

^{8}Be (1966LA04)(See Energy Level Diagrams for ^{8}Be) GENERAL: See (1956KU1A, 1957FR1B, 1958WI1E, 1959BA1F, 1959BA1D, 1959BR1E, 1959WI1B, 1960BI1E, 1960KU05, 1960PE11, 1960PH1A, 1960PH1C, 1960TA1C, 1961BA1E, 1961CL10, 1961VA17, 1962IN02, 1962IN1A, 1962IW1A, 1963BR1N, 1963BU1C, 1963DA1C, 1963FR1G, 1963KU03, 1963MA1E, 1963MO1H, 1963NA1E, 1963SH1G, 1964AM1D, 1964BA1Y, 1964BE1N, 1964BE1M, 1964BR1H, 1964DA1G, 1964DU1D, 1964GR1J, 1964MA1G, 1964VO1B, 1965BA2H, 1965BE1H, 1965MA2B, 1965MA1G, 1965NE1C, 1965TR1B, 1965YU1D). See also Table 8.5 [Table of Energy Levels] (in PDF or PS).
The weighted mean of direct Q determinations to 1957 is Q = 94.1 ± 0.7 keV (1957VA11). Reported widths are 4.5 ± 3 eV (1956RU41), 6.8 ± 0.6 eV (1962BA1C), ≤ 3.5 eV (1956HE57), > 0.1 eV (1955TR03): see Table 8.8 (in PDF or PS). (1966BE05) find Q = 92.12 ± 0.05 keV, Γ = 6.8 ± 1.7 eV.
At E_{α} = 39 MeV, σ < 0.7 mb (1952WA31).
See ^{7}Li.
Reported differential cross section measurements are cited in Table 8.7 (in PDF or PS). The course of the derived phase shifts with increasing energy from E_{α} = 0.15 to 120 MeV is exhibited in (1956RU41, 1958NI05, 1960JO03, 1963TO02, 1965DA1A). The swave phase shift, δ_{0}, decreases smoothly from 180° at 0.3 MeV. The absence of measurable effects in the range E_{α} = 0.15 to 0.2 MeV yields an upper limit of 3.5 eV on the width of the ground state (1956HE57). Analysis of the 0  6 MeV data leads to Γ(g.s.) = 4.5 ± 3 eV (1956RU41), 6.8 ± 0.6 eV (1962BA1C): see Table 8.8 (in PDF or PS). The dwave phase shift becomes appreciable for E_{α} > 2.5 MeV and passes through resonance at E_{α} = 6 MeV (J = 2^{+}, E_{x} = 3.18 MeV, Γ = 1.5 MeV). The gwave shift rises from E_{α} ≈ 11 MeV and indicates a broad J^{π} = 4^{+} level at E_{x} = 11.4 MeV. The l = 6 and l = 8 phase shifts become active above E_{α} ≈ 30 and 50 MeV respectively. Dispersion formula fits are somewhat unsatisfactory, but indicate J^{π} = 6^{+} and 8^{+} levels at E_{x} ≈ 28 and ≈ 57 MeV respectively. Both the excitation energies and the reduced widths for all five levels are approximately proportional to J(J + 1) (1965DA1A). Sharp oscillations in the excitation functions at 15° and 45° are observed corresponding to ^{8}Be*(16.6) and (16.9). Since no oscillations were observed at 27.8°, these states are assigned J^{π} = 2^{+} (1964SH19). Optical model analysis of α  α scattering is discussed by (1960IG02, 1965DA1A); analysis in terms of twonucleon forces is given by (1959VA1F, 1961SC1B). See also (1959BU07, 1959WI1F, 1960BI1E, 1961GO1T, 1961SH1F, 1962IG1B, 1962SH1F, 1963WI1H, 1964EN1C, 1965OK1B).
Not observed: (1953SA1A, 1954SI07).
The yield curve has been measured for E_{d} = 0.06 to 5.5 MeV (1952BA64, 1954HI34, 1956NE13, 1957SL01). A broad swave resonance is indicated at E_{d} = 0.41 MeV, Γ = 0.45 MeV (1952BA64, 1956NE13). The forward cross section rises from ≈ 22 mb/sr at E_{d} = 1.1 MeV to ≈ 57 mb/sr at 5.5 MeV without sharp resonances (1957SL01). Above E_{d} = 0.6 MeV, angular distributions indicate a strong admixture of stripping process (1956NE13). Comparison of the yields n_{0}/n_{1} (^{7}Be(0) and ^{7}Be*(0.43)) and p_{0}/p_{1} (^{7}Li(0) and ^{7}Li*(0.48)) over the energy range E_{d} = 0.4 to 3.2 MeV shows that the angular distributions are closely similar for n and p. The yield ratios are also closely equal over this range, consistent with the assumption of charge symmetry. The ratio n_{0}/n_{1} increases rapidly as E_{d} falls below 0.8 MeV, suggesting a change in the reaction mechanism there (1957WI24, 1963BI27, 1963CR08).
Cross sections and angular distributions have been measured for E_{d} = 30 keV to 5.4 MeV ( 1959AJ76, 1963BI27, 1963ME09, 1964PA06). A broad maximum near E_{d} = 1.0 MeV is interpreted as indicating a level at E_{d} = 0.4 MeV (1950WH02). In the range E_{d} = 1 to 5 MeV there is evidence for both direct interaction and compound nucleus formation (1963BI27, 1963ME09, 1964PA06): at back angles the (d, p_{1}) data show evidence of the E_{d} = 3.7 MeV resonance (see ^{6}Li(d, α)^{4}He). See also ^{6}Li(d, n)^{7}Be and (1964FE01).
Excitation functions have been measured for E_{d} = 2 to 4.8 MeV; they do not show any clear resonance behavior (1964PA06). See also ^{6}Li.
The cross section for tritium production rises rapidly to 190 mb at 1 MeV, then more slowly to 290 mb near 4 MeV. There is evidence of deviation from isotropy near 0.4 MeV (1955MA20). See also ^{5}Li.
See ^{5}He.
Cross sections and angular distributions have been measured for E_{d} = 0.03 to 12 MeV (1948HE01, 1950WH02, 1962HA15, 1962JE02, 1963AN10, 1963ME09, 1964MA2D, 1964PA06, 1965MA13). Maxima are observed at E_{d} = 0.8 MeV, Γ_{lab} ≈ 0.8 MeV, and E_{d} = 3.75 MeV, Γ_{lab} ≈ 1.4 MeV. Analysis of the angular distributions in terms of twolevel interference favors J^{π} = 2^{+} for the upper level, and J^{π} = 0^{+} or 2^{+} for the lower (1963ME09, 1964PA06). The upper level appears to have a large deuteron width, θ^{2}_{d} ≈ 0.2, and small θ^{2}_{α} ≈ 0.025 and θ^{2}_{p} < 0.005 (1964PA06). A more elaborate analysis appears to require that both levels, E_{x} = 22.54 and 25.23 MeV, have J^{π} = 2^{+} and that a third broad J^{π} = 0^{+} level exist at E_{x} = 24.02 MeV (1965FR02): see Table 8.10 (in PDF or PS). The same parameters give a good account of the data up to E_{d} = 9.5 MeV. There is no evidence of further resonances (1965MA13). See also (1959HA29, 1960HA14, 1963EL1D, 1963FR1G, 1964FE01).
At E(^{3}He) = 1.2 to 2 MeV, proton groups are reported corresponding to ^{8}Be(0), ^{8}Be*(2.9) and possibly ^{8}Be*(12.3) (1956MO19, 1956SC01). At E(^{3}He) = 3.5 to 4.2 MeV, groups with Q = 0.163, 0.143 and 0.854 MeV (± 10 keV) are observed, corresponding to the 16.6, 16.9 and 17.6 MeV states (1961ER01): see Table 8.11 (in PDF or PS). The differential cross sections for groundstate protons show backward peaking at E(^{3}He) = 5, 6 and 7 MeV, forward peaking at E(^{3}He) = 13 and 17 MeV, and both forwards and backward peaks in the intermediate region (1963MA02). Analysis of the angular distribution of protons leading to the E_{x} = 16.6 MeV level indicates stripping, with L = 0 and a large deuteron width (1963MO1K, 1964MO1L). See also (1963WE1B, 1965KA1F, 1965RO1R, 1965YO1D).
At E_{α} = 43 MeV, deuteron groups corresponding to ^{8}Be(0) and ^{8}Be*(2.9) are reported (1959ZE1A); at E_{α} = 48 MeV, an additional group ascribed to ^{8}Be*(11.3 ± 0.4) is observed (1962CE01). Angular distributions of d_{0} and d_{1} show forward peaking, with that of d_{0} exhibiting pronounced oscillatory characteristics. Attempts to fit the observations with direct interaction theory are only moderately successful (1959ZE1A, 1962CE01). See also (1959ST30, 1962KO13, 1963BL20, 1963DE1G, 1963DE29, 1963WE1B, 1964DE1K).
In addition to αgroups to the ground and 2.9 MeV states, there is evidence for a cluster reaction mechanism in which ^{6}Li combines with a deuteron cluster to produce a state of ^{8}Be at 20.95 ± 0.3 MeV, Γ = 3.4 MeV. At E(^{6}Li) = 1.9 MeV, the cross section is 1.3 mb, or 23 times that for groundstate alpha particles (1963KA20). On the other hand (1964QU01) find that the αparticle spectrum is consistent with the involvement of a ^{8}Be level near 22 MeV, with Γ ≈ 0.4 MeV. See also (1962CO05). The ^{8}Be state decays by proton and α emission: Γ_{p}/Γ_{α} = 1.64 (1962GA21). At E(^{6}Li) = 3.2 MeV, alpha groups corresponding to ^{8}Be* = 16.6, 16.9, (17.6), 18.15 MeV are reported (1964CA1G). See also (1960SH01, 1962CO21, 1963LE19, 1963TA1B, 1964GA1E, 1964SH05, 1965MA2A, 1965NO1A).
Cross sections and angular distributions have been reported from E_{p} = 30 keV to 14.5 MeV. Two γrays are observed, γ_{0} to the ground state and γ_{1} to the broad, 2^{+}, excited state at 2.9 MeV: E_{γ} = (17.2, 14.3) + 7/8 E_{p}. 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 MeV (see, however, (1963PE15)): see Table 8.12 (in PDF or PS). In the range E_{p} = 2.5 to 9 MeV, broad resonances are reported at E_{p} ≈ 5 MeV (γ_{0}), Γ ≈ 5 MeV (1959GE33, 1963MI08, 1963PE15 (Γ = 5.5 MeV)), at E_{p} ≈ 7.3 MeV (γ_{1}), Γ ≈ 8 MeV, and possibly at E_{p} ≈ 6 MeV (γ_{1}). The E_{p} ≈ 5 MeV resonance (E_{x} ≈ 21.6 MeV) is presumed to represent the giant dipole resonance based on ^{8}Be(0), while the γ_{1} resonance, 2.0 ± 0.5 (1963MI08), 3 ± 0.5 MeV (1963RE09) higher is similarly related to ^{8}Be*(2.9). Angular distributions from E_{p} = 2.0 to 7.5 MeV are approximately isotropic (except at 2.59 MeV), suggesting l = 0 capture (1963MI08, 1963PE15). The integrated (γ, p) cross section, determined by reciprocity is 22 ± 4 MeV · mb (1963RE09), 20 MeV · mb (1964TA05). See also (1965TA1E). Angular distributions near the E_{p} = 0.44 MeV resonance show strong cos θ interference terms which vanish at resonance. At resonance the radiation is nearly isotropic, consistent with pwave formation, J^{π} = 1^{+}, with channel spin ratio σ(J_{c} = 2)/σ(J_{c} = 1) = 5. A detailed study of the angular distributions of γ_{0} and γ_{1} yields a small cos^{2}θ term for γ_{0}: A_{2} = 0.067 ± 0.025 (1961ME10), A_{2} = 0.028 ± 0.003 (1958NE17, 1961BR02), while γ_{1} is isotropic: A_{2} = 0.004 ± 0.008 (1961ME10); see, however, (1958NE17, 1961BR02). Analysis of these data together with γα correlations leads to Γ(E2)/Γ(M1) for γ_{1} = 0.018 ± 0.009 (1961ME10), 0.044 ± 0.014 (1960GR21). With Γ_{γ} = 25 eV, one obtains Γ(γ_{0}) = 16.7 eV, Γ(γ_{1}, M1) = 8.15 ± 0.07 eV, Γ(γ_{1}, E2) = 0.15 ± 0.07 eV. The observed E2 strength is about 15 times smaller than predicted by intermediate coupling shell model (1961ME10). See (1957KU58). The channel spin mixture σ(2)/σ(1) is 3.2 ± 0.5 (1961ME10), 4.1 ± 0.1 (1958NE17). The relative intensity of γ_{0}/γ_{1} at resonance is 2.0 (1961ME10), 2.3 ± 0.04 (1960MA23: θ = 90°), 1.8 ± 0.2 (1963BA58); the ratio falls rapidly above resonance and is approximately constant at 0.54 ± 0.08 for E_{p} = 0.8 to 1.0 MeV (1960MA23: see also (1961BR02)). There is evidence for an increase in the ratio at E_{p} = 1.03 MeV (1964SC19). At E_{p} = 5.4, 6.5, 7.5 and 8.6 MeV, the ratios are 0.5 ± 0.07, 0.3 ± 0.04, 0.2 ± 0.04 and 0.2 ± 0.04, respectively (1964TA05). Angular distributions in the range E_{p} = 0.2 to 1.1 MeV indicate interference with swave and dwave nonresonant radiation (1960MA33: see also (1961BR02)); at E_{p} = 1.03 MeV the resonant radiation is isotropic, suggesting pwave, J = 1^{+}, σ(2)/σ(1) = 5 (1960MA33). Angular distributions from E_{p} = 0.8 to 1.7 MeV appear to require interference of the E_{p} = 0.44 and 1.03 (1^{+}) MeV levels with at least two oddparity levels, possibly those at E_{p} = 2.1 and 5.8 MeV (1964SC19). A pairspectrometer measurement yields E_{γ} = 17.647 ± 0.015 MeV for γ_{0} at the E_{p} = 440 keV resonance: from the spectrum of γ_{1} an excitation energy of E_{x} = 2.6 ± 0.15, Γ = 0.7 ± 0.1 MeV is obtained for the first excited state (1963BA58). See Table 8.9 (in PDF or PS). At E_{p} = 440 keV, αparticles from ^{8}Be*(16.63) are observed, indicating the existence of the γtransition ^{8}Be*(17.64 → 16.63). The total resonant cross section is 6.45 ± 0.7 μb (1965WIZZ). The coincidence spectrum at resonance shows the 1.02 MeV γray (17.64 → 16.63), and a weak branch (5.9 ± 2)% (1965WI07), (7.5 ± 2)% (1965KO05), to the 16.92 MeV state. There is no indication of resonance in the yield of αparticles from ^{8}Be*(16.6) at E_{p} = 1.03 MeV (1965WI07). Evidence from this and other reactions involving ^{8}Be*(16.6) and (16.9) indicates that neither has a pure isospin character (1965KO05, 1965MA1G). See also (1964PA13). A careful study of γ  α coincidence spectra at E_{p} = 441 keV reveals only the 2.9 MeV level in the range E_{x} = 2 to 7 MeV; the αspectra can be matched with a singlelevel dispersion formula with E_{λ} = 5.95 MeV, γ^{2}_{α} = 11.9 MeV · fm, θ^{2} = (1.7), R = 4.48 fm (1960GE07). A report of other γ  α groups by (1962CA13) is ascribed to contamination (1964MA25, 1964MI10, 1964PR04, 1964WE1C). For a review of earlier work, see (1959AJ76). See also (1960SI10, 1960SI1D, 1963FE03, 1963SC1N, 1963TR08)
This reaction is widely used as a source of monochromatic neutrons: see summary by (1960GI1A). The threshold is E_{p} = 1880.36 ± 0.22 keV (1963MA1R: see ^{7}Be); a second threshold, for neutrons leading to ^{7}Be*(0.43), occurs at E_{p} = 2376 ± 2 keV (1960MA1G), and above E_{p} = 7 MeV, neutrons corresponding to ^{7}Be*(4.55) may be produced (1963BO06). Reaction cross sections and angular distributions have been reported by (1948TA16: to 2.55 MeV), (1964BU08: 2.4 to 3.0 MeV; n_{1}), (1957NE22, 1958MA07: to 5.5 MeV), (1959GA08: to 3.25 MeV), (1961BE05: 2.6 to 4.2 MeV; n_{0} and n_{1} groups separately), (1961NI04: 2.7 to 3.5 MeV), (1963BO06: 3 to 13 MeV; n_{0}, n_{1}, n_{2}), (1964BA16: 4 to 14 MeV) and by (1960HI04: 8 to 14 MeV; n_{0}, n_{1}, n_{2}). See also (1959AJ81, 1960GI1A, 1962AU01, 1963PA1K). The yield of ground state neutrons (n_{0}) rises steeply from threshold and shows pronounced resonances at E_{p} = 2.25 (σ ≈ 0.57 b) and 4.9 MeV (σ ≈ 0.36 b) (1963BO06). The yield of n_{1} also rises steeply from threshold (1964BU08) and exhibits a broad maximum near E_{p} = 3.5 MeV (1961BE05). The behavior of the cross section near the n_{0} threshold indicates a broad resonance with J^{π} = 2^{}, T = (0), (l = 0) at E_{p} = 1.9 MeV with γ^{2}_{n}/γ^{2}_{p} ≈ 5.0 (Table 8.13 (in PDF or PS)). 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 (1957NE22, 1958MA07, 1959WE1A, 1960GI1A, 1961BE05). The broad peak at 4.9 MeV can be fitted by J^{π} = 3^{(+)} with Γ = 1.1 MeV, γ^{2}_{n} ≈ γ^{2}_{p} (1963BO06). An additional resonance at E_{p} = 3.0 MeV may be indicated (1957NE22, 1961BE05). The behavior of the n_{1} cross section can be fitted in terms of a single level with J^{π} = 1^{} at E_{p} = 3.55 MeV (1964BU08). Polarization of the neutrons has been measured by (1961DA04, 1962EL01: 2.0 to 2.4 MeV), (1959CR84: 3.5 to 5 MeV), (1961AU02: 2 to 3 MeV), (1965MO1L: 3.1 to 3.3 MeV), (1965AN09: 3.0 to 4.0 MeV), (1959BA34, 1960BA27: 3 to 6 MeV), (1963MI01, 1963MI06, 1963MI20, 1964MI14: 4 to 5 MeV), (1962BE11: 4 to 10 MeV) and others (1959AJ76, 1963HA1G). Dominant effects are ascribed to the narrow 3^{+} level at E_{p} = 2.25 MeV and a broad 2^{} background level. At least one level is needed near threshold, and at the higher energies (E_{p} > 2.6 MeV) two additional levels are indicated (1961AU02). Neutron spectra and polarizations have been measured at E_{p} = 143 MeV by (1962BO33, 1963BO1N). Some contribution from quasifree scattering is indicated: see (1963VA1C, 1965VA23).
Absolute differential cross sections are reported for E_{p} = 0.4 to 12 MeV (1953WA27, 1956MA12, 1965GL03) and for E_{p} = 14.5, 20.0 and 31.5 MeV by (1956KI54). Anomalies appear at E_{p} = 0.44, 1.03, 1.88, 2.1, 2.5, 4.2 and 6.0 MeV (see Table 8.14 (in PDF or PS)). Both the 0.44 and 1.03 MeV resonances are ascribed to pwaves, J = 1^{+}, with channel spins 1 and 2 in a ratio of 1 to 5 (1953CH1A, 1955LI1B: compare ^{7}Li(p, γ)^{8}Be). The structure at E_{p} = 2.1 MeV may indicate a state with J^{π} ≤ 3^{+} (1956MA12), 3^{} (1957NE22). The E_{p} = 4.2 MeV resonance is ascribed to an almost pure singleparticle level in ^{8}Be at 20.9 MeV (1965GL03). The polarization of 14.5 and 40 MeV protons scattered from ^{7}Li has been studied by (1962RO20) and (1963HW01). See also (1961RO20). See also (1961JO17, 1961JO18, 1965AN12) and (1959AJ76).
A pronounced resonance appears in the yield of inelastically scattered protons (1951BR10, 1954MO04) and 0.48 MeV γrays (1954KR06) at E_{p} = 1.03 MeV (see Table 8.14 (in PDF or PS)); it is an s or pwave resonance interfering with a nonresonant wave of opposite parity (1954MO04: see also (1955LI1B)). Excitation functions for the proton group to the 0.48 MeV state have been measured for E_{p} = 2.3 to 12 MeV: a peak is observed at 5.6 MeV (1965GL03). See also (1964FA08). The yield of 0.48 MeV γrays rises smoothly from E_{p} = 1.5 to 3.0 MeV except for a pronounced cusp at 1.881 MeV (1955HA34, 1957NE22). See also (1962CA13).
See ^{6}Li.
See ^{5}Li.
Excitation functions and angular distributions have been reported by (1962LU01: 0.4 to 3.3 MeV), (1948HE01: 0.5 to 3.8 MeV), (1958CO62: 0.1 to 0.6 MeV), (1963SA10: 3.0 to 5.5 MeV), (1962CA12: 1.5 to 4.8 MeV), (1960AL18: 12 MeV), (1961HA27: 2.8 to 12 MeV), (1962TE04, 1962TE07: 3.3 to 6.6 MeV), (1964MA51: 4 to 12 MeV), (1962MA40: 15, 18.6 MeV) and (1962CA13, 1963CA1K: 0.5 to 2.5 MeV; see, however, (1964MA25, 1964MI10)). Polarization effects have been studied by (1964AN08: 0.5 to 2.0 MeV), (1962BE14: 1 to 3.2 MeV), (1964AS04: 2 to 3.5 MeV), (1965BO07: 3.2 to 5.3 MeV). A broad resonance occurs at E_{p} = 3.0 MeV, Γ ≈ 1 MeV, σ_{max} ≈ 90 mb (1948HE01): see Table 8.15 (in PDF or PS). A second prominent peak appears at E_{p} = 5.6 MeV, Γ ≈ 1 MeV (1961HA27, 1962TE04, 1964MA51). Some structure is reported near E_{p} = 6.0 to 6.5 MeV, and a further peak occurs at E_{p} = 9.0 MeV (1964MA51). An earlier suggestion that a J = 0 resonance near E_{p} ≈ 0 is involved appears to be contradicted by polarization data (1962BE14). The states at E_{x} = 19.9 MeV and 22.1 MeV (E_{p} = 3.0 and 5.5 MeV resonances) appear to have J = 2^{+} (1959AJ76, 1961HA27, 1962TE04, 1962TE07, 1965FR02) and to have ^{6}Li + d parentage (1962TE01, 1965FR02). Levels at E_{x} = 23 MeV (E_{p} = 6.5 MeV) and 25.2 MeV (E_{p} = 9.0 MeV) are assigned J^{π} = 4^{+} and 2^{+}, respectively (G. Temmer, private communication). See also (1960BO13, 1962PE20, 1962WE13, 1963AN09, 1964MA2D).
For E_{d} = 3.6 to 7.3 MeV, neutron timeofflight spectra indicate states in ^{8}Be at 0, 2.9, 16.64 ± 0.015, 16.9 ± 0.05, 17.64 and 18.15 MeV. Angular distribution of neutrons corresponding to the 16.6, 17.6 and 18.15 MeV states are strongly forward; l_{n} = 1 for the 16.6 MeV state, consistent with J = 2^{+} (1960DI02). At E_{d} = 2 MeV, recoil proton spectra show only the ground state and E_{x} = 2.9 MeV groups; in the range E_{x} < 9 MeV, no others appear with intensity > 10% of the groundstate group. The spectrum yields E_{x} = 3.1 ± 0.1, Γ = 1.75 ± 0.1 MeV; comparison with the shape calculated from known α  α phase shifts suggest a considerable contribution of threebody processes (1964JO04). Reported slow neutron thresholds are listed in Table 8.16 (in PDF or PS). See also (1964JO1D, 1964JO1F, 1965DI1F). Alphaparticle spectra indicate groups corresponding to the break up of ^{8}Be*(16.6) and (16.9) (1963BI22, 1963PA04, 1964GL03). Alpha particles attributed to ^{8}Be*(11.4) are also reported (1963PA04). In the range E_{x} = 15.0 to 18.5 MeV, no αemitting states other than the 16.6 and 16.9 MeV levels are observed (1964GL03). See also (1965BI1F, 1965JO19, 1965MA1G, 1965MA1K). A large number of additional states with E_{x} < 16.1 MeV has been suggested in addition to ^{8}Be*(0, 2.9, 11.4): for a listing of early references, see (1959AJ76, 1964JO04). See also (1958CA1E, 1960AG03, 1960JU04, 1963MI1M, 1964MI1J).
At E(^{3}He) = 24.3 MeV, angular distributions of deuterons corresponding to the ground and first excited states of ^{8}Be have been measured (1963WE1B). At E(^{3}He) = 9 to 10 MeV, excitation of ^{8}Be*(17.6) is observed (1965GR08). See also (1964DU1E).
The angular distributions of the tritons to the ground state of ^{8}Be have been determined at a number of energies up to 48 MeV; the distributions indicate strong contribution of direct interaction (1959ST1B, 1960GO04, 1960MA15, 1960VL03, 1962MA59, 1963WE1B). At E_{α} = 40 MeV, higher states are also observed (1960VL03).
At thermal energies, the (n, p) cross section is (5.1 ± 0.6) × 10^{4} b (1955HA34), the (n, α) cross section is ≤ 0.1 mb (1962BA1B, 1963BA34) and the (n, γα) cross section is 155 mb (1963BA34). These observations are consistent with odd parity of ^{7}Be; the small value of σ(n, α) leads to an estimated F^{2} < 4 × 10^{10} for the intensity of a positive parity admixture (1963BA34). Comparison of the thermal cross section for reaction (a) with the (p, n) cross section observed in the inverse reaction supports the assignment J = 3/2 for ^{7}Be(0) (1957NE22). See also (1959AJ76).
For E_{d} = 0.8 to 1.7 MeV, proton groups are observed corresponding to the ground state and the 2.9 MeV level: Γ(2.9) = 1.6 ± 0.4 (1959SP1A), 1.53 ± 0.04 MeV (1960KA17). A dispersion formula fit yields parameters E_{x} = 2.90 ± 0.06 MeV, γ^{2} = 0.60 MeV, θ^{2} = 0.64, R = 5.75 fm (1960KA17): see Table 8.9 (in PDF or PS).
^{8}Li decays mainly to the broad 2.9 MeV, 2^{+} level of ^{8}Be, which decays into two αparticles. The βspectrum, which extends to ≳ 14 MeV, has been studied by (1950HO01), (1960FA02) and others, while the αspectrum, extending to ≈ 10 MeV, has been reported by (1938RU01, 1948BO20, 1955FR29, 1960BI10, 1960BI06, 1960FA04, 1961DE1E) and others: see (1955AJ61). The two spectra correspond well, except perhaps for low βenergies (1960GR10). For E_{α} ≲ 5 MeV, the spectrum is closely matched by a densityofstates derived from the experimental dwave phase shift of α  α scattering; at higher energies, an increasing excess of αparticles appears which may reflect transition into the tail of the J^{π} = 2^{+} level at E_{x} = 16.67 MeV (1960GR10, 1963AL19, 1963DA05). See also ^{8}B(β^{+}). Studies of the distribution of recoil momenta and neutrinorecoil correlation indicate that the decay is at least 90% GT, and that the GT portion is at least 90% axial vector. The observations indicate J = 2^{+} for ^{8}Li (1958BA1E, 1958LA08, 1959LA11, 1959LA05). The angular correlations W(θ_{βα}) have been measured for the decays of ^{8}Li and ^{8}B as a test of the conserved vector current theory of βdecay. The observed correlation is of the form W(θ) = 1 + Acos θ + Bcos^{2}θ; reported values of A and B are listed in Table 8.17 (in PDF or PS). With shell model calculations of the matrix element Γ_{γ}(M1) for ^{8}Be*(T = 1) → ^{8}Be*(2.9 MeV), the CVC theory predicts δ ≡ B(^{8}Li)  B(^{8}B) = (7 ± 2) × 10^{3} W_{β} (1960KU05, 1960WE1A); conversely, if CVC is assumed correct, the experiment yields Γ(M1) = 1.9 ± 0.6 eV (1962NO02). See also (1963IS04). See also (1958KE1B, 1959JA1B, 1960NO01, 1960NO05, 1960ST23, 1961FO1C, 1963DA05, 1963HU1G, 1963LE1K, 1964TO1D).
The decay proceeds mainly to ^{8}Be*(2.9). The α and β spectra correspond closely to those of ^{8}Li, when account is taken of the different Qvalues (1960FA04). The ratio ft(^{8}B)/ft(^{8}Li) = 1.096 (1964TO1D). Detailed study of the high energy portion of the αspectrum reveals a maximum near E_{α} = 8.3 MeV, corresponding to transitions to ^{8}Be*(16.62). The observed shape is reproduced with a BreitWigner densityofstates function with parameters E_{x} = 16.67 MeV, Γ = 150 to 190 keV; parameters E_{x} = 16.62, Γ = 95 keV are less good, but acceptable. With the former set, log ft = 2.9 (using τ_{1/2} = 0.774 ± 0.005 sec); with the latter, log ft = 3.03. In either case, the low ftvalue supports the identification T = 1, J = 2^{+} for ^{8}Be*(16.63) (1964MA35). See, however, (1965MA1G). See also (1960FA02, 1960GR10, 1963DI17) and see ^{8}Li(β^{})^{8}Be for a discussion of the work on β  α angular correlations.
For reaction (a), see ^{9}Be. The (n, 2n) reaction appears to proceed largely via excited states of ^{9}Be, with subsequent decay to ^{8}Be, mainly ^{8}Be*(2.9) (1959CH1E, 1961MY01, 1963JE05, 1964BO31): see ^{9}Be and ^{10}Be. For reaction (c), see (1962ST12) and ^{9}Be. See also (1959WI41, 1960KO1G, 1961JE01, 1962CU05, 1965LO1K).
At E_{p} = 5.2 MeV, the αspectrum shows a sharp groundstate group α_{0}, and a broad group, α_{1}, corresponding to ^{8}Be*(2.9). A pronounced anomaly appears at E_{x} ≈ 0.75 MeV, on the side of the α_{1} group, which is apparently a "ghost" of α_{0}. A quantitative account is given with a densityofstates function derived from α  α scattering phase shifts (1961BE1E: see also (1962BA1C, 1962HA23, 1963AL19)). At E_{p} = 95 to 155 MeV, ^{8}Be states at 0, 2.9, 11.4, 16.6, 18.8 and (23) MeV are excited (1956SE1A, 1963BA1R, 1963RA01). See also (1959AJ76, 1959FI1B, 1960PH1B, 1964SH07, 1964TO1D, 1964YA1A), ^{9}Be and ^{10}B.
Angular distributions of groundstate tritons have been measured at a number of energies up to 20 MeV: see (1959AJ76) and (1959VL24, 1960NE09, 1960NE11, 1961RE03, 1962BI11, 1965JA07). The width of the 2.9 MeV state is 0.8 MeV (1955CU16), 1.35 ± 0.15 MeV (1959VL24). See also (1959FI1B, 1959KU1C, 1959ZA01, 1962HA23, 1963OG1A).
At E(^{3}He) = 3.0 and 4.0 MeV, angular distributions of the αparticles to the groundstate of ^{8}Be and to the levels at 2.9, 16.6, 16.9 and 17.6 MeV have been measured. The excitation energy and width of the first excited state are found to be 2.90 ± 0.04 MeV and 1.35 ± 0.15 MeV (1963DO08): see Table 8.9 (in PDF or PS). The parameters of the higher states (from (1961ER01) and (1963DO08)) are given in Table 8.11 (in PDF or PS). The angular distributions are amenable to analysis by direct interaction except in the case of the 16.6 MeV state which appears to involve compound nucleus formation (1963DO08) (compare ^{7}Li(d, n)^{8}Be). For angular distribution data at lower energies, see (1955AJ61) and (1963WE08). The αparticles corresponding to the 2.9 MeV excited state are superposed on a broad, intense continuum extending to E_{x} > 16 MeV. Some part of this spectrum may be ascribed to a broad level at E_{x} = 12.5 MeV, with Γ ≈ 5 MeV, but the main contribution appears to be due to a direct 3α breakup (1963DO11: see also (1963WE08)). (1964MO19) find, on the other hand, that the sequential decay, via ^{8}Be*(2.9) and (16.93) dominates the reaction. See, however, (1965MO1M). Angular correlation studies confirm J^{π} = 2^{+} for ^{8}Be*(16.9) (1964MO19, 1965MO1N). See also (1962WE1C, 1964BL12, 1965MA1G).
For reaction (a) see (1960MA1H, 1961LE1K). For reaction (b) see ^{9}Be.
Angular distributions of the tritons to the ground and 2.9 MeV states of ^{8}Be have been measured at E_{n} = 14.4 MeV (1964VA14). See also (1959AJ76, 1964VA1E) and ^{11}B.
Alpha groups are reported corresponding to ^{8}Be states at 0, 2.9 (1960BE15, 1960BI11, 1961CI02, 1961LE10, 1963PU02, 1964YA1A; and see (1959AJ76)), 16.6 and 16.8 MeV (1961ER01: see Table 8.11 (in PDF or PS)). A coincidence study of the α_{1} group yields the following parameters for the level shape: E_{res} = 3.15 MeV, Γ = 2.04 MeV, E_{λ} = 4.00 MeV, γ^{2} = 3.4 MeV · fm, θ^{2} = 0.60, R = 5.5 fm (1963PU02: E relative to E(2α)). (1953TR04) reports E_{λ} = 5.29 MeV (relative to 2α), γ^{2} = 13.4 MeV · fm, θ^{2} ≈ 2, R = 4.48 fm: see Table 8.9 (in PDF or PS). Arguments are presented for the assignments J = 2^{+}, T = 1 for E_{x} = 16.63 and J^{π} = 0^{+} or 2^{+}, T = 0 for E_{x} = 16.93 MeV. Comparison of yields with ^{6}Li(^{3}He, p)^{8}Be* indicates gross violation of the isospin selection rule, possibly to be ascribed to intermixture in the compound nucleus stage (1961ER01). See, however, (1965MA1G). There is no evidence for an earlier reported level at E_{x} = 16.08 MeV (1961ER01). See also (1961TE02, 1962TE02, 1965LE09).
See (1964ET02, 1965AL1B, 1965ET1A, 1965WA1M) and ^{12}C.
See ^{11}B.
Alpha groups are reported corresponding to the ground and 2.9 MeV state: see (1959AJ76) and (1962AL20). At E_{p} = 3 to 5 MeV, the αspectrum shows an anomaly at E_{x} ≈ 0.75 MeV, ascribed to successive twobody decays with a final densityofstates related to α  α scattering phase shifts (1961BE1E: see ^{9}Be(p, d)^{8}Be and (1963BR03, 1964BR05, 1964DE1H)). See also ^{12}C and (1959KA12, 1959KA13, 1961KO08, 1962BE21, 1963PH1A, 1964BA1C, 1964YA1A, 1965DU1C, 1965LE09, 1965PH1A, 1965SW1B).
See (1965OL01).
At E(^{3}He) = 3.0 MeV, ^{8}Be*(2.9) is produced with an intensity 20 times that of the ground state (1964YO06).
Reaction (a) involves states of ^{8}Be at 0, 2.9, 16.6, 16.9 and (17.6) MeV: see (1955GO59, 1959AJ76, 1964TO1A). See also (1961SE13, 1963SH04, 1964LE1C). At E_{α} = 25.4 MeV, the fourbody breakup (^{12}C + α → 4α) is greatly favored over reaction (b) (1962BR14: see also (1961VA38, 1962VA25)). See also (1961GO1T, 1962IG1B, 1963LA02). Reaction (c) at E_{p} = 15 to 29 MeV proceeds predominantly through the ground state and the 2.9 MeV level. It is not clear whether higher levels of ^{8}Be are involved (1955NE18, 1960VA10, 1962VA1A, 1963VA04). See also (1963JA07, 1964BA1C, 1964KE1F, 1964SY02, 1965YU1C, 1965YU1D). For reaction (d) see (1955FR35, 1960VA10, 1964BR25). See also ^{12}C.
See (1963DR1B, 1964BL1C, 1964DA1B, 1965BE1W, 1965DE1V, 1965SL1C).
See (1965WI1A).
For reaction (a) see (1955AJ61, 1959AJ76, 1964TO1E) and ^{12}C. For reaction (b) see (1964BR1U) and ^{12}C.
This reaction has not been observed: see (1962LA15).
