
^{7}Be (1988AJ01)(See Energy Level Diagrams for ^{7}Be) GENERAL: See also (1984AJ01) and Table 7.7 [Table of Energy Levels] (in PDF or PS) here. Nuclear models: (1983BU1B, 1983FU1D, 1983HO22, 1983PA06, 1984BA53, 1984KA06, 1984WA02, 1985FI1E, 1986FI07, 1986KR12, 1986VA13). Special states: (1982PO12, 1983BU1B, 1983HO22, 1984FI20, 1984WA02, 1985FI1E, 1986FI07, 1986VA13, 1986XU02, 1988KW02). Electromagnetic transitions, giant resonances: (1984KA06, 1985FI1E, 1986FI07, 1986ME13). Astrophysical questions: (1984EN1A, 1984HA1B, 1984RA1E, 1985BO1E, 1985GI1C, 1985DE1K, 1985KL1A, 1986BA50, 1986HU1D, 1986MA1U, 1986ME13, 1987FI1C, 1987KA1U, 1987MA1X, 1987MA2C, 1987RA1D, 1988KA07). Complex reactions involving ^{7}Be: (1981AS04, 1983AS05, 1983EN04, 1983GU1A, 1983MA53, 1983OL1A, 1983SO08, 1983ST1A, 1983WA19, 1984BE1E, 1984GL06, 1984GO03, 1984GR08, 1984HI1A, 1984MO29, 1984NE1A, 1984ST1B, 1985BA1L, 1985JA18, 1985MO08, 1985MO17, 1985MO24, 1985ST1B, 1985TA18, 1985TR1B, 1985WO11, 1986AV1B, 1986AV07, 1986BL12, 1986CA30, 1986CS1A, 1986GL1E, 1986GO1B, 1986ME06, 1986MO13, 1986WE1C, 1986XU02, 1986XU1B, 1987AU1C, 1987BA38, 1987BL13, 1987CH26, 1987DE37, 1987DU07, 1987FE1A, 1987GE1B, 1987GL05, 1987GR11, 1987HA45, 1987JA06, 1987KO15, 1987LY04, 1987NA01, 1987NI04, 1987PO23, 1987ST01, 1987TAZU, 1987TR05, 1987VI14, 1987WA09, 1987YA16, 1988BE09, 1988BL09, 1988BUZI, 1988BU1Q, 1988CA06, 1988CEZZ, 1988GO1F, 1988KI05, 1988KW02, 1988LI1A, 1988PO1F, 1988RU01, 1988SA19, 1988VA1E, 1988VUZZ). Applications: (1983AS03, 1984EN1A, 1985TA1D, 1986FI1C, 1987FI1C, 1988IV1A). Reactions involving pions and kaons: (1983KA19, 1984HU1C, 1985LA20, 1985MO1F, 1987KA09, 1988GIZU). Hypernuclei: (1982KA1D, 1983SH38, 1983SH1E, 1984MI1C, 1984MI1E, 1984ZH1B, 1985AH1A, 1986DA1B, 1987MI38, 1987PO1H, 1988TA29). Other topics: (1983FU1D, 1983PA06, 1985AN28, 1987AJ1A, 1988FIZT, 1988KW02). Ground state of ^{7}Be: (1983ANZQ, 1984KA06, 1985AN28, 1985FI1E, 1985HA18, 1985TA18, 1986KO1U, 1987KA1U, 1987KA22, 1988KA07). The interaction nuclear radius of ^{7}Be is 2.22 ± 0.02 fm (1985TA18). [See also for derived nuclear matter, charge and neutron matter r.m.s. radii].
The decay is complex: see ^{7}Li.
The capture cross sections have been measured for E_{α} = 0.250 to 5.80 MeV and at E(^{3}He) = 19 to 26 MeV [see (1974AJ01, 1984AJ01)], at E_{c.m.} = 195 to 686 keV (1988HI06), and at E_{α} = 385 to 2728 keV (1984OS03) and 1225 keV (1984AL24). One of the main reasons for doing these measurements is to determine the astrophysical S(0) factor. The values of S(0) appear, on the average, to be higher if the experiment involves measurement of the 0.48 MeV γ following εcapture rather than if it involves a direct measurement of the capture γrays. It is not entirely clear why this should be so. Contaminant production of ^{7}Be may be involved: see (1988HI06) and e.g. (1984AL24, 1985FI1D, 1986LA22). Earlier measurements, sometimes recalculated, are discussed by (1986LA22, 1987KA1R, 1988HI06). The latter adopt best values of S(0) = 0.51 ± 0.02 keV · b [prompt γrays] and 0.58 ± 0.02 keV · b [^{7}Be activity] (1988HI06). See also (1984AL24, 1985FI1D, 1987KA1R, 1988BA86). Theoretical calculations are in general agreement with the experimental values. For instance (1985BU02) from a clustermodel calculation obtain S(0) = 0.47 ± 0.02 keV · b while (1983WA13, 1984WA06) obtain S(0) = 0.60 keV · b. The solar model calculations of (1982BA80) used S_{34}[S(0)] = 0.52 ± 0.02 keV · b. It appears clear that the uncertainty in S_{34} is not of severe consequence to the solar neutrino problem [see, e.g. (1985FI1D)]. For astrophysical considerations see (1984AJ01) and (1982BA1J, 1982KA1E, 1983FO1A, 1983HA1B, 1984DA1H, 1984HA1M, 1984IW01, 1984WA11, 1984YA1A, 1985BA1Q, 1985BO1K, 1985CA41, 1985DE1K, 1985KA1H, 1985KA1K, 1986BA50, 1986FI15, 1986KA45, 1986ME13, 1987AR1J, 1987AS05, 1987RO25, 1987WE1C, 1988FO1A, 1988KAZY, 1988KA07, 1988KA1H). See also (1986LI04; theor.).
Elasticscattering studies have been reported for E = 0.25 to 198.4 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at E_{α} = 56.3 to 95.5 MeV (1985NE08, 1986YA14). Polarization measurements have been carried out at E = 4.3 to 98 MeV [see (1979AJ01)] and at E(^{3}pol. He) = 55 to 95 MeV (1986YA14). For l ≤ 4, only fwave phase shifts show resonance structure for E(^{3}He) < 18 MeV, corresponding to ^{7}Be*(4.57, 6.73, 9.27): see Table 7.7 (in PDF or PS). No structure corresponding to ^{7}Be*(7.21) (J^{π} = 5/2^{}) is seen in the elastic data. The swave phase shift is somewhat greater than hardsphere. The decay of ^{7}Be*(9.27) (J^{π} = 7/2^{}) to ^{6}Li(0) requires fshell configuration admixture. An estimate of the yield of groundstate protons relative to those corresponding to ^{6}Li*(2.19) yields γ^{2}(p_{0})/γ^{2}(p_{1}) = (16^{+5}_{10})%. A phaseshift analysis (singlelevel Rmatrix) has been carried out for E(^{3}He) = 18 to 32 MeV: the pwave phase shifts indicate a 1/2^{} state at E_{x} ≈ 16.7 MeV (E_{r} = 26.4 MeV), with γ = 6.5 MeV. There is the suggestion also of broad l = 4 and 5 states at E(^{3}He) > 30 MeV [E_{x} > 19 MeV]: see (1984AJ01). The differential cross section for reaction (b) has been determined for E(^{3}He) = 8 to 28 MeV [see (1979AJ01)] and at E_{α} =22.2 to 26.5 MeV. Resonances are observed corresponding to ^{7}Be*(7.21, 9.27) in the p_{0} yield, to ^{7}Be*(9.27) in the p_{1} yield and to states at E_{x} ≈ 10 MeV (T = 1/2) and 11.0 MeV (T = 3/2) in the yield of 3.56 MeV γrays. The evidence for the latter derives mainly from interference arguments. There is also some evidence for an extremely broad J^{π} = 1/2^{} structure at E_{x} ≥ 10 MeV [see also ^{6}Li(p, p)]: see Table 7.8 (in PDF or PS) and (1974AJ01, 1984AJ01). For α + ^{3}He correlations see (1987PO03). See also the "Complex Reactions" section here. For elastic and inelastic inclusive scattering cross sections at p_{α} = 7.0 GeV/c see (1984SA39, 1987BA13). See also (1984IW01; astrophysics) and (1981PL1A, 1983HO22, 1983LO09, 1984BL21, 1984FI20, 1984HO1C, 1984HU1C, 1984KA01, 1985FR1F, 1986FR12, 1987KA09, 1987OSZZ, 1987TA06, 1988FIZT; theor.).
Angular distributions have been reported at E_{α} = 61.5 to 158.2 MeV (1982GL01) and 198.4 MeV (1985WO11) for the transitions to ^{7}Be*(0 + 0.43). See also ^{8}Be.
At low energies (E_{p} = 0.2 to 1.2 MeV) gamma transitions are observed to the ground (γ_{0}) and to the 0.43 MeV (γ_{1}) states. The yield shows no resonance and the branching ratio remains approximately constant at (61 ± 5)% to the ground state and (39 ± 2)% to ^{7}Be*(0.43): see (1974AJ01, 1984AJ01). Angular distributions of γ_{0} and γ_{1} have been studied at E_{p} = 0.50, 0.80 and 1.00 MeV (1987TI05). At E_{p} = 44.4 MeV, ^{7}Li*(4.57) is strongly populated (1985HA05). See also (1983OS04), (1983HA1B, 1984BO1C, 1985CA41; astrophysics) and (1985BL1B).
Measurements of elastic angular distributions have been reported for E_{p} = 0.5 to 600 MeV: see (1966LA04, 1974AJ01) and ^{6}Li. Two resonances are reported at E_{p} = 1.84 and 5 MeV in the elastic yield [^{7}Be*(7.21, 9.9)]. The parameters of the lower resonance are shown in Table 7.4 (in PDF or PS). The 5 MeV resonance has γ ≈ 1.8 MeV and appears to also be formed by pwaves: γ^{2}_{p} is then 3 ± 2 MeV · fm. A weak rise near E_{p} = 8 to 9 MeV may indicate a further level, ^{7}Be* ≈ 13 MeV. A broad resonance at E_{p} = 14 MeV has also been suggested. Polarization measurements have been carried out for E_{p} = 1.2 to 800 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at E_{pol. p} = 4 to 10 MeV (1986BE1H; p_{0}) and 25 and 35 MeV (1982ROZT, 1983PO1B, 1983POZX; p_{0}, p_{1}). A phaseshift analysis for E_{p} = 0.5 to 5.6 MeV shows that only ^{2}S, ^{4}S and ^{4}P are involved. The ^{4}P_{5/2} phase resonates at E_{p} = 1.8 MeV, and the broad resonance at 5 MeV can be reproduced equally well by either ^{4}P_{3/2} or ^{4}P_{1/2}: tensor polarization measurements are necessary to distinguish between the two: see (1974AJ01). The reaction cross section for formation of ^{6}Li*(2.19) has been measured for E_{p} = 3.6 to 9.40 MeV: a broad resonance indicates the presence of a state with E_{x} ≈ 10 MeV, γ = 1.8 MeV, J^{π} = (3/2, 5/2)^{}, T = 1/2. The crosssection and angular distributions of p_{2} (^{6}Li*(3.56)) for E_{p} = 4.26 to 9.40 MeV are analyzed in terms of two J^{π} = 3/2^{} states at E_{x} ≈ 10 and 11 MeV: see reaction 3. The total cross section for formation of ^{6}Li*(3.56) decreases slowly with energy for E_{p} = 24.3 to 46.4 MeV. The total reaction cross section has been measured for E_{p} = 25.0 to 48 MeV (1985CA36). K^{y}_{y} spectra at E_{pol. p} = 50, 65 and 80 MeV, θ = 3°  20°, are reported by (1987SA46). For the inclusive cross section at E_{p} = 200 MeV [back angles] see (1984AV07). For reaction (b) see ^{5}He. For reaction (c) see ^{6}Li. See also (1983GLZZ, 1984BA1U, 1987TO06), (1986PO1F, 1986SA1Q; applications), (1986BA88, 1986PF1A) and (1981NE1B, 1981PL1A, 1983HO22, 1983KA37, 1986SA30, 1987KN04; theor.).
The yield of neutrons increases approximately monotonically from threshold to E_{p} = 14.3 MeV: see (1974AJ01). The transverse polarization transfer, D_{NN} (0°), for the g.s. transition has been measured for E_{pol. p} = 30 to 160 MeV: see (1986TA1E, 1984TA07) and ^{6}Be. Polarization measurements are reported at E_{pol. p} = 50 and 80 MeV (1987SA46) and at 52.8 MeV (1988HE08) [K^{y'}_{y} (0°) = 0.33 ± 0.04; also K^{z'}_{z})]. See also (1986MC09; E_{pol. p} = 800 MeV), ^{6}Be, (1984BA1U, 1986SA1Q) and (1986RA21).
Thermonuclear reaction rates and the astrophysical Sfactor have been derived from the lowenergy (E_{p} < 0.7 MeV) cross section measurements: S(0) ≈ 3.1 MeV ⋅ b: see (1974AJ01, 1979AJ01, 1984AJ01). At higher energies the cross section exhibits a broad, low maximum near E_{p} = 1 MeV and a pronounced resonance at E_{p} = 1.85 MeV (γ < 0.5 MeV). No other structure is reported up to E_{p} = 5.6 MeV. Measurements between E_{p} = 0.4 and 3.4 MeV show that the polarizations are generally large and positive: see (1974AJ01). Angular distributions have been reported for E_{p} = 0.15 to 45 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at 47.8, 53.5, 58.5 and 62.5 MeV (1984NE05). See also (1983SZZY, 1986KI1G), (1985CA41; astrophys.), (1986MC1D; applications) and (1984KR1B; theor.).
Angular distributions of the n_{0} and n_{1} groups have been measured at E_{d} = 0.20 to 15.25 MeV: see (1974AJ01, 1979AJ01). The n_{1}γ correlations are isotropic, indicating J^{π} = 1/2^{} for ^{7}Be*(0.43). Broad maxima are observed in the ratio of lowenergy to highenergy neutrons at E_{d} = 4.2 and 5.1 MeV [^{7}Be*(6.5, 7.2), γ_{c.m.} = 1.2 and 0.5 MeV, respectively]: see (1966LA04). See also ^{8}Be and (1988KO1C).
Angular distributions of the d_{0} and d_{1} groups to ^{7}Be*(0, 0.43) have been measured at E(^{3}He) = 8, 10, 14 and 18 MeV and at E(^{3}pol. He) = 33.3 MeV [^{7}Be*(4.57) is also populated]: see (1974AJ01, 1984AJ01).
Forwardangle differential cross sections have been measured at E_{π+} = 20 MeV (1987IR01; also at 155° and 166°), at 33.5, 41.1, 48.7 and 58.8 MeV (1985IR01, 1985IR02), 70 to 180 MeV [see (1984AJ01)] and from 300 to 550 MeV (1988RO03).
The excitation energy of ^{7}Be*(0.43) is 429.20 ± 0.10 keV, τ_{m} = 192 ± 25 fsec: see (1979AJ01). Angular distributions of n_{0} and n_{1} have been reported at E_{p} = 1.9 to 119.8 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at 200, 300 and 400 MeV (1987WAZT; prelim.; n_{0 + 1}). ^{7}Be*(4.55, 6.51, 7.19, 10.79) have also been populated: see (1974AJ01, 1979AJ01). The ratios of σ_{1}/σ_{0} (^{7}Be*(0.43)/^{7}Be_{g.s.}) have been measured at 24.8, 35 and 45 MeV and yield the ratio of spinflip to spinnonflip strength V_{0τ}/V_{τ}^{2} (1980AU02). See also ^{8}Be, (1983KI1B, 1984BR32, 1984JEZZ, 1984TA07, 1985JE1A, 1985TAZY, 1987HE24, 1988HE08), (1984KE1B, 1985BA66, 1985KE1D, 1986CO1L; applications), (1983RA1C, 1984TAZS, 1985GO1F, 1987GO1V, 1987RA32) and (1983KR10, 1984PE12; theor.).
See (1987AL10; E(^{7}Li) = 65 MeV).
Angular distributions of t_{0} and t_{1} have been measured at E(^{3}He) = 3.0 to 4.0 MeV and at E(^{3}pol. He) = 33.3 MeV: see (1974AJ01, 1984AJ01). The width of ^{7}Be*(4.57), γ_{c.m.} = 175 ± 7 keV: see (1974AJ01). See also ^{10}B.
This reaction has been studied at E(^{6}Li) = 14, 25 and 35 MeV/A. ^{7}Be*(0, 0.43) are strongly populated and ^{7}Be*(4.57, 7.21) are also evident. At the highest energy the reaction mechanism is predominantly onestep (1987WI09, 1986AN29). See also 6He, (1988AL1G, 1988BUZH, 1988BU1Q), (1986AU1C, 1987AU04, 1988AN1J) and (1984BA53; theor.).
Angular distributions of tritons have been measured at E_{p} = 43.7 and 46 MeV [see (1979AJ01)] and at 50 and 72 MeV (1984ZA07; t_{0+1}, t_{2}). The 11 MeV state has E_{x} = 11.01 ± 0.04 MeV, γ = 298 ± 25 keV, J^{π} = 3/2^{}, T = 3/2 [the J^{π}; T assignments are based on the similarity of the angular distribution to that in the (p, ^{3}He) reaction to ^{7}Li*(11.13)]: see (1979AJ01).
Angular distributions have been studied for E_{p} = 2.8 to 7.0 MeV [see (1974AJ01)] and for 18 to 45 MeV (1986HA27; α_{0}, α_{1}, α_{2}; see for spectroscopic factors). E_{x} of ^{7}Be*(0.43) = 428.89 ± 0.13 keV (1979RI12). See also ^{11}C in (1985AJ01), (1983DO07) and (1988KOZL; applied).
See ^{5}He.
See ^{7}Li.
See ^{7}Li.
See ^{6}Li and (1987KW03; theor.).
See ^{7}Li.
Angular distributions involving ^{7}Be*(0, 0.43) have been reported at E(^{3}He) = 25.5 to 70 MeV [see (1979AJ01, 1984AJ01)] and at E(^{3}pol. He) = 33.4 MeV (1986CL1B; also A_{y}; prelim.). See also (1986RA15; theor.).
At E_{α} = 42 MeV, angular distributions have been measured involving ^{7}Be*(0, 0.43) and ^{9}Be_{g.s.}: see (1974AJ01). Angular distributions have also been measured at E_{α} = 49.0 and 80.1 MeV (1984GO03).
See (1984BA53; theor.).
Angular distributions have been reported at E(^{3}He) = 25.5 to 70 MeV to ^{7}Be*(0, 0.43) and to various states of ^{12}C: see ^{12}C in (1985AJ01). See also (1986BA89; theor.).
Angular distributions have been studied at E(^{7}Li) = 50 MeV involving ^{7}Be*(0, 0.43) and various states of ^{16}N (1984CO20, 1986CL03). See also ^{16}N in (86AJ04) and (1984BA53; theor.).
See (1986RA15; theor.).
