 2.25 MeV]. The ^{3}S_{1} phase begins to turn postive after 2.2 MeV suggesting a 1^{} state at E_{p} = 2.5 MeV: see Table 8.10 (in PDF or PS). The polarization data show structures at E_{p} = 1.9 and 2.3 MeV. (1979AR10) have performed a phaseshift analysis of the (p, p) data: they find no indication of a possible 1^{} state with 17.4 < E_{x} < 18.5 MeV [see, however, reaction 15 in (1979AJ01)]. The absence of a 1^{} state in this E_{x} region indicates that the shellmodel residual interaction for negativeparity, S = 0, T = 0 states of ^{8}Be is deficient (1979AR10). An attempt has been made to observe the T = 2 state [^{8}Be*(27.47)] in the p_{0}, p_{1} and p_{2} yields. None of these shows the effects of the T = 2 state. Table 8.5 (in PDF or PS) displays the upper limit for γ_{p0}/γ. The inclusive cross section has been reported at E_{p} = 640 MeV (1981ER07). See also (1982AB1D), (1979AJ01) and (1979VE08, 1981BA36, 1983BA2H; theor.).
The excitation function for d_{0} measured for E_{p} = 11.64 to 11.76 MeV does not show any effect from the T = 2 state [^{8}Be*(27.47)]: see (1979AJ01). Poalrization measurements are reported at E_{p} = 200 and 400 MeV (1981LI1B) and 450 to 530 MeV (1981IR1A) [both prelim.]. See also (1979VE08; theor.).
The cross section follows the expression E^{1} e^{B√E(square root of E)}, with B = 91.5 ± 4.5 keV^{1/2}, in the range E_{p} = 23 to 50 keV. The cross section in that interval rises from 0.013 to 2.4 μb. Taking into account ^{8}Be J^{π} = 2^{+} levels at 16.7, 16.9 and 20.6 MeV, an Rmatrix fit for E_{p} = 131 to 561 keV leads to a quadratic energy dependence for the Sfactor: S = 0.065[1 + 1.82E  2.51E^{2}] MeV · b, over the energy range E_{p} = 0 to 600 keV. Excitation functions and angular distributions have been measured at many energies in the range E_{p} = 23 keV to 45.2 MeV [see (1979AJ01)] and at E_{p} = 47.8, 53.5, 58.5 and 62.5 MeV (1982BA1V). Polarization measurements have been carried out for E_{p} = 0.8 to 10.6 MeV [see (1974AJ01)]: in the range E_{p} = 3 to 10 MeV the asymmetry has one broad peak in the angular distribution at all energies except near 5 MeV; the peak value is 0.98 ± 0.04 at 6 MeV and is essentially 1.0 for E_{p} = 8.5 to 10 MeV. Broad resonances are reported to occur at E_{p} = 3.0 MeV [γ ≈ 1 MeV] and at ≈ 5.7 MeV [γ ≈ 1 MeV]. Structures are also reported at E_{p} = 6.8 MeV and at E_{p} = 9.0 MeV: see (1979AJ01). The 9.0 MeV resonance is also reflected in the behavior of the A_{2} coefficient. The experimental data on the yields and on polarization appear to require including two 0^{+} states [at E_{x} ≈ 19.7 and 21.8 MeV] with very small αparticle widths, and four 2^{+} states [at E_{x} ≈ 15.9, 20.1, 22.2 and 25 MeV]. See, however, reaction 4. A 4^{+} state near 20 MeV was also introduced in the calculation but its contribution was negligible. The observed discrepancies are said to be probably due to the assumption of pure T = 0 for these states. At E_{p} = 11.64 to 11.76 MeV the excitation function does not show any effect due to the T = 2 state at E_{x} = 27.47 MeV. See (1979AJ01) for references. A study of the ^{7}Li(p, α)^{4}He* reaction to ^{4}He*(20.1) [0^{+}] at E_{p} = 4.5 to 12.0 MeV shows a broad maximum at E_{x} ≈ 24 MeV: see reaction 10 (1978GE12, 1980CA13). See also (1981BA1R), (1975ZI1A, 1980PE1N; astrophysics) and (1978FI1D, 1979DO19; theor.).
The population of ^{8}Be*(0, 3.0, 16.6, 16.9, 17.6, 18.2, 18.9, 19.1, 19.2) has been reported in reaction (a). For the parameters of ^{8}Be*(3.0) see Table 8.4 (in PDF or PS) in (1974AJ01). Angular distributions of n_{0} and n_{1} have been reported at E_{d} = 0.7 to 3.0 MeV and at E_{d} = 15.25 MeV. The angular distributions of the neutrons to ^{8}Be*(16.6, 17.6, 18.2) are fit by l_{p} = 1: see (1974AJ01, 1979AJ01). Reaction (b) appears to proceed primarily via ^{8}Be*(3.0, 16.6, 16.9) and ^{5}He_{g.s.}: see (1974AJ01). However, ^{8}Be*(11.4) may also be involved [E_{x} = 11.4 ± 0.05 MeV, γ_{c.m.} = 2.8 ± 0.2 MeV] as many state(s) at E_{x} ≈ 20 MeV: see (1979AJ01). See also (1980NE1B), (1978BA1F; applied) and ^{9}Be.
See (1979AJ01).
Deuteron groups are observed to ^{8}Be*(0, 3.0, 16.6, 16.9, 17.6, 18.2). For the parameters of ^{8}Be*(3.0) see Table 8.4 (in PDF or PS) in (1974AJ01). For the J^{π} = 1^{+} mixed isospin states see Table 8.6 (in PDF or PS). Angular distributions have been measured for E(^{3}He) = 0.9 to 24.3 MeV [see (1974AJ01, 1979AJ01)] and at E(pol. ^{3}He) = 33.3 MeV (1981BA1P; to ^{8}Be*(16.6, 17.6, 18.2)). See also ^{10}B and (1982AR08).
Angular distributions have been measured to E_{α} = 50 MeV: see (1966LA04, 1974AJ01, 1979AJ01). The ground state of ^{8}Be decays isotropically in the c.m. system: J^{π} = 0^{+}. At E_{α} = 10 MeV an anomaly ("ghost") is observed at E_{x} ≈ 0.5 MeV. Sequential decay (reaction (b)) is reported at E_{α} = 50 MeV via ^{8}Be*(0, 3.0, 11.4, 16.6, 16.9, 19.9): see (1974AJ01). See also (1978ZE03, 1979ZE1B, 1980ZE05, 1982BE1K, 1983BE1P; theor.).
At thermal energies, the (n, p) cross section is (4.8 ± 0.9) x 10^{4} b (1981MUZQ), the (n, α) cross section is ≤ 0.1 mb and the (n, γα) cross section is 155 mb. See also (1974AJ01) and (1983BA2H; theor.).
See (1974AJ01).
^{8}Li decays mainly to the broad 3.0 MeV, 2^{+} level of ^{8}Be, which decays into two αparticles. Both the βspectrum and the resulting αspectrum have been extensively studied: see (1955AJ61, 1966LA04). See also ^{8}B(β^{+}). Studies of the distribution of recoil momenta and neutrinorecoil correlation indicate that the decay is overwhelmingly GT, axial vector [see reaction 1 in ^{8}Li] and that the ground state of ^{8}Li has J^{π} = 2^{+}: see (1980MC07). Betaα angular correlations have been measured for the decays of ^{8}Li and ^{8}B for the entire finalstate distribution: see Table 8.10 (in PDF or PS) in (1979AJ01). No evidence was seen for secondclass currents. Recently (1980MC07) have measured the β  ν  α correlations as a function of E_{x} in the decay of ^{8}Li and ^{8}B, detecting both αparticles involved in the ^{8}Be decay. They find that the decay is GT for 2 < E_{x} < 8 MeV. The absence of Fermi decay strength is expected because the isovector contributions from the tails of ^{8}Be*(16.6, 16.9) interfere destructively in this energy region: see (1980MC07). The results are consistent with the CVC predictions (1980MC07). See also (1978FO31), (1982BO1T) and (1979DE15, 1980OK01, 1981HO06; theor.).
The decay [see reaction 1 in ^{8}B] proceeds mainly to ^{8}Be*(3.0) [see Table 8.4 (in PDF or PS) in (1974AJ01) for its parameters]. Detailed study of the highenergy portion of the αspectrum reveals a maximum near E_{α} = 8.3 MeV, corresponding to transitions to ^{8}Be*(16.63), for which parameters E_{x} = 16.67 MeV, γ = 150 to 190 keV or E_{x} = 16.62 MeV, γ = 95 keV are derived. Log ft = 3.3. The energy distribution of the αparticles has been measured. Analysis of this data and of data from αα scattering in a threelevel Rmatrix formalism indicate a 2^{+} state of ^{8}Be at E_{x} = 12.0^{3.0}_{+3.5} MeV and γ = 14^{3}_{+4} MeV (a_{2} = 6.0 ± 0.5 fm): see (1974AJ01). For β^{+}α angular correlation studies see reaction 27. See also (1982BO1T).
Neutron groups to ^{8}Be*(0, 3.0) have been studied for E_{γ} = 18 to 26 MeV: see (1974AJ01, 1979AJ01) and ^{9}Be. Reaction (b) appears to proceed largely via excited states of ^{9}Be with subsequent decay mainly to ^{8}Be*(3.0): see (1966LA04, 1974AJ01), ^{9}Be and ^{10}Be. Reaction (c) has been studied at E_{p} = 45 and 47 MeV: the reaction primarily populates ^{8}Be*(0, 3.0): see (1979AJ01), ^{9}Be and ^{9}B. See also (1978JE01). For reactions (d) and (e) see (1974AJ01) and ^{9}Be. For reaction (e) see (1979AJ01).
Angular distributions are reported to ^{8}Be*(0, 3.0, 11.4) (unresolved) at E_{π+} = 50 MeV (1980BA43).
Angular distributions of deuteron groups have been reported at E_{p} = 0.11 to 185 MeV [see (1974AJ01, 1979AJ01)], 14.3 and 26.2 MeV (1981BE53; d_{0}, d_{1}; and see below), 18.6 MeV (1983BE1D; d_{0}) and 50 and 72 MeV (1982ZA1B; d_{0}, d_{1} and d) to ^{8}Be*(16.9 ± 17.6, 19.2). For spectroscopic factors see (1979AJ01). The angular distributions to ^{8}Be*(0, 3.0, 16.9, 17.6, 18.2, 19.1) are consistent with l_{n} = 1: see (1974AJ01) and (1982ZA1B). For spectroscopic factors see (1979AJ01). An anomalous group is reported in the deuteron spectra between the d_{0} and the d_{1} groups. At E_{p} = 26.2 MeV, its (constant with θ) E_{x} = 0.6 ± 0.1 MeV. Analyses of the spectral shape and transfer cross sections are consistent with this "ghost" feature being part of the BreitWigner tail of the J^{π} = 0^{+} ^{8}Be_{g.s.}: it contains < 10% of the g.s. transfer strength (1981BE53). See also (1981OV02). An analysis of reported γ_{c.m.} for ^{8}Be*(3.0) in this reaction shows that there is no E_{p} dependence: (1981BE53) report that the average γ_{c.m.} at E_{p} = 14.3 and 26.2 MeV is 1.47 ± 0.04 MeV. γ_{c.m.} = 5.5 ± 1.3 eV for ^{8}Be_{g.s.} and 5.2 ± 0.1 MeV for ^{8}Be*(11.4). Spectroscopic factors for ^{8}Be_{g.s.} (including the "ghost" anomaly) and ^{8}Be*(3.0) are 1.23 and 0.22, respectively, at E_{p} = 14.3 MeV, and 1.53 and 1.02, respectively, at E_{p} = 26.2 MeV (1981BE53). Studies of the width of ^{8}Be*(3.0) in this reaction and in reactions 32, 42, 47 and 51 are reported by (1981OV02): the width is not appreciably (< 10%) reaction dependent but the nearness of the decay threshold indicates that care must be taken in comparing decay widths from reaction and from scattering data. (1981OV02) find a mean E_{R} = 3130 ± 25 keV (resonance energy in the α + α c.m. system) [E_{x} = 3038 ± 25 keV] and γ_{c.m.} = 1.50 ± 0.02 MeV for ^{8}Be*(3.0): the corresponding observed and formal reaction widths and channel radii are γ^{2}_{R} = 580 ± 50 keV, γ^{2}_{λ} = 680 ± 100 keV and s = 4.8 fm. See (1979AJ01) for the earlier work. For reaction (b) [FSI through ^{8}Be*(0, 3.0)] see (1974AJ01) and (1982LA11; E_{p} = 30 MeV).
Angular distributions have been measured for E_{d} = 0.3 to 28 MeV: see (1979AJ01). At E_{d} = 27.97 MeV angular distributions of triton groups to ^{8}Be*(16.6, 16.9, 17.6, 18.2, 19.1, 19.2, 19.8) have been analyzed using DWUCK: absolute C^{2}S are 0.074, 1.56, 0.22, 0.17, 0.41, 0.48, 0.40 respectively. See also Table 8.6 (in PDF or PS). An isospin amplitude impurity of 0.21 ± 0.03 is found for ^{8}Be*(17.6, 18.2) (1977OO01). See also ^{9}Be(d, ^{3}He) [reaction 13] in ^{8}Li. For a study of the parameters of ^{8}Be*(3.0) see reaction 31 (1981OV02). A kinematically complete study of reaction (b) at E_{d} = 26.3 MeV indicates the involvement of ^{8}Be*(0, 3.0, 11.4, 16.9, 19.9 + 20.1): see (1974AJ01). See also (1982LA09).
Angular distributions have been measured in the range E(^{3}He) = 3.0 to 26.7 MeV and at E(pol. ^{3}He) = 33.3 MeV (to ^{8}Be*(16.9, 17.6, 19.2)) [S = 1.74, 0.72, 1.17, assuming mixed isopsin for ^{8}Be*(16.9)]. The possibility of a broad state at E_{x} ≈ 25 MeV is also suggested. See (1979AJ01) and Table 8.5 (in PDF or PS) here. Reaction (b) has been studied at E(^{3}He) = 2.9 to 10 MeV [see (1979AJ01)] and at 1.0 to 2.8 MeV (1978AR21, 1979BA27, 1981FA02, 1981FA07). The reaction has been reported to proceed via ^{8}Be*(0, 3.0, 11.4, 16.6, 16.9, 19.9, 22.5): see (1979AJ01) and (1978AR21, 1981FA07). In addition, observation of the quasifree reaction process is reported by (1981FA07). See also ^{9}Be and ^{12}C in (1980AJ01).
Angular distributions (reactions (c) and (e)) have been studied at E(^{12}C) = 12 and 15 MeV and E(^{16}O) = 11, 15 and 18 MeV (1970BA49). See also (1982HU06) for reaction (c). See (1979AJ01) for earlier references.
Angular distributions for the transition to the first T = 2 state ^{8}Be*(27.49), and to ^{8}Li*(10.82) reached in the (p, ^{3}He) reaction, are very similar. They are both consistent with L = 0 using a DWBA (LZR) analysis: see (1979AJ01). The particle decay of this state has been studied by (1979FR04): see Table 8.5 (in PDF or PS).
Using stopped pions, ^{8}Be states at ≈ 3 and ≈ 19 MeV are populated. The 19 MeV structure may be due to a superposition of three peaks at 17, 19 and 22 MeV: see (1979AJ01).
See (1979AJ01) and ^{11}B in (1980AJ01).
At E_{p} = 39.4 MeV angular distribution measurements have been carried out for the ^{3}He groups to ^{8}Be*(0, 3.0, 16.6, 16.9): see (1974AJ01).
Angular distributions have been reported at E_{d} = 0.5 to 7.5 MeV: see (1974AJ01, 1979AJ01). At E_{d} = 7.5 MeV the population of ^{8}Be*(16.63, 16.92) is closely the same consistent with their mixed isospin character while ^{8}Be*(17.64) is relatively weak consistent with its nearly pure T = 1 character. ^{8}Be*(16.63, 16.92, 17.64, 18.15) have been studied for E_{d} = 4.0 to 12.0 MeV. Interference between the 2^{+} states [^{8}Be*(16.63, 16.92)] varies as a function of energy. The crosssection ratios for formation of ^{8}Be*(17.64, 18.15) vary in a way consistent with a change in the population of the T = 1 part of the wave function over the energy range: at the higher energies, there is very little isospin violation. At higher E_{x} only the 3^{+} state at E_{x} = 19.2 MeV is observed, the neighboring 3^{+} state at E_{x} = 19.07 MeV is not seen. γ_{16.6} = 90 ± 5 keV, γ_{16.9} = 70 ± 5 keV, ΔQ = 290 ± 7 keV: see Table 8.6 (in PDF or PS). In reaction (b) at E_{d} = 13.6 MeV sequential decay is indicated via ^{8}Be*(0, 3.0, 11.4, 16.6 + 16.9, 19.9 + 20.2, 25.2, 27.4, 28.6) and possibly via a state with E_{x} = 15 MeV, γ = 1.0 ± 0.2 MeV (1981NE08). See (1974AJ01, 1979AJ01) for the earlier work, ^{12}C in (1980AJ01) and (1981DU1F; theor.).
At E_{α} = 27.2 MeV (1982DO1F) and 150 MeV (1981DE1C) angular distributions are obtained involving ^{8}Be*(0, 3.0) + ^{6}Li_{g.s.}. See also (1979AJ01) and ^{6}Li.
Angular distributions have been obtained at E(^{7}Li) = 24 MeV to ^{8}Be*(0, 3.0, 11.4): see (1979AJ01).
Angular distributions have been measured at E_{p} = 0.78 to 45 MeV [see (1974AJ01, 1979AJ01)] and at E_{p} = 125 to 498 keV (1979DA03; α_{0}) and 6 to 18 MeV (1983BU06; α_{0}, α_{1}). For the parameters of ^{8}Be*(3.0) see reaction 31 (1981OV02). Reaction (b) has been studied for E_{p} = 0.15 to 10.5 MeV [see (1974AJ01)] and at 20 MeV (1981LA07). The reaction proceeds predominantly by sequential twobody decay via ^{8}Be*(0, 3.0). See also ^{12}C in (1980AJ01), (1981HO13) and (1981DU1F; theor.).
For the decay of excited states of ^{12}C to ^{8}Be*(0, 3.0), see (1983NEZZ) and ^{12}C in (1985AJ01).
At E(^{3}He) = 25.6 MeV angular distributions have been obtained for the ^{6}Li ions to ^{8}Be*(0, 16.6, 16.9, 17.6). In the range E(^{3}He) = 25.2 to 26.3 MeV, the group to ^{8}Be*(18.2) [J^{π} = 1^{+}; T = 0] is not observed: its intensity is < 0.15 of the intensity to ^{8}Be*(17.6) [J^{π} = 1^{+}; T = 1]: see (1979AJ01).
At E_{α} = 27.2 MeV angular distributions involving ^{7}Li*(0, 0.48) and ^{8}Be_{g.s.} as well as the "ghost" state [see e.g. reaction 31] have been studied by (1983DO1F): the cross section for formation of the "ghost" state is anomalously large. See (1979AJ01) and ^{7}Li.
For reactions (a) and (b) see ^{12}C in (1975AJ02, 1980AJ01). For reaction (c) see (1979GI11).
These reactions involve ^{8}Be*(0, 3.0): see (1974AJ01, 1979AJ01), (1983AN02; reaction (a) at E_{n} = 10  35 MeV) (1981DE08; reaction (b) at E_{p} = 45 MeV) and ^{12}C in (1980AJ01). See also (1978GO14; theor.) and ^{13}C in (1981AJ01, 1986AJ01) and ^{13}N in (1981AJ01, 1886AJ01).
Angular distributions have been obtained at E_{d} = 12.7 to 51.8 MeV [see (1974AJ01, 1979AJ01)] and at E_{d} = 13.6 MeV (1981DO15; to ^{8}Be*(0) and to "ghost" anomaly), 54.25 MeV (1980YA02: to ^{8}Be*(0, 3.0, 11.4)). S_{α} = 0.79, 1.08, 1.27 for ^{8}Be*(0, 3.0, 11.4) [FRDWBA] (1980YA02). For the parameters of ^{8}Be*(3.0) see reaction 31 (1981OV02). For reaction (b) see (1979HE06). See also (1978BE1H) and (1983GA1J; theor.).
Angular distributions have been obtained at E(^{3}He) = 25.5 to 70 MeV [see (1979AJ01)] and at 41 MeV (1981LE01): ^{8}Be*(0, 3.0, 11.4, 16.6, 16.9, 17.6) have been populated. See also ^{7}Be.
This reaction has been studied up to E_{α} = 104 MeV: see (1979AJ01). Angular correlations involving ^{8}Be*(0, 3.0) have been studied at E_{α} = 90 MeV: S_{α} (PWIA) = 2.9 ± 0.4 and 2.8 ± 0.3, respectively; S_{α} (DWIA) for ^{8}Be_{g.s.} = 2.4 ± 0.4. Angular distributions at E_{α} = 65 MeV (reaction (b)) lead to S_{α} = 0.55 and 0.75 (DWBA) for ^{8}Be*(0, 3.0). ^{8}Be*(11.4) was also observed. Reaction (a) has also been studied at E_{α} = 65 MeV (1983YA01). See also (1981RU10), (1978BE1G), (1981BA20; theor.), ^{12}C in (1985AJ01) and ^{16}O in (1982AJ01).
Angular distributions involving ^{8}Be_{g.s.} + ^{13}C_{g.s.} have been reported at E(^{9}Be) = 20 to 22.9 MeV (1979BO06) and at E(^{12}C) = 10.5, 12.0 and 13.5 MeV (1982TA21).
Angular distributions involving ^{8}Be_{g.s.} + ^{16}O_{g.s.} have been reported at E(^{12}C) = 11.9 to 22 MeV (1980WA16, 1982TA21) and at ≈ 37 MeV (see (1979AJ01)). See also ^{16}O in (1977AJ02, 1982AJ01). For ^{8}Be*(3.0) see (1981OV02). See also (1979GO1C).
See reaction 20 in ^{20}Ne in (1983AJ01).
See ^{6}Li.
Angular distributions have been obtained at E(^{3}He) = 3.3, 5.0 and 5.8 MeV for the transition to ^{8}Be_{g.s.} + ^{8}Be_{g.s.}: see (1974AJ01). See also ^{16}O in (1982AJ01).
See (1979BE1J).
An angular distribution involving ^{8}Be_{g.s.} and ^{14}C_{g.s.} has been obtained at E(^{9}Be) = 28.8 MeV (1980BO21).
See (1980BE04, 1980BE15) and (1979AJ01).
See (1979SA1G).
