
^{10}Be (1966LA04)(See Energy Level Diagrams for ^{10}Be) GENERAL: See (1956KU1A, 1957FR1B, 1959BA1F, 1960KU1B, 1960TA1C, 1961BA1E, 1961TR1B, 1963BU1C, 1963VL1A, 1963WA1M, 1964FR1D, 1964GR1J, 1964VO1B, 1964WA1F, 1964WA1K). See also Table 10.1 [Table of Energy Levels] (in PDF or PS).
The weighted mean endpoint energy is 0.556 ± 0.003 MeV (1951LI26). The mean half life is (2.7 ± 0.4) × 10^{6} y (1949HU19): log ft = 13.65 (1951FE1A). The spectrum is of the D_{2} type (1950WU1A).
The neutron yield exhibits broad resonances at E_{t} = 0.84 and 1.70 MeV (1951CR01), 0.71 ± 0.02 MeV (1962SE1A), 0.765 and 1.735 MeV (1961VA43), and a weak structure at E_{t} = 0.24 MeV (1960SE12). The width of the 0.77 MeV resonance is 160 ± 50 keV (1962SE1A). Excitation functions for α_{0}, α_{1} and α_{2} (corresponding to ^{6}He*(0, 1.8, 3.4) see, however, (1965AJ01) for evidence relevant to the existence of a state at 3.4 MeV in ^{6}He) show a weak maximum at 1.10 MeV, a weak minimum at 1.30 MeV and a broad maximum at 1.80 MeV (Γ ≈ 0.5 MeV). Angular distributions are complex and suggest direct interaction: the maximum at E_{t} = 1.80 MeV may result from interference effects (1961HO23). Angular distributions of α_{0} and α_{1} at E_{t} = 0.24 MeV suggest J = 2^{+} for the 17.8 MeV state (1954AL38). See also (1963JA1E) and (1959AJ76).
Angular distributions of p_{0} at E_{α} = 13.6 and 14.7 MeV (1962KO13) and 30 MeV (1960KL03) show an oscillatory character with strong peaking in the back hemisphere. The p_{1} distributions are smoother, but they also show backward peaks (see also (1956WA29)). An explanation in terms of heavyparticle stripping is discussed by (1962HO1C). See also (1962MA59) and (1960MA15).
See (1964CA16).
The thermal capture cross section is 9.5 ± 1.0 mb (1964ST25). Reported γtransitions are listed in Table 10.2 (in PDF or PS) (1960BA01, 1961JA19, 1963DR02).
The total cross section data is summarized in (1964ST25). Angular distributions are summarized in (1963GO1M). The coherent scattering length (thermal, bound) is 7.7 fm (1961WI1A). The spin dependent thermal cross section is < 30 mb (1952PA1A). In the region E_{n} = 0 to 16 MeV, four resonances are reported, at 0.62, 0.81, 2.73 and 4.3 MeV: see Table 10.3 (in PDF or PS). Polarization and differential cross sections are reported for E_{n} = 0.2 to 2 MeV by (1961LA1A, 1962EL01, 1964LA04). Analysis of these data indicates that the E_{n} = 0.62 MeV (E_{x} = 7.37 MeV) resonance has J^{π} = 3^{}, formed by l = 2, with equal participation of channels J_{c} = 1 and 2. Interference with hardsphere (R = 5.6 fm) swave background and with a broad l = 1, J = 3^{+} state is observed. Below E_{n} = 0.5 MeV, the scattering cross section reflects the effect of bound 1^{} and 2^{} states with E_{λ} ≈ 0.2 MeV, γ^{2} ≈ 0.05 MeV, presumably to be identified with ^{10}Be*(5.96, 6.26). The resonant behavior near 0.815 MeV is consistent with J^{π} = 2^{+}, formed by l = 1 (1964LA04). See also (1964GO1L). The finding that the level at E_{x} = 7.37 MeV has J = 3^{} is in good accord with comparisons of reduced widths with the presumed T = 1, T_{z} = 0 analogue in ^{10}B at E_{x} = 8.89 MeV; for R = 5.8 fm,
The structure at E_{n} = 2.73 MeV is ascribed to two levels: a broad state at about 2.85 MeV with J = 2^{+}, and a narrow one, Γ ≈ 100 keV, at E_{n} = 2.73 MeV with a tentative assignment of J = 4^{} (1951BO45, 1959FO1A). A weak dip near 4.3 MeV is ascribed to a level with J ≥ 1 (1961FO07). Elastic scattering studies for E_{n} > 14 MeV are reported by (1958NA09, 1960MC04, 1960PE25, 1960SA25). See also (1959AJ76). Optical model analyses have been carried out by (1960HO14, 1963LU10). See also (1960WA07, 1962OT01, 1962PE10, 1963NE1H, 1964CR1B).
Data on nonelastic cross sections are summarized by (1964ST25). The processes involved include (n, 2n) and (n, n')^{9}Be* → n + ^{8}Be; the (n, α) process is relatively weak. The total nonelastic cross section rises rapidly from threshold at E_{n} ≈ 2.5 MeV to ≈ 600 mb at E_{n} = 6 MeV, and then falls slowly to 500 mb at 14 MeV. In the range 3.5 to 6.0 MeV, ^{9}Be(n, n')^{9}Be*(2.43) accounts for about half of the nonelastic cross section (1959MA34: see (1964ST25)): see also ^{9}Be. At E_{n} = 14 MeV, ^{8}Be*(2.9) is frequently involved (1959CH1E, 1961MY01). See also ^{9}Be and (1959MA1C, 1961CA23, 1961CO1E, 1963DI1F, 1963GO1M, , 1963KU1F, 1963MC1C, 1963ZU1B).
At E_{n} ≈ 15.5 MeV, σ(n, p) = 0.7 mb (1959AL83, 1963AL18, 1964ST25). See also (1960BU1C).
At E_{n} = 14 MeV, σ(n, t)=18 ± 1.5 mb (1958WY67). See also (1958VA33). Measurement of γrays from ^{9}Be(n, t)^{7}Li*(0.48) gives σ(n, t_{1}) = 20, 10, and 30 mb at E_{n} = 13.6, 14.1 and 14.7 MeV (1960BE18).
The cross section for production of ^{6}He has been measured for E_{n} = 0.7 to 8.6 MeV (1957ST95, 1958VA33, 1961BA53); see also (1964ST25). (1957ST95) find only a smooth rise to a broad maximum of 104 ± 7 mb at 3.0 MeV, followed by a gradual decrease to 70 mb at 4.4 MeV. No indication of resonance is found at E_{n} = 2.7 MeV. From E_{n} = 3.9 to 8.6 MeV, the cross section decreases smoothly from 100 mb to 32 mb (1961BA53). The cross section at E_{n} = 14 MeV is 10 ± 1 mb (1953BA04). See also (1960BU1C, 1963CH1C, 1964GA11).
Parameters of levels observed in this reaction are listed in Tables 10.4 (in PDF or PS) and 10.5 (in PDF or PS). Angular distributions of proton groups have been studied at many energies: see (1958ZE01, 1959AJ76, 1960MA32, 1961IS01, 1961RE04, 1962SL04, 1964SC12). Except at the lowest energies, the stripping process appears to dominate: see (1959BO1C, 1960BE1B, 1960LU04, 1960LU1B, 1960NA1A, 1963SM05, 1963TA1A, 1964BA1V). See also (1964ZA1B). The mean life of the 3.37 MeV level is 0.15 ± 0.03 psec (1965WA1P), some ten times shorter than the singleparticle value. On the I.P.M. an effective charge [1 + (0.5 ± 0.2)]e is required; strong collective effects are indicated (1963WA03, 1963WA1M): see also (1959BO49, 1959KO1B). For the 6.18 MeV level, τ_{m} > 0.5 psec, consistent with an E0 transition (1963WA17). Internal pair correlations establish the multipolarities of the transitions: 3.37 (E2), 5.96 (E1), and 6.18 (E0) (1964WA05); however, (1965FO1G) report that J^{π}(5.96) = 2^{} from γγ correlation studies ^{†}. The mean life of ^{10}Be*(5.96) is < 0.08 psec (1965WA1P). The absence of a groundstate transition from ^{10}Be*(6.26) supports the assignment J^{π} = 2^{} for this level (1958ME81, 1963WA17): see also (1959CH28, 1959GO78).
^{†} See Note added in proof section in the Introduction. The (pγ) correlation through ^{10}Be*(3.37) has the form 1 + AP_{2}(cos θ_{γ}), where θ_{γ} is measured from the recoil direction. Reported values of A lie in the range 0.2 to 0.4 (1957CO54, 1959TA01, 1959ZA01, 1960GO18, 1961RE04, 1962KO14, 1963AC01, 1963NE09, 1964ZA03). These values are consistent with the assumption of a ^{3}P_{2} state in LS coupling, but not with ^{1}D_{2}. Pure jj coupling leads to A = 0, as does the collective model. Approximate agreement can be obtained in intermediate coupling with a/k = 4.5 (1962PI1A): see also (1960KU1B, 1961RO1K). Polarization of the protons has been studied by (1959HI1E, 1960GR11, 1960HI09, 1961VA03, 1962AL10, 1962PA12, 1963NE09, 1963NE16, 1964RE04, 1965HE1B). See also (1961TE02).
Not reported.
Not reported.
See (1948EG1A, 1955JA18, 1964PA1M).
Not reported.
Not reported.
In the summed proton spectrum, structure is observed corresponding to Q = 10.9 ± 0.35, 14.7 ± 0.4, 21.1 ± 0.4, 35 ± 1 MeV (1958TY49, 1962GA09, 1962GA23, 1962GO1P, 1964TI02, 1965RI1A, 1966TY01). See also (1958MA1B, 1963BE42, 1963RI1B, 1964BA1C), and ^{11}B.
Not reported.
See (1961HO01).
See (1963SA1K).
See ^{14}C.
