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USNDP

7Be (1984AJ01)


(See Energy Level Diagrams for 7Be)

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 7Be: (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 7Be: (1982FI13, 1982NG01).

1. 7Be(ε)7Li Qm = 0.862

The decay is complex: see 7Li.

2. 4He(3He, γ)7Be Qm = 1.5876

The capture cross section has been measured for Eα = 0.38 to 5.80 MeV [see (1974AJ01)], 0.250 to 2.954 MeV (1982KR05), 0.385 to 2.730 MeV (1982OS02), at Ec.m. = 0.897 MeV (1983RO1C) and for E(3He) = 19 to 26 MeV (1983WA05; γ0+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 Ec.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 Ec.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 7Be decay to 7Li*(0.48)) [see reaction 28 in 7Li] (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. C2S = 1.0 for 7Be*(0, 0.43) (1982KR05). See also (1980BA1P, 1980BA2M, 1980PE1N, 1981BA2F, 1981RO1W, 1982BA80; astrophysics) and (1981KI01, 1981LI01, 1982TA1G, 1983WA1M; theor.).

3. (a) 4He(3He, 3He)4He Eb = 1.5876
(b) 4He(3He, p)6Li Qm = -4.0182

Elastic scattering studies have been reported for E = 1.72 to 140 MeV [see (1974AJ01, 1979AJ01)] and at Eα = 0.25 to 2.95 MeV (1982KR05) and 140 MeV (1980RO03) and at E(3He) = 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 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 (1978LU05). The work of (1978BA75) is consistent with the results of (1978LU05) and, in addition, suggests broad l = 4 and 5 states at E(3He) > 30 MeV [Ex > 19 MeV].

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 (1980NE08; p0). 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 through 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). See also (1980NE08). See aslo (1981BA1Q), (1978BR1A, 1979KA1G, 1982YA1A) and (1978DU1D, 1978TA1A, 1979KOZV, 1979LE11, 1979WI1B, 1981FI1B, 1981SH07, 1982AZ01, 1982FU01, 1982KA11, 1982LE23, 1983HO1F, 1983SA1G; theor.).

4. 4He(α, n)7Be Qm = -18.9902

See (1978GL03, 1979AL1F), (1979AJ01) and 8Be.

5. 6Li(p, γ)7Be Qm = 5.606

Gamma transitions are observed to the ground (γ0) and to the 0.43 MeV (γ1) states. The yield shows no evidence of resonance for Ep = 0.2 to 1.0 MeV and the branching ratio remains approximately constant at (62 ± 5)% to the ground state, 38% to 7Be*(0.43), < 4% to 7Be*(4.57): see (1974AJ01). The total cross section for Ep = 0.2 to 1.2 MeV has been obtained by (1979SW02): at Ep = 0.8 MeV it is 3.1 ± 0.4 μb, in good agreement with previous values. The branching ratio to 7Be*(0.43) is (41 ± 3)% (1979SW02). The weighted mean of this and previous measurements is (39 ± 2)% (1979SW02). See also (1980BA34).

6. (a) 6Li(p, p)6Li Eb = 5.606
(b) 6Li(p, 2p)5He Qm = -4.59
(c) 6Li(p, pα)2H Qm = -1.4753

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 155 MeV [see (1974AJ01, 1979AJ01)] and at Epol. p = 25 and 35 MeV (1982ROZT; 00, p1) and 800 MeV (1979GL1C; p2). 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 is 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 reaction cross section has been measured for Ep = 25.0 to 48 MeV: see (1979AJ01).

For reaction (b) see 5He, (1978NA18; Epol. p = 635 MeV) and (1979AJ01). For reaction (c) see 6Li 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.).

7. 6Li(p, n)6Be Qm = -5.070 Eb = 5.606

The yield of neutrons increases approximately monotonically from threshold to Ep = 14.3 MeV. Polarization measurements are reported at Ep = 30 and 50 MeV: see (1974AJ01). See also 6Be.

8. 6Li(p, α)3He Qm = 4.0182 Eb = 5.606
Q0 = 4018.2 ± 1.1 keV: see (1981RO02)

Over the range Ep = 25 to 50 keV, the cross section rises from 0.8 to 72 μb: in the formula σ ≈ E-1e-B/√E(square root of E), B = 90 ± 6 keV1/2. Cross-section measurements for Ep = 62 to 188 keV show deviation from an s-wave Gamow plot above ≈ 130 keV (1966GE11). Using cross-section measurements at Ep = 136 → 297 keV, as well as the (1966GE11) results, (1979EL10) calculate S(0) = 3.145 MeV · b [Ec.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 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. The Ep = 1.9 MeV resonance appears in A1 and A2: see (1974AJ01).

Angular distributions have been reported for Ep = 0.15 to 45 MeV [see (1974AJ01, 1979AJ01)] and at Ep = 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.).

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 n-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 (1979HO04, 1980GU26) in 8Be.

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: all the distributions show an l = 1 maximum at small angles: see (1974AJ01). At E(pol. 3He) = 33.3 MeV angular distributions and Ay measurements to 7Be*(0, 0.43) have been analyzed using coupled channels and DWBA. 7Be*(4.57) is also populated (1981BA38).

11. 6Li(α, t)7Be Qm = -14.208

See (1979AJ01).

12. (a) 7Li(γ, π-)7Be Qm = -140.429
(b) 7Li(π+, π0)7Be Qm = 3.742

For reaction (a) see (1979BO23). Forward-angle differential cross sections to 7Beg.s. have been measured at Eπ+ = 48 MeV (1982LEZY), and 70 → 180 MeV (1980BA27, 1982DO02). See also (1982AL35).

13. 7Li(p, n)7Be Qm = -1.644

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 are reported at Ep = 1.9 to 50 MeV [see (1974AJ01, 1979AJ01)] and at 119.8 MeV (1979GO16, 1980GO07; n0+1). The population of 7Be*(4.55, 6.51, 7.19, 10.79) has also been observed: see (1974AJ01, 1979AJ01). The ratios σ10 (7Be*(0.43)/7Beg.s.) have been measured at 24.8, 35 and 45 MeV: an analysis of these yields the ratio of spin-flip to spin-nonflip strength |Vστ/Vτ|2 (1980AU02). 1983TAZY report cross-section measurements at Ep = 60 to 200 MeV. See also (1981SH1F, 1982KI1F, 1982TAZQ), (1979CH1B, 1980SE1D, 1982SA1M; applied), (1982GO1C, 1982PE06, 1982TA03), (1982GU1D, 1983GU1G; theor.) and 8Be.

14. 7Li(3He, t)7Be Qm = -0.881

Angular distributions of t0 and t1 have been measured at E(3He) = 3.0 to 4.0 MeV [see (1974AJ01)] and at E(pol. 3He) = 33.3 MeV (1981BA37). The width of 7Be*(4.57), Γc.m. = 175 ± 7 keV: see (1974AJ01). See also 10B.

15. 9Be(p, t)7Be Qm = -12.082

Angular distributions of tritons have been measured at Ep = 43.7 MeV (7Be*(0, 0.43, 4.57, 6.51, 11.01)) and 46 MeV (7Be*(0 + 0.43, 4.57, 6.51, 10.69)), and at Ep = 50 and 72 MeV (1982ZA1B; t0, t1). 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).

16. 9Be(3He, 5He)7Be Qm = -0.88

See reaction 23 in 5He.

17. 10B(p, α)7Be Qm = 1.146

Angular distributions have been measured for Ep = 2.8 to 7.0 MeV: see (1974AJ01). Ex = 428.89 ± 0.13 keV (1979RI12). See also 11C in (1980AJ01, 1985AJ01).

18. 10B(d, 5He)7Be Qm = -1.97

See (1982DO1E).

19. 10B(3He, 6Li)7Be Qm = -2.873

See 6Li.

20. 10B(α, 7Li)7Be Qm = -16.200

At Eα = 45.6 MeV the angular distributions of the 7Li and of the 7Be ions, corresponding to the ground-state 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 7Li and 7Be are very similar: see (1974AJ01).

21. 12C(γ, nα)7Be Qm = -26.265

See (1979KI04).

22. 12C(p, 6Li)7Be Qm = -22.565

See 6Li.

23. 12C(d, 7Li)7Be Qm = -17.539

See 7Li.

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

Angular distributions are reported at E(3He) = 25.5 to 30 MeV involving 7Be*(0, 0.43) [see (1979AJ01)] and at 41 MeV (1981LE01) and 15O in (1981AJ01).

25. 12C(α, 9Be)7Be Qm = -24.691

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

26. 13C(p, 7Li)7Be Qm = -20.261

See 7Li.

27. 16O(3He, 12C)7Be Qm = -5.5744

Angular distributions are reported at E(3He) = 25.5, 30 and 70 MeV to 7Be*(0, 0.43) and various states of 12C [see 12C in (1980AJ01)] and at 41 MeV (1981LE01).

28. 16O(α, 13C)7Be Qm = -21.2058

See 13C in (1981AJ01).

29. 19F(d, 14C)7Be Qm = -7.140

The angular distributions to 7Be*(0, 0.43) + 14Cg.s. has been measured at Ed = 14.9 MeV: see (1974AJ01).

30. (a) 19F(3He, 15N)7Be Qm = -2.426
(b) 20Ne(3He, 16O)7Be Qm = -3.146

See 15N in (1981AJ01) and 16O in (1982AJ01).