(See Energy Level Diagrams for 8Be)
Shell model: (1965CO25, 1965VO1A, 1966BA26, 1966GU06, 1966HA18, 1966PA15, 1967BA1K, 1967BO1C, 1967HS1A, 1967PA10, 1967ST1C, 1967SV1A, 1968BA1L, 1968FA1B, 1968GO01, 1969AB1D, 1969GU1E, 1969GU03, 1969IK1A, 1969KU1F, 1969SV1A, 1970BA75, 1970BO1J, 1970CO1H, 1970DE1F, 1970GU11, 1970KO04, 1970KR1D, 1970NO1C, 1970RU1A, 1970TU01, 1970WO12, 1970ZO1A, 1971BO22, 1971BO29, 1971CO28, 1971GU20, 1971HA1U, 1971NO02, 1972AB12, 1972BO38, 1972HA05, 1972LE1L, 1973BO07, 1973HA05, 1973HA49, 1973JO1K).
Collective and deformed models: (1962MO1B, 1965VO1A, 1967LA09, 1967PA10, 1969AB05, 1969RU04, 1970BO41, 1970GO1Q, 1971BO22, 1971BO29, 1971HO19, 1972AB1C, 1972BO38, 1972HA05, 1972HO56, 1973BO07, 1973HO40, 1973KO1F, 1973KU13, 1973PE08).
Cluster and α-particle model: (1965IN1A, 1965NE1B, 1966KA1A, 1966PA15, 1966WE1C, 1969AB1B, 1969AB1D, 1969IK1A, 1969KU1C, 1969KU1F, 1969ME1C, 1969TA1C, 1970BA75, 1970YU1B, 1971AB07, 1971AB1B, 1971FR06, 1971KH06, 1971LE1N, 1971NO02, 1972AB1C, 1972AB19, 1972AK10, 1972BA59, 1972FR1B, 1972GR42, 1972HA05, 1972HI16, 1972HO56, 1972IK1A, 1972LE1L, 1972VA45, 1973HO40, 1973VA1N).
Special levels: (1966BA26, 1966BR1H, 1966DA02, 1966GU06, 1966PA15, 1966ST1D, 1967BA1N, 1967HO03, 1967HS1A, 1967MA1B, 1967ST1C, 1968GO01, 1968LA1B, 1969BA43, 1969GU03, 1969HA1G, 1969HA1F, 1969SH1A, 1970BO1J, 1970KI1D, 1970PE18, 1970RU1A, 1971AN03, 1971CO28, 1971GU20, 1971NO02, 1972BE1E, 1972HA1R, 1973AS02, 1973BO07, 1973FE1J, 1973HO40, 1973MA1K, 1973ST1Q, 1973VA1N).
Electromagnetic transitions: (1965CO25, 1966BA26, 1966PA15, 1966WA1E, 1967HS1A, 1968LA1B, 1969AB05, 1969HA1G, 1969HA1F, 1971BO22, 1972AB12, 1972BO38, 1972HA05, 1972NA05, 1973AS02, 1973BO07, 1973HA49, 1973HA1Q).
Other topics: (1965CO25, 1965VO1A, 1966DA02, 1966GU06, 1966HA18, 1966PA15, 1966TO04, 1966YO1B, 1967BA1K, 1967BA12, 1967BA1M, 1967BO1G, 1967BO1C, 1967BR1E, 1967CA17, 1967DI1B, 1967LA09, 1967LA1G, 1967PA10, 1967SV1A, 1968BA1L, 1968FA1B, 1968GO01, 1968LA1B, 1968NE1C, 1969AB05, 1969GU03, 1969KU1F, 1969HO1M, 1969KE1B, 1969NA1E, 1969NA1L, 1969RU04, 1969SH1A, 1969SV1A, 1970BA75, 1970BO1J, 1970CO1H, 1970HO1J, 1970KO04, 1970KR1D, 1970NO1C, 1970PE18, 1970RU1A, 1970TU01, 1970ZO1A, 1971AN03, 1971DE1V, 1971GR1L, 1971GR2C, 1971HO19, 1971JE1B, 1971SO11, 1971ZA1D, 1972AB12, 1972AN05, 1972EL1C, 1972FR1B, 1972HA05, 1972HA57, 1972LE1L, 1972LE23, 1972PN1A, 1972ST1C, 1972VA45, 1973HA05, 1973JO1K, 1973JU2A, 1973KO26, 1973NA26, 1973RA1E, 1973RO1R, 1973ST1Q).
Ground state: (1965CO25, 1965VO1A, 1966BA26, 1966TO1B, 1967BO1G, 1967BR1E, 1967LA1G, 1967PA10, 1968BA1L, 1968BO19, 1968FA1B, 1969AB05, 1969GU03, 1969KE1B, 1969KU1F, 1970KO04, 1970KR1D, 1970TU01, 1971BO29, 1971GR1L, 1971GR2C, 1971RU14, 1972AB12, 1972GR42, 1972LE1L, 1973KO26, 1973MA1K, 1973VA1N).
Adjusted mass excess† of 8Be: 4941.87 ± 0.13 keV (1972WA1G).
† Not used in Qm calculations in this paper.
Radiative widths have been measured for 8Be*(16.6, 16.9): see (1974NA1H: Eα = 31 to 35 MeV).
Alpha - α scattering reveals the ground state as a resonance with Q0 = 92.12 ± 0.05 keV, Γc.m. = 6.8 ± 1.7 eV, [τ = (0.97 ± 0.24) × 10-16 sec] (1966BE05, 1968BE02). Effective range theory analysis of higher energy scattering yields widths consistent with this value but subject to considerable uncertainty (1966TO1B). However, (1967KE1B, 1967KE1E) and (1967RA1B) have carried out such analyses yielding Γ = 6.14 ± 0.04 eV and 6.4+0.8-0.5 eV, respectively. Using a three-level, one-channel R-matrix formalism (1968BA2D) find Γ = 5.1 ± 0.4 eV for the ground state of 8Be. R-matrix analysis of the s-wave scattering and of the 9Be(p, d)8Be reaction indicates the presence of a second 0+ state at Ex ≈ 6 ± 3 MeV, Γ = 9 ± 4 MeV (a0 = 7 fm) (1968BA2D). For Eα = 30 to 70 MeV the l = 0 phase shift shows resonant behavior at Eα = 40.7 MeV, corresponding to a 0+ state at Ex = 20.2 MeV, Γ < 1 MeV, Γα/Γ < 0.5. No evidence for other 0+ states is seen above Eα = 43 MeV (1972BA83).
The d-wave phase shift becomes appreciable for Eα > 2.5 MeV and passes through resonance at Eα = 6 MeV (Ex = 3.18 MeV, Γ = 1.5 MeV, Jπ = 2+) (1963TO02). See Table 8.4 (in PDF or PS). Analyses by many-level R-matrix theory of the α-scattering, of the 9Be(p, d)8Be reaction and of the 8Li and 8B β-decays lead to approximately correct values for the Ex and Γ of 8Be*(2.9) and suggest a second 2+ state at Ex ≈ 8.5 MeV, Γ ≈ 10.5 MeV (1969BA43: a2 = 6.75 fm), Ex = 12.0-3.0+3.5 MeV, Γ = 14-3+4 MeV (1969CL10: a2 = 6.0 ± 0.5 fm). Five 2+ levels are observed from the l = 2 phase shifts measured from Eα = 30 to 70 MeV: 8Be*(16.6, 16.9) with Γα = Γ, and states with Ex = 20.2, 22.2 and 25.2 MeV. The latter has a small Γα (1972BA83). See also reaction 11.
The l = 4 shift rises from Eα ≈ 11 MeV and indicates a broad 4+ level at Ex = 11.4 ± 0.3 MeV (1959BR71). See also (1973CH1W). A rapid rise of δ4 at Eα = 40 MeV corresponds to a 4+ state at 19.9 MeV with Γα/Γ ≈ 0.96; Γ < 1 MeV and therefore Γα < 1 MeV, which is < 5% of the Wigner limit. A broad 4+ state is also observed near Eα = 51.3 MeV (Ex = 25.5 MeV) but there is no evidence for a previously reported state at Ex = 27.5 MeV (1972BA83).
Over the range Eα = 30 to 70 MeV a gradual increase in δ6 is observed (1972BA83). Some indications of a 6+ state at Ex ≈ 28 MeV and of an 8+ state at ≈ 57 MeV have been reported by (1965DA1A), with Γc.m. ≈ 20 and ≈ 73 MeV, respectively. The elastic scattering has been studied at Eα = 140 MeV by (1972FR1K). For a listing of the older work see Table 8.7 (in PDF or PS) [(dσ/dΩ)], Table 8.8 (in PDF or PS) [parameters of 8Be states from 4He(α, α)] and Table 8.9 (in PDF or PS) [parameters of 8Be*(2.9)] in (1966LA04). See also (1972FR1J). For studies of inelastic scattering of α-particles from 4He see (1969GR06, 1971HA41) and the review in (1973FI04). See also (1965SL1A, 1967ST30, 1968CO1M).
The bremsstrahlung cross section has been measured at Eα = 9.35 MeV and for Eα = 11.4 to 13.5 MeV: no significant enhancement is found at the final state energy corresponding to 8Be*(2.9) (1972FR02, 1973FR17). The cross section has also been measured for Eα = 12.1 to 18.7 MeV by (1972PE16).
See also (1965PR1A, 1965TA1D, 1966AB1A, 1966AL1G, 1966EN1A, 1966HI1A, 1966OK1A, 1967AB1A, 1967AL1E, 1967BE1N, 1967CH1H, 1967KE1C, 1967KE10, 1967PA1E, 1968BA1H, 1968HA1G, 1968HA1C, 1968KE1E, 1968PA1L, 1968SA1F, 1968SH1G, 1968TA1L, 1968TK1A, 1969AF1B, 1969BA1W, 1969BA1Y, 1969DO03, 1969KE1D, 1969KE09, 1969RE12, 1969SA1D, 1968TH1C, 1969TR1C, 1970CH1P, 1970CH1R, 1970EF01, 1970FE1C, 1970KH1C, 1970KU15, 1970LO1F, 1970PI1B, 1971BR30, 1971KU10, 1971KU22, 1971LE23, 1971MU1H, 1971NE1C, 1971PI1F, 1971RE1F, 1972DE29, 1972GI1G, 1972GO16, 1972GR1R, 1972HI16, 1972KA1K, 1972ME23, 1972OK02, 1973GR1M, 1973HA57, 1973PE08, 1973RA27, 1973YU1A; theor.).
The yield curve has been measured for Ed = 0.06 to 5.5 MeV [see (1966LA04) and (1966SC26)], and at Ed = 12 to 17 MeV (1970GA07: population of 7Be*(0 + 0.43)). A broad s-wave resonance is indicated at Ed = 0.41 MeV, Γ = 0.45 MeV (1952BA1A, 1956NE13). Polarization measurements are reported at Ed = 0.27 to 0.60 MeV (1966MI06; n1) and 2.5 to 3.7 MeV (1970TH08; n0, n1). The distributions observed by (1970TH08) are quite constant over the range 2.5 to 3.7 MeV, indicating that the predominant reaction mechanism is direct. See also 7Be.
Comparisons of the populations of 7Be*(0, 0.43) and of 7Li*(0, 0.48) have been made at many energies, up to Ed = 7.2 MeV. The n/p ratios are closely equal for analog states, consistent with charge symmetry (1957WI24, 1963BI1B, 1963CR08). See also (1966AU1A).
Excitation functions have been measured for Ed = 30 keV to 5.4 MeV [see (1966LA04) and (1966LO18, 1968BE1P, 1969BL14)]. A broad maximum near Ed = 1.0 MeV is interpreted as indicating a level at Ed = 0.4 MeV (1950WH02). In the range Ed = 1 to 5 MeV there is evidence for both direct interaction and compound nucleus formation (1963BI1B, 1963ME09, 1964PA06): at back angles the (d, p1) data show evidence of the Ed = 3.7 MeV resonance [see 6Li(d, α)4He]. An anomaly is observed in the p1/p0 intensity ratio at Ed = 6.945 MeV, corresponding to the Jπ = 0+; T = 2 analog of the ground state of 8He: Ex = 27.483 ± 0.010 MeV, Γ = 10 ± 3 keV, Γp0 ≪ Γp1, Γp0 < Γd (1969BL14). The parameters of this state have been calculated by (1969BA36).
Polarization measurements have been made at Ed = 0.6 and 0.96 MeV (1969NA1J, 1972SE09; p0, p1) and at Ed = 2.1 to 10.9 MeV (1968DU09, 1968FI07, 1970FI07; p0, p1). The latter report pronounced differences in the angular distributions of the vector analyzing power of the two ln = 1 transitions to 7Li*(0, 0.48). See also (1972FI1E, 1973FI1C). For reaction (b) see (1966FR06). See also 7Li and (1966AU1A, 1966BR25).
The yield of elastically scattered deuterons has been measured for Ed = 2 to 4.8 MeV (1964PA06), 4.0 to 6.5 MeV (1966BR1J), and 6.33 to 7.14 MeV (1969BL14): no resonances are reported. At Ed = 12.0 MeV, θlab = 95°, the differential cross section for elastic scattering is 9.82 ± 0.20 mb/sr (1971BI11). See also 6Li and (1972FI1E, 1973FI1C).
Cross sections and angular distributions (reaction (a)) have been measured for Ed = 0.03 to 12 MeV: see (1966LA04) and (1969LE22: Ed = 40 to 130 keV), (1966LO18: 0.2 to 2 MeV), (1968BE1P: 0.3 to 1.0 MeV), (1965RO1E, 1969DE31, 1969HU17: 0.35 to 1.50 MeV), (1966BR25: 1.0 to 2.0 MeV), (1964AN1A: 1.0 to 2.5 MeV), (1967CL06: 3 to 12 MeV) and (1969BL14: 6.33 to 7.14 MeV). Polarization measurements are reported at Ed = 0.40, 0.60, 0.80, 0.96 MeV (1971NE12, 1972SE09), 0.7 to 2.2 MeV (1967PL02), 2.1 to 10.9 MeV (1968DU07), 4.3, 6.3, 8.0, 10.1 and 11.8 MeV (1968BU13) and at E(6Li) = 0.6 MeV (1970HO11). See also (1967BU1B, 1972KO1P).
Maxima are observed at Ed = 0.8 MeV, Γlab ≈ 0.8 MeV and Ed = 3.75 MeV, Γlab ≈ 1.4 MeV (1963ME09, 1964PA06). Analysis of these and other data up to Ed = 12 MeV indicate a 2+, 0+, (6+), 2+, 4+ sequence of states: see Table 8.10 (in PDF or PS) in (1966LA04) (1965FR02, 1967CL06). See, however, reaction 4.
The assignment of Jπ = 2+ to 8Be*(22.2) is consistent with the polarization information (1971NE12, 1972SE09), but the 0+ state may actually be virtual with respect to 6Li + d (1972SE09) [8Be*(20.3): see reaction 4 and (1972BA83)]. At Ed = 6.945 MeV, the α-yield shows an anomaly corresponding to 8Be*(27.48), the Jπ = 0+; T = 2 analog of the 8He ground state (1969BL14). See also reaction 7 and (1969BA36; theor.).
Proton groups are observed to 8Be*(0, 2.9, 16.63, 16.91, 17.64): see (1966LA04) and Tables 8.4 (in PDF or PS) and 8.5 (in PDF or PS). The excitation of 8Be*(18.15, 19.0, 19.4, 19.9) is also reported by (1971GL07). Angular distributions have been measured at E(3He) = 1.4 to 1.8 MeV (1969VI05; p0, p1) and 5, 6, 7, 9, 10, 13 and 17 MeV (1965FL03; p0, p1; PWBAE analysis). A gradual change is observed from a dominant back angle maximum to a dominant forward maximum (1965FL03). Measurements of the energies of all the particles emitted in this reaction and reactions 23, 38 and 42 show that the apparent width of 8Be*(2.9) does not depend on the relative velocity of the spectator particle: Ex = 2.83 ± 0.20 MeV, Γ = 1.75 ± 0.30 MeV (1969NU01). See also Table 8.4 (in PDF or PS).
Deuteron groups have been observed to 8Be*(0, 2.9, 11.3 ± 0.4) (1959ZE1A, 1962CE01). Angular distributions have been measured at Eα = 20 and 24 MeV (1973GR1N), 20.5 to 24.5 MeV and at 38 MeV (1965DE1F; d0), 43 MeV (1959ZE1A; d0, d1) and 48 MeV (1962CE01; d0, d1). At Eα = 12 MeV (θ = 15° and 20°) the deuteron spectrum does not show a "ghost" anomaly at Ex = 0.1 - 0.5 MeV (1971BE52). A study of reaction (b) shows that the peak due to 8Be*(2.9) is best fitted by using Γ = 1.2 ± 0.3 MeV (1969BA18): see also Table 8.4 (in PDF or PS). See also (1968LA1E) and (1971BU1K; theor.). For reaction (b) see 6Li. See also (1966LA04).
This reaction proceeds via 8Be*(0, 2.9, 16.6, 16.9, 22.5), and there is indication also that the direct three-body break-up (reaction (b)) is possible (1971GA1N, 1971GA21, 1972GA32: Emax(6Li) = 13.0 MeV). The involvement of a state at Ex = 19.9 MeV (Γ = 1.3 MeV) is suggested by (1966MA40). See also (1971GL07). Good agreement with the shapes of the peaks corresponding to 8Be*(16.6, 16.9) is obtained by using a simple two-level formula with interference, corrected for the effect of final state Coulomb interactions, assuming Γ(16.6) = 90 and Γ(16.9) = 70 keV: see also Table 8.5 (in PDF or PS) (1971NO04). See also (1968NO03, 1969IN06). The ratio of the intensities of the groups corresponding to 8Be*(16.6, 16.9) remains constant for E(6Li) = 4.3 to 5.5 MeV: I(16.6)/I(16.9) = 1.22 ± 0.08 (1966KI09, 1966MA40). Partial angular distributions for the α0 group have been measured at fourteen energies for E(6Li) = 4 to 24 MeV (1970FR06). For reaction (b) see also (1966BE22).
For a review of the older work see (1966LA04). See also (1964MA26, 1967AL1F, 1967CH34, 1968DA20, 1971PO1D), (1966BR1G, 1967CA1D), (1966BA1T, 1966EL1A, 1966RO1E, 1966RO1F, 1966RO1H, 1972JO1D; theor.) and 12C.
Cross sections and angular distributions have been reported from Ep = 30 keV to 18 MeV. Gamma rays are observed to the ground (γ0) and to the broad, 2+, excited state at 2.9 MeV (γ1) and to 8Be*(16.6, 16.9) (γ3, γ4). Resonances for both γ0 and γ1 occur at Ep = 0.44 and 1.03 MeV, and for γ1 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 Ep ≈ 5 MeV (γ0), Γ ≈ 4 - 5 MeV, and at Ep ≈ 7.3 MeV (γ1), Γ ≈ 8 MeV. The Ep ≈ 5 MeV resonance (Ex ≈ 22 MeV) represents the giant dipole resonance based on 8Be(0) while the γ1 resonance, ≈ 2.3 MeV higher, is based on 8Be*(2.9). The γ0 and γ1 giant resonance peaks each contain about 10% of the dipole sum strength (1966FI1B, 1968BL1E, 1970FI1B). The main trend between Ep = 8 and 17.5 MeV is a decreasing cross section (1970FI1B). See, however, (1967FE04). See also Table 8.6 (in PDF or PS).
At the Ep = 0.44 MeV resonance (Ex = 17.64 MeV) the radiation is nearly isotropic consistent with p-wave formation, Jπ = 1+, with channel spin ratio σ(Jc = 2)/σ(Jc = 1) = 3.2 ± 0.5 (1961ME10). Radiative widths for the γ0 and γ1 decay are displayed in Table 8.7 (in PDF or PS). The E2/M1 amplitude ratio for the 17.6 → 2.9 transition varies over the energy of the broad final state: the average value is δ = 0.21 ± 0.04 (1967CO19). See also (1967CO29).
8Be*(16.63, 16.91) are 2+ states with mixed T = 0, 1 isospin [see (1965MA1G, 1966MA03, 1968PA09, 1969SW01)], with the lower state of 7Li + p parentage and the higher of 7Be + n parentage (1965SW03, 1968PA09). A careful study of the α-breakup of 8Be*(16.63, 16.91) for Ep = 0.44 to 2.45 MeV shows that the non-resonant part of the cross section for production of 8Be*(16.63) is accounted for by an extranuclear direct-capture process. Resonances for production of 8Be*(16.63, 16.91) are observed at Ep = 0.44, 1.03 and 1.89 MeV [8Be*(17.64, 18.15, 18.9)]. The results are consistent with the hypothesis of nearly maximal isospin mixing for 8Be*(16.63, 16.91): decay to these states is not observed from the 3+ states at Ex = 19 MeV, but rather from the 2- state at 18.9 MeV excitation (1969SW01). See also reaction 17. (1968PA09) find squared T = 1 components of 40% and 60% in 8Be*(16.6, 16.9) and of 95% and 5% in 8Be*(17.6, 18.2). Gamma - α angular correlation measurements at Ep = 0.44 MeV show that the 17.64 → 16.63 γ is nearly pure M1 δ(E2/M1) = -0.014 ± 0.013 (1969SW02). See also (1965SW03). Radiative widths are shown in Table 8.7 (in PDF or PS).
Recent measurements of cross sections have been made for Ep = 1.9 to 2.36 MeV (1967BE61; σt), 1.93 to 2.66 MeV (1969LE23), 2.1 to 3.8 MeV (1971BU1D), 2.4 to 6.0 MeV (1972PR03; n1γ), 2.6 to 5.4 MeV (1972EL19; n0), 3 to 10 MeV (1966HA1J; n1γ), 3.2 to 5.4 MeV (1972EL19; n1), 23 to 52 MeV (1967LO07; n1γ), and 30 and 50 MeV (1969CL06; n0, n1). See also (1973WA34). The shape of the neutron yield near threshold has been studied by (1966PA03). Polarization measurements are reported at Ep = 2.05 to 3.00 MeV (1973RO35, 1973RO2E), 3.0 to 4.0 MeV (1971HA27; n0, n1), 3.0 to 5.5 MeV (1971TH07; n0, n1) and 30 and 50 MeV (1969RO20). For a report on the earlier yield and polarization measurements, see (1966LA04). For angular distributions, see 7Be.
The yield of ground state neutrons (n0) rises steeply from threshold and shows pronounced resonances at Ep = 2.25 and 4.9 MeV (1963BO06). The yield of n1 also rises steeply from threshold (1964BU08) and exhibits a broad maximum near Ep = 3.2 MeV (1961BE05, 1972PR03) and a broad dip at Ep ≈ 5.5 MeV, also observed in the p1 yield (1972PR03).
Multi-channel scattering length approximation analysis of the 2- partial wave near the n0 threshold indicates that the 2- state at Ex = 18.9 MeV is virtual relative to the threshold and that its width Γ = 50 ± 20 keV (1974AR10). The ratio of the cross section for 7Li(p, γ)8Be*(18.9) γ / → 8Be*(16.6 + 16.9) [obtained by (1969SW01)] to the thermal neutron capture cross section 7Be(n, γ)8Be*(18.9) γ / → 8Be*(16.6 + 16.9) [obtained by (1973BA1J)], provides a rough estimate of the isospin impurity of 8Be*(18.9): σp,γ/σn,γ ≈ 1.5 × 10-5 and therefore the T = 1 isospin impurity is < 4% in intensity (1974AR10).
The structure at Ep = 2.25 MeV is ascribed to a 3+, T = (1), l = 1 resonance with Γn ≈ Γp and γ2n/γ2p = 3 to 10: see (1966LA04). See also (1973RO35). At higher energies the broad peak in the n0 yield at Ep = 4.9 MeV can be fitted by Jπ = 3(+) with Γ = 1.1 MeV, γ2n ≈ γ2p (1963BO06). The behavior of the n1 cross section can be fitted by assuming a 1- state at Ex = 19.5 MeV and a J = 0, 1, 2, positive-parity state at 19.9 MeV [presumably the 20.2 MeV state reported in reaction 4]. In addition the broad dip at Ep ≈ 5.5 MeV may be accounted for by the interference of two 2+ states (1972PR03). See Table 8.8 (in PDF or PS).
The ratio of the cross sections of the (p, n1) reaction to 7Be*(0.43) to that for the (p, p1) reaction to the analog state 7Li*(0.48) has been measured for Ep = 2.4 to 6.0 MeV (1972PR03), 3 to 10 MeV (1966HA1J) and 23 to 52 MeV (1967LO07). At the lower energies it deviates markedly from unity and varies strongly with energy (1966HA1J). At the higher energies the measurements seem to indicate that the spin-flip, isospin-flip part of the effective interaction is essentially independent of energy while the pure central part appears to decrease as the energy increases (1967LO07). See also (1969CL06).
Absolute differential cross sections for elastic scattering have been reported for Ep = 0.4 to 12 MeV (1953WA27, 1956MA12, 1965GL03), 14.5, 20.0 and 31.5 MeV (1956KI54) and more recently at 0.85 to 2.0 MeV (1966BA1Q), at 1.36 MeV (1969LE08) and at 6.868 MeV (1971BI11). The yield of inelastically scattered protons (p1, to 7Li*(0.48)) and of 0.48 MeV γ-rays have been measured in the range Ep = 0.8 to 12 MeV (1951BR10, 1954KR06, 1954MO04, 1955HA34, 1957NE1A, 1965GL03, 1966BA1Q, 1972PR03).
Polarization measurements are reported at Ep = 0.67 to 2.45 MeV (1973BR13; p0), 2.7 to 10.6 MeV (1969KI04; p0, p1), 14.5 MeV (1965RO22; p0), 49.8 MeV (1971MA13, 1971MA44; p0, p1), 152 MeV (1966RO1C; p0) and 155 MeV (1968GE04; p0, p2). For earlier measurements see (1966LA04). For a summary of angular distribution studies see 7Li.
Anomalies in the elastic scattering appear at Ep = 0.44, 1.03, 1.88, 2.1, 2.5, 4.2 and 5.6 MeV. Resonances at Ep = 1.03, 3 and 5.5 MeV and an anomaly at Ep = 1.88 MeV appear in the inelastic channel. A phase shift analysis and a review of the existing cross section data by (1973BR13) show that the 0.44 and 1.03 MeV resonances are due to 1+ states which are a mixture of 5P1 and 3P1 with a mixing parameter of +25°; that the 2- state at the neutron threshold (Ep = 1.88 MeV) has a width of about 50 keV [see also reaction 17]; and that the Ep = 2.05 MeV resonance corresponds to a 3+ state. The anomalous behavior of the 5P3 phase around Ep = 2.2 MeV appears to result from the coupling of the two 3+ states [resonances at Ep = 2.05 and 2.25 MeV]. The 3S1 phase begins to turn positive after 2.2 MeV suggesting a 1- state at Ep = 2.5 MeV (1973BR13): see Table 8.9 (in PDF or PS) and (1972PR03).
An attempt has been made to find the T = 2 analog of the ground state of 8He: no resonances were observed in either the p0 or the p1 yield for Ep = 11.1 to 11.9 MeV (1968HA1H). Measurements of the intensity ratios of the reactions (p, p1) and (p, n1) have been made by (1966HA1J, 1967LO07, 1972PR03): see reaction 17.
The cross section follows the expression E-1e-B/√E (square root of E), with B = 91.5 ± 4.5 keV1/2, in the range Ep = 23 to 50 keV. The cross section in that interval rises from 0.013 to 2.4 μb (1967FI05). In the range Ep = 131 to 561 keV, the cross section increases from 0.16 ± 0.02 to 3.7 ± 0.4 mb (1971SP05; and T.A. Tombrello, private communication). The cross section has also been measured for Ep = 0.04 to 0.13 MeV by (1969LE22). Taking into account 8Be Jπ = 2+ levels at 16.7, 16.9 and 20.6 MeV, (1972BA41) has made an R-matrix fit to the revised data of (1971SP05) and has obtained a quadratic energy dependence for the S-factor: S = 0.065[1 + 1.82E - 2.51E2] MeV · b, over the energy range Ep = 0 to 600 keV.
Excitation functions and angular distributions have been measured at many energies up to 18.6 MeV: see (1966LA04) for earlier references. Recently, differential cross-section measurements are reported by (1966MA03, 1969SW01: Ep = 0.4 to 2.45 MeV), (1969LE08: Ep = 1.36 MeV) and (1967CR05: Ep = 41.3 and 45.2 MeV). Polarization measurements have been carried out for Ep = 0.8 to 3 MeV (1968PE03), 2.7 to 10.6 MeV (1969KI04), 3.00 to 10.04 MeV (1968PL01), 5.5 to 6.7 MeV (1966BO09), and 7.4 to 10.4 MeV (1968AR04). See also (1966LA04) for a listing of the earlier references and (1966DA1B, 1971PL1C). In the range Ep = 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 Ep = 8.5 to 10 MeV (1968PL01, 1969KI04) [see Fig. 12 in (1969KI04) and Fig. 6 (1968PL01) for contour maps of the asymmetry].
Broad resonances are reported to occur at Ep = 3.0 MeV, Γ ≈ 1 MeV (1948HE1A) and at Ep = 5.6 MeV, Γ ≈ 1 MeV (1961HA27, 1962TE04, 1964MA51). Some structure is also reported near Ep = 6.0 to 6.5 MeV, and at Ep = 9.0 MeV (1964MA51). The latter is also reflected in the behavior of the A2 coefficient (1968PL01). The experimental data on yields and on polarization have been analyzed by (1970KU1H, 1971KU10): the data appear to require including two 0+ states [at Ex ≈ 19.7 and 21.8 MeV] with very small α-particle widths, and four 2+ states [at Ex ≈ 15.9, 20.1, 22.2 and 25 MeV]. See, however, reaction 4 and (1972BA83). 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 (1971KU10).
At Ed = 2 MeV, recoil proton spectra show only the ground state and 8Be*(2.9). No other groups with Ex < 9 MeV appear with intensity > 10% of n0. The spectrum yields Ex = 3.1 ± 0.1, Γ = 1.75 ± 0.1 MeV (1964JO04) [(1971RO05) report Ex = 3.10 ± 0.09, Γ = 1.74 ± 0.08 MeV]. See Table 8.4 (in PDF or PS). At higher deuteron energies the population of 8Be*(16.6, 16.9, 17.6, 18.2, 18.9, 19.1, 19.2) is reported and lp = 1 is obtained for the transitions to 8Be*(16.6, 17.6, 18.2): see (1960DI02, 1966DI1B, 1967KE1A, 1967KE1F). Angular distributions of the n0 and n1 groups to 8Be*(0, 2.9) are reported by (1966JU1A: Ed = 0.7 and 0.8 MeV), (1969NU1C: Ed = 0.90 to 1.09 MeV), (1966MI09: Ed = 1 MeV), and by (1970OSZY: Ed = 1.62 to 2.97 MeV). See also (1966LA04) for earlier references, (1966MA1J, 1966NU1B, 1966PO1D, 1968SA14, 1970SA20, 1970SA25, 1970SA29, 1973JO1L, 1973WE19) and the important theoretical paper by (1969BA43).
Reaction (b) appears to proceed primarily by sequential decay via 8Be*(2.9, 16.6, 16.9) and 5He(0): see (1967VA11). See also (1966AS04, 1966MI09, 1967JE01, 1972DE44, 1973HE26, 1973MC13). However, (1969HO11) deduce the involvement of a state with Ex = 11.4 ± 0.05 MeV, Γc.m. = 2.8 ± 0.2 MeV. See also (1973KA32). Attempts to observe n - α rescattering ("proximity scattering") proceeding via 8Be*(16.6, 16.9) have been unsuccessful: see (1968VA12, 1971SW10, 1972BR08). See also (1969TH02, 1971TH08) and the discussion in 5He.
Deuteron groups are observed to 8Be*(0, 2.9, 16.6, 16.9, 17.6). The group to 8Be*(2.9) is well fitted by Ex = 2.82 MeV, Γ = 1.27 MeV (1971PI06). See also reaction 13 (1969NU01). The Jπ = 1+ mixed isospin state have Ex = 16.627 ± 0.005 and 16.901 ± 0.005 MeV and Γ = 113 ± 3 and 77 ± 3 keV (1967MA12): see also Table 8.5 (in PDF or PS) and (1971PI06). Angular distributions have been measured at E(3He) = 0.90 and 1.10 MeV (1971ST35; d0), 3 MeV (1972LI31; d0, d1), and at 10 MeV by (1970DI12, 1970DI1F; d0, d1) and by (1968CO07; d to 8Be*(16.6, 16.9)). Spin-dependent effects in the angular distributions of d0 and d1 obtained by (1963WE1B) at 24.3 MeV are discussed by (1967SI1A). The angular distribution to 8Be*(16.6) is forward peaked, that for 8Be*(16.9) is roughly isotropic (1968CO07). See also (1964MA57).
The angular distributions of the t0 group have been measured at many energies up to 48 MeV: see (1966LA04). Recently, measurements have been carried out at Eα = 23.2 and 25.0 MeV (1973VA1A; t0, t1), 30 MeV (1972ME07; t0, t1; PWBAE and DWBA analysis) and at 50 MeV (1970LA14; t0). The ground state of 8Be does decay isotropically in the c.m. system and therefore Jπ = 0+ (1970LA14). Spin-dependent effects in the angular distributions for t0 and t1 obtained by (1963WE1B: Eα = 28 MeV) are discussed by (1967SI1A). At Eα = 10 MeV an anomaly ("ghost") is observed in the 8Be excitation spectrum at Ex ≈ 0.5 MeV. It may be due to interference of the 0+ states 8Be*(0, 6.) [see reaction 4] or to thresholds of particle channels (1971BE52).
At thermal energies, the (n, p) cross section is (4.8 ± 0.9) × 104 b (1955HA34, 1973MU14), the (n, α) cross section is ≤ 0.1 mb (1962BA1B, 1963BA34) and the (n, γα) cross section is 155 mb (1963BA34). These values, and comparison of the (p, n) cross section with that of reaction (a), support the Jπ = 3/2- assignment for 7Be(0) (1957NE1A, 1963BA34). The role of these reactions in astrophysical phenomena is discussed by (1968FO1A, 1969BA1N). See also (1959AJ76) and reaction 17.
For Ed = 0.8 to 1.7 MeV, proton groups are observing corresponding to the ground state and 8Be*(2.9): derived parameters for the latter are shown in Table 8.4 (in PDF or PS) (1959SP1A, 1960KA17). See also (1969BA43; theor.).
8Li decays mainly to the broad 2.9 MeV, 2+ level of 8Be, which decays into two α-particles. Both the β-spectrum and the resulting α-spectrum have been extensively studied. There appears to be an increasing excess of α-particles with Eα which may reflect transitions into the tail of the Jπ = 2+ level at Ex = 16.67 MeV. See (1959AJ76, 1966LA04) for earlier references. See also (1969KL08) and 8B(β+).
Studies of the distribution of recoil momenta and neutrino recoil correlation indicate that the decay is overwhelmingly GT, axial vector [see reaction 1 in 8Li] and that the ground state of 8Li has Jπ = 2+: see (1966LA04).
Angular correlations have been measured for the decays of 8Li and 8B as a test of the conserved vector current theory of β-decay. The values of the coefficients are displayed in Table 8.10 (in PDF or PS). See also (1973TR1J, 1973TR1K, 1973TR1L). The experimental value of δ [δ ≡ B(8Li) - B(8B)] is (5.4 ± 0.4)Wβ, consistent with CVC theory (1966EI02).
A recent asymmetry measurement is reported by (1971VA19). See also (1971VA1E, 1973NE10). Measurements of the excitation spectra in the decays of 8Li and 8B show no evidence for second class currents: |gIT| < 7 × 10-4 (1971WI05). See also (1966JA1C) and (1960KU05, 1960WE1A, 1966BA26, 1966LI1C, 1968KR10, 1969BA43, 1970DA21, 1971LI1H, 1971WI18, 1971WI1C, 1972EM02, 1972HO23, 1972MI1M, 1972WI28, 1972WI1C, 1973EM1B, 1973HA49, 1973TO14, 1973WI11, 1974WI1L; theor.).
The decay proceeds mainly to 8Be*(2.9) [see Table 8.4 (in PDF or PS) for its parameters]. Detailed study of the high energy portion of the α-spectrum reveals a maximum near Eα = 8.3 MeV, corresponding to transitions to 8Be*(16.63), for which parameters Ex = 16.67 MeV, Γ = 150 to 190 keV or Ex = 16.62 MeV, Γ = 95 keV are derived. Using τ1/2 = 769 ± 4 msec, log ft = 2.9. The low ft value supports the identification Jπ = 2+; T = 1 for 8Be*(16.63) (1964MA35). See, however, (1965MA1G). The energy distribution of α-particles has also been measured by (1969CL10). Analysis of this data and of data from α - α scattering in a three level R-matrix formalism indicate a 2+ state of 8Be at Ex = 12.0-3.0+3.5 MeV and of Γ = 14-3+4 MeV (a2 = 6.0 ± 0.5 fm) (1969CL10). See also (1969BA43; theor.).
Reaction (b) appears to proceed largely via excited states of 9Be, with subsequent decay to 8Be, mainly 8Be*(2.9): see (1966LA04), 9Be and 10Be. At En = 14 MeV the cross section at 20° for production of dineutrons is < 2 mb/sr (1966RO1G). See also (1965GO1C, 1965GO1E, 1966BO1C, 1966BO1F, 1966FE1C, 1967BO1F, 1970PR1E)).
Angular distributions of deuteron groups have been reported at Ep = 0.11 to 0.55 MeV (1973SI27; d0), 0.30 to 0.90 MeV (1968BE1N; d0), 5 to 11 MeV (1972HU03; d0) [analysis by DWBA and BHMM (1967BU23); derived spectroscopic factors], 13.0, 14.0, 15.0 and 21.35 MeV (1972VO1H; d0), 17.0, 21.0, 25.0, 29.1 MeV (1973MO01; d0, d1), 33.6 MeV (1967KU10, 1970KU1D: deuterons to 8Be*(0, 2.9, 16.95, 17.62, 18.18, 19.21); also derived spectroscopic factors) [also saw 8Be*(11.4); determined Γc.m.(16.95) = 103 ± 15 keV, Γc.m.(19.21) = 208 ± 30 keV], 40.8 MeV (1966MA22: deuterons to 8Be*(16.63, 16.91)), 46 MeV (1967VE01: deuterons to 8Be*(0, 2.9, 16.9, 17.6, 18.2, 19.1) [also report 8Be*(24.5)], 100 MeV (1968LE01: deuterons to 8Be*(0, 2.9, 16.9, 18.9)) [also saw 8Be*(11.0, 23.0, 26.0)], 155 MeV (1969BA05, 1969TO1A: deuterons to 8Be*(0, 2.9) [Γ = 2.0 ± 0.1 MeV], 11.5 [Γ = 8 ± 1 MeV], 16.8 ± 0.2, 18.9 ± 0.3) [also saw 8Be*(17.6 ± 0.4, 21.5 ± 0.3)] and 185 MeV (1969SU02: deuterons to 8Be*(0, 2.94 ± 0.08, 11.3 ± 0.3, 16.87 ± 0.06, 17.58 ± 0.08, 18.10 ± 0.10, 19.16 ± 0.07, 22.0 ± 0.15, 22.9 ± 0.15)) [also report 8Be*(20.0 ± 0.2 (?)); Γc.m.(2.9) = 1.5 ± 0.1 MeV; Γc.m.(22.0, 22.9) ≥ 1 MeV (the angular distributions for these two states are not clear cut)]. (1971SC26) have analyzed the angular distributions obtained by (1967VE01, 1968LE01) using DWBA with a local-energy approximation and have derived spectroscopic factors. With the exception of 8Be*(11.4, 22.0, 22.9) the angular distributions are consistent with l = 1. The yield of the deuterons corresponding to 8Be*(16.63) is very low: [≈ 5% compared to 8Be*(16.91)] as expected by predictions of the cluster model (1966MA22: Ep = 40.8 MeV). See also (1967KU10) and reaction 21 in 9Be in (1966LA04).
Anomalies in the deuteron spectrum between the d0 and the d1 groups have been reported at various energies [see (1966LA04) and (1967FI1D, 1967HA1K, 1971BE52, 1971MI1C)]. The shape of the deuteron spectrum near 8Be*(2.9) requires a2 ≈ 7.1 fm (1969BA43). See also reaction 4 and (1968BA2D). At Ep = 17 MeV, for the transitions to 8Be*(0, 2.9) the ratios of σ(p, d)/σ(p, d) = 11.8 and 14.1, respectively (1967CO09, 1969CO06). See also (1968NA1A; theor.).
Reaction (b) at Ep = 9 MeV is dominated by strong final state interactions through 8Be*(0, 2.9) and 6Li*(2.19) with little or no yield from a direct three-body decay (1971EM01). See also (1967FI1D). See also 10B and (1966CA1E, 1966LA20, 1967OG1A, 1967RO07, 1968TI1A, 1972QU01) and (1967BA1M, 1967JO1D, 1968BO1P, 1970BO1K; theor.).
At Ed = 11.8 MeV, angular distributions have been obtained for the tritons to 8Be*(0, 2.9) (1967FI07): S = 0.51 and 0.75, respectively (DWBA analysis). At Ed = 38 MeV, angular distributions of the tritons to 8Be*(16.91, 17.64, 19.0) have been compared with those of the 3He to the analog states in 8Li. The cross-section ratios σ17.64/σ0.98(8Li) = 0.45 ± 0.04 and σ16.91/σ0(8Li) = 0.75 ± 0.04, consistent with the pure T = 1 nature of 8Be*(17.64) and the mixed T nature of 8Be*(16.91) [and 8Be*(16.63)] (1966GA21; abstract). Angular distributions have also been measured at Ed = 0.3 to 1.0 MeV (1968BE1E; t0), 0.9 to 3.1 MeV (1973SA1Q; t0), 15.0 MeV (1969AR1B; t0) and at many other energies up to Ed = 20 MeV: see (1966LA04). The ghost anomaly which is seen near the t0 group has been studied at Ed = 2.5 MeV: it is interpreted as being due to an extreme threshold effect (1971BE52). See also (1967DE1J) and (1970BO1K, 1973HE1J; theor.). A kinematically complete study of reaction (b) at Ed = 26.3 MeV indicates the involvement of 8Be*(0, 2.9, 11.4, 16.9, 19.9 + 20.1). Parameters obtained for 8Be*(2.9, 11.4) are Ex = 3.20 ± 0.03 and 11.70 ± 0.07 MeV, Γ = 1.72 ± 0.09 and 4.41 ± 0.5 MeV (1973SO08).
Angular distributions have been measured at E(3He) = 3.0 MeV (1968MO05; α16.91), 3.0 and 4.0 MeV (1963DO08; α0, α2.9, α16.6, α16.9, α17.6), 18.0, 22.7, 26.7, 32.3 MeV (1965AR07; α0, α1) and 26.7 MeV (1968AR12; α16.9, α17.6, α18.1, α19.2). See also (1959AJ76) and (1967SI1A). The parameters of the observed states are shown in Tables 8.4 (in PDF or PS) and 8.5 (in PDF or PS) (1961ER01, 1963DO08).
Reaction (b) has been studied at E(3He) = 1.6 MeV (1970EH1A), 3.0 MeV (1966SU04, 1968MO05) and 3.0 and 4.0 MeV (1972TA04). See also (1966LA04) and (1967ST1E). The reaction proceeds by sequential decay via 8Be*(0, 2.9, 11.4, 16.6, 16.9, 19.9, 22.5) (1972TA04). The angular correlation via 8Be*(16.91) is consistent with Jπ = 2+ for that state (1968MO05). Jπ = 2+ is also indicated for 8Be*(16.63) (1966SU04). See also (1968TH1G). For reaction (c) see (1967ST1D). See also (1964MA57, 1966CA08, 1966DI1C, 1967OG1A, 1970CA28, 1971TR1B, 1972RO1N), (1967HO1C) and (1970BO1K, 1971OS05, 1972TH04, 1973RO28; theor.).
At E(6Li) = 3.5 MeV the population of 8Be*(2.9) is very small but 8Beg.s. is involved (1968JA08). See also (1966LA04). For reaction (b) see (1966LE10) and (1968TO1C; theor.). For reaction (c) see (1970BA1J, 1970BA1Y). For reaction (d) see (1968KN1A, 1970BA1J, 1970BA1Y). Reaction (e) has been studied at E(18O) = 16 and 20 MeV (1971KN05). See also (1968FA04). For reaction (f) see (1968FA04).
Angular distributions have been measured at En = 14.4 MeV (1964VA14; t0, t1). Reaction (b) has been studied at the same energy by (1967VA12). See also (1971MI1H) and (1967BA1E; theor.). See also 11B in (1975AJ02).
At Ep = 49.5 MeV angular distribution measurements have been carried out for the 3He groups to 8Be*(0, 2.9, 16.6, 16.9): the ratio dσ(16.63)/dσ(16.91) has a mean value of 0.65 ± 0.05 for θ = 15° to 30°, suggesting possibly a preferential excitation of the T = 1 components of these two states. The ratio of the differential cross sections dσ(p, t) [to 8Bg.s.] to dσ(p, 3He) [to 8Be*(16.63, 16.91)] (15° to 30°) seems to also suggest this (1971SQ01).
Angular distributions have been reported at Ed = 0.5 to 1.0 MeV (1968FR07; α0, α1), 0.8 to 2.5 MeV (1968CO31; α0, α1), 3.0 to 7.2 MeV (1967LE1C; α0) and 7.5 MeV (1966BR08; α to 8Be*(16.63, 16.91, 17.64, 18.15)). At Ed = 7.5 MeV the total cross section for formation of 8Be*(16.63), σt(16.63), is about 1.15 σt(16.91), consistent with the mixed isospin character of these two states. σt(18.15) is ≈ 0.85 σt(16.91), but the other nearby 1+ state 8Be*(17.64) has σt(17.64) ≈ 0.07 σt(16.91), consistent with the nearly pure T = 1 nature of 8Be*(17.64) (1966BR08). These four states [8Be*(16.63, 16.91, 17.64, 18.15)] have been studied for Ed = 4.0 to 12.0 MeV. Interference between the 2+ states [8Be*(16.63, 16.91)] varies as a function of energy. The cross section ratios for formation of 8Be*(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 Ex only the 3+ state at Ex = 19.2 MeV is observed, the neighboring 3+ state at Ex = 19.06 MeV is not seen. The Jπ = 1+; T = 0 state is found to have Ex = 18.146 ± 0.005 MeV (based on 17.638 for the Jπ = 1+; T = 1 state) and Γ = 138 ± 6 keV (1970CA12). There is some question as to whether a two-level fit can be made for the α groups to 8Be*(16.63, 16.91). ((1970CA12) and W.D. Callender, private communication) are dubious about this, feeling that other 2+ states have to be brought into the calculation. Based on a two-level fit they find the following average values: Γ16.6 = 113 keV, Γ16.9 = 80 keV, ΔQ = 302 keV. However, (1971NO04) state that the two-level fit is appropriate if the spectra are properly corrected for effects of final state Coulomb interactions: Γ16.6 = 90 ± 5 keV, Γ16.9 = 70 ± 5 keV, ΔQ = 290 ± 7 keV. See also (1966BR22) and (1970KI1D; theor.). For a listing of the parameters of observed states see Tables 8.4 (in PDF or PS) and 8.5 (in PDF or PS) (1961ER01, 1969NU01, 1970CA12).
Angular correlation studies [Ed ≤ 3 MeV] indicate that reaction (b) takes place mainly by a sequential process involving 8Be*(0, 2.9, 11.4, 16.6, 16.9): see (1968LO01, 1970ST02, 1971LA14) and (1967CA13, 1968AS01). (1968LO01) report Ex = 2.7 ± 0.2 MeV, Γ = 1.0 ± 0.1 MeV, and Γ = 3.0 ± 0.5 MeV for 8Be*(11.4). See also (1967CA13, 1970ST02). For a study of rescattering effects see (1972VA1L).
At E(3He) = 2.45 and 6.00 MeV this reaction proceeds primarily by sequential decay via 8Be*(0, 2.9) and via 5Li, 9B and 12C states [see also the latter nuclei] (1966WA16). See also (1966WI08, 1968KR02, 1970BE1F), (1966LA04, 1967HO1C) and (1967PR1B; theor.).
At Eα = 46 MeV angular distributions obtained for the transitions to 8Be*(0, 2.9) are consistent with a direct interaction mechanism (1970ZE03).
See 11B in (1975AJ02).
Angular distributions have been measured at Ep = 0.78 to 12.00 MeV (1963SY01, 1968WA1G; α0), 1.4, 2.0 and 2.6 MeV (1972GE19; α0, α1 (not at 2.0)), 12, 20, 24 and 30 MeV (1971CA16; α0), 26.7 and 38 MeV (1969GA03, 1970GU06; α0), 40 MeV (1971KA21; α0, α1 and α to 8Be*(12.5) [Γ = 4.0 ± 0.5 MeV] and to 8Be*(16.6 + 16.9, 17.6, 18.1, 19.0)) and at Ep = 45 MeV (1971DE2B, 1972DE01, 1972DE02; α0, α1). At Ep = 45 MeV the angular distributions are typical of a direct reaction mechanism, with a rise in the backward direction indicative of heavy particle stripping (1972DE01, 1972DE02). Observed parameters for 8Be*(2.9) are shown in Table 8.4 (in PDF or PS) (1969NU01, 1971KA21). At Ep = 40 MeV, θ = 20°, dσ16.6/dσ16.9 = 2.3 ± 0.4 (1971KA21).
Reaction (b) has been studied for Ep = 0.15 to 9.5 MeV. The reaction proceeds predominantly by sequential two-body decay via 8Be*(0, 2.9): see, e.g., (1965BR18, 1968CH01, 1972HU04). See also (1967KA09, 1967MA11, 1968GI03, 1969QU01, 1970CO03, 1971KO22, 1972MI1J). Some papers report very narrow widths in this reaction for 8Be*(2.9). However, (1972HU04) find a good fit to the data with Ex = 2.99 MeV, Γ = 1.45 MeV when an interference term is included. The interference effect is attributable to the identity of the three α-particles and to the ambiguity in their order of emission (1965BR18).
See also 12C in (1968AJ02, 1975AJ02), (1966LA04), (1966LO1G, 1967CO29, 1967EN1A, 1967FL12, 1967TR1B, 1968LA1C, 1969LA1B, 1969TR1D, 1972DZ10, 1973PR1C), (1969PH1B) and (1969GO13, 1970GO1J, 1970GO33, 1970GO49, 1970KO1K, 1970MC25, 1970MC1T, 1970SC01, 1972TH1M, 1973DU1D, 1973GO35; theor.).
This reaction has been studied for E(3He) = 1.4 to 5.8 MeV. Angular distributions have been measured at E(3He) = 5.2 MeV involving 8Beg.s. + 6Lig.s., 8Beg.s. + 6Li*3.56, and 8Be*2.9 + 6Lig.s. (1967YO02, 1967YO1C, 1968ME13).
Angular distributions have been reported at Eα = 28.4 and 29.0 MeV for 8Beg.s. + 7Lig.s., 8Beg.s. + 7Li*0.48 and 8Be*2.9 + 7Li (29 MeV only) by (1968KA24) and at 42 MeV for 8Beg.s. + 7Lig.s. and 8Beg.s. + 7Li*0.48 by (1968MI05). At Eα = 65 MeV 8Be*(16.6 + 16.9, 20.0) are apparently also excited (1973WO06). See also (1966GE12) and 7Li. For reaction (b) see (1969FU09).
This reaction has been studied for 13 ≤ Ep ≤ 160 MeV. At low energies it involves 8Be(0); at higher energies 8Be*(0, 2.9) (1966RO1D, 1967GA01, 1969LU1B, 1970GO12, 1970KE1B, 1972MA62). It is not clear whether higher states are also involved: see (1970KE1B). See also (1966LA04) and (1966JA1B, 1968YA1C, 1972YA1B).
Angular distributions have been determined at Ed = 19.5 MeV (1971GU07), 28 MeV (1972BE1T, 1972BE29: 8Be(0)) and 51.8 MeV (1970EI05: both 8Be*(0, 2.9)). At Ed = 28 MeV a structure is observed which is attributed to the process 12C(d, α)10B → α + 6Li (1972CO23). At Ed = 55 MeV the population of 8Be*(11.4, 16.6 + 16.9) is also reported (1971MC04). See also (1966DA1C, 1970AN1E), (1967OG1A, 1972GA1E) and (1968RO1D, 1970EL1F, 1971DR02, 1973HE1J; theor.). See also 12C and (1966LA04).
Angular distributions have been measured for the transitions to 7Beg.s. + 8Beg.s. and 7Be*0.43 + 8Beg.s. at E(3He) = 25.5 to 29 MeV (1972PI1A, 1973PI1B, 1973PI1D), 28 MeV (1970DE12, 1973KL1B) and at 35.7 MeV (1969ZE1A, 1970FO1D). The transitions to 7Beg.s.+0.43 + 8Be*2.9 have also been studied by (1970DE12). See also (1967ZA1B, 1973ST1N) and (1969NE1D; theor.).
This reaction has been studied up to Eα = 104 MeV. At Eα = 25 MeV it involves 8Be(0) (1966BO28); at Eα = 28.0, 37.4, 70, 90 and 104 MeV, the reaction goes via 8Be*(0, 2.9) (1965YA02, 1967TA1C, 1968YA02, 1971BR1G, 1972SH1J) and at 90 MeV it may, in addition, involve the broad 4+ state at 11.4 MeV (1970JA06). See also (1966LA04) and (1965KU1B, 1967ME1C; theor.).
Angular distributions have been measured for E(12C) = 11.6 to 13.4 MeV (1972CO1H). At E(12C) = 50 to 65 MeV the population of 8Be*(0, 2.9) is reported by (1972FL1C). See also (1968JA1F, 1970JA1B, 1972GR1T, 1973CR1A, 1973SC1J).
Angular distributions have been measured at Ep = 45 MeV for the transitions to 8Be*(0, 2.9) (1971BR07).
Angular distributions are reported at Ed = 14.6 MeV for the transitions to 8Beg.s. + 7Lig.s. and 8Beg.s. + 7Li*0.48 (1967DE03).
This reaction has not been observed: see (1962LA15).