(See Energy Level Diagrams for 10Be)
GENERAL: References to articles on general properties of 10Be published since the previous review (1988AJ01) are grouped into categories and listed, along with brief descriptions of each item, in the General Tables for 10Be located on our website at: (www.tunl.duke.edu/nucldata/General_Tables/10be.shtml).
The interaction nuclear radius of 10Be 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 10Be*(3.37) = 10.5 ± 1.0 e2 · fm4.
10Be atomic excitations: Isotope shifts for various 1S and 1D Rydberg series atomic excitations in 9Be and 10Be were measured in (1988WE09).
The half-life of 10Be is (1.51 ± 0.04) × 106 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(6He) = 151 MeV, angular distributions were measured to investigate two-neutron 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, Ecm = 11.6 MeV and 15.9 MeV, indicate that a simple di-neutron exchange is not dominant and give evidence that the structure of 6He is more complex than an alpha-plus-di-neutron model (1999RA15). See also (2000BB06).
Molecular cluster states in 10Be were studied by bombarding 6Li targets with E(6He) = 17 MeV projectiles and detecting the 10Be + d and 6He + 4He reaction products (1999MI39). In reaction (a) reconstruction of the missing energy indicates that 10Be*(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+]) [Jπ in brackets]. However, see reaction 7 which indicates Jπ = 3- for Ex = 10.2 MeV.
The yield of γ0 and γ1 has been studied for Et = 0.4 to 1.1 MeV [10Be*(17.79) is said to be involved]: see (1984AJ01). The neutron yield exhibits a weak structure at Et = 0.24 MeV and broad resonances at Et ≈ 0.77 MeV [Γlab = 160 ± 50 keV] and 1.74 MeV: see (1966LA04) [10Be*(17.79, 18.47)]. The total cross section for reaction (c), the yield of neutrons (reaction (b) to 9Be*(14.39)), and the yield of γ-rays from 7Li*(0.48) (reaction (d)) all show a sharp anomaly at Et = 5.685 MeV: Jπ = 2-; T = 2 is suggested for a state at Ex = 21.22 MeV. The total cross section for α0 (reaction (e)) and the all-neutrons yield do not show this structure: see (1984AJ01, 1988AJ01). An additional anomaly in the proton yield is reported at Et = 8.5 MeV [10Be*(23.2)] [see (1987AB15)]. For reaction (c) a reanalysis of the proton yields indicate two states at Ex = 21.216 ± 0.023 and 23.138 ± 0.140 MeV with Γcm = 80 ± 30 and 440 ± 178 keV, respectively (1990GU36). For reaction (e) the angular distributions of α0 and α1 products were measured at Et = 151 and 272 keV, and the analysis suggests possible evidence for a 2+ resonance, 10Be*(17.3), at Eres = 117 ± 3 keV with Γlab = 253 ± 1 keV (1987AB09). Differential cross sections and S-factors are reported by (1983CE1A) for Et = 70 to 110 keV for 6He*(0, 1.80). The zero-energy S-factor for 6He*(1.80) is 14 ± 2.5 MeV · b. The relevance to a Li-seeded tritium plasma is discussed by (1983CE1A). See also (1985CA41; astrophys.).
Cross sections have been measured to 10Be*(3.37, 6.2 [u], 7.4 [u] [u = unresolved]) at E(3He) = 235 MeV. The ground-state group is not seen: its intensity at θlab = 20° is ≤ 0.1 of that to 10Be*(3.37) (1984BI08).
Angular distributions were measured at Eα = 65 MeV (1994HA16). Observed states are shown in 10.8 (in PDF or PS). For 10Be*(11.76) the angular distribution is consistent with L = 3 which supports a Jπ = 4+ assignment. It is suggested that the 11.76 MeV state is the 4+ member of the ground-state Kπ = 0+ rotational band (g.s. [0+], 3.37 [2+], 11.76 [4+] [Jπ 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 well-suited for spectroscopic studies of levels that decay to excited states of the component isotopes, i.e. α1 + 6He*(1.8). Values of Γα/Γ = (3.5 ± 1.2) × 10-3 and 0.16 ± 0.04 for 10Be*(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 Ex = 9.56 ± 0.02 MeV and determined Γcm = 141 ± 10 keV and Jπ = 2+. Assuming that the 10Be*(9.56) state is 2+ suggests that it is probably a member of the Kπ = 1+ band and the 3- 10.15 MeV level is probably in the Kπ = (1-, 2-) band (2001CU06, 2002LI15). See also (2004MI07) and Fig. 8 in (2002LI15).
The work of (1996SO17) reported a new level that decays by α-emission at Ex = 10.2 MeV with Γ < 400 keV. The level energy is identified as Ex = 10.15 ± 0.02 MeV by (2001CU06) who also determined Γcm = 296 ± 15 keV and, based on α + 6He decay angular correlations, Jπ = 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 Γn; it is neither observed in fast neutron capture nor in the 9Be + n decay channel.
A natural parity state at 11.23 ± 0.05 MeV with Γcm = 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 Jπ = 0-. See 10.10 (in PDF or PS) for other states observed in (2003FL02).
For reaction (d), angular distributions of α1 and α2+3+4+5 were reported in (1969CA1A). Groups corresponding to 10Be*(0, 3.4, 6.0, 7.4, 9.4, 10.7, 11.9, 17.9) and possibly 10Be*(18.8) were reported in (1971GL07). See (1974AJ01).
A calculation estimating the impact of 9Li(p, α)6He β / → 6Li and other reactions on the production of primordial 6Li in Big Bang nucleosynthesis is given in (1997NO04).
The thermal capture cross section is 8.49 ± 0.34 mb (1986CO14). Reported γ-ray transitions are displayed in 10.7 (in PDF or PS) (1983KE11). Partial cross sections involving 10Be*(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 γ-rays from 9Be + n using En = 622 keV neutrons to populate the Jπ = 3- D-wave resonance at 10Be*(7.372) (1994KI09); Γn = 17.5 keV. Capture to the Jπ = 2+ states at 10Be*(3.368, 5.958) was observed, and Γγ = 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 d-state single particle neutron motion and the E1 giant resonance.
The scattering amplitude (bound) a = 7.778 ± 0.003 fm, σfree = 6.151 ± 0.005 b (1981MUZQ). The difference in the spin-dependent scattering lengths, b+ - b- is +0.24 ± 0.07 (1987GL06). See also (1987LY01). Total cross section measurements have been reported for En = 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 n0 and n2).
Observed resonances are displayed in 10.11 (in PDF or PS). Analysis of polarization and differential cross section data leads to the Jπ = 3-, 2+ assignments for 10Be*(7.37, 7.55), respectively. Below En = 0.5 MeV the scattering cross section reflects the effect of bound 1- and 2- states, presumably 10Be*(5.960, 6.26). There is also indication of interference with s-wave background and with a broad l = 1, Jπ = 3+ state. The structure at En = 2.73 MeV is ascribed to two levels: a broad state at about 2.85 MeV with Jπ = (2+), and a narrow one at En = 2.73 MeV, Γcm ≈ 100 keV, with a probable assignment of Jπ = 4-. The 4- assignment results from a study of the polarization of the n0 group at En = 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 10Be*(9.27). A weak dip at En ≈ 4.3 MeV is ascribed to a level with J ≥ 1. See (1974AJ01) for references. The analyzing power has been measured for En = 1.6 to 15 MeV [see (1984AJ01)] and at Epol. n = 9 to 17 MeV (1984BY03; n0, n2).
The non-elastic and the (n, 2n) cross sections rise rapidly to ≈ 0.6 b (≈ 0.5 b for (n, 2n)) at En ≈ 3.5 MeV and then stay approximately constant to En = 15 MeV: see (1979AJ01, 1984AJ01). For total γ-ray production cross sections for En = 2 to 25 MeV, see (1986GO1L). See also references cited in (1988AJ01).
Cross sections have been measured at En = 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 En = 13.3 - 15.0 (t1), at 22.5 MeV (see (1979AJ01)), and at 14.6 MeV (1987ZA01). A measurement of the 9Be(n, tγ1)7Li inclusive cross sections that encompassed En = 12 - 200 MeV observed peaks corresponding to 10Be*((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 6He 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 En = 3.9 to 8.6 MeV, the cross section decreases smoothly from 100 mb to 32 mb. Excitation functions have been measured for α0 and α1 for En = 12.2 to 18.0 MeV: see (1979AJ01) for references.
Angular distributions for reaction (a) have been studied at Ep = 185 to 800 MeV [see (1984AJ01)] and at Epol. p = 650 MeV (1986HO23; to 10Be*(0, 3.37)). States at Ex = 6.07 ± 0.13, 7.39 ± 0.13, 9.31 ± 0.24, 11.76 MeV have also been populated. Ay measurements involving 10Be*(0, 3.37) are reported at Epol. p = 200 to 250 MeV [see (1984AJ01)] and at 650 MeV (1986HO23).
Angular distributions of proton groups have been studied at many energies in the range Ed = 0.06 to 17.3 MeV and at 698 MeV [see (1979AJ01, 1984AJ01, 1988AJ01) and (1997YA02)], as well as at Epol. d = 2.0 to 2.8 MeV (1984AN16, 1984DE46; p0, p1; also VAP) and Ed = 12.5 MeV (1987VA13; p0, p1). The angular distributions show ln = 1 transfer for 10Be*(0, 3.37, 5.958, 7.54), ln = 0 transfer for 10Be*(5.960, 6.26), ln = 2 transfer for 10Be*(7.37). 10Be*(6.18, 9.27, 9.6) are also populated, as are two states at Ex = 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). 10Be*(9.27, 9.6, 11.76) have Γcm = 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 9Be(d, p0) and (d, p1) were measured for the energy range Ecm = 57 - 139 keV (1997YA02, 1997YA08). Astrophysical S(E)-factors were deduced and the spectroscopic factor S = 0.92 was deduced for 9Be(d, p0). (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 Ed = 1.0 MeV, p + γ coincidences were measured. In this experiment Ex = 3368.34 ± 0.43 keV was measured, which confirms Ex = 3368.03 ± 0.03 keV [ 10.5 (in PDF or PS)] for 10Be*(3.3) (1999BU26): see reaction 55.
At Ed = 15.3 MeV the p0 and p1 + γ1 double-differential cross sections were measured and evaluated with coupled-channel calculations which suggest that multistep processes are important in the reaction mechanism (2001ZE09).
Attempts to understand the γ-decay of 10Be*(5.96) and its population in 9Be(n, γ)10Be led to the discovery that it consisted of two states separated by 1.6 ± 0.5 keV. The lower of the two has Jπ = 2+ and decays primarily by a cascade transition via 10Be*(3.37) [it is the state fed directly in the 9Be(n, γ) decay]; the higher state has Jπ = 1- and decays mainly to the 10Beg.s.. Angular distributions measured with the γ-ray detector located normal to the reaction plane lead to ln values consistent with the assignments of 2+ and 1- for 10Be*(5.9584, 5.9599) obtained from the character of the γ-decay. 10Be*(6.18) decays primarily to 10Be*(3.37): Eγ = 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 10Be*(3.37) see (1987VA13) and references in (1974AJ01). For polarization measurements see 11B in (1990AJ01).
Angular distributions have been studied at Eα = 65 MeV to 10Be*(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 - 2n-cluster states, by analogy with cluster states in 9Be. The analysis further suggests that states at 5.960, 6.263, 7.371, 9.27 and 11.76 MeV (with Jπ = 1-, 2-, 3-, 4- and 5-, respectively) comprise the Kπ = 1- rotational band.
At E(6He) = 25 MeV/A, 1- and 2-neutron transfer cross sections were measured in a study of n - n correlations for neutrons in 6He (2003GE05). The reaction was dominated by 1-neutron transfer.
Angular distributions have been measured at E(7Li) = 34 MeV (reactions (a) and (b)) to 10Beg.s., S = 2.07, and 10Be*(3.4), S = 0.42 (p1/2), 0.38 (p3/2): see (1979AJ01). At E(7Li) = 52 MeV, states are reported at 10Be*(0, 3.37, ≈ 6 (multiplet), 7.5 (doublet), 9.6, 10.2 11.8) (2001MI39). At E(8Li) = 11 MeV (1989KO17) and 14.3 MeV (1989BE28, 1993BE22) angular distributions for 10Be*(0, 3.37) have been measured. A DWBA analysis of the E(8Li) = 14.3 MeV data yields spectroscopic factors of Sg.s. = 4.0 and S3.37 = 0.2 (p1/2). At E(9Be) = 20 MeV an angular distribution involving 8Beg.s. + 10Beg.s. has been measured: transitions to excited states of 10Be are very weak (1985JA09).
At E(9Be) = 20 MeV an angular distribution involving 8Beg.s. and 10Beg.s. was measured: transitions to excited states are weak (1985JA09). At E(9Be) = 48 MeV, excited states of 10Be were populated (2003AS04): see 10.13 (in PDF or PS). The excitation energy of 10Be states was deduced from the measured energy of the 8Be recoil, which was detected as two α particles. The α-particle energy spectra were analyzed in a CCBA model analysis to justify their interpretation of spin values.
The 10Be core excitations in the 11Be ground state were determined by measuring 10Be fragments in coincidence with γ-rays in 9Be(11Be, 10Be + γ)X at 60 MeV/A. The γ-rays corresponding to 10Be*(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 11Be ground state which is dominated by a 1s single-particle component (2000AU02). In a different experiment at E(11Be) = 46 MeV/A, γ-ray plus 10Be coincidences were observed. The γ-rays 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 9Be(11B, 10B)10Be were measured at E(11B) = 45 MeV for the angular range θlab = 10 - 165° (2003KY01). The quasi-symmetric distributions involving 10Be*(0, 3.368) and 10B*(0.0.78, 1.74, 2.154, 3.587) were analyzed in a coupled-reaction-channels method. Spectroscopic amplitudes are discussed for all possible 1- and 2-step processes. Analysis indicates that the reaction proceeds primarily by one-step proton- or neutron transfer.
At E(14N) = 217.9 MeV, 10Be*(0, 3.37, 5.960, 6.25, 7.37, 9.27, 11.8, 15.34) states are reported with Jπ = 0+, 2+, 1-(+2+), 2-, 3-, 4-, (5-), (6-), respectively (2003BO24, 2003BO38). The data are interpreted by assuming that the levels are α-cluster molecular states with the binding energy provided by the excess neutrons. In this analysis, the members of the Kπ = 1- rotational band are described by the formula, Ex ≈ 0.25 [J(J + 1) - 1 × 2] + 5.96 MeV. See also (2003HO30).
Angular distributions of the p0 and p1 groups have been measured at Ep = 12.0 to 16.0 MeV. The reaction was measured in inverse kinematics by scattering 59.2 MeV 10Be projectiles from protons (2000IW02) and measuring the 10Be recoils and associated de-excitation γ-rays. Scattering reactions involving 10Be*(0, 3.77, 5.96) were observed. For the first excited state, a deformation length of δ = 1.80 ± 0.25 fm, β2 = 0.635 ± 0.042 and (Mn/Mp)/(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 Ed = 12.0 and 15.0 MeV: see (1974AJ01).
Theoretical analysis of elastic and inelastic 11Be scattering suggest enhancement of the fusion process due to strong multi-step 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 10Be - n - 10Be (1995IM01).
Differential cross sections have been measured to 10Be*(0, 3.37) at Eγ = 230 to 340 MeV [see (1984AJ01)] and at Ee = 185 MeV (1986YA07) and 200 MeV (1984BLZY). A theoretical study of γ + N → π + N dynamics, for Eγ = 183 and 320 MeV (1994SA02), indicates that core polarization non-local effects due to off-shell dynamics must be accounted for rigorously to obtain agreement with data. See also (1990BE49) for calculations at Eγ ≈ 200 MeV and (1990ER03) for Eγ = 180 - 320 MeV.
Partial capture rates leading to the 2+ states 10Be*(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 10Be*(0, 3.4, 6.0, 7.5, 9.4). Branching ratios have been obtained: those to 10Be*(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 En = 96 MeV, the 10Be excitation spectra was evaluated by carrying out a multipole decomposition up to Ex = 35 MeV (2001RI02) to deduce the Gamow-Teller strength distribution; while low-lying states were unresolved, the high excitation spectra was dominated by a broad L = 1 peak that was centered at Ex = 22 MeV. Also see (1974AJ01) and 11B in (1990AJ01). For reaction (b) at Ed = 55 MeV, states are reported at 10Be*(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 Jπ = 0+ 10Beg.s. and the Jπ = 2+ states at 3.37, 5.96 and 9.4 MeV.
At Et = 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 0-degree (t, 3He) cross section and the Gamow-Teller strength deduced from β-decay measurements is discussed. The 3.37, 5.96 and 9.4 MeV states are identified as spin-flip Gamow-Teller excitations (ΔS =1, ΔT = 1). Jπ = 3+ is suggested for the 9.4 MeV state, though 2+ or 4+ cannot be ruled out. Shell model predictions indicate Jπ = 3+ Isobaric Analog States (IAS) in 10Be, 10B and 10C at approximately 9, 11 and 8 MeV, respectively (1993WA06, 2001MI29). However, the uncertainty in Jπ and lack of observation of these states in 10B and 10C prevents an acceptance of this suggested Jπ = 3+ state as a new level at the present time; we associate this level with the 9.56 MeV, Jπ = 2+ level in 10.5 (in PDF or PS). The 2+ states at 3.37 and 5.96 MeV are Gamow-Teller excitations and the IAS of the 3.35 and 5.3 MeV states in 10C. The values B(GT-) = 0.68 ± 0.02 from 10B(p, n)10C*(5.38) and B(GT+) = 0.95 ± 0.13 from 10B(t, 3He)10Be*(5.96) may indicate that the nuclear structure of 10Be and 10C differs because of the presence of the Coulomb force, giving rise to isospin symmetry violation.
At E(7Li) = 39 MeV, 10Be*(0, 3.37, 5.96) states were observed (1988ET02). At this energy sequential processes are blocked, due to isospin mixing, and the one-step mechanism is most important. Also see (1989ET03).
New constraints on the 11Li β-decay branch that feeds the 11Be ground state indicate that the 11Li β-delayed single neutron emission probability is P1n = 87.6 ± 0.8% (1997BO01).
The β-delayed neutrons following 11Li decay were measured by (1997MO35); results of their observations are presented in 10.14 (in PDF or PS). A different technique, utilizing a β-neutron-γ-ray 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 11Be state at Ex = 8.03 MeV; this new state is implied by both an ≈ 1.5 MeV neutron in coincidence with the 2590 keV 10Be*(5.96 → 3.36) γ-ray, and an ≈ 3.6 MeV neutron in coincidence with the 3368 keV 10Be*(3.36 → 0) γ-ray. However, the interpretation of β - n coincidences by (1997MO35) included low-energy neutrons from the unobserved 11Be*(3.87, 3.96) → 10Be*(3.36) + n and 11Be*(6.51, 6.70, 7.03) → 10Be*(≈ 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 11Be at Ex = 8.03 MeV, (2003FY01) developed a procedure to evaluate Doppler broadening in isotropic γ-ray decay that occurs, for example, following β-delayed neutron decay. A model was developed that indicates a well-defined γ-ray spectrum shape that depends on recoil velocity after decay, the level lifetime, and recoil energy-losses/stopping powers in the target. The 2590 keV γ-ray from 10Be*(5.958) decay was evaluated, and the observed Doppler broadening was consistent with population of this level via neutron-decay from a 11Be level around Ex = 8.6 - 9.1 MeV. This interpretation favors the analysis of (1997AO01, 1997AO04).
Angular distributions were measured for E(11Be) = 35 MeV/A (2000FO17, 2001WI05). The 10Beg.s., 3.4 MeV and unresolved states near 6 MeV were observed. The spectroscopic factors for the 10Be*(3.37) state inferred from standard DWBA and coupled-channels analysis differ by roughly a factor of 1.7. A "best estimate" for describing the 11Be ground-state wave function includes a 16% core excitation of the 10Be*(3.34) state [2+ Ä d]. Also see (1999TI04, 2000YI02). For calculations at E(11Be) = 800 MeV see (1998CA18).
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 quasi-quantum multi-step reaction model.
Angular distributions have been measured at Ed = 11.8 and 22 MeV to 10Beg.s. [see (1974AJ01)] and at 52 MeV to 10Be*(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 10Be*(9.6): see (1979AJ01).
Fusion evaporation products from 11B + 7Li were measured at E(7Li) = 5.5 - 19 MeV by detecting the reaction products and corresponding γ-rays (2000VL04). Reactions were observed indicating 10Beg.s. and 10Be* + γ(3368). Results were used to evaluate the 7Li + 11B fusion barrier and the angular momentum achieved in the compound nucleus.
Photo-breakup reactions on 12C have been reported for Eγ = 80 - 700 MeV (see 10.16 (in PDF or PS)). Two-nucleon photoemission shows promise as a means to study short-range nucleon-nucleon correlations, however it is necessary to understand the reaction mechanism and final state interactions. Between the Giant Dipole Resonance and the Δ-resonance, γ-ray absorption is primarily on clusters or pairs of nucleons which are emitted after photon absorption. Above the Δ resonance (Ex ≈ 300 MeV) γ-rays 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 missing-mass 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).
Electro-production of proton pairs on 12C targets has been reported for electron energies ranging from E = 0.1 - 14.5 GeV: see 10.16 (in PDF or PS). The 10Beg.s. is observed, but low-lying resonances are not resolved. Above Ex = 25 MeV, peaks corresponding to (1p)2, (1p1s) and (1s)2 proton pair removal are observed. As in (γ, 2p) reactions [see reaction 37], two-nucleon emission induced by virtual photons also shows promise as a means to study short-range nucleon-nucleon 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 12C is discussed in (1987GA11).
At En = 40 - 56 MeV, the pulse shape response for discriminating various final-state channels resulting from n + 12C interactions in NE213 and BC401a liquid scintillator was measured by (1994MO41). See also (1989BR05) for calculated cross sections at En = 15 - 60 MeV.
At E(6He) = 18 MeV, this reaction was studied by detecting the triple coincidence (10Be + 2α) (2004MI05). The kinematical reconstruction indicates that 10Be*(0, 3.37) and the multiplet near Ex ≈ 6 MeV participate in this reaction.
The 10Be*(0, 3.368) states, and higher lying unresolved states were observed at E(9Be) = 40.1 MeV (1999CA48).
At E(11B) = 190 MeV, the Jπ = 0+ 10Beg.s. and Jπ = 2+ excited states at 10Be*(3.36, 5.95, 9.4) excited states are observed (1998BE63).
Excited states in 10Be were reconstructed from the α+6He relative energy spectra at E(12Be) = 378 MeV (2001FR02). Tentative evidence was found for states at Ex = 13.2, 14.8 and 16.1 MeV, while other known levels were observed at 11.9 and 17.2 MeV.
At E(12C) = 357 MeV, the 10Be*(0, 3.37, 5.96, 7.54, 9.4) levels were populated (1996ST29). The Jπ = 0+ 10Be ground state is strongly populated and appears to result from a two-proton transfer which tends to leave the neutron configuration undisturbed.
At E(15N) = 318.5 MeV, known 10Be levels at 0, 3.37, 5.96, 7.37 and 9.5 MeV were observed (2001BO35). Additional measurements by (2001BO35) at E(15N) = 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 Eπ+ = 50, 100, 140 and 180 MeV (1992RA11).
See 12C in (1990AJ01).
Angular distributions were measured at E(3H) = 38 MeV (1989SI02). 10Be*(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 10Be excited states than shell model calculations predict.
At E(18O) = 102 MeV, a study of α-unbound states in 22Ne indicated that 10Be*(0, 3.37) participate in the reaction (2002CU04).
Astrophysical production of 10Be has been evaluated by measuring formation cross sections for protons incident on 16O and 28Si at Ep = 30 - 500 MeV (1997SI29), on 12C at Ep = 40 - 500 MeV (2002KI19) and on O, Mg, Al, Si, Mn, Fe and Ni targets at Ep = 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 10Be concentrations found in lunar rocks. See (1997BA2M, 1997GR1H, 1997MU1D, 1997ZO1C) for surveys of terrestrial 10Be concentrations, and see (2000NA34) for a model estimating 14N, 16O(p, 10Be) and (n, 10Be) cross sections for Ep = 10 MeV - 10 GeV and for discussion of various atmospheric transport models for distributing 10Be.
Spallation cross sections for Ep = 50 - 250 MeV protons on 16O 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 10Be from Ep = 12 GeV proton induced spallation reactions on Al through Au targets was measured by (1993SH27). Overall, 10Be production cross sections are found to increase with increasing target mass.
At E(10Be) ≈ 30 MeV/A, the 10Be + 12C reaction was observed to populate various exit channels (2004AH02, 2004AS02). States at Ex = 9.6 ± 0.1 and 10.2 ± 0.1 MeV were observed in the 6He + α breakup channel. Cross sections were given for breakup channels populating 8Be*(0, 3.0) and 9Be*(2.43), and other cross section were given for the (n, p) charge exchange reaction and proton pickup reaction that populate 10B and 11B, respectively.
For reaction (b), fragmentation of 10Be was measured on Si targets for E(10Be) = 20 - 60 MeV/A (1996WA27) and E(10Be) = 30 - 60 MeV/A (2001WA40). The total reaction cross section was found to be near 1.55 b in this energy region, and Rrmstotal(10Be) ≈ 2.38 fm is deduced from the cross section data.
The de-excitation of 10Be* nuclei formed in the ternary cold fission of 252Cf → 146Ba + 96Sr + 10Be*(3.37) yields γ-rays that are roughly 6 keV lower in energy (1998RA16) than expected from the accepted excitation energy of Ex = 3368.03 ± 0.03 keV. The absence of Doppler broadening suggests that the 10Be 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).