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USNDP

7Be (1988AJ01)


(See Energy Level Diagrams for 7Be)

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 7Be: (1981AS04, 1983AS05, 1983EN04, 1983GU1A, 1983MA53, 1983OL1A, 1983SO08, 1983ST1A, 1983WA19, 1984BE1E, 1984GL06, 1984GO03, 1984GR08, 1984HI1A, 1984MO29, 1984NE1A, 1984ST1B, 1985BA1L, 1985JA1B, 1985MO08, 1985MO17, 1985ST1B, 1985TA18, 1985TR1B, 1985WO11, 1986AV1B, 1986AV07, 1986BL12, 1986CA30, 1986CS1A, 1986GL1E, 1986GO1B, 1986ME06, 1986MO1C, 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 7Be: (1983ANZQ, 1984KA06, 1985AN28, 1985FI1E, 1985HA18, 1985TA18, 1986KO1U, 1987KA1U, 1987KA22, 1988KA07).

The interaction nuclear radius of 7Be is 2.22 ± 0.02 fm (1985TA18). [See also for derived nuclear matter, charge and neutron matter r.m.s. radii].

1. 7Be(ε)7Li Qm = 0.862

The decay is complex: see 7Li.

2. 4He(3He, γ)7Be Qm = 1.587

The capture cross sections have been measured for Eα = 0.250 to 5.80 MeV and at E(3He) = 19 to 26 MeV [see (1974AJ01, 1984AJ01)], at Ec.m. = 195 to 686 keV (1988HI06), and at Eα = 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 ε-capture rather than if it involves a direct measurement of the capture γ-rays. It is not entirely clear why this should be so. Contaminant production of 7Be 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 γ-rays] and 0.58 ± 0.02 keV · b [7Be activity] (1988HI06). See also (1984AL24, 1985FI1D, 1987KA1R, 1988BA86). Theoretical calculations are in general agreement with the experimental values. For instance (1985BU02) from a cluster-model 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 S34[S(0)] = 0.52 ± 0.02 keV · b. It appears clear that the uncertainty in S34 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.).

3. (a) 4He(3He, 3He)4He Eb = 1.587
(b) 4He(3He, p)6Li Qm = -4.0185

Elastic-scattering studies have been reported for E = 0.25 to 198.4 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at Eα = 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(3pol. He) = 55 to 95 MeV (1986YA14).

For l ≤ 4, only f-wave phase shifts show resonance structure for E(3He) < 18 MeV, corresponding to 7Be*(4.57, 6.73, 9.27): see Table 7.7 (in PDF or PS). No structure corresponding to 7Be*(7.21) (Jπ = 5/2-) is seen in the elastic data. The s-wave phase shift is somewhat greater than hard-sphere. The decay of 7Be*(9.27) (Jπ = 7/2-) to 6Li(0) requires f-shell configuration admixture. An estimate of the yield of ground-state protons relative to those corresponding to 6Li*(2.19) yields γ2(p0)/γ2(p1) = (16+5-10)%. A phase-shift analysis (single-level R-matrix) has been carried out for E(3He) = 18 to 32 MeV: the p-wave phase shifts indicate a 1/2- state at Ex ≈ 16.7 MeV (Er = 26.4 MeV), with γ = 6.5 MeV. There is the suggestion also of broad l = 4 and 5 states at E(3He) > 30 MeV [Ex > 19 MeV]: see (1984AJ01).

The differential cross section for reaction (b) has been determined for E(3He) = 8 to 28 MeV [see (1979AJ01)] and at Eα =22.2 to 26.5 MeV. Resonances are observed corresponding to 7Be*(7.21, 9.27) in the p0 yield, to 7Be*(9.27) in the p1 yield and to states at Ex ≈ 10 MeV (T = 1/2) and 11.0 MeV (T = 3/2) in the yield of 3.56 MeV γ-rays. The evidence for the latter derives mainly from interference arguments. There is also some evidence for an extremely broad Jπ = 1/2- structure at Ex ≥ 10 MeV [see also 6Li(p, p)]: see Table 7.8 (in PDF or PS) and (1974AJ01, 1984AJ01). For α + 3He correlations see (1987PO03). See also the "Complex Reactions" section here. For elastic and inelastic inclusive scattering cross sections at pα = 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.).

4. 4He(α, n)7Be Qm = -18.990

Angular distributions have been reported at Eα = 61.5 to 158.2 MeV (1982GL01) and 198.4 MeV (1985WO11) for the transitions to 7Be*(0 + 0.43). See also 8Be.

5. 6Li(p, γ)7Be Qm = 5.606

At low energies (Ep = 0.2 to 1.2 MeV) gamma transitions are observed to the ground (γ0) and to the 0.43 MeV (γ1) states. The yield shows no resonance and the branching ratio remains approximately constant at (61 ± 5)% to the ground state and (39 ± 2)% to 7Be*(0.43): see (1974AJ01, 1984AJ01). Angular distributions of γ0 and γ1 have been studied at Ep = 0.50, 0.80 and 1.00 MeV (1987TI05). At Ep = 44.4 MeV, 7Li*(4.57) is strongly populated (1985HA05). See also (1983OS04), (1983HA1B, 1984BO1C, 1985CA41; astrophysics) and (1985BL1B).

6. (a) 6Li(p, p)6Li Eb = 5.606
(b) 6Li(p, 2p)5He Qm = -4.59
(c) 6Li(p, pα)2H Qm = -1.4750

Measurements of elastic angular distributions have been reported for Ep = 0.5 to 600 MeV: see (1966LA04, 1974AJ01) and 6Li. Two resonances are reported at Ep = 1.84 and 5 MeV in the elastic yield [7Be*(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 p-waves: γ2p is then 3 ± 2 MeV · fm. A weak rise near Ep = 8 to 9 MeV may indicate a further level, 7Be* ≈ 13 MeV. A broad resonance at Ep = 14 MeV has also been suggested. Polarization measurements have been carried out for Ep = 1.2 to 800 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at Epol. p = 4 to 10 MeV (1986BE1H; p0) and 25 and 35 MeV (1982ROZT, 1983PO1B, 1983POZX; p0, p1). A phase-shift analysis for Ep = 0.5 to 5.6 MeV shows that only 2S, 4S and 4P are involved. The 4P5/2 phase resonates at Ep = 1.8 MeV, and the broad resonance at 5 MeV can be reproduced equally well by either 4P3/2 or 4P1/2: tensor polarization measurements are necessary to distinguish between the two: see (1974AJ01).

The reaction cross section for formation of 6Li*(2.19) has been measured for Ep = 3.6 to 9.40 MeV: a broad resonance indicates the presence of a state with Ex ≈ 10 MeV, γ = 1.8 MeV, Jπ = (3/2, 5/2)-, T = 1/2. The cross-section and angular distributions of p2 (6Li*(3.56)) for Ep = 4.26 to 9.40 MeV are analyzed in terms of two Jπ = 3/2- states at Ex ≈ 10 and 11 MeV: see reaction 3. The total cross section for formation of 6Li*(3.56) decreases slowly with energy for Ep = 24.3 to 46.4 MeV. The total reaction cross section has been measured for Ep = 25.0 to 48 MeV (1985CA36). Kyy spectra at Epol. p = 50, 65 and 80 MeV, θ = 3° - 20°, are reported by (1987SA46).

For the inclusive cross section at Ep = 200 MeV [back angles] see (1984AV07). For reaction (b) see 5He. For reaction (c) see 6Li. See also (1983GLZZ, 1984BA1U, 1987TO06), (1986PO1F, 1986SA1Q; applications), (1986BA88, 1986PF1A) and (1981NE1B, 1981PL1A, 1983HO22, 1983KA37, 1986SA30, 1987KN04; theor.).

7. 6Li(p, n)6Be Qm = -5.071 Eb = 5.606

The yield of neutrons increases approximately monotonically from threshold to Ep = 14.3 MeV: see (1974AJ01). The transverse polarization transfer, DNN (0°), for the g.s. transition has been measured for Epol. p = 30 to 160 MeV: see (1986TA1E, 1984TA07) and 6Be. Polarization measurements are reported at Epol. p = 50 and 80 MeV (1987SA46) and at 52.8 MeV (1988HE08) [Ky'y (0°) = -0.33 ± 0.04; also Kz'z)]. See also (1986MC09; Epol. p = 800 MeV), 6Be, (1984BA1U, 1986SA1Q) and (1986RA21).

8. 6Li(p, α)3He Qm = 4.0185 Eb = 5.606

Thermonuclear reaction rates and the astrophysical S-factor have been derived from the low-energy (Ep < 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 Ep = 1 MeV and a pronounced resonance at Ep = 1.85 MeV (γ < 0.5 MeV). No other structure is reported up to Ep = 5.6 MeV. Measurements between Ep = 0.4 and 3.4 MeV show that the polarizations are generally large and positive: see (1974AJ01).

Angular distributions have been reported for Ep = 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.).

9. 6Li(d, n)7Be Qm = 3.381

Angular distributions of the n0 and n1 groups have been measured at Ed = 0.20 to 15.25 MeV: see (1974AJ01, 1979AJ01). The n1-γ correlations are isotropic, indicating Jπ = 1/2- for 7Be*(0.43). Broad maxima are observed in the ratio of low-energy to high-energy neutrons at Ed = 4.2 and 5.1 MeV [7Be*(6.5, 7.2), γc.m. = 1.2 and 0.5 MeV, respectively]: see (1966LA04). See also 8Be and (1988KO1C).

10. 6Li(3He, d)7Be Qm = 0.112

Angular distributions of the d0 and d1 groups to 7Be*(0, 0.43) have been measured at E(3He) = 8, 10, 14 and 18 MeV and at E(3pol. He) = 33.3 MeV [7Be*(4.57) is also populated]: see (1974AJ01, 1984AJ01).

11. 6Li(6Li, 5He)7Be Qm = 1.01

See (1987MI34) and 5He.

12. 7Li(π+, π0)7Be Qm = 3.742

Forward-angle differential cross sections have been measured at Eπ+ = 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).

13. 7Li(p, n)7Be Qm = -1.644
Ethresh. = 1880.443 ± 0.020 keV (1985WH1A)

The excitation energy of 7Be*(0.43) is 429.20 ± 0.10 keV, τm = 192 ± 25 fsec: see (1979AJ01). Angular distributions of n0 and n1 have been reported at Ep = 1.9 to 119.8 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at 200, 300 and 400 MeV (1987WAZT; prelim.; n0 + 1). 7Be*(4.55, 6.51, 7.19, 10.79) have also been populated: see (1974AJ01, 1979AJ01). The ratios of σ10 (7Be*(0.43)/7Beg.s.) have been measured at 24.8, 35 and 45 MeV and yield the ratio of spin-flip to spin-nonflip strength |V/Vτ|2 (1980AU02). See also 8Be, (1983KI1B, 1984BR32, 1984JEZZ, 1984TA07, 1985JE1A, 1985TAZY, 1987HE24, 1988HE08), (1984KE1B, 1985BA66, 1985KE1D, 1986CO1L; applications), (1983RA1C, 1984TAZS, 1985GO1F, 1987GO1V, 1987RA32) and (1983KR10, 1984PE12; theor.).

14. (a) 7Li(d, 2n)7Be Qm = -3.869
(b) 7Li(t, 3n)7Be Qm = -10.126

See (1987AL10; E(7Li) = 65 MeV).

15. 7Li(3He, t)7Be Qm = -0.880

Angular distributions of t0 and t1 have been measured at E(3He) = 3.0 to 4.0 MeV and at E(3pol. He) = 33.3 MeV: see (1974AJ01, 1984AJ01). The width of 7Be*(4.57), γc.m. = 175 ± 7 keV: see (1974AJ01). See also 10B.

16. 7Li(6Li, 6He)7Be Qm = -4.369

This reaction has been studied at E(6Li) = 14, 25 and 35 MeV/A. 7Be*(0, 0.43) are strongly populated and 7Be*(4.57, 7.21) are also evident. At the highest energy the reaction mechanism is predominantly one-step (1987WI09, 1986AN29). See also 6He, (1988AL1G, 1988BUZH, 1988BU1Q), (1986AU1C, 1987AU04, 1988AN1J) and (1984BA53; theor.).

17. 9Be(p, t)7Be Qm = -12.082

Angular distributions of tritons have been measured at Ep = 43.7 and 46 MeV [see (1979AJ01)] and at 50 and 72 MeV (1984ZA07; t0+1, t2). The 11 MeV state has Ex = 11.01 ± 0.04 MeV, γ = 298 ± 25 keV, Jπ = 3/2-, T = 3/2 [the Jπ; T assignments are based on the similarity of the angular distribution to that in the (p, 3He) reaction to 7Li*(11.13)]: see (1979AJ01).

18. 10B(p, α)7Be Qm = 1.146

Angular distributions have been studied for Ep = 2.8 to 7.0 MeV [see (1974AJ01)] and for 18 to 45 MeV (1986HA27; α0, α1, α2; see for spectroscopic factors). Ex of 7Be*(0.43) = 428.89 ± 0.13 keV (1979RI12). See also 11C in (1985AJ01), (1983DO07) and (1988KOZL; applied).

19. 10B(d, 5He)7Be Qm = -1.97

See 5He.

20. 10B(α, 7Li)7Be Qm = -16.200

See 7Li.

21. 11B(3He, 7Li)7Be Qm = -7.076

See 7Li.

22. 12C(p, 6Li)7Be Qm = -22.566

See 6Li and (1987KW03; theor.).

23. 12C(d, 7Li)7Be Qm = -17.540

See 7Li.

24. 12C(3He, 8Be)7Be Qm = -5.779

Angular distributions involving 7Be*(0, 0.43) have been reported at E(3He) = 25.5 to 70 MeV [see (1979AJ01, 1984AJ01)] and at E(3pol. He) = 33.4 MeV (1986CL1B; also Ay; prelim.). See also (1986RA15; theor.).

25. 12C(α, 9Be)7Be Qm = -24.692

At Eα = 42 MeV, angular distributions have been measured involving 7Be*(0, 0.43) and 9Beg.s.: see (1974AJ01). Angular distributions have also been measured at Eα = 49.0 and 80.1 MeV (1984GO03).

26. 12C(7Li, 12B)7Be Qm = -14.231

See (1984BA53; theor.).

27. 16O(3He, 12C)7Be Qm = -5.5746

Angular distributions have been reported at E(3He) = 25.5 to 70 MeV to 7Be*(0, 0.43) and to various states of 12C: see 12C in (1985AJ01). See also (1986BA89; theor.).

28. 16O(7Li, 16N)7Be Qm = -11.281

Angular distributions have been studied at E(7Li) = 50 MeV involving 7Be*(0, 0.43) and various states of 16N (1984CO20, 1986CL03). See also 16N in (86AJ04) and (1984BA53; theor.).

29. 24Mg(3He, 20Ne)7Be Qm = -7.723

See (1986RA15; theor.).