
^{7}Be (1979AJ01)(See Energy Level Diagrams for ^{7}Be) GENERAL: See also (1974AJ01) and Table 7.6 [Table of Energy Levels] (in PDF or PS). Nuclear models: (1974KA11). Astrophysical question: (1973BA1H, 1973IB1A, 1973SM1A, 1973TR1C, 1973WE1D, 1974KO1C, 1974PA10, 1974RA09, 1974SH1D, 1975HO1C, 1975KI14, 1975SC1H, 1976BE1C, 1976BO1E, 1976CL1A, 1976CO1B, 1976FU1B, 1976GI1C, 1976HE15, 1976PE1A, 1976RA1C, 1976SI1C, 1976VI1A, 1977AU1B, 1977BA1V, 1977BI1E, 1977GA1C, 1977HA1L, 1977KO1J, 1977MO1E, 1977SC1D, 1977SI1D, 1978ME1D). Electromagnetic transitions: (1974KU06, 1974MU1B, 1976KU07). Special levels: (1974IR04, 1974KA11, 1976IR1B). Applied work: (1976WI1B). Special reactions: (1974BA70, 1974BO08, 1974DI16, 1974HA11, 1974KA22, 1974PA10, 1974PE1C, 1974RA09, 1974RA11, 1975FU01, 1975HO12, 1975HU10, 1975RA12, 1975RA14, 1975RA21, 1975RA25, 1975RE18, 1975RU09, 1975WI1D, 1975ZE01, 1975ZE03, 1976BE1K, 1976BO08, 1976BU16, 1976CU05, 1976DI01, 1976HE15, 1976HU1D, 1976IN04, 1976LE1F, 1976MA1D, 1976MI13, 1976OS04, 1976RA1C, 1976SI1D, 1976ST11, 1977AR06, 1977AS03, 1977BI1E, 1977GO07, 1977ST34, 1977ST1G, 1977YA1B, 1978BI08, 1978CU01, 1978DI04, 1978GE1C, 1978GR1F, 1978WE1D). Reactions involving pions and kaons: (1975GI1B, 1976EN02, 1977AL21 : [Cross section for ^{7}Li(π^{+}, π^{0})^{7}Be to ^{7}Be*(0, 0.43) for E_{π} = 90 to 210 MeV (1977AL21).], 1977SP1B, 1977WA02, 1978WA02). Other topics: (1974DA1B, 1974IR04, 1975PN1A, 1976IR1B). Ground state properties of ^{7}Be: (1975BE31).
The decay is complex: see ^{7}Li.
In the range E_{α} = 0.38 to 5.80 MeV the cross section rises from 8 × 10^{3} to 4 μb (1963PA12, 1969NA24). The capture proceeds mainly by E1, with both s and dwaves contributing above E_{α} = 1 MeV (1963TO06). The branching ratio γ_{1}/γ_{0} [^{7}Be*(0.43)/^{7}Be(0)] is approximately constant at 37% for E_{α} = 0.57 to 3.2 MeV (1963PA12, 1969NA24). The zeroenergy intercept of the crosssection factor S = 0.61 ± 0.07 keV · b and (dS/dE)_{0} = (5.8 ± 0.3) × 10^{4} b using all the data. If the lowenergy data (E_{c.m.} ≤ 0.7 MeV) is fitted using a direct capture calculation (1963TO06) the zeroenergy intercept of the crosssection factor is S = 0.51 ± 0.05 keV · b and (dS/dE)_{0} = (2.8 ± 0.4) × 10^{4} b (1969NA24). A secondorder (in energy) polynomial fit to the lowenergy data (E_{c.m.} ≤ 0.8 MeV) determines S = 0.61 ± 0.07 keV · b and (dS/dE)_{0} = (5.8 ± 0.3) × 10^{4} b (1969NA24). Recent papers discussing the astrophysical implications of this reaction are (1971BA1A, 1974VA1C, 1976NO1C).
Elastic scattering studies have been reported for E(^{3}He) = 1.72 to 140 MeV [see (1974AJ01)] and at E_{α} = 22.8 to 26.4 MeV (1976ZA11) and 65.3 to 102.7 MeV (1973FE1B). The total reaction cross section at E(^{3}He) = 28 MeV is 433 ± 10 mb (1977KO09). Polarization measurements have been carried out at E(^{3}He) = 7.8 to 13 MeV and E_{α} = 4.3 to 18.5 MeV [see (1974AJ01)], E(^{3}He) = 18 → 32 MeV (1978LU05), and at E_{α} = 24.5 to 42 MeV (1976BA1L; on ^{3}Hebar), E(^{3}Hebar) = 38.2 MeV (1976BI1C) and at E_{α} = 98 MeV (1973FE1B). For an Rmatrix analysis of the ^{2}F_{5/2} state at E_{x} = 6.73 MeV, see (1976DO1B). 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) (1967SP10). 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 pwave splitting agrees with (1964BA09, 1967SP10). 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 ground state protons relative to those corresponding to ^{6}Li*(2.19) yields γ^{2}(p_{0})/γ^{2}(p_{1}) = (16^{+5}_{10})% (1967SP10). A phase shift 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 (1978LU05). At higher energies [E(^{3}He) = 27.2 to 42.8 MeV] (1969SC16) report that the s and fwave phase shifts fall appreciably below the predictions of resonating group calculations, while (1970BR42) see some indication of broad resonant structure at E(^{3}He) ≈ 34 MeV, in rough qualitative agreement with such calculations. The bremsstrahlung cross section at E(^{3}He) = 7.4 MeV is 12.6 ± 3.4 μb/sr^{2} (1973FR17). The differential reaction cross section for reaction (b) has been determined for E(^{3}He) = 8 to 18 MeV (1967SP10) and at 28 MeV (1977KO09: d_{0}, d_{1}, d_{2}): resonances are observed corresponding to ^{7}Be*(7.21, 9.27) in the p_{0} yield and to ^{7}Be*(9.27) in the p_{1} yield: see Table 7.7 (in PDF or PS) (1967SP10). A study of the γrays from ^{6}Li*(3.56) (p_{2}) carried out at E(^{3}He) = 13.8 to 18.5 MeV shows the excitation of two J^{π} = 3/2^{} states at E_{x} ≈ 10.0 MeV (T = 1/2) and 11.00 ± 0.05 MeV (Γ = 400 ± 50 keV, θ^{2}_{p2} = 0.13 ± 0.02, T = 3/2). The T = 3/2 resonance is evidenced mainly through interference. There is also some evidence for an extremely broad J^{π} = 1/2^{} structure at E_{x} ≳ 10 MeV (1967HA07, 1967HA08: see also ^{6}Li(p, p)^{6}Li). At E(^{3}He) = 28 MeV sequential breakup via ^{6}Li*(2.19) significantly contributes to the reaction mechanism (1977KO09). See also (1975TO1A, 1978BR1E) and (1974BA40, 1974KO03, 1974TE05, 1975BA05, 1975CL1C, 1975KU09, 1975TA1A, 1977BA1N, 1977BU01, 1977SA1C, 1978LE13; theor.).
The production cross section for ^{7}Be has been measured for E_{α} = 39.4 to 47.4 MeV: it is essentially equal to that for the (α, p) reaction above 43 MeV but is smaller below because of threshold effects. See also (1977RA1B; prelim., E_{α} = 400, 600 and 1000 MeV). For a discussion of the production of ^{7}Li in the galaxy, see (1975KI14, 1977KI12) and reaction 4 in ^{7}Li. See also (1974KO1C; astrophys.) and ^{8}Be.
Gamma transitions are observed to the ground (γ_{0}) and to the 0.43 MeV (γ_{1}) states. The yield shows no evidence of resonance for E_{p} = 0.2 to 1.0 MeV and the branching ratio remains approximately constant at (62 ± 5)% to the ground state, 38% to ^{7}Be*(0.43), < 4% to ^{7}Be*(4.57): see (1974AJ01).
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) (1963MC09). 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 (1963HA53). A broad resonance at E_{p} = 14 MeV is suggested by (1977NE1A). Polarization measurements have been carried out for E_{p} = 1.2 to 155 MeV [see (1974AJ01)], at E_{pbar} = 32 MeV (1976MO1B: p_{1}, p_{2}). A phase shift 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 (1969PE22). An Rmatrix analysis of the ^{2}F_{5/2} state at E_{x} = 6.73 MeV is reported by (1976DO1B). 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 (1967HA07, 1967HA08). The crosssection and angular distributions of p_{2} (^{6}Li*(3.56)) for E_{p} = 4.26 to 9.40 MeV is analyzed in terms of two J^{π} = 3/2^{} states at E_{x} ≈ 10 and 11 MeV: see reaction 3 (1967HA07, 1967HA08). The total cross section for formation of ^{6}Li*(3.56) decreases slowly with energy for E_{p} = 24.3 to 46.4 MeV (1968AU06). The reaction cross section has been measured for E_{p} = 25.0 to 48 MeV by (1976SO1B). For reaction (b) see ^{5}He and (1977NA16). For reaction (c) see ^{6}Li and the polarization measurements of (1974DU10) and (1976DU1C) at E_{p} = 40 and 19.4 MeV, respectively. See also (1977FR1F, 1978FR1D), (1977MC1C; applied) and (1975BA05, 1977BI1E, 1978MA37; theor.).
The yield of neutrons increases approximately monotonically from threshold to E_{p} = 14.3 MeV (1964BA16). For polarization measurements at E_{p} = 30 and 50 MeV, see (1969RO20). See also ^{6}Be.
See ^{5}Li.
Over the range E_{p} = 25 to 50 keV, the cross section rises from 0.8 to 72 μb: in the formula σ ≈ E^{1}e^{B/√E(square root of E)}, B = 90 ± 6 keV^{1/2} (1967FI05). Crosssection measurements for E_{p} = 62 to 188 keV show deviation from an swave Gamow plot above ≈ 130 keV (1966GE11). Using crosssection measurements at E_{p} = 151 and 317 keV, as well as the (1966GE11) data (1971SP05) calculate S(0) = 3.0 MeV · b. See also (1978EL1A: E_{p} = 0.1 to 1.0 MeV). 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 (1951BA79, 1956MA91) and (1977LI01: Γ < 0.5 MeV; E_{p} = 1.0 to 2.6 MeV). No other structure is reported up to E_{p} = 5.6 MeV: see (1974AJ01). Measurements between E_{p} = 0.4 and 3.4 MeV show that the polarizations are generally large and positive. The E_{p} = 1.9 MeV resonance appears in A_{1} and A_{2} (1968BR18). Angular distributions have been reported for E_{p} = 0.15 to 16 MeV [see (1974AJ01)] and at E_{p} = 0.5 to 1.82 MeV (1974JO08), 1.0 to 2.0 MeV (1977LI01), 25.5 to 45 MeV (1974SC24) and 45 MeV (1971BR12). Angular distributions at E_{p} = 8 to 18.5 MeV have been analyzed using a finiterange multiinteraction DWBA formalism. The analysis leads to reduced widths of 0.69 for α + d in a relative sstate, 0.04 for α + d in a relative dstate and 0.44 for ^{3}He + t in a relative sstate (1973WE07). A polarization measurement is reported at E(^{6}Li) = 16.8 MeV (1976FI1B). See (1971BR12) for a discussion of the search for excited states of ^{3}He. See also (1974VA1B), (1978PR1B; applied) and (1973LI23, 1975CL1C, 1975WI1C; theor.).
Angular distributions of the n_{0} and n_{1} groups have been measured at E_{d} = 0.24 to 3.5 MeV [see (1974AJ01)] and at E_{d} = 0.204 to 0.873 MeV (1977EL09) and 15.25 MeV (1975AZ02). The nγ correlations are isotropic, indicating J^{π} = 1/2^{} for ^{7}Be*(0.43) (1956NE13). 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] (1957SL01). See also (1974MCZS, 1975MC02, 1977GL05) in ^{8}Be.
Angular distributions of the d_{0} and d_{1} groups to ^{7}Be*(0, 0.43) have been measured at E_{d} = 8, 10, 14 and 18 MeV: all the distributions show an l = 1 maximum at small angles. The DWBA analysis leads to a ratio of spectroscopic factors S*/S [for ^{7}Be*(0.43)/^{7}Be(0)] = 1.55, in fair agreement with other measurements (1968LU02).
Angular distributions of t_{0}, t_{1} and t_{2} have been reported at E_{α} = 40 to 46 MeV: see (1974AJ01). [Some of the reported work is unpublished.]
See (1977RU06) and ^{12}C in (1980AJ01).
E_{thresh.} = 1880.59 ± 0.08 keV [recommended by (1970RO07)]. The excitation energy of ^{7}Be*(0.43) is 429.20 ± 0.10 keV (1972BO02); τ_{m} = 192 ± 25 fsec (1966PA11). [(1976DO10) report 136 ± 10 fsec.] Angular distributions are reported at E_{p} = 1.9 to 50 MeV [see (1974AJ01)] and at 2.1 to 3.8 MeV (1974BU16: n_{0}), 3.1 to 4.9 MeV (1976BR1E: n_{1}), 14.9 and 17.8 MeV (1974AR05: n_{0}, n_{1} (not resolved at the lower energy)), 15.1 to 26 MeV (1976PO06: n_{0}, n_{1}), and 24.8, 35.0 and 45.0 MeV (1977SC37: n_{0}, n_{1}). (1976PO06) also report the population of ^{7}Be*(4.55, 6.51, 7.19, 10.79). See also (1977RI07: E_{p} = 800 MeV) and (1974AJ01). See also (1976RO10, 1977LO10), (1973RY03, 1974JA1M, 1976NE1B, 1976WA1E, 1978GO1E; applied), (1977ME1C; theor.) and ^{8}Be.
Angular distributions have been measured at E(^{3}He) = 3.0 to 4.0 MeV (1969OR01: t_{0}, t_{1}). See also (1974AJ01). The width of ^{7}Be*(4.57), Γ_{c.m.} = 175 ± 7 keV (1971PI06). See also (1974LO1B).
See (1974AJ01).
Angular distributions of tritons have been measured at E_{p} = 43.7 MeV (1965DE08, 1966CE05, 1968BR23: ^{7}Be*(0, 0.43, 4.57, 6.51, 11.01)) and 46 MeV (1967VE01: ^{7}Be*(0 + 0.43, 4.57, 6.51, 10.69)). The 11 MeV state has E_{x} = 11.01 ± 0.04 MeV (1968BR23), 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)] (1965DE08). The ratio of the cross section for formation of ^{7}Be*(0.43) to that for formation of ^{7}Li*(0.48) [in the (p, ^{3}He) mirror reaction] has been measured for E_{p} = 14.8 to 27 MeV (1975HA1K).
Angular distributions have been measured for E_{p} = 2.8 to 7.0 MeV (1964JE01). See also (1966YO1A), (1974AJ01) and ^{11}C in (1975AJ02).
At E(^{3}He) = 30.0 MeV angular distributions have been obtained for the transitions to ^{7}Be*(0, 0.43) + ^{6}Li*(0, 2.19): see (1970DE12, 1972OH01).
At E_{α} = 45.6 MeV (1969FO06) have measured the angular distributions of the ^{7}Li and of the ^{7}Be ions, corresponding to the ground state transitions. At a given angle the intensities of the two ions are the same, implying that the wave functions of the ground states of ^{7}Li and ^{7}Be are very similar (1969FO06).
See (1977KO27).
See (1974AJ01).
See (1971RO1A).
Angular distributions have been measured at E_{p} = 36.0, 40.7, 45.0, 50.0 and 56.8 MeV (1971BR07, 1971HO25; ^{7}Be*(0 + 0.43)) and 51.9 MeV (1976KA14; ^{7}Be*(0, 0.43)). See also (1978KU02; theor.).
At E_{d} = 39.8 MeV angular distributions have been measured for the transitions ^{7}Li(0) + ^{7}Be(0), ^{7}Li*(0.48) + ^{7}Be(0), ^{7}Li(0) + ^{7}Be*(0.43) and ^{7}Li*(0.48) + ^{7}Be*(0.43). The ratios of the ^{7}Li(0) and ^{7}Be(0) cross sections show asymmetries exceeding 20% (1971YO06). See also (1974VA1A).
Angular distributions have been obtained at E(^{3}He) = 25.5 to 29 MeV (1976PI10: ^{7}Be*(0, 0.43)) and 28 and 30 MeV (1970DE12: ^{7}Be*(0, 0.43)+^{8}Be*(0, 2.9)). See also (1974AJ01), (1976PA07, 1973OG1A), (1974DO03; theor.) and ^{15}O in (1976AJ04).
At E_{α} = 42 MeV, angular distributions have been measured to ^{7}Be*(0, 0.43) + ^{9}Be(0) (1972RU03).
At E_{p} = 45.0 MeV the angular distribution has been measured for the transition to ^{7}Li(0) + ^{7}Be(0) (1971BR07).
See (1976RO04).
See ^{13}C in (1976AJ04).
See (1974AJ01).
Angular distributions are reported at E(^{3}He) = 30 MeV (1970DE12: to ^{12}C*(0, 4.4, 7.7, 9.6) + ^{7}Be*(0, 0.43)). See also (1974AJ01).
At E_{α} = 42 MeV, angular distributions have been obtained for the transitions to ^{7}Be*(0, 0.43) + ^{13}C(0) (1972RU03).
The angular distributions to ^{7}Be*(0 + 0.43) + ^{14}C(0) has been measured at E_{d} = 14.9 MeV (1967DE03).
(1970DE12) have studied at E(^{3}He) = 30 MeV the angular distributions to ^{15}N(0) + ^{7}Be*(0, 0.43) and to ^{16}O*(0, 6.06 + 6.13) + ^{7}Be*(0, 0.43).
