
^{7}Be (1984AJ01)(See Energy Level Diagrams for ^{7}Be) GENERAL: See also (1979AJ01) and Table 7.7 [Table of Energy Levels] (in PDF or PS). Nuclear models: (1978RE1A, 1979WI1B, 1980HA1M, 1981KU13, 1982FI13, 1983WA1M). Astrophysical questions: (1978BU1B, 1979MO04, 1979RA20, 1979RA1C, 1980CA1C, 1980LA1G, 1980WI1M, 1983LI01). Applied work: (1979LA1E, 1982HA1D, 1983HA1W). Complex reactions involving ^{7}Be: (1978DI1A, 1978DU1B, 1978HA40, 1978HE1C, 1979BO22, 1979KA07, 1979LO11, 1979PO10, 1979RA20, 1979SC1D, 1979VI05, 1980GR10, 1980MI01, 1980WI1K, 1980WI1L, 1980WO05, 1981CI03, 1981GR08, 1981ME13, 1981MO20, 1981TA22, 1982BO1J, 1982BO1N, 1982BO35, 1982FU04, 1982GL01, 1982GR09, 1982GU1H, 1982HA1V, 1982HI12, 1982LU01, 1982LY1A, 1982MO1N, 1983PU01, 1983SA06). Reactions involving pions and kaons: (1978WA1B, 1979AL1J, 1979BO23, 1979SI16, 1980BA27, 1980LE02, 1981OS04, 1981SI09, 1982AL31, 1982DO02, 1982LEZY, 1983IRZZ, 1983PIZW). Hypernuclei: (1978PO1A, 1978SO1A, 1981WA1J). Other topics: (1979BE1H, 1982NG01). Ground state of ^{7}Be: (1982FI13, 1982NG01).
The decay is complex: see ^{7}Li.
The capture cross section has been measured for E_{α} = 0.38 to 5.80 MeV [see (1974AJ01)], 0.250 to 2.954 MeV (1982KR05), 0.385 to 2.730 MeV (1982OS02), at E_{c.m.} = 0.897 MeV (1983RO1C) and for E(^{3}He) = 19 to 26 MeV (1983WA05; γ_{0+1} excitation function at 90°). The branching ratios DC → 429/DC → 0 and the cross section for the DC → 429 branch have been measured for E_{c.m.} = 107 to 1266 keV: the branching ratio is approximately constant at 0.43 ± 0.02 over that energy range; the cross section is 0.117 ± 0.016 nb at 107 keV. It increases to 421 ± 39 nb at E_{c.m.} = 1266 keV (1982KR05). These data lead to a value of S(0) = 0.56 ± 0.03 keV · b (using microscopic DC model calculations, and a branching ratio, 10.42 ± 0.06%, for the ^{7}Be decay to ^{7}Li*(0.48)) [see reaction 28 in ^{7}Li] (1983VO01). (1982OS02) obtain S(0) = 0.52 ± 0.03 keV · b and (1983RO1C) find 0.63 ± 0.04 keV · b. See also (1974AJ01) and (1981WI04; theor.). (1983RO1C) suggest, prior to (1983VO01), that S(0) = 0.56 ± 0.07 keV · b should be adopted. C^{2}S = 1.0 for ^{7}Be*(0, 0.43) (1982KR05). See also (1980BA1P, 1980BA2M, 1980PE1N, 1981BA2F, 1981RO1W, 1982BA80; astrophysics) and (1981KI01, 1981LI01, 1982TA1G, 1983WA1M; theor.).
Elastic scattering studies have been reported for E = 1.72 to 140 MeV [see (1974AJ01, 1979AJ01)] and at E_{α} = 0.25 to 2.95 MeV (1982KR05) and 140 MeV (1980RO03) and at E(^{3}He) = 18 to 70 MeV (1978BA75) and 198.4 MeV (1980RO03). Polarization measurements have been carried out at E = 4.3 to 98 MeV: see (1979AJ01). 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 (1978LU05). The work of (1978BA75) is consistent with the results of (1978LU05) and, in addition, suggests broad l = 4 and 5 states at E(^{3}He) > 30 MeV [E_{x} > 19 MeV]. 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 (1980NE08; p_{0}). 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 through 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). See also (1980NE08). See aslo (1981BA1Q), (1978BR1A, 1979KA1G, 1982YA1A) and (1978DU1D, 1978TA1A, 1979KOZV, 1979LE11, 1979WI1B, 1981FI1B, 1981SH07, 1982AZ01, 1982FU01, 1982KA11, 1982LE23, 1983HO1F, 1983SA1G; theor.).
See (1978GL03, 1979AL1F), (1979AJ01) 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). The total cross section for E_{p} = 0.2 to 1.2 MeV has been obtained by (1979SW02): at E_{p} = 0.8 MeV it is 3.1 ± 0.4 μb, in good agreement with previous values. The branching ratio to ^{7}Be*(0.43) is (41 ± 3)% (1979SW02). The weighted mean of this and previous measurements is (39 ± 2)% (1979SW02). See also (1980BA34).
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 155 MeV [see (1974AJ01, 1979AJ01)] and at E_{pol. p} = 25 and 35 MeV (1982ROZT; 0_{0}, p_{1}) and 800 MeV (1979GL1C; 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: 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 cross section 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. 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 reaction cross section has been measured for E_{p} = 25.0 to 48 MeV: see (1979AJ01). For reaction (b) see ^{5}He, (1978NA18; E_{pol. p} = 635 MeV) and (1979AJ01). For reaction (c) see ^{6}Li and (1979AJ01). Studies of inclusive cross sections are reported at 640 MeV (1981ER07) and 400 GeV (1979BA28, 1979FR12, 1980NI09). For pion and kaon production see (1980NI09; 400 GeV). See also (1982AB1D) and (1981FR1R, 1981FR1T, 1981KR15, 1982ST15; theor.).
The yield of neutrons increases approximately monotonically from threshold to E_{p} = 14.3 MeV. Polarization measurements are reported at E_{p} = 30 and 50 MeV: see (1974AJ01). See also ^{6}Be.
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}. 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} = 136 → 297 keV, as well as the (1966GE11) results, (1979EL10) calculate S(0) = 3.145 MeV · b [E_{c.m.} = 1 keV → 500 keV]. Thermonuclear reaction rates are also derived (1979EL10). See also (1979SH14; 125 → 700 keV; S(0) = 3 MeV · b) and (1979AJ01). 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. The E_{p} = 1.9 MeV resonance appears in A_{1} and A_{2}: see (1974AJ01). Angular distributions have been reported for E_{p} = 0.15 to 45 MeV [see (1974AJ01, 1979AJ01)] and at E_{p} = 125 to 700 keV (1979SH14), 136 to 297 keV (1979EL10) and 47.8, 53.5, 58.5 and 62.5 MeV (1982BA1V). See also (1979DE1E, 1979HA1C, 1980HA1Y, 1981JA1F; applied), (1981HO1E) and (1978PL1A; 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 nγ 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 (1979HO04, 1980GU26) in ^{8}Be.
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: all the distributions show an l = 1 maximum at small angles: see (1974AJ01). At E(pol. ^{3}He) = 33.3 MeV angular distributions and A_{y} measurements to ^{7}Be*(0, 0.43) have been analyzed using coupled channels and DWBA. ^{7}Be*(4.57) is also populated (1981BA38).
See (1979AJ01).
For reaction (a) see (1979BO23). Forwardangle differential cross sections to ^{7}Be_{g.s.} have been measured at E_{π+} = 48 MeV (1982LEZY), and 70 → 180 MeV (1980BA27, 1982DO02). See also (1982AL35).
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} are reported at E_{p} = 1.9 to 50 MeV [see (1974AJ01, 1979AJ01)] and at 119.8 MeV (1979GO16, 1980GO07; n_{0+1}). The population of ^{7}Be*(4.55, 6.51, 7.19, 10.79) has also been observed: see (1974AJ01, 1979AJ01). The ratios σ_{1}/σ_{0} (^{7}Be*(0.43)/^{7}Be_{g.s.}) have been measured at 24.8, 35 and 45 MeV: an analysis of these yields the ratio of spinflip to spinnonflip strength V_{στ}/V_{τ}^{2} (1980AU02). 1983TAZY report crosssection measurements at E_{p} = 60 to 200 MeV. See also (1981SH1F, 1982KI1F, 1982TAZQ), (1979CH1B, 1980SE1D, 1982SA1M; applied), (1982GO1C, 1982PE06, 1982TA03), (1982GU1D, 1983GU1G; theor.) and ^{8}Be.
Angular distributions of t_{0} and t_{1} have been measured at E(^{3}He) = 3.0 to 4.0 MeV [see (1974AJ01)] and at E(pol. ^{3}He) = 33.3 MeV (1981BA37). The width of ^{7}Be*(4.57), Γ_{c.m.} = 175 ± 7 keV: see (1974AJ01). See also ^{10}B.
Angular distributions of tritons have been measured at E_{p} = 43.7 MeV (^{7}Be*(0, 0.43, 4.57, 6.51, 11.01)) and 46 MeV (^{7}Be*(0 + 0.43, 4.57, 6.51, 10.69)), and at E_{p} = 50 and 72 MeV (1982ZA1B; t_{0}, t_{1}). 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 measured for E_{p} = 2.8 to 7.0 MeV: see (1974AJ01). E_{x} = 428.89 ± 0.13 keV (1979RI12). See also ^{11}C in (1980AJ01, 1985AJ01).
See (1982DO1E).
See ^{6}Li.
At E_{α} = 45.6 MeV the angular distributions of the ^{7}Li and of the ^{7}Be ions, corresponding to the groundstate transitions, have been measured. 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: see (1974AJ01).
See (1979KI04).
See ^{6}Li.
See ^{7}Li.
Angular distributions are reported at E(^{3}He) = 25.5 to 30 MeV involving ^{7}Be*(0, 0.43) [see (1979AJ01)] and at 41 MeV (1981LE01) and ^{15}O in (1981AJ01).
At E_{α} = 42 MeV, angular distributions have been measured involving ^{7}Be*(0, 0.43) and ^{9}Be_{g.s.}: see (1974AJ01).
See ^{7}Li.
Angular distributions are reported at E(^{3}He) = 25.5, 30 and 70 MeV to ^{7}Be*(0, 0.43) and various states of ^{12}C [see ^{12}C in (1980AJ01)] and at 41 MeV (1981LE01).
See ^{13}C in (1981AJ01).
The angular distributions to ^{7}Be*(0, 0.43) + ^{14}C_{g.s.} has been measured at E_{d} = 14.9 MeV: see (1974AJ01).
See ^{15}N in (1981AJ01) and ^{16}O in (1982AJ01).
