A=7Be (1974AJ01)

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 d-waves contributing above E_α = 1 MeV (1963TO06). The branching ratio γ₁/γ₀ [⁷Be*(0.43)/⁷Be(0)] is approximately constant at 37% for E_α = 0.57 to 3.2 MeV (1963PA12, 1969NA24). The zero-energy intercept of the cross-section factor S = 0.61 ± 0.07 keV · b and (dS/dE)₀ = -(5.8 ± 0.3) × 10^-4 b using all of the data. If the low-energy data (E_cm ≤ 0.7 MeV) is fitted using a direct capture calculation (1963TO06) the zero-energy intercept of the cross-section factor is S = 0.51 ± 0.05 keV · b and (dS/dE)₀ = -(2.8 ± 0.4) × 10^-4 b (1969NA24). A second-order (in energy) polynominal fit to the low-energy data (E_cm ≤ 0.8 MeV) determines S = 0.61 ± 0.07 keV · b and (dS/dE)₀ = -(5.8 ± 0.3) b (1969NA24). Recent papers discussing the astrophysical implications of this reaction are (1967TO1B, 1968BA2E, 1971CA1B, 1972KA1B, 1973BA2C, 1973TR1E). See also (1966LA04).

3. (a) ⁴He(³He, ³He)⁴He E_b = 1.5864
(b) ⁴He(³He, p)⁶Li Q_m = -4.0200

Elastic scattering studies have previously been reported for E(³He) = 2.5 to 30 MeV and for E_α = 11 to 41 MeV: See (1966LA04). More recent measurements have been made at E(³He) = 1.72, 2.46, 2.98 MeV (1971CH42), 5 to 18 MeV (1967SP10), 12.0 to 19.0 MeV (1967DU1B), 17.8 to 30.0 MeV (1970JA04), 18 to 70 MeV (1969BA2B), 19.5 to 51.1 MeV (1970BR42), 27.2 to 42.8 MeV (1969SC16) and at E_α = 5.94 to 7.90 MeV (1968IV01), 42 MeV (1970VI01), 43.4 to 58.2 MeV (1969CA1E), 66 to 104 MeV (1971FE02, 1971FE03, 1973FE11) and 140 MeV (1972FR1J, 1972PU1C, 1972FR1K). Differential cross sections have been calculated by (1973KO1Q) for E_cm < 44.5 MeV using the one-channel resonating = group method, and including exchange terms and odd-even absorption. Polarization measurements have been carried out at E(³He) = 7.8 to 13.0 MeV (1969AR07, 1971AR1K) and at 11.5 to 13.0 MeV (1970MC07), and at E_α = 4.33 to 9.83 MeV (1972BO42), 7.5 to 18.5 MeV (1970HA1M, 1970HA1P, 1972HA64), 13.0 MeV (1971AR1K) and 98 MeV (1973FE11). The ratios of γ² to the Wigner limit are, respectively, 0.31^-0.09_+0.04 and 0.29^-0.16_+0.07 for ⁷Be*(0, 0.43) (1972BO42).

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 7.6 (in PDF or PS) (1967SP10, 1968IV01). No structure corresponding to ⁷Be*(7.21) (J^π = 5/2^-) is seen in the elastic data. The s-wave phase shift is somewhat greater than hard-sphere; the p-wave splitting agrees with (1964BA09, 1967SP10). The decay of ⁷Be*(9.27) (J^π = 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% (1967SP10). At higher energies [E(³He) = 27.2 to 42.8 MeV] (1969SC16) report that the s- and f-wave phase shifts fall appreciably below the predictions of resonating group calculations, while (1970BR42) see some indication of broad resonant structure at E(³He) ≈ 34 MeV, in rough qualitative agreement with such calculations. For inelastic scattering in reaction (a) see (1971HA21) and (1973FI04). The bremsstrahlung cross section at E(³He) = 7.4 MeV is 12.6 ± 3.4 μb/sr² (1973FR17).

The differential reaction cross section for reaction (b) has been determined for E(³He) = 8 to 18 MeV: resonances are observed corresponding to ⁷Be*(7.21, 9.27) in the p₀ yield and to ⁷Be*(9.27) in the p₁ yield: see Table 7.6 (in PDF or PS) (1967SP10). A study of the gamma rays from ⁶Li*(3.56) (p₂) carried out at E(³He) = 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, θ²_p₂ = 0.13 ± 0.02, T = 3/2). The T = 3/2 resonance is evidenced mainly through interference. There is also evidence for an extremely broad J^π = 1/2^- structure at E_x ≳ 10 MeV (1967HA07, 1967HA08: see also ⁶Li(p, p)⁶Li).

4. ⁴He(α, n)⁷Be Q_m = -18.9921

See ⁸Be.

5. ⁶Li(p, γ)⁷Be Q_m = 5.6064

Gamma transitions are observed to the ground (γ₀) and to the 0.43 MeV (γ₁) 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 ⁷Be*(0.43), < 4% to ⁷Be*(4.57) (1955BA59, 1956WA03, 1969JO1K, 1969SW1C). At E_p = 1.06 MeV a resonance in the yield of 0.43 MeV γ-rays is reported by (1968WO1E), corresponding to⁷Be*(6.52). See, however, (1963MC09). See also (1966LA1D) and (1966LA04).

6. (a) ⁶Li(p, p)⁶Li E_b = 5.6064
(b) ⁶Li(p, 2p)⁵He Q_m = -4.59

Measurements of elastic angular distributions have recently been reported by (1968ME25: E_p = 14 to 15.8 MeV). Earlier measurements are listed in (1966LA04). Two resonances are reported at E_p = 1.84 and 5 MeV in the elastic yield [⁷Be*(7.21, 9.9)]. The parameters of the lower resonance are shown in Table 7.3 (in PDF or PS) (1963MC09). The 5 MeV resonance has Γ ≈ 1.8 MeV and appears to also be formed by p-waves: γ²_p is then 3 ± 2 MeV · fm. A weak rise near E_p = 8 to 9 MeV may indicate a further level, ⁷Be* ≈ 13 MeV (1963HA53). Differential cross sections are reported by (1971BI11: 6.868 MeV) and by (1969LE08: 1.36 MeV). See also ⁶Li. Polarization measurements (elastic scattering) have been carried out at E_p = 1.21 to 3.22 MeV (1969PE22), 14.5 MeV (1965RO22), 49.8 MeV (1971MA13), 152 MeV (1966RO1C), and 155 MeV (1968GE04). A phase-shify analysis for E_p = 0.5 to 5.6 MeV shows that only ²S, ⁴S and ⁴P are involved. The ⁴P_5/2 phase resonantes at E_p = 1.8 MeV, and the broad resonance at 5 MeV can be reproduced equally well by either ⁴P_3/2 or ⁴P_1/2: tensor polarization measurements are necessary to distinguish between the two (1969PE22). See (1966LA04) for earlier results. An S-matrix analysis of the cross section of this reaction and of reactions 3 and 9 has been reported by (1966HU1C, 1968LE1K).

The reaction cross section for formation of ⁶Li*(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 cross section and 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 ⁶Li*(3.56) decreases slowly with energy for E_p = 24.3 to 46.4 MeV (1968AU06). Polarization measurements involving the p₁ and p₂ groups have been carried out E_p = 49.8 MeV (1971MA44). For the total scattering cross section at 1 GeV, see (1967IG1A).

See also (1967CA1G, 1968OL1B), (1971PL1C), (1966LE1E, 1969WA11, 1970LE02, 1972BR20, 1973LA26; theor.). For reaction (b) see ⁶Li, ⁵He and (1973NA1M).

7. ⁶Li(p, n)⁶Be Q_m = -5.070 E_b = 5.6064

The yield of neutrons increases approximately monotonically from threshold to E_p = 14.3 MeV (1964BA16). See also (1971BU1D). For polarization measurements at E_p = 30 and 50 MeV, see (1969RO20). See also (1969CL06, 1971JU05), (1970RA33; theor.) and ⁶Be.

8. ⁶Li(p, d)⁵Li Q_m = -3.44 E_b = 5.6064

See ⁵Li.

9. ⁶Li(p, α)³He Q_m = 4.0200 E_b = 5.6064

Over the range E_p = 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 keV^1/2 (1967FI05). Cross section measurements for E_p = 62 to 188 keV show deviation from an s-wave Gamow plot above ≈ 130 keV (1966GE11). Using cross-section measurements at E_p = 151 and 317 keV, as well as the (1966GE11) data, (1971SP05) calculate S(0) = 3.0 MeV · b. See also (1969AU1C).

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). No other structure is reported up to E_p = 5.6 MeV (1963JE03, 1964FA03). 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 A₁ and A₂ (1968BR18). S-matrix analysis of the cross section of this reaction and of reactions 3 and 6 are reported by (1966HU1C, 1968LE1K). Angular distributions are reported at E_p = 151 and 317 keV (1971SP05), at E_p = 0.5 to 1.82 MeV (1969JO1J), 3 to 45 MeV (1973SC1V) and 12, 14 and 16 MeV (1973WE07). Angular distributions at E_p = 8 to 18.5 MeV have been analyzed using a finite-range multi-interaction DWBA formalism. The analysis leads to reduced widths of 0.69 for α + d in a relative s-state, 0.04 for α + d in a relative d-state and 0.44 for ³He + t in a relative s-state (1973WE07). Yield and cross section measurements are reported by (1968BE1P: 0.3 to 1.0 MeV) and (1969LE08: E_p = 1.36 MeV). See also (1974GO1V) and see (1966LA04) for earlier measurements.

Searches for excited states of ³He have been unsuccessful: see (1968OL1B: E_p = 20 MeV), (1971BR12, 1972BU16: E_p = 45 MeV). See also (1970KO25, 1972BE1Y). See (1971BR12, 1973FI04) for discussions of the excited states of ⁴He.

See also (1967SP09, 1967VA1F) and (1969BE1M, 1969BO1G, 1972CL1C, 1972HU09: theor.).

10. ⁶Li(d, n)⁷Be Q_m = 3.3818

Two neutron groups are observed, corresponding to ⁷Be*(0, 0.43). Angular distributions of the n₀ and n₁ groups have been measured at E_d = 0.24 to 3.5 MeV [see (1966LA04) and (1966SC26)]: l_p = 1, J^π ≤ 5/2^- for both states. At E_d = 12, 15 and 17 MeV differential cross sections for the population of ⁷Be(g.s. + 0.43) have been measured by (1970GA07).

The n-γ correlations are isotropic, indicating J^π = 1/2^- for ⁷Be*(0.43) (1956NE13): E_γ = 428.9 ± 2 keV (1952TH24). Broad maxima are observed in the ratio of low-energy to high-energy neutrons at E_d = 4.2 and 5.1 MeV [⁷Be*(6.5, 7.2), Γ_cm = 1.2 and 0.5 MeV, respectively] (1957SL01).

11. ⁶Li(³He, d)⁷Be Q_m = 0.1126

Angular distributions of the d₀ and d₁ groups to ⁷Be*(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 ⁷Be*(0.43)/⁷Be(0)] = 1.55, in fair agreement with other measurements (1968LU02). See also (1964MA57) and (1970JA1J: theor.).

12. ⁶Li(α, t)⁷Be Q_m = -14.2082

Angular distributions of triton groups have been reported at E_α = 40 MeV (1965OG03: ⁷Be*(0 + 0.43, 4.57 + (5.0 ± 0.3)), 43 MeV (1967DE1K: ⁷Be*(0, 0.43)) and 46 MeV (1969FO1C: ⁷Be*(0, 0.43, 4.57)). See also (1967OG1A).

13. ⁷Li(p, n)⁷Be Q_m = -1.64422

E_thresh. = 1880.612 ± 0.090 keV (1970RO07); the recommended value for E_thresh. based on this and on other experiments is 1880.59 ± 0.08 keV (1970RO07). See also (1966MA60, 1966RO09, 1967MA1D, 1973MA1V). The excitation energy of the first excited state is 429.20 ± 0.10 keV (1972BO02). The lifetime of ⁷Be*(0.43), τ_m = 1.92 ± 0.2 msec. The ratio of this lifetime to that of ⁷Li*(0.48) is 1.82 ± 0.20. This value, and the values of τ_m are in agreement with intermediate coupling calculations assuming LS coupling predominates (a/K < 3.6) (1966PA11).

Angular distributions are reported at E_p = 1.9 to 2.36 MeV (1967BE61; n₀), 2.1 to 3.8 MeV (1971BU1D; n₀), 2.6 to 5.4 MeV (1972EL19; n₀), 3.2 to 5.4 MeV (1972EL19; n₁), at 17.5 MeV (1972AZ01; n₀, n₁, n₂) and at 30 and 50 MeV (1969CL06; n₀ + n₁). Above E_p ≈ 7 MeV, neutrons corresponding to ⁷Be*(4.57) are seen (1959AJ81, 1960HI04, 1963BO06). At E_p = 30 to 50 MeV, neutron groups are observed to states at E_x = 4.61 ± 0.07, 7.21 ± 0.06, 9.6 ± 0.3, 11.3 ± 0.2, 12.3 ± 0.2, 13.24 ± 0.15, 14.39 ± 0.15, 15.3 ± 0.2, 16.3 ± 0.2, 18.3 ± 0.2, 19.7 ± 0.3 ande 20.5 ± 0.2 MeV (1965BA39). See also (1967LO07, 1969JU1A, 1970BO1U, 1971DA24, 1971WA1J), (1966PA04, 1969MA1P, 1969MA1G, 1968TH1H, 1971TH1K; theor.), (1966LA04) and ⁸Be.

14. ⁷Li(³He, t)⁷Be Q_m = -0.8804

Angular distributions have been measured at E(³He) = 3.0 to 4.0 MeV (1969OR01; t₀, t₁), 8.7 and 9.7 MeV (1968MA1W; t₀, t₁), 14 MeV (1969NU1A; t₀, t₁) and 25.2 MeV (1968BR1G; t₀, t₁, t₂). The width of ⁷Be*(4.57), Γ_cm = 175 ± 7 keV (1971PI06). See also (1967BL1E) and (1971WE1L, 1971WE1M; theor.).

15. ⁷Li(⁶Li, ⁶He)⁷Be Q_m = -4.372

At E(⁶Li) = 31.8 MeV, the reaction is observed to ⁷Be*((0 + 0.43), 4.57) (1971CH1B).

16. ⁹Be(p, t)⁷Be Q_m = -12.0831

Angular distributions of tritons have been measured at E_p = 43.7 MeV (1965DE08, 1966CE05, 1968BR23: ⁷Be*(0, 0.43, 4.57, 6.51, 11.01)) and 46 MeV (1967VE01: ⁷Be(0 + 0.43, 4.57, 6.51, 10.79)). 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, ³He) reaction to ⁷Li*(11.13)] (1965DE08). See also (1967MC14), (1969BA1Z, 1969IN1A) and (1967BA1E; theor.).

17. ¹⁰B(p, α)⁷Be Q_m = 1.1462

Alpha groups corresponding to ⁷Be*(0, 0.43) have been studied by many observers: see (1952AJ38, 1959AJ76). Some reported values for the energy of the first excited state are: 431 ± 5 keV (1950VA01), 434.4 ± 4 keV (1951BR10), 429 ± 3 keV (1952CR30), 428.5 ± 1.8 keV (1952TH24). In addition the excitation of ⁷Li*(4.72 ± 0.08, 6.27 ± 0.10, 7.21 ± 0.10, (14.6 ± 0.3)) is reported by (1955RE16). At E_p = 18.6 MeV (θ = 30°) (1968PA15) find that the intensity of a group to ⁷Be*(14.6) is < 2% that reported by (1955RE16). Angular distributions have been measured at E_p = 2.8 to 7.0 MeV (1964JE01). See also ¹¹C in (1975AJ02) and (1966LA04).

18. ¹⁰B(³He, ⁶Li)⁷Be Q_m = -2.874

At E(³He) = 30.0 MeV angular distributions have been obtained for the transitions to ⁷Be*(0, 0.43) + ⁶Li*(0, 2.19): see (1970DE12, 1972OH01).

19. ¹⁰B(α, ⁷Li)⁷Be Q_m = -16.202

At E_α = 45.6 MeV (1969FO06) have measured the angular distributions of the ⁷Li and of the ⁷Be 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 ⁷Li and ⁷Be are very similar (1969FO06). See also (1971RO1A, 1971SI28, 1973NA1N; theor.).

20. ¹¹B(d, ⁶He)⁷Be Q_m = -11.563

At E_d = 40 MeV the cross section of the ground-state reaction is twice (to ± 10%) that for the reaction to ⁶Li*(3.56) + ⁷Li(0), in agreement with isospin conservation (1972GO1P).

21. ¹¹B(³He, ⁷Li)⁷Be Q_m = -7.079

See (1971RO1A).

22. ¹²C(p, ⁶Li)⁷Be Q_m = -22.569

At E_p = 36.0, 40.7, 45.0, 50.0 and 56.8 MeV angular distributions have been obtained for the transitions to ⁷Be*(0 + 0.43) (1971BR07, 1971HO25, 1971HO1K).

23. ¹²C(d, ⁷Li)⁷Be Q_m = -17.543

At E_d = 39.8 MeV angular distributions have been measured for the transitions ⁷Li(0) + ⁷Be(0), ⁷Li*(0.43) + ⁷Be(0), ⁷Li(0) + ⁷Be*(0.43) and ⁷Li*(0.43) + ⁷Be*(0.43). The ratios of the ⁷Li(0) and ⁷Be(0) cross sections show asymmetries exceeding 20% (1971HO1K, 1971YO06). See also (1971SI28; theor.).

24. ¹²C(³He, ⁸Be)⁷Be Q_m = -5.780

Angular distributions have been obtained at E(³He) = 25.5 to 29 MeV (1972PI1A, 1973PI1D: ⁷Be*(0, 0.43)), 28 and 30 MeV (1970DE12, 1973KL1B: ⁷Be*(0, 0.43) + ⁸Be*(0, 2.9)), 35.6 MeV (1969NE1D, 1969ZE1A, 1970FO1D: ⁷Be*(0, 0.43)) and 37 and 41 MeV (1967ZA1B: ⁷Be*(0 + 0.43)). See also (1965EN01).

25. ¹²C(α, ⁹Be)⁷Be Q_m = -24.694

At E_α = 42 MeV, angular distributions have been measured to ⁷Be*(0, 0.43) + ⁹Be(0) (1972RU03).

26. ¹³C(p, ⁷Li)⁷Be Q_m = -20.264

At E_p = 45.0 MeV the angular distribution has been measured for the transition to ⁷Li(0) + ⁷Be(0) (1971BR07).

27. ¹⁶O(p, ¹⁰B)⁷Be Q_m = -25.270

See (1969HO1H).

28. ¹⁶O(³He, ¹²C)⁷Be Q_m = -5.575

Angular distributions are reported at E(³He) = 25.5 to 29 MeV (1972PI1A: to ⁷Be*(0, 0.43)), 30 MeV (1970DE12, 1973KL1B: to ¹²C*(0, 4.4, 7.7, 9.6) + ⁷Be*(0, 0.43)) and 41 MeV (1967ZA1B).

29. ¹⁶O(α, ¹³C)⁷Be Q_m = -21.207

At E_α = 42 MeV, angular distributions have been obtained for the transitions to ⁷Be*(0, 0.43) + ¹³C(0) (1972RU03).

30. ¹⁹F(d, ¹⁴C)⁷Be Q_m = -7.140

The angular distribution to ⁷Be*(0 + 0.43) + ¹⁴C(0) has been measured at E_d = 14.9 MeV (1967DE03).

31. (a) ¹⁹F(³He, ¹⁵N)⁷Be Q_m = -2.426
(b) ²⁰Ne(³He, ¹⁶O)⁷Be Q_m = -3.144

(1970DE12, 1973KL1B) have studied, at E(³He) = 30 MeV, the angular distributions to ¹⁵N(0) + ⁷Be*(0, 0.43) and to ¹⁶O*(0, 6.06 + 6.13) + ⁷Be*(0, 0.43).