
^{10}Be (2004TI06)(See Energy Level Diagrams for ^{10}Be) GENERAL: References to articles on general properties of ^{10}Be published since the previous review (1988AJ01) are grouped into categories and listed, along with brief descriptions of each item, in the General Tables for ^{10}Be located on our website at: (nucldata.tunl.duke.edu/nucldata/General_Tables/10be.shtml). See also 2 in (1988AJ01) [Electromagnetic Transitions in A = 510] (in PDF or PS), 10.5 [Table of Energy Levels] (in PDF or PS) and 10.6 [Electromagnetic transitions in ^{10}Be] (in PDF or PS). The interaction nuclear radius of ^{10}Be is 2.46 ± 0.03 fm [(1985TA18), E = 790 MeV/A; see also for derived nuclear matter, charge and neutron matter r.m.s. radii].
B(E2)(↓) for ^{10}Be*(3.37) = 10.5 ± 1.0 e^{2} · fm^{4}. ^{10}Be atomic excitations: Isotope shifts for various ^{1}S and ^{1}D Rydberg series atomic excitations in ^{9}Be and ^{10}Be were measured in (1988WE09).
The halflife of ^{10}Be is (1.51 ± 0.04) × 10^{6} years; this is the weighted average of 1.51 ± 0.06 Ma (1987HO1P), 1.53 ± 5% Ma (1993MI26) and 1.48 ± 5% Ma (1993MI26). The log ft = 13.396 ± 0.012. For the earlier work see (1974AJ01). See also (1992WA02, 1990HO28, 1998MA36).
At E(^{6}He) = 151 MeV, angular distributions were measured to investigate twoneutron exchange and the cluster configurations that dominate in the reaction. The data are consistent with a significant spatial correlation for the exchanged neutrons (1998TE03). Measurements at lower energies, E_{cm} = 11.6 MeV and 15.9 MeV, indicate that a simple dineutron exchange is not dominant and give evidence that the structure of ^{6}He is more complex than an alphaplusdineutron model (1999RA15). See also (2000BB06).
Molecular cluster states in ^{10}Be were studied by bombarding ^{6}Li targets with E(^{6}He) = 17 MeV projectiles and detecting the ^{10}Be + d and ^{6}He + ^{4}He reaction products (1999MI39). In reaction (a) reconstruction of the missing energy indicates that ^{10}Be*(0, 3.37) participate in the reaction as well as unresolved states at 6 MeV and 7.5 MeV. In reaction (b) the 10.2 MeV level is observed, and due to its apparent cluster nature it is suggested that this state could be the 4^{+} member in the rotational band (6.18 [0^{+}], 7.54 [2^{+}], 10.2 [4^{+}]) [J^{π} in brackets]. However, see reaction 7 which indicates J^{π} = 3^{} for E_{x} = 10.2 MeV.
The yield of γ_{0} and γ_{1} has been studied for E_{t} = 0.4 to 1.1 MeV [^{10}Be*(17.79) is said to be involved]: see (1984AJ01). The neutron yield exhibits a weak structure at E_{t} = 0.24 MeV and broad resonances at E_{t} ≈ 0.77 MeV [Γ_{lab} = 160 ± 50 keV] and 1.74 MeV: see (1966LA04) [^{10}Be*(17.79, 18.47)]. The total cross section for reaction (c), the yield of neutrons (reaction (b) to ^{9}Be*(14.39)), and the yield of γrays from ^{7}Li*(0.48) (reaction (d)) all show a sharp anomaly at E_{t} = 5.685 MeV: J^{π} = 2^{}; T = 2 is suggested for a state at E_{x} = 21.22 MeV. The total cross section for α_{0} (reaction (e)) and the allneutrons yield do not show this structure: see (1984AJ01, 1988AJ01). An additional anomaly in the proton yield is reported at E_{t} = 8.5 MeV [^{10}Be*(23.2)] [see (1987AB15)]. For reaction (c) a reanalysis of the proton yields indicate two states at E_{x} = 21.216 ± 0.023 and 23.138 ± 0.140 MeV with Γ_{cm} = 80 ± 30 and 440 ± 178 keV, respectively (1990GU36). For reaction (e) the angular distributions of α_{0} and α_{1} products were measured at E_{t} = 151 and 272 keV, and the analysis suggests possible evidence for a 2^{+} resonance, ^{10}Be*(17.3), at E_{res} = 117 ± 3 keV with Γ_{lab} = 253 ± 1 keV (1987AB09). Differential cross sections and Sfactors are reported by (1983CE1A) for E_{t} = 70 to 110 keV for ^{6}He*(0, 1.80). The zeroenergy Sfactor for ^{6}He*(1.80) is 14 ± 2.5 MeV · b. The relevance to a Liseeded tritium plasma is discussed by (1983CE1A). See also (1985CA41; astrophys.).
Cross sections have been measured to ^{10}Be*(3.37, 6.2 [u], 7.4 [u] [u = unresolved]) at E(^{3}He) = 235 MeV. The groundstate group is not seen: its intensity at θ_{lab} = 20° is ≤ 0.1 of that to ^{10}Be*(3.37) (1984BI08).
Angular distributions were measured at E_{α} = 65 MeV (1994HA16). Observed states are shown in 10.8 (in PDF or PS). For ^{10}Be*(11.76) the angular distribution is consistent with L = 3 which supports a J^{π} = 4^{+} assignment. It is suggested that the 11.76 MeV state is the 4^{+} member of the groundstate K^{π} = 0^{+} rotational band (g.s. [0^{+}], 3.37 [2^{+}], 11.76 [4^{+}] [J^{π} in brackets]).
Resonant particle decay spectroscopy measurements have been reported for reactions (a), (b), (c), (e), (f): see 10.9 (in PDF or PS) for an overview of experimental conditions. These measurements are particularly wellsuited for spectroscopic studies of levels that decay to excited states of the component isotopes, i.e. α_{1} + ^{6}He*(1.8). Values of Γ_{α}/Γ = (3.5 ± 1.2) × 10^{3} and 0.16 ± 0.04 for ^{10}Be*(7.542, 9.6), respectively, are determined by (2002LI15). See also (2004AR01) for a cluster model analysis. New evidence suggests that the previously accepted level energy at 9.4 MeV corresponds to the level presently observed at 9.6 MeV (1996SO17, 2001MI39, 2002LI15). (1997CU03, 2001CU06) measured E_{x} = 9.56 ± 0.02 MeV and determined Γ_{cm} = 141 ± 10 keV and J^{π} = 2^{+}. Assuming that the ^{10}Be*(9.56) state is 2^{+} suggests that it is probably a member of the K^{π} = 1^{+} band and the 3^{} 10.15 MeV level is probably in the K^{π} = (1^{}, 2^{}) band (2001CU06, 2002LI15). See also (2004MI07) and Fig. 8 in (2002LI15). The work of (1996SO17) reported a new level that decays by αemission at E_{x} = 10.2 MeV with Γ < 400 keV. The level energy is identified as E_{x} = 10.15 ± 0.02 MeV by (2001CU06) who also determined Γ_{cm} = 296 ± 15 keV and, based on α + ^{6}He decay angular correlations, J^{π} = 3^{}. This is in contrast with a J = 4 spin value that was suggested by (1996SO17). The 10.2 MeV level appears to have a small Γ_{n}; it is neither observed in fast neutron capture nor in the ^{9}Be + n decay channel. A natural parity state at 11.23 ± 0.05 MeV with Γ_{cm} = 200 ± 80 keV is identified by (2001CU06) along with inconclusive evidence for states at 13.1, 13.9 and 14.7 MeV. (2002LI15) observed a new state at 18.15 ± 0.05 MeV with Γ = 100 ± 30 keV; based on reaction systematics they deduce J^{π} = 0^{}. See 10.10 (in PDF or PS) for other states observed in (2003FL02). For reaction (d), angular distributions of α_{1} and α_{2+3+4+5} were reported in (1969CA1A). Groups corresponding to ^{10}Be*(0, 3.4, 6.0, 7.4, 9.4, 10.7, 11.9, 17.9) and possibly ^{10}Be*(18.8) were reported in (1971GL07). See (1974AJ01).
A calculation estimating the impact of ^{9}Li(p, α)^{6}He β / → ^{6}Li and other reactions on the production of primordial ^{6}Li in Big Bang nucleosynthesis is given in (1997NO04).
The thermal capture cross section is 8.49 ± 0.34 mb (1986CO14). Reported γray transitions are displayed in 10.7 (in PDF or PS) (1983KE11). Partial cross sections involving ^{10}Be*(0, 3.37, 5.96) are listed in (1987LY01). See also the references cited in (1988AJ01). Retardation of E1 strength was found in a measurement of the capture γrays from ^{9}Be + n using E_{n} = 622 keV neutrons to populate the J^{π} = 3^{} Dwave resonance at ^{10}Be*(7.372) (1994KI09); Γ_{n} = 17.5 keV. Capture to the J^{π} = 2^{+} states at ^{10}Be*(3.368, 5.958) was observed, and Γ_{γ} = 0.62 ± 0.06 and 0.11 ± 0.08 eV were deduced, respectively. Simple capture models indicate that capture to the 3368 keV state is appreciably hindered, which is explained by assuming a strong coupling between the dstate single particle neutron motion and the E1 giant resonance.
The scattering amplitude (bound) a = 7.778 ± 0.003 fm, σ_{free} = 6.151 ± 0.005 b (1981MUZQ). The difference in the spindependent scattering lengths, b^{+}  b^{} is +0.24 ± 0.07 (1987GL06). See also (1987LY01). Total cross section measurements have been reported for E_{n} = 0.002 eV to 2.6 GeV/c [see (1979AJ01, 1984AJ01)] and at 24 keV (1983AI01), 7 to 15 MeV (1983DA22; also reaction cross sections) and 10.96, 13.89 and 16.89 MeV (1985TE01; for n_{0} and n_{2}). Observed resonances are displayed in 10.11 (in PDF or PS). Analysis of polarization and differential cross section data leads to the J^{π} = 3^{}, 2^{+} assignments for ^{10}Be*(7.37, 7.55), respectively. Below E_{n} = 0.5 MeV the scattering cross section reflects the effect of bound 1^{} and 2^{} states, presumably ^{10}Be*(5.960, 6.26). There is also indication of interference with swave background and with a broad l = 1, J^{π} = 3^{+} state. The structure at E_{n} = 2.73 MeV is ascribed to two levels: a broad state at about 2.85 MeV with J^{π} = (2^{+}), and a narrow one at E_{n} = 2.73 MeV, Γ_{cm} ≈ 100 keV, with a probable assignment of J^{π} = 4^{}. The 4^{} assignment results from a study of the polarization of the n_{0} group at E_{n} = 2.60 to 2.77 MeV. A rapid variation of the polarization over this interval is observed, and the data are consistent with 4^{} (l = 2) for ^{10}Be*(9.27). A weak dip at E_{n} ≈ 4.3 MeV is ascribed to a level with J ≥ 1. See (1974AJ01) for references. The analyzing power has been measured for E_{n} = 1.6 to 15 MeV [see (1984AJ01)] and at E_{pol. n} = 9 to 17 MeV (1984BY03; n_{0}, n_{2}). The nonelastic and the (n, 2n) cross sections rise rapidly to ≈ 0.6 b (≈ 0.5 b for (n, 2n)) at E_{n} ≈ 3.5 MeV and then stay approximately constant to E_{n} = 15 MeV: see (1979AJ01, 1984AJ01). For total γray production cross sections for E_{n} = 2 to 25 MeV, see (1986GO1L). See also references cited in (1988AJ01).
Cross sections have been measured at E_{n} = 14.1  14.9 MeV for reaction (a), and at 16.3  18.8 MeV for reaction (b): see (1979AJ01). For reaction (c), measurements have been reported at E_{n} = 13.3  15.0 (t_{1}), at 22.5 MeV (see (1979AJ01)), and at 14.6 MeV (1987ZA01). A measurement of the ^{9}Be(n, tγ_{1})^{7}Li inclusive cross sections that encompassed E_{n} = 12  200 MeV observed peaks corresponding to ^{10}Be*((17.79), 18.55, 21.22, 22.26, (24.0)) (2002NE02). For the 18.55 and 24.0 MeV states, the peaks were observed at 18.76 and 23.4 MeV, respectively.
The cross section for production of ^{6}He shows 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. From E_{n} = 3.9 to 8.6 MeV, the cross section decreases smoothly from 100 mb to 32 mb. Excitation functions have been measured for α_{0} and α_{1} for E_{n} = 12.2 to 18.0 MeV: see (1979AJ01) for references.
Angular distributions for reaction (a) have been studied at E_{p} = 185 to 800 MeV [see (1984AJ01)] and at E_{pol. p} = 650 MeV (1986HO23; to ^{10}Be*(0, 3.37)). States at E_{x} = 6.07 ± 0.13, 7.39 ± 0.13, 9.31 ± 0.24, 11.76 MeV have also been populated. A_{y} measurements involving ^{10}Be*(0, 3.37) are reported at E_{pol. p} = 200 to 250 MeV [see (1984AJ01)] and at 650 MeV (1986HO23). For reaction (b), the K^{+} production cross sections were measured for E_{p} = 835  990 MeV (1988KO36). Calculations for one and twostep K^{+} production for E_{p} = 0.8  3 GeV are given in (2000PA15).
Angular distributions of proton groups have been studied at many energies in the range E_{d} = 0.06 to 17.3 MeV and at 698 MeV [see (1979AJ01, 1984AJ01, 1988AJ01) and (1997YA02)], as well as at E_{pol. d} = 2.0 to 2.8 MeV (1984AN16, 1984DE46; p_{0}, p_{1}; also VAP) and E_{d} = 12.5 MeV (1987VA13; p_{0}, p_{1}). The angular distributions show l_{n} = 1 transfer for ^{10}Be*(0, 3.37, 5.958, 7.54), l_{n} = 0 transfer for ^{10}Be*(5.960, 6.26), l_{n} = 2 transfer for ^{10}Be*(7.37). ^{10}Be*(6.18, 9.27, 9.6) are also populated, as are two states at E_{x} = 10.57 ± 0.03 and 11.76 ± 0.02 MeV. The state reported by (1974AN27) at 9.4 MeV is most likely the 9.6 MeV 2^{+} state based on its separation from the 9.27 MeV state (2001CU06). ^{10}Be*(9.27, 9.6, 11.76) have Γ_{cm} = 150 ± 20, 291 ± 20 and 121 ± 10 keV, respectively. See (1979AJ01) for references. See also (1989SZ02, 1995LY03, 1998LE27, 2000GE16). Angular distributions and excitation functions for ^{9}Be(d, p_{0}) and (d, p_{1}) were measured for the energy range E_{cm} = 57  139 keV (1997YA02, 1997YA08). Astrophysical S(E)factors were deduced and the spectroscopic factor S = 0.92 was deduced for ^{9}Be(d, p_{0}). (2000GE16) analyzed σ(E) and S(E) for E = 0.085  11 MeV and evaluated the impact of this reaction for forming heavier B, C and N nuclei in nucleosynthesis. At E_{d} = 1.0 MeV, p + γ coincidences were measured. In this experiment E_{x} = 3368.34 ± 0.43 keV was measured, which confirms E_{x} = 3368.03 ± 0.03 keV [ 10.5 (in PDF or PS)] for ^{10}Be*(3.3) (1999BU26): see reaction 55. At E_{d} = 15.3 MeV the p_{0} and p_{1} + γ_{1} doubledifferential cross sections were measured and evaluated with coupledchannel calculations which suggest that multistep processes are important in the reaction mechanism (2001ZE09). Attempts to understand the γdecay of ^{10}Be*(5.96) and its population in ^{9}Be(n, γ)^{10}Be led to the discovery that it consisted of two states separated by 1.6 ± 0.5 keV. The lower of the two has J^{π} = 2^{+} and decays primarily by a cascade transition via ^{10}Be*(3.37) [it is the state fed directly in the ^{9}Be(n, γ) decay]; the higher state has J^{π} = 1^{} and decays mainly to the ^{10}Be_{g.s.}. Angular distributions measured with the γray detector located normal to the reaction plane lead to l_{n} values consistent with the assignments of 2^{+} and 1^{} for ^{10}Be*(5.9584, 5.9599) obtained from the character of the γdecay. ^{10}Be*(6.18) decays primarily to ^{10}Be*(3.37): E_{γ} = 219.4 ± 0.3 keV for the 6.18 → 5.96 transition. See 10.12 (in PDF or PS) for a listing of the information on radiative transitions obtained in this reaction and lifetime measurements. For (p, γ) correlations through ^{10}Be*(3.37) see (1987VA13) and references in (1974AJ01). For polarization measurements see ^{11}B in (1990AJ01).
Angular distributions have been studied at E_{α} = 65 MeV to ^{10}Be*(0, 3.37, 5.96, 6.26, 7.37, 7.54, 9.33 [u], 11.88). DWBA analyses of these lead to spectroscopic factors (1980HA33) which are in poor agreement with those reported in other reactions: see (1984AJ01). Cluster model analyses of the reaction (1996VO03, 1997VO06, 1997VO17) explain the levels between 5.95 and 6.26 MeV as 2α  2ncluster states, by analogy with cluster states in ^{9}Be. The analysis further suggests that states at 5.960, 6.263, 7.371, 9.27 and 11.76 MeV (with J^{π} = 1^{}, 2^{}, 3^{}, 4^{} and 5^{}, respectively) comprise the K^{π} = 1^{} rotational band.
At E(^{6}He) = 25 MeV/A, 1 and 2neutron transfer cross sections were measured in a study of n  n correlations for neutrons in ^{6}He (2003GE05). The reaction was dominated by 1neutron transfer.
Angular distributions have been measured at E(^{7}Li) = 34 MeV (reactions (a) and (b)) to ^{10}Be_{g.s.}, S = 2.07, and ^{10}Be*(3.4), S = 0.42 (p_{1/2}), 0.38 (p_{3/2}): see (1979AJ01). At E(^{7}Li) = 52 MeV, states are reported at ^{10}Be*(0, 3.37, ≈ 6 (multiplet), 7.5 (doublet), 9.6, 10.2 11.8) (2001MI39). At E(^{8}Li) = 11 MeV (1989KO17) and 14.3 MeV (1989BE28, 1993BE22) angular distributions for ^{10}Be*(0, 3.37) have been measured. A DWBA analysis of the E(^{8}Li) = 14.3 MeV data yields spectroscopic factors of S_{g.s.} = 4.0 and S_{3.37} = 0.2 (p_{1/2}). At E(^{9}Be) = 20 MeV an angular distribution involving ^{8}Be_{g.s.} + ^{10}Be_{g.s.} has been measured: transitions to excited states of ^{10}Be are very weak (1985JA09).
At E(^{9}Be) = 20 MeV an angular distribution involving ^{8}Be_{g.s.} and ^{10}Be_{g.s.} was measured: transitions to excited states are weak (1985JA09). At E(^{9}Be) = 48 MeV, excited states of ^{10}Be were populated (2003AS04): see 10.13 (in PDF or PS). The excitation energy of ^{10}Be states was deduced from the measured energy of the ^{8}Be recoil, which was detected as two α particles. The αparticle energy spectra were analyzed in a CCBA model analysis to justify their interpretation of spin values.
The ^{10}Be core excitations in the ^{11}Be ground state were determined by measuring ^{10}Be fragments in coincidence with γrays in ^{9}Be(^{11}Be, ^{10}Be + γ)X at 60 MeV/A. The γrays corresponding to ^{10}Be*(3.37, 5.96, 6.26) were observed in 6.1%, 6.6% and 9.1% of the events, respectively. This indicates a small 0d admixture to the ^{11}Be ground state which is dominated by a 1s singleparticle component (2000AU02). In a different experiment at E(^{11}Be) = 46 MeV/A, γray plus ^{10}Be coincidences were observed. The γrays corresponding to transitions between 6.263 → 3.368 MeV, 5.96 → 0 MeV and 3.368 → 0 MeV were observed (2001CH46), though in this case excitation energies were not resolved in the charged particle spectra. See (1992WA22, 2000PA53) for calculations of spectroscopic factors. Also see (1995KE02, 1996ES01, 1999TO07).
Differential cross sections for ^{9}Be(^{11}B, ^{10}B)^{10}Be were measured at E(^{11}B) = 45 MeV for the angular range θ_{lab} = 10  165° (2003KY01). The quasisymmetric distributions involving ^{10}Be*(0, 3.368) and ^{10}B*(0.0.78, 1.74, 2.154, 3.587) were analyzed in a coupledreactionchannels method. Spectroscopic amplitudes are discussed for all possible 1 and 2step processes. Analysis indicates that the reaction proceeds primarily by onestep proton or neutron transfer.
At E(^{14}N) = 217.9 MeV, ^{10}Be*(0, 3.37, 5.960, 6.25, 7.37, 9.27, 11.8, 15.34) states are reported with J^{π} = 0^{+}, 2^{+}, 1^{}(+2^{+}), 2^{}, 3^{}, 4^{}, (5^{}), (6^{}), respectively (2003BO24, 2003BO38). The data are interpreted by assuming that the levels are αcluster molecular states with the binding energy provided by the excess neutrons. In this analysis, the members of the K^{π} = 1^{} rotational band are described by the formula, E_{x} ≈ 0.25 [J(J + 1)  1 × 2] + 5.96 MeV. See also (2003HO30).
Angular distributions of the p_{0} and p_{1} groups have been measured at E_{p} = 12.0 to 16.0 MeV. The reaction was measured in inverse kinematics by scattering 59.2 MeV ^{10}Be projectiles from protons (2000IW02) and measuring the ^{10}Be recoils and associated deexcitation γrays. Scattering reactions involving ^{10}Be*(0, 3.77, 5.96) were observed. For the first excited state, a deformation length of δ = 1.80 ± 0.25 fm, β^{2} = 0.635 ± 0.042 and (M_{n}/M_{p})/(N/Z) = 0.51 ± 0.12 are deduced. For the 5.96 MeV level, the branching ratio for decay via the 3.368 MeV state is 14 ± 6% of the branch for decay directly to the ground state. For reaction (b), elastically scattered deuterons have been studied at E_{d} = 12.0 and 15.0 MeV: see (1974AJ01).
Theoretical analysis of elastic and inelastic ^{11}Be scattering suggest enhancement of the fusion process due to strong multistep processes in the inelastic and transfer transitions of the active neutron. In some cases, a neck formation is suggested that is analogous to a "covalent bond" for ^{10}Be  n  ^{10}Be (1995IM01).
Differential cross sections have been measured to ^{10}Be*(0, 3.37) at E_{γ} = 230 to 340 MeV [see (1984AJ01)] and at E_{e} = 185 MeV (1986YA07) and 200 MeV (1984BLZY). A theoretical study of γ + N → π + N dynamics, for E_{γ} = 183 and 320 MeV (1994SA02), indicates that core polarization nonlocal effects due to offshell dynamics must be accounted for rigorously to obtain agreement with data. See also (1990BE49) for calculations at E_{γ} ≈ 200 MeV and (1990ER03) for E_{γ} = 180  320 MeV.
Partial capture rates leading to the 2^{+} states ^{10}Be*(3.37, 5.96) have been reported: see (1984AJ01). A review of muon capture rates (1998MU17), discusses a renormalization of the nuclear vector and axial vector strengths.
The photon spectrum from stopped pions is dominated by peaks corresponding to ^{10}Be*(0, 3.4, 6.0, 7.5, 9.4). Branching ratios have been obtained: those to ^{10}Be*(0, 3.4) are (2.02 ± 0.17)% and (4.65 ± 0.30)%, respectively [absolute branching ratio per stopped pion] (1986PE05). See (1979AJ01) for the earlier work. Also see (1998NA01).
The cross section for reaction (a) at thermal neutron energies is σ = 6.4 ± 0.5 mb, which is one order of magnitude lower than that of the (n, t) channel (1987LA16). At E_{n} = 96 MeV, the ^{10}Be excitation spectra was evaluated by carrying out a multipole decomposition up to E_{x} = 35 MeV (2001RI02) to deduce the GamowTeller strength distribution; while lowlying states were unresolved, the high excitation spectra was dominated by a broad L = 1 peak that was centered at E_{x} = 22 MeV. Also see (1974AJ01) and ^{11}B in (1990AJ01). For reaction (b) at E_{d} = 55 MeV, states are reported at ^{10}Be*(0, 3.37, 5.96, 7.37, 7.54, 9.27 [u], 9.4 [u]) [u = unresolved] (1979ST15), and angular distributions are given for the J^{π} = 0^{+} ^{10}Be_{g.s.} and the J^{π} = 2^{+} states at 3.37, 5.96 and 9.4 MeV.
At E_{t} = 381 MeV, states were observed at 0, 3.37, 5.96 and 9.4 MeV with some strength at 12  13.25 MeV (1997DA28, 1998DA05). A proportionality between the 0degree (t, ^{3}He) cross section and the GamowTeller strength deduced from βdecay measurements is discussed. The 3.37, 5.96 and 9.4 MeV states are identified as spinflip GamowTeller excitations (ΔS =1, ΔT = 1). J^{π} = 3^{+} is suggested for the 9.4 MeV state, though 2^{+} or 4^{+ } cannot be ruled out. Shell model predictions indicate J^{π} = 3^{+} Isobaric Analog States (IAS) in ^{10}Be, ^{10}B and ^{10}C at approximately 9, 11 and 8 MeV, respectively (1993WA06, 2001MI29). However, the uncertainty in J^{π} and lack of observation of these states in ^{10}B and ^{10}C prevents an acceptance of this suggested J^{π} = 3^{+} state as a new level at the present time; we associate this level with the 9.56 MeV, J^{π} = 2^{+} level in 10.5 (in PDF or PS). The 2^{+} states at 3.37 and 5.96 MeV are GamowTeller excitations and the IAS of the 3.35 and 5.3 MeV states in ^{10}C. The values B(GT_{}) = 0.68 ± 0.02 from ^{10}B(p, n)^{10}C*(5.38) and B(GT_{+}) = 0.95 ± 0.13 from ^{10}B(t, ^{3}He)^{10}Be*(5.96) may indicate that the nuclear structure of ^{10}Be and ^{10}C differs because of the presence of the Coulomb force, giving rise to isospin symmetry violation.
At E(^{7}Li) = 39 MeV, ^{10}Be*(0, 3.37, 5.96) states were observed (1988ET02). At this energy sequential processes are blocked, due to isospin mixing, and the onestep mechanism is most important. Also see (1989ET03).
New constraints on the ^{11}Li βdecay branch that feeds the ^{11}Be ground state indicate that the ^{11}Li βdelayed single neutron emission probability is P_{1n} = 87.6 ± 0.8% (1997BO01). The βdelayed neutrons following ^{11}Li decay were measured by (1997MO35); results of their observations are presented in 10.14 (in PDF or PS). A different technique, utilizing a βneutronγray triple coincidence was employed by (1997AO01, 1997AO04): see 10.15 (in PDF or PS). While the overall shape of the neutron energy spectra measured by (1997MO35) and (1997AO01, 1997AO04) are in excellent agreement, the analysis of their data leads to different interpretations and conflicting results. The measurements of (1997AO01, 1997AO04) reported involvement of a new ^{11}Be state at E_{x} = 8.03 MeV; this new state is implied by both an ≈ 1.5 MeV neutron in coincidence with the 2590 keV ^{10}Be*(5.96 → 3.36) γray, and an ≈ 3.6 MeV neutron in coincidence with the 3368 keV ^{10}Be*(3.36 → 0) γray. However, the interpretation of β  n coincidences by (1997MO35) included lowenergy neutrons from the unobserved ^{11}Be*(3.87, 3.96) → ^{10}Be*(3.36) + n and ^{11}Be*(6.51, 6.70, 7.03) → ^{10}Be*(≈ 6) + n decay branches into the analysis, and with their inferred branching ratios it was not necessary to introduce a new state at 8.03 MeV. To address the question of a possible level in ^{11}Be at E_{x} = 8.03 MeV, (2003FY01) developed a procedure to evaluate Doppler broadening in isotropic γray decay that occurs, for example, following βdelayed neutron decay. A model was developed that indicates a welldefined γray spectrum shape that depends on recoil velocity after decay, the level lifetime, and recoil energylosses/stopping powers in the target. The 2590 keV γray from ^{10}Be*(5.958) decay was evaluated, and the observed Doppler broadening was consistent with population of this level via neutrondecay from a ^{11}Be level around E_{x} = 8.6  9.1 MeV. This interpretation favors the analysis of (1997AO01, 1997AO04). For earlier work see (1984AJ01, 1988AJ01) where population of complex decay branches are reported.
Angular distributions were measured for E(^{11}Be) = 35 MeV/A (2000FO17, 2001WI05). The ^{10}Be_{g.s.}, 3.4 MeV and unresolved states near 6 MeV were observed. The spectroscopic factors for the ^{10}Be*(3.37) state inferred from standard DWBA and coupledchannels analysis differ by roughly a factor of 1.7. A "best estimate" for describing the ^{11}Be groundstate wave function includes a 16% core excitation of the ^{10}Be*(3.34) state [2^{+} Ä d]. Also see (1999TI04, 2000YI02). For calculations at E(^{11}Be) = 800 MeV see (1998CA18).
See (1984AL22) and ^{11}B in (1990AJ01). See also (1979AJ01).
Structure is observed in the summed proton spectrum corresponding to Q = 10.9 ± 0.35, 14.7 ± 0.4, 21.1 ± 0.4, 35 ± 1 MeV: see (1974AJ01). See also (1994SH21) for a quasiquantum multistep reaction model.
Angular distributions have been measured at E_{d} = 11.8 and 22 MeV to ^{10}Be_{g.s.} [see (1974AJ01)] and at 52 MeV to ^{10}Be*(0, 3.37, 5.96, 9.6): S = 0.65, 2.03, 0.13, 1.19 (normalized to the theoretical value for the ground state); π = + for ^{10}Be*(9.6): see (1979AJ01).
Fusion evaporation products from ^{11}B + ^{7}Li were measured at E(^{7}Li) = 5.5  19 MeV by detecting the reaction products and corresponding γrays (2000VL04). Reactions were observed indicating ^{10}Be_{g.s.} and ^{10}Be* + γ(3368). Results were used to evaluate the ^{7}Li + ^{11}B fusion barrier and the angular momentum achieved in the compound nucleus.
See (1985PO02).
Photobreakup reactions on ^{12}C have been reported for E_{γ} = 80  700 MeV (see 10.16 (in PDF or PS)). Twonucleon photoemission shows promise as a means to study shortrange nucleonnucleon correlations, however it is necessary to understand the reaction mechanism and final state interactions. Between the Giant Dipole Resonance and the Δresonance, γray absorption is primarily on clusters or pairs of nucleons which are emitted after photon absorption. Above the Δ resonance (E_{x} ≈ 300 MeV) γrays may interact with a single nucleon to form a Δ, which then either decays into a nucleon plus pion, or the Δ may interact with another nucleon leading to emission of a pair of nucleons. The missingmass spectra show strong peaks corresponding to (1p)^{2} and (1p1s) proton pair removal, while the (1s)^{2} peak is weak and broad which makes that contribution difficult to identify. Ejectile energy correlations appear to indicate that final state interactions play a role at low missing mass, however at high missing mass the energy appears to be divided between the two protons and hence final state interactions are not relevant. Polarization observables were measured by (2001PO19) and asymmetries were observed to be smaller than expected. See also (1994RY02, 1996RY04, 1998RY01, 1999IR01).
Electroproduction of proton pairs on ^{12}C targets has been reported for electron energies ranging from E = 0.1  14.5 GeV: see 10.16 (in PDF or PS). The ^{10}Be_{g.s.} is observed, but lowlying resonances are not resolved. Above E_{x} = 25 MeV, peaks corresponding to (1p)^{2}, (1p1s) and (1s)^{2} proton pair removal are observed. As in (γ, 2p) reactions [see reaction 37], twonucleon emission induced by virtual photons also shows promise as a means to study shortrange nucleonnucleon correlations; however the reaction mechanism and final state interactions must be understood. See also (1996RY04, 1997RY01, 2003AN15).
The reaction mechanism for the absorption of stopped pions on α, np and pp clusters in ^{12}C is discussed in (1987GA11).
At E_{n} = 40  56 MeV, the pulse shape response for discriminating various finalstate channels resulting from n + ^{12}C interactions in NE213 and BC401a liquid scintillator was measured by (1994MO41). See also (1989BR05) for calculated cross sections at E_{n} = 15  60 MeV.
At E(^{6}He) = 18 MeV, this reaction was studied by detecting the triple coincidence (^{10}Be + 2α) (2004MI05). The kinematical reconstruction indicates that ^{10}Be*(0, 3.37) and the multiplet near E_{x} ≈ 6 MeV participate in this reaction.
At E(^{6}Li) = 80 MeV, ^{10}Be*(0, 3.37, 5.96, 7.54, (9.4; J^{π} probably 2^{+}), 11.8) are populated and the angular distribution to ^{10}Be_{g.s.} has been measured: see (1976WE09, 1977WE03).
The ^{10}Be*(0, 3.368) states, and higher lying unresolved states were observed at E(^{9}Be) = 40.1 MeV (1999CA48).
At E(^{11}B) = 190 MeV, the J^{π} = 0^{+} ^{10}Be_{g.s.} and J^{π} = 2^{+} excited states at ^{10}Be*(3.36, 5.95, 9.4) excited states are observed (1998BE63).
Excited states in ^{10}Be were reconstructed from the α+^{6}He relative energy spectra at E(^{12}Be) = 378 MeV (2001FR02). Tentative evidence was found for states at E_{x} = 13.2, 14.8 and 16.1 MeV, while other known levels were observed at 11.9 and 17.2 MeV.
At E(^{12}C) = 357 MeV, the ^{10}Be*(0, 3.37, 5.96, 7.54, 9.4) levels were populated (1996ST29). The J^{π} = 0^{+} ^{10}Be ground state is strongly populated and appears to result from a twoproton transfer which tends to leave the neutron configuration undisturbed.
At E(^{15}N) = 318.5 MeV, known ^{10}Be levels at 0, 3.37, 5.96, 7.37 and 9.5 MeV were observed (2001BO35). Additional measurements by (2001BO35) at E(^{15}N) = 240 MeV observed known levels at 3.37, 5.96, 7.37 [u] + 7.54 [u], 9.27 [u] + 9.55, 10.5, 11.8 MeV [u = unresolved] and new levels at 13.6 ± 0.1, 15.3 ± 0.2, 16.9 ± 0.2 MeV with Γ = 200 ± 50 keV, 0.8 ± 0.2 MeV and 1.4 ± 0.3 MeV, respectively.
The mechanism for π^{+} absorption on 2 and 3 nucleon clusters in targets ranging from Li to C was studied using pions at E_{π+} = 50, 100, 140 and 180 MeV (1992RA11).
See ^{12}C in (1990AJ01).
Angular distributions were measured at E(^{3}H) = 38 MeV (1989SI02). ^{10}Be*(0, 3.36, 5.96) levels were observed and a DWBA analysis was used to extract spectroscopic factors shown in 10.17 (in PDF or PS). The results indicate that more strength goes to the ^{10}Be excited states than shell model calculations predict.
See (1985KO04).
At E(^{18}O) = 102 MeV, a study of αunbound states in ^{22}Ne indicated that ^{10}Be*(0, 3.37) participate in the reaction (2002CU04).
Astrophysical production of ^{10}Be has been evaluated by measuring formation cross sections for protons incident on ^{16}O and ^{28}Si at E_{p} = 30  500 MeV (1997SI29), on ^{12}C at E_{p} = 40  500 MeV (2002KI19) and on O, Mg, Al, Si, Mn, Fe and Ni targets at E_{p} = 100 MeV  2.6 GeV (1990DI13, 1990DI06, 1993BO41). The results of (1997SI29) suggest " soft solar proton spectrum with relatively few high energy protons over the last few million years" when compared with ^{10}Be concentrations found in lunar rocks. See (1997BA2M, 1997GR1H, 1997MU1D, 1997ZO1C) for surveys of terrestrial ^{10}Be concentrations, and see (2000NA34) for a model estimating ^{14}N, ^{16}O(p, ^{10}Be) and (n, ^{10}Be) cross sections for E_{p} = 10 MeV  10 GeV and for discussion of various atmospheric transport models for distributing ^{10}Be. Spallation cross sections for E_{p} = 50  250 MeV protons on ^{16}O were measured and were compared with Monte Carlo predictions from MCNPX (1999CH50); these data are relevant, for example, for estimating secondary radiation induced in proton therapy treatments. The target mass dependence of the cross sections for formation of ^{10}Be from E_{p} = 12 GeV proton induced spallation reactions on Al through Au targets was measured by (1993SH27). Overall, ^{10}Be production cross sections are found to increase with increasing target mass. For reaction (b), the ^{10}Be production cross sections for neutron induced reactions on C, N and O targets were measured at E_{n} = 14.6 MeV by (2000SU23). See also (2000NA34).
At E(^{10}Be) ≈ 30 MeV/A, the ^{10}Be + ^{12}C reaction was observed to populate various exit channels (2004AH02, 2004AS02). States at E_{x} = 9.6 ± 0.1 and 10.2 ± 0.1 MeV were observed in the ^{6}He + α breakup channel. Cross sections were given for breakup channels populating ^{8}Be*(0, 3.0) and ^{9}Be*(2.43), and other cross section were given for the (n, p) charge exchange reaction and proton pickup reaction that populate ^{10}B and ^{11}B, respectively. For reaction (b), fragmentation of ^{10}Be was measured on Si targets for E(^{10}Be) = 20  60 MeV/A (1996WA27) and E(^{10}Be) = 30  60 MeV/A (2001WA40). The total reaction cross section was found to be near 1.55 b in this energy region, and R_{rms}^{total}(^{10}Be) ≈ 2.38 fm is deduced from the cross section data.
The deexcitation of ^{10}Be* nuclei formed in the ternary cold fission of ^{252}Cf → ^{146}Ba + ^{96}Sr + ^{10}Be*(3.37) yields γrays that are roughly 6 keV lower in energy (1998RA16) than expected from the accepted excitation energy of E_{x} = 3368.03 ± 0.03 keV. The absence of Doppler broadening suggests that the ^{10}Be is formed and decays while in the potential well of the heavier Ba and Sr nuclei (1998RA16). A theoretical analysis of the reaction explains the observation as an anharmonic perturbation, which shifts the excitation energy lower (2000MI07).
