
^{9}Be (1966LA04)(See Energy Level Diagrams for ^{9}Be) GENERAL: See (1958BL57, 1959BA1D, 1959BR1E, 1959PI45, 1959TH16, 1960HE04, 1960KU1B, 1960PH1A, 1960SP08, 1960TA1C, 1960VA1H, 1961BA1G, 1961BA1E, 1961CL10, 1961GU1B, 1961KU1C, 1962BA1C, 1962IN02, 1962SC12, 1962TA1H, 1963HI1B, 1963MA1E, 1963SC1P, 1964AM1D, 1964BA29, 1964BA1Y, 1964BE1M, 1964GR1J, 1964NE1E, 1964RE1C, 1964ST1B, 1965BO1M, 1965KU1E, 1965MU1A, 1965NE1C, 1965RO1H, 1965WO01). See also Table 9.2 [Table of Energy Levels] (in PDF or PS). Ground state: μ = 1.1776 nm; Q = ± 0.03 b (1965FU1G).
The differential cross section for reaction (a) at 90° measured up to E_{t} = 1.90 MeV increases rapidly with energy below the coulomb barrier and then approaches a constant value. At 1.50 MeV, the total cross section for formation of the ground state of ^{7}Li is 190 mb; that for the first excited state is 4 times less (1961HO21: see also (1957JA37)). Angular distributions for both groups show maxima in the forward hemisphere. It is suggested that the large cross section indicates a cluster exchange process  here the exchange of t and d (1961HO1F, 1961HO21). The 0° differential cross section for reaction (c) increases monotonically between 0.10 and 2.4 MeV (1960SE12, 1961VA43, 1962SE1A) except for a resonance at E_{t} = 1.875 MeV, corresponding to an excited state of ^{9}Be at 18.937 MeV. The total cross section for neutron production at E_{t} = 2.12 MeV is 324 ± 32 mb (1961VA43). See also (1963JA1E). The 90° differential cross section for reaction (d) rises from 0.75 mb/sr at 0.62 MeV to 5.7 mb/sr at 1.8 MeV and then decreases slowly to 5.3 mb/sr at 2.2 MeV (see (1957JA37)). See also ^{5}He, ^{7}Li, ^{8}Li and ^{8}Be.
Angular distributions of groundstate protons have been measured at E_{α} = 10.15, 11.5 and 13.5 MeV (1960MA15) 13.6 and 14.7 MeV (1962KO13) and 30 MeV (1960KL03). At 30 MeV, strong backward peaking is evident (1960KL03). A qualitative account of the observations can be given if heavyparticle stripping (p + ^{5}He + α) is assumed (1962HO1C). See also (1956WA29).
See (1964KI02).
In the region E_{d} = 0.1 to 1.1 MeV, a resonance in the yield of capture γrays is observed at E_{d} = 362 ± 3 keV (1965WO01), 361 ± 2 keV (1965IM01), corresponding to an excited state in ^{9}Be at 16.973 ± 0.002 MeV. The width of the level is less than 470 eV (c.m.). The small width of the level and the correspondence with ^{9}Li*(2.69) argues for T = 3/2 (1965WO01). The angular distribution of the γrays to the ground state is isotropic to within 7%. The branching ratios to the ground state, and to the levels at 1.67, 2.43, 3.03 and 4.70 MeV are 100/8.5 ± 4.3/10.6 ± 5.3/ ≤ 4.5/9.6 ± 4.8. An upper limit for nonresonant, direct capture is 1.6 μb. The neutron decay of ^{9}Be*(2.43) and ^{9}Be*(4.70) is observed (1965IM01).
The cross sections for reactions (a) and (b) have been measured for E_{d} = 70 to 110 keV (1955RA14), 30 to 250 keV (1953SA1A) and 330 to 400 keV (1965IM01). The 0.36 MeV resonance is observed here also, in the yield of neutrons with E_{n} > 10 MeV: the ratio of the partial width of the 16.97 MeV level for emission of neutrons to ^{8}Be_{g.s.} to that for emission of γrays is ≈ 1.5, while Γ_{α0}/Γ_{γ} < 20 (1965IM01). The yield of neutrons has been measured from 0.2 to 4.8 MeV by (1952BA1A, 1957SL01: see also (1947BE1A, 1949WH1A)), and the yield of αparticles has been measured from E_{d} = 0.2 to 0.3 MeV by (1964MA60) and for 0.7 to 3.0 MeV by (1963PA04). Resonances for neutron production are observed at E_{d} = 0.68, 0.98 and (1.8) MeV (Table 9.4 (in PDF or PS)). At E_{d} = 0.90 MeV, αparticles from reaction (b) are isotropic within 2%, consistent with formation by swave deuterons (1957RI39). The angular correlation of groundstate αparticles with those resulting from the breakup of ^{5}He indicates J = 5/2^{} for the ^{9}Be level mainly responsible for the reaction at E_{d} = 0.9 MeV (1956RI37); a similar observation at E_{d} = 0.16 MeV suggests J = 3/2^{} for the responsible level (1957FA10). See also (1964FE01). At E_{d} = 0.9 MeV, reactions (a) and (c) account for less than 10% of the disintegrations at this energy (1956RI37). Polarization of groundstate neutrons has been measured by (1962HE06). The excitation function for reaction (b) shows indications of the E_{d} = 0.7 and 1.0 MeV resonances (unresolved in this work) as well as broad structure at E_{d} = 2.5 MeV. There is no indication of resonance at 1.8 MeV in this groundstate αyield. Also reported are αparticles from reaction (a) associated with the ^{8}Be excited states at 11.3, 16.6 and 16.9 MeV; the αparticles from the decay of the 11.3 MeV state seem to show resonance behavior at E_{d} = 0.7, 1.0 and 1.75 MeV. It is not clear whether the αparticles corresponding to ^{8}Be*(16.6) show resonance at E_{d} = 2.5 MeV or whether the ^{8}Be*(16.9) αparticles are appearing at this point (1963PA04). See also (1964BI10, 1965BI1F, 1965JO19), ^{5}He and ^{8}Be.
The yield of ^{8}Li (groundstate protons) has been measured for E_{d} = 0.29 to 0.78 MeV. A resonance is observed at E_{d} = 360 ± 3 keV with Γ < 2 keV. The ratio Γ_{p}/Γ_{γ} is ≈ 0.5 (1965IM01, 1965WO01): see also ^{7}Li(d, γ)^{9}Be. The yield of ^{8}Li(p_{0} + p_{1}) has been measured in the range E_{d} = 0.4 to 3.3 MeV by (1952BA1A, 1954BA46, 1960KA05) and from 1.1 to 4 MeV by (1956BE1A: stacked foils). Groundstate protons have been examined from E_{d} = 1.0 to 4.0 MeV by (1960SE08, 1963SE1F). Resonances are reported at 0.77, 1.02, (1.375), 2.0, 2.5 and 3.7 MeV (Table 9.4 (in PDF or PS)), apparently superposed on a rising background. The total cross section at E_{d} = 0.77 MeV is 150 ± 35 mb (1954BA46), 176 ± 15 mb (1960KA05), From E_{d} = 1.0 to 4.0 MeV, angular distributions are unusually well described by stripping theory; the resonance at E_{d} = 1.375 MeV shows no effect on the angular distribution (1960SE08, 1963SE1F). The yield of 0.95 MeV γrays from ^{7}Li(d, p)^{8}Li* rises smoothly from E_{d} = 1.9 to 3.3 MeV. Above E_{d} = 2.3 MeV, the isotropy of the γrays is taken to indicate predominance of the stripping process (1962CH14).
The upper limit for the relative partial width for elastic scattering at E_{d} = 0.36 MeV (^{9}Be* = 16.97), Γ_{d0}/Γ_{γ}, is 400 (1965IM01). The elastic scattering has been studied from E_{d} = 0.4 to 1.8 MeV by (1964FO13). The scattering cross sections lie below the Rutherford values at the lower energies. A marked increase occurs in the range E_{d} = 0.8 to 1.0 MeV, and a conspicuous anomaly occurs at E_{d} = 1.0 MeV. A rising background is ascribed to other overlapping resonances. The scattering below E_{d} = 1.0 MeV can be satisfactorily accounted for by swaves: the variation of parameters is consistent with  but does not require  a level at E_{d} = 0.8 MeV. The resonance at 1 MeV appears to be due to pwave deuterons (1964FO13). See also ^{7}Li and (1958RO49).
The cross section for reaction (a) rises steeply from threshold to 95 mb at E_{d} = 2.4 MeV and then more slowly to about 165 mb at E_{d} = 4.1 MeV (1955MA20). See also ^{6}He and ^{6}Li.
See (1959AJ77, 1962SE1A) and ^{10}Be.
Observed proton groups are listed in Table 9.5 (in PDF or PS) (1955AL57, 1958MO99, 1963CA02, 1965CO1F, 1965MA1E). The γdecay of the narrow 14.39 MeV state to the ground and 2.4 MeV states indicates Γ_{γ0}/Γ_{p} = 0.023 ± 0.005, Γ_{γ1}/Γ_{p} = 0.04 ± 0.01. Assuming Γ_{γ0} = 18 eV (see ^{9}Be(e, e')), Γ = 0.8 ± 0.3 keV for the 14.39 MeV state. This level is presumed to be the lowest T = 3/2 state of ^{9}Be, analogous to the ^{9}Li ground state (1965GR08, 1965LY01). There is some evidence also for the γdecay of a state at ≈ 17 MeV, presumably the T = 3/2 analogue of the first excited state of ^{9}Li (1965GR08: see also ^{7}Li(d, γ)). See also (1961WO05) and ^{10}B.
The groundstate angular distribution has been observed at E_{α} = 48 MeV (1960CE01). See also (1962MA59).
At E(^{7}Li) = 2.9 MeV, αparticle groups are observed corresponding to ^{9}Be*(0, 1.75, 2.4, 3.0, 11.9 ± 0.2 MeV); the last has Γ = 500 ± 100 keV. No other levels are observed for E_{x} < 13.0 MeV (1964ME07). See also (1963GA02, 1963HU02, 1964KI02, 1965BE1X).
^{9}Li decays to the ground state (25 ± 15 %) and to ^{9}Be*(2.4) (75 ± 15 %): log ft = 5.5 ± 0.2 and 4.7 ± 0.2, respectively. The allowed character of the transition is consistent with ^{9}Be*(2.4) = 5/2^{} and ^{9}Li(0) = 3/2^{} or 5/2^{} (1963AL18). See also ^{9}Li.
See (1964LO1C).
The photoneutron cross section has been measured from threshold (E_{γ} = 1664 ± 4 keV: (1956CO56)) to 320 MeV: see Table 9.6 (in PDF or PS). A sharp peak occurs just above threshold, at E_{γ} = 1.70 MeV (1960WA06, 1961JA13) followed by a weak maximum at 2.4 MeV, a strong sharp peak at 2.95 MeV, and a broad maximum at 4.6 MeV (1961JA13). (1959TH15) find welldefined peaks at 11.3 ± 0.2 and 13.3 ± 0.2 MeV, with integrated cross sections of 4.0 and 3.9 MeV · mb. A considerable yield in the range 8  11 MeV is also indicated (1959TH16). The giant resonance occurs at 20  22 MeV (1953JO1B, 1953NA1A, 1956CO59). At E_{γ} = 6.1 MeV, the main processes appear to involve ^{9}Be(γ, n)^{8}Be*(2.9) and reaction (b) (1954CA1A). For E_{γ} = 18 to 25 MeV, ≈ 80% of (γ, n) processes lead to ^{8}Be*(16.6) (1964BE30). See also (1960SE1D, 1965KO08, 1965KO1B). The total nuclear absorption cross section is about 2 mb at E_{γ} = 10 MeV: a deep minimum at ≈ 13 MeV is followed by a rise to ≈ 5 mb at 18 MeV and a slow decrease to ≈ 3 mb at 35 MeV (1965WY02). Fine structure is reported at E_{γ} = 20.47 ± 0.04 and 20.73 ± 0.04 MeV (1964TE04). See also (1962MI15). Measurements involving timeofflight analysis of the neutron energies show the 1.7 and 3 MeV resonances in groundstate neutrons (n_{0}), but ascribe the 4.6 MeV structure to slow neutrons, arising from reactions (b), (c) or from n_{1} to ^{8}Be*(2.9): groundstate neutrons account for < 10% of the total at this energy. The yield of n_{0} remains essentially constant from 5 to 16 MeV, aside from a broad maximum near 10 MeV and a shallow minimum at 13 MeV. The yield of n_{1} rises sharply near 6 MeV, showing signs of a sharp peak at 7 MeV and remains high until about 10 MeV where it falls rapidly to a minimum at 13  14 MeV. There is evidence of a broad peak near 12 MeV (1963DE1J). For E_{γ} = 5.6 to 8.5 MeV, the relative contribution of n_{0} ranges from 0.5 to 0.3 (1963BO32). Angular distributions of neutrons from the 1.67 and 4.6 MeV levels are isotropic; those from the 2.4 MeV level show slightly higher yield at θ = 90°. Neutrons from the 3.0 MeV level have the distribution σ(θ) = 1 + (1.0 ± 0.2)sin^{2}θ, compatible with E1 excitation to a 5/2^{+} Dstate (1961JA13: see also (1949HA1A, 1961BA1G)). Some fore and aft asymmetry may indicate the presence of oddparity amplitudes (1965PH1B). The fact that the 3.0 MeV state is strongly excited in (γ, n) and not in 180° (e, e') (M1 excitation) also indicates positive parity (1961BL1D). The same argument suggests positive parity (E1 transitions) for levels at 1.7, 6.8, 7.9, 9.2, 11.3 and 13.3 MeV (1959TH16). For E_{γ} = 5.6 to 8.5 MeV, angular distributions are of the form 1 + Asin^{2}θ, with A = 0.20 to 0.27, consistent with P_{3/2} → D_{3/2} transitions (1962BO08, 1962BO21, 1963BO32). Evidence for polarization of neutrons is reported by (1964CO17). See also (1959KU84, 1961VA09, 1964AL33). Calculations of the (γ, n) cross section near threshold have been made by (1960FR1B), using a singleparticle model with a diffusesurface SaxonWoods potential and assuming a 1/2^{+} level at E_{x} = 1.70 MeV. A good account of the observations is obtained, but with a rather large diffuseness parameter, a = 1.2 fm, in the final state. If the parameter is taken to be a = 0.6 fm, the calculated cross section is about 1.6 times too high. According to (1961BL1D), a model in which the neutron in ^{9}Be(0) is strongly coupled to a deformed ^{8}Be core leads to a sizable probability of excitation of the core to the 2^{+} state, reducing the calculated cross section at 1.7 MeV. The 4.7 MeV structure is then ascribed to transformations in which ^{8}Be is left in the excited 2^{+} state. A calculation of the lowenergy excitation function has been made by (1963CO05) using the same model as (1960FR1B) but fixing the final state diffuseness parameter at a = 0.6 fm, and varying the final state potential depth. The slope and magnitude of the observed (γ, n) cross section are best accounted for by a bound sstate, with energy 19^{+9}_{5} keV below threshold (1963CO05). (1961BA1G) considers couplings of 1s and 1d neutrons to ^{8}Be(0) and ^{8}Be(2^{+}). With the 1.7 MeV level assumed 1/2^{+}, 3/2^{+} and 5/2^{+} levels are predicted at 4.88 and 4.05 MeV, respectively. It is suggested that the 3.03 MeV level is an unresolved combination of 1/2^{} and 5/2^{+}. See also (1961GU1C, 1961KO1J, 1962CU05, 1962KO11, 1963CO1D, 1963SA09, 1964BI1E, 1964FR1C, 1964MA2E, 1965WE1E). The cross section for reaction (c) is < 1 μb at E_{γ} = 1.63 MeV (1952AL26, 1952AL30). For reaction (d) see (1957LO1A).
The yield shows structure in the energy region corresponding to the ^{9}Be levels at 17  19 MeV (1962CL06), followed by the giant resonance at E_{γ} = 22.2 MeV (1953HA1A: Γ = 4.7 MeV, σ = 2.72 mb), ≈ 23 MeV (1962CL06: σ = 2.64 ± 0.30 mb). The angular and energy distributions of photoprotons in various energy intervals have been studied by (1956CO59, 1956KL19, 1962CH26, 1963KI1C, 1965KO08). At E_{brems.}(peak) = 335 MeV, the polarization of photoprotons at 45°, 56° and 90° is small and is consistent with zero (1962LI13). See also (1959CH25, 1961MA36, 1962CU05, 1962MI15, 1962VO1D) and (1959AJ76).
The cross section for reaction (a) is appreciable only for γenergies greater than the sum of the threshold energy and the binding energy of the most weakly bound nucleon in ^{7}Li. The main processes involved are then thought to be those in which the emission of deuterons is accompanied by one or more nucleons (1962BA62, 1962CH26, 1962VO1D). See also (1959CH25, 1960SH1D, 1962CU05, 1962MA1F, 1963BA1K, 1964SH1B, 1965KO08) and (1959AJ76).
Elastic scattering of electrons has been studied at E_{e} = 42, 80, 125, 150, 190 and 300 MeV (1953HO79, 1954MC45, 1959ME24, 1963GO04). Analysis of the 190 and 300 MeV results has been carried out in terms of various models for the charge distribution; the r.m.s. radius is about 2.60 ± 0.2 fm, depending on the model. At large values of momentum transfer, a static spherical distribution seems inadequate and a contribution from the quadrupole distribution may be required (1959ME24). According to (1960WA1J) the 300 MeV data can be matched with a Fermi distribution plus a quadrupole distortion consistent with Q = 0.02 b. See also (1961WA1C, 1963GU1A). Magnetic scattering at θ = 180° gives indication of both M1 and M3 contributions (1965RA1C: see also (1963GO04)). Inelastic scattering reveals a number of levels from 1.6 to 16.9 MeV (see Table 9.7 (in PDF or PS)). Of these, only the 2.43, (14.7), and (16.9) MeV levels are strong in 180° scattering, where M1 transitions should dominate (1960BA47, 1962BA1D, 1962ED02). Studies of the 2.4 and 6.7 MeV levels at smaller angles reveal strong E2 components; quantitative comparison with form factors and absolute cross sections predicted by the αrotational model (1960IN1A) indicate J^{π} = 5/2^{} and 7/2^{}, respectively, for these two levels. The excitation energies and transition widths are consistent with the assumption that they are members of a K = 3/2^{} rotational band based on the ground state. The derived intrinsic g.s. quadrupole moment Q_{0} = 0.26 ± 0.01 b is nearly twice that obtained from the spectroscopic value Q_{0} = 5 × 0.029 b (1963NG01). In both this work and calculations of (1962KU1C) the rotational αmodel shows increasing deviations from experiment for momentum transfer q > 1 fm^{1}; the Nilsson model has the same fault, but in opposite sense. An intermediate coupling model with enhanced quadrupole charge distribution is superior (1962KU1C). See also (1961WA1C, 1965RA1D). Comparison of the inelastic scattering from the 1.6 MeV level at two angles indicates that this level is most probably excited by E1 (1963NG01). The fact that the 1.6, 3.0 and 4.7 MeV levels appear strongly in (γ, n) but not in (e, e') at 180° suggests that these levels are excited by E1 transitions (1962ED02). [The 14.7 MeV level is presumably the T = 3/2, J = (3/2)^{} analogue of the ^{9}Li ground state; the 16.9 MeV level may correspond to the first excited state.] In the range 17 to 49 MeV, inelastic scattering appears to be largely via E1, E3, M2 to the exclusion of M1, E2, M3 (1962NG02, 1963NG1B, 1964NG1A).
The neutron spectrum observed when ^{9}Be is bombarded with 3.7 MeV neutrons exhibits a structure which is consistent with the excitation of the ground states and the levels at 1.7, 2.4 and 3.1 MeV, with subsequent neutron emission from the latter two. It is concluded that the (n, 2n) process at this energy proceeds mainly via discrete states of ^{9}Be (1957HU14, 1958WA05). Timeofflight studies from E_{n} = 2.6 to 6.0 MeV show that about 1/2 of the inelastic processes involve ^{9}Be*(2.43). A continuous distribution may be ascribed either to ^{9}Be*(1.7) or to (n, 2n). Examination of the spectra at E_{n} = 3.5 MeV yields the result that the 2.43 MeV level decays only 12 ± 5 % via ^{8}Be_{g.s.} (1959MA34). At E_{n} = 14 MeV, evidence is found for the participation of the 6.8 MeV level. A search for an angular correlation between outgoing neutrons yielded a negative result (1963JE05). At E_{n} = 14 MeV, the cross section for production of ^{9}Be*(2.4) is 200 ± 45 mb (1961CO1E), 200 ± 100 mb (1961MY01), 170 ± 30 mb (1958AN32) comparison with σ(n, 2n) = 500 mb (1964ST25) indicates that about 1/3 of the (n, 2n) processes proceed via ^{9}Be*(2.4) (1958AN32). Elastic and inelastic neutron angular distributions show forward peaking at E_{n} = 14 MeV (1958AN32, 1958NA09). See also (1958BE1E, 1959CH1E, 1959SA04, 1959WI41, 1960BA24, 1960BA28, 1960LU1B, 1960MC04, 1963OP1A, 1964BO31, 1964CR1B, 1965LO1K, 1965RO1U) and ^{10}Be.
Elastic scattering has been studied at E_{p} = 6 MeV (1963BL20), 5 to 15 MeV (1964BI19), 10 MeV (1956RA32), 6, 8 and 12 MeV (1963TE1B), 12 MeV (1958SU14), 14.5, 20 and 31.5 MeV (1956KI54), 16.6 to 36.6 MeV (1965AR1E), 18.9 MeV (1956DA03), 31 MeV (1953WRZZ, 1954FI35, 1956BE14), 48 MeV (1965WI1H), 142 MeV (1961TA06), 143 MeV (1964ST16), 160 MeV (1965RO1T), 316 MeV (1956CH80) and 725 MeV (1965MC04). All angular distributions show pronounced diffraction maxima characteristic of the optical model. Analysis in terms of the diffusesurface optical model is discussed by (1957ME21). See also (1956KL55, 1959HI1H, 1959JO43, 1960NE09, 1960NE11, 1960SA28, 1961IS05, 1961JO18, 1961RE03, 1964CR1B, 1964SA1L, 1964VE1A). Inelastic scattering is observed to states at 1.7, 2.4, 3.1, 4.8, 6.8, 7.9, 11.3 MeV and others: see Table 9.8 (in PDF or PS). The structure at ^{9}Be*(1.7) is unsymmetrical, rising abruptly from threshold at Q = 1.669 MeV to a peak within < 14 keV (1962BR09). The width at halfmaximum is 175 ± 25 keV (c.m.), indicating dominant swave emission of neutrons (1960SP08). According to (1960SP08) the structure does not represent a true state, but results from the spatial localization of the lowenergy neutron and ^{8}Be after emission of the inelastically scattered proton. Using a specialized densityofstates function, they obtain a good match to the experimental shape in this hypothesis. See also (1963PH1A). On the other hand, (1962BA1C) find an equally good fit with a densityofstates function of BreitWigner shape, corresponding to a J^{π} = 1/2^{+} level at E_{x} = 1.75 MeV with width γ^{2}_{0} = 1.01 MeV (R = 4.35 fm), parameters which also fit the (γ, n) cross section. At E_{p} = 18.9 MeV, the 1.7 MeV group is not observed; the upper limit to the intensity of the group is < 2% of that to the 2.4 MeV state (1962SC12). See also (1955GO48, 1956BO18, 1958MI1C, 1958SU14, 1964BI19, 1964SC1F, 1965WI1H). The energy of the 2.4 MeV level is given as 2433 ± 5 (1951BR72), 2434 ± 5 (1956BO18), 2432 ± 4 (1955GO48), 2430 ± 5 keV (1960SP08); the width is ≤ 1 keV (1955GO48), ≤ 3 keV (1960SP08). Angular distributions of protons leading to the 2.4 MeV state are not well matched by plane wave direct interaction calculations (1962SC12). The 12 MeV data suggest l = 0 and 2 (J^{π} = 1/2^{} or 5/2^{}) (1958SU14) while the 31 MeV data are best fitted by l = 2 (1956BE14, 1958SU14, 1962SC12). It appears that the relative inelastic cross sections for various levels are largely independent of bombarding energy or particle; in particular, the 2.4 and 6.8 MeV levels are always strong and the 1.7, 3.0 and 4.8 MeV levels always weak. It is suggested that the strong excitation of the former is relative to a collective enhancement of electric multipole transition strengths connecting them to the ground state (1958BL57, 1959PI45, 1962SC12). The excitation energies and inelastic cross sections are consistent with the assumption that they have J^{π} = 5/2^{} and 7/2^{}, respectively. On the collective model, they are members of the ground state K = 3/2^{} band: the J = 9/2^{} member is then expected at 10  11 MeV (1958BL57). See also (1964JA03, 1965HA17). The 3 MeV state has a width 250 ± 50 keV (1960SP08): E_{x} = 3.03 ± 0.03 MeV (1956BO18), 3.04 ± 0.05 MeV (1960SP08). Comparison of the width with that of the mirror level ^{9}B*(2.79) suggests that the level decays either to ^{8}Be(0) via dwave or to ^{8}Be(2^{+}) via swave: J = 3/2^{+}, 5/2^{+} (1960SP08). See also (1955GR12, 1958TY46, 1960LU1B, 1961IS05, 1963BA1R, 1963BL20, 1963RU05).
Angular distributions of groundstate deuterons have been studied at E_{p} = 4.9, 5.5 MeV (1961RE03), 5 to 8 MeV (1951HA1A), 6.8 MeV (1960NE09, 1960NE11), 7 MeV (1964YA1A), 10 MeV (1956RA32), 12 MeV (1958SU14), 16.5 MeV (1956RE04), 22 MeV (1953CO1C), 31 MeV (1956BE14), 95 MeV (1956SE1A) and 155 MeV (1963BA1R, 1963RA01). The distributions in the range E_{p} = 5 to 31 MeV are substantially identical, contrary to the prediction of the simple Butler theory with fixed cutoff radius (1956GL25). An analysis by (1961RE03) (see Table 9.9 (in PDF or PS)), shows good agreement for the 12 to 31 MeV data with inclusion of a volume interaction, leading to θ^{2}_{n} = 1.2%. Polarization of the deuterons has been studied at E_{p} = 3 MeV (1961LA17). See also (1960BA26, 1965MO27). At E_{p} = 95 MeV, states of ^{8}Be near 16 to 18 MeV are strongly excited (1956SE1A). At E_{p} = 155 MeV, states at ≈ 16.6 and ≈ 18.9 MeV are excited with 0° differential cross sections of 3.6 and 1.15 mb/sr, respectively (1963BA1R, 1963RA01).
Angular distributions and excitation functions for E_{p} = 3 to 12 MeV suggest direct interaction. Analysis with DWBA in terms of ^{9}Be → ^{6}Li + t (l = 1) yields fair agreement for α_{0} but not for α_{1} (1963BL20). The observed large cross section at back angles suggests that ^{9}Be is better described as ^{4}He + ^{5}He (1963SC1P). See also (1964YA1A, 1965MO27).
The summed proton spectrum in reaction (a), observed at E_{p} = 155 to 450 MeV shows two peaks, with Q = 16.7 ± 0.3 and Q = 25.8 ± 0.4 MeV, corresponding to removal of a pproton and an sproton respectively (1958MA1B, 1958TY49, 1961PU1A, 1962GA09, 1962GA23, 1962IN1A, 1963BE1A, 1963BE42, 1963BO1R, 1963RI1B, 1964BA1C, 1964TI02, 1965RI1A, 1966TY01). At E_{p} = 155 MeV, p  α correlations (reaction (c)) give evidence for a substructure ^{9}Be = ^{5}He + ^{4}He in a relative sstate with a probability of 7% (1963RU05). For reaction (b), see ^{7}Li.
Elastic scattering has been studied at intermediate energies by (1961BA06, 1962GR14: 7.8 MeV), (1963FR1F: 12.8 MeV), (1961IS04, 1963SA1G: 14.7 to 18.1 MeV), (1964HE01: 15.8 MeV), (1958SU14: 24 MeV), (1962SL03: 27.7 MeV). All show pronounced diffraction patterns. See also (1947GU1A, 1952EL01, 1959ZA01) and ^{11}B. Inelastic groups are reported to states at 1.7, 2.4, 3.0, 4.8 and 6.8 MeV (1955RA41, 1956GR37, 1958MI1C, 1958SU14). The angular distributions to the 2.4 MeV state have been studied at E_{d} = 15, 24 and 27.7 MeV (1956HA90, 1958SU14, 1962SL03). Analysis by direct interaction theory yields l = 2, J = 1/2^{}, 5/2^{} or 7/2^{}. See also (1958BL57, 1959BL31, 1960EL09, 1960LU1B).
Comparison of (d, t) and (p, d) pickup cross sections leads to an estimated form factor for the triton of 4 ± 1 fm^{1} (1961RE03); this values is about 4 times larger than that estimated by (1960MA32).
See (1960IG01, 1962WE1C, 1964GO1J).
See ^{8}Be.
Elastic scattering has been studied at E_{α} = 9.5 to 20 MeV (1965TA1C), 18.4 MeV (1964LU02), 23.8 MeV (1964GR39), 28 MeV (1964YA1A), 42 MeV (1956FA02: see (1958BL57)) and 48 MeV (1958SU14). Inelastic groups are observed to ^{9}Be*(1.8, 2.4, 3.0, 6.8, 11.3) (1955RA41, 1958SU14, 1964LU02, 1964YA1A). The angular distribution of the groups corresponding to the 1.8 MeV "level" is consistent with J^{π} = 1/2^{+} (1964LU02). The angular distribution of the Q = 2.4 MeV group, at E_{α} = 48 MeV, indicates l = 2, J = 1/2^{}, 5/2^{} or 7/2^{} (1958SU14). Analysis based on the rotational model leads to a deformation coefficient β_{2} = 0.46 (1959BL31), 0.34 ± 0.01 (1964GR39). Measurement of the momentum and angular distributions of αparticles from the breakup of ^{9}Be*(2.4) indicates that the decay proceeds mainly via ^{4}He + ^{5}He, or by direct threebody breakup. Gamma decay is < 1%, neutron emission to ^{8}Be(0) is < 10% (1957BO83: see also (1959MA34) in ^{9}Be(n, n')^{9}Be*, and (1962ST12)). At E_{α} = 25.4 MeV, the continuum has been analyzed in terms of a combination of three and fourbody breakup. At low energies the results are consistent with a mixture of ^{9}Be + α → ^{8}Be(0) + α + n, ^{9}Be*(2.4) → 2α + n or ^{5}He + ^{4}He (1962BR14). The third excited state is located at E_{x} = 3.04 ± 0.03 MeV, with Γ = 300 ± 50 keV (1964LU02). See also (1958BL57, 1959PI45, 1962ST12, 1964GO1K, 1965SA1K) and ^{13}C.
Angular distributions of ^{8}Li nuclei observed for E(^{7}Li) = 2 to 4.0 MeV, show pronounced peaks at θ_{lab} = 60° to 30°. The decrease of peak angle with increasing energy suggests a neutron transfer process (1957NO17, 1959NO40, 1960NO1A). The radial distribution of the ^{9}Be neutron is deduced for R = 15 to 30 fm (1960AL1H, 1960GE1B). See also (1963LE10, 1965PO1F).
Elastic scattering in reactions (a) and (b) for E_{c.m.} = 3 to 15 MeV has been studied for angles near 90° (c.m.). The fact that no diffraction structure was found may reflect a more diffuse surface for ^{9}Be than for ^{12}C (1961KU1D, 1963KU1L). At E(^{14}N) = 27.3 MeV no agreement is found with the predictions of a sharp cutoff model for elastic scattering (1959HA28). See also (1963WI1G).
See (1956GO1G).
At E_{n} = 14 MeV, groups are observed corresponding to ^{9}Be*(0, 2.43); no other groups are observed below E_{x} ≈ 5.5 MeV. The angular distributions of the deuterons indicate odd parity, 1/2 < J ≤ 9/2 for both states (1954RI15). See also (1955FR1F, 1956FR18, 1963CE1B, 1964TO1C) and ^{11}B.
The summed proton spectrum at E_{p} = 460 MeV yields Q = 6.7 ± 0.5, 11.9 ± 0.5, 17.1 ± 0.6 (all l ≠ 0), and Q = 30.5 ± 0.6 MeV (l = 0) (1966TY01). See also (1958TY49, 1961PU1A, 1962GA09, 1962GA23). See also (1963RI1B, 1964TI02) and ^{10}B.
At E_{d} = 10 MeV, θ = 30°, groups corresponding to ^{9}Be*(0, 1.7, 2.4, 3.0) are observed with relative intensities 1.0/0.07/0.70/0.16 (1965SY02).
At E_{t} = 1 MeV, αgroups are observed corresponding to ^{9}Be*(2.39, 3.06) (1955AL57). See also (1963HO19).
At E(^{14}N) = 27.5 MeV, the ground state angular distribution shows a single maximum at θ_{c.m.} = 30° (σ(θ) = 1.3 mb/sr). The total groundstate transfer cross section is 1.34 ± 0.30 mb, corresponding to an interaction radius R_{min} ≈ 2.2(A^{1/3}_{1} + A^{1/3}_{2}) fm (1962NE01).
Not reported.
Not reported. For reaction (b), see (1964BA1C).
Alpha groups are reported corresponding to states at (1.75), 2.4 and 3.0 MeV (1956BO18, 1958KA31, 1958MI1C). The width of the 1.75 MeV structure is 224 ± 25 keV (1958KA31, 1966PU02). The energy of the 2.4 MeV state is 2422 ± 5 keV (1951VA08), 2431 ± 6 keV (1954EL10), 2424 ± 5 keV (1956BO18). The next state is at 3.02 ± 0.03 MeV (1955LE36), 3.05 ± 0.03 MeV (1956BO18). Its width is ≈ 0.3 MeV (1956BO18), Γ_{c.m.} = 257 ± 25 keV (1958KA31, 1966PU02). See also (1955HO48, 1961TE02, 1963RO22, 1964GR19, 1964YA1A). The ratio of the γdecay width to the total width, Γ_{rad}/Γ, of the 2.4 MeV state is (1.15 ± 0.15) × 10^{4} (1964PU04). Since Γ_{rad} is known from (e, e') (see (1962ED02) and Table 9.4 (in PDF or PS)), Γ = 1.0 ± 0.2 keV. For the 1.7 MeV state Γ_{rad}/Γ < 2.6 × 10^{5} (1964PU04, 1966PU02).
Analysis of 128 cloud chamber stars involving ^{9}Be*(2.4) leads to the conclusion that the probability of ^{9}Be*(2.4) → n + ^{8}Be(0) is 13 ± 5 % (1965MO09). See also (1955GR21, 1962BA15, 1962BA25, 1963AL10, 1963DA12, 1963SE08, 1964BR25, 1964CH28).
See (1953MI31).
