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GENERAL: See also Table 9.1 [Table of Energy Levels] (in PDF or PS).

Theory: See (1955DA1E, 1955FR1F, 1956BL1B, 1956DE1C, 1956KU1A, 1957BA1H, 1957PA1A, 1958KU1B).

1. (a) 6Li(t, d)7Li	Qm = 0.994	Eb = 17.687
(b) 6Li(t, p)8Li	Qm = 0.803
(c) 6Li(t, n)8Be	Qm = 16.021
(d) 6Li(t, α)5He	Qm = 15.158
(e) 6Li(t, n)4He + 4He	Qm = 16.115

The differential cross section at 90° for reaction (a) rises steeply from 8.8 mb/sr at E_t = 0.72 MeV to 19 mb at 0.90 MeV, and then more slowly to 21 mb at E_t = 1.15 MeV. For reaction (d), the differential cross section at 90° rises from 0.75 mb/sr at 0.62 MeV to 5.7 mb/sr at 1.8 MeV and then decreases slowly to 5.3 mb/sr at 2.2 MeV (R.W. Crews, quoted in (1957JA37)).

See also (1952PE02), ⁵He, ⁷Li, ⁸Li and ⁸Be.

2. 6Li(α, p)9Be

Qm = -2.125

See (1956WA29).

3. 7Li(d, p)8Li

Qm = -0.192

Eb = 16.693

Cross sections have been measured for E_d = 0.4 to 1.8 MeV by (1952BA64), and for E_d = 0.7 to 3.3 MeV by (1954BA46); see (1957JA37). The yield for E_d = 1.1 to 4.0 MeV has been measured by (1956BE1A). Resonances are observed at 0.80 and 1.04 MeV (1952BA64, 1954BA46), 1.4 MeV (1952BA64: see, however, (1954BA46)), 2.0, 2.5 and 3.7 MeV (1956BE1A: see, however, (1954BA46)). See also (1955AJ61).

4. (a) 7Li(d, n)8Be	Qm = 15.026	Eb = 16.693
(b) 7Li(d, α)5He	Qm = 14.163
(c) 7Li(d, n)4He + 4He	Qm = 15.121

The cross section for (a) has been measured for E_d = 70 to 110 keV by (1955RA14) and that for (b) has been measured for E_d = 30 to 250 keV by (1953SA1A). Resonances for neutron production occur, in the range E_d = 0.2 to 4.8 MeV, at E_d = 0.68 (Γ = 250 keV), 0.98 (Γ = 60 keV) and 1.8 MeV (Γ = 400 keV) (1952BA64, 1957SL01). At E_d = 0.90 MeV, the α-particles in reaction (b) are isotropic to within 2%, consistent with formation by s-wave deuterons. No evidence is found for direct interaction effects at this energy (1957RI39). The angular correlation of ground-state α-particles with those resulting from breakup of ⁵He indicate J = 5/2^- (1956RI37), J = 3/2^- (1957FA10), for the ⁹Be level mainly responsible for this reaction at E_d = 0.9 MeV. Reactions (a) and (c) account for less than 10% of the disintegrations at this energy (1956RI37). See also ⁵He, ⁸Be and (1956CA1B).

5. (a) 7Li(d, d)7Li		Eb = 16.693
(b) 7Li(d, t)6Li	Qm = -0.994
(c) 7Li(d, 3He)6He	Qm = -4.512

The cross section for reaction (b) rises steeply from threshold to 95 mb at E_d = 2.4 MeV, and then more slowly to about 165 mb at E_d = 4.1 MeV (1955MA20). See also ⁶He and ⁷Li.

6. 7Li(t, n)9Be

Qm = 10.435

Not observed.

7. 7Li(3He, p)9Be

Qm = 11.200

At E_d = 0.7 and 1 MeV, proton groups are observed corresponding to excited states of ⁹Be at 1.83 ± 0.04 MeV (Γ < 0.4 MeV), 2.39 ± 0.08 MeV (Γ < 0.2 MeV), 3.10 ± 0.04 MeV (Γ < 0.3 MeV), 4.74 ± 0.08 MeV (Γ = 1.25 ± 0.25 MeV) and (9.1 ± 0.2 MeV) (Γ = 1.2 MeV) (1954MO92, 1955AL57, 1958MO99). The 1.8-MeV level admits a description in terms of an s-wave n - ⁸Be interaction with a scattering length a = 23 × 10^-13 cm (1958MO99: see ¹¹B(d, α)⁹Be).

8. 7Li(α, d)9Be

Qm = -7.151

Not observed.

9. 9Li(β-)9Be* → 8Be + n

Qm = 12.4

See ⁹Li.

10. (a) 9Be(γ, n)8Be	Qm = -1.667
(b) 9Be(γ, α)5He	Qm = -2.529
(c) 9Be(γ, n)4He + 4He	Qm = -1.572
(d) 9Be(γ, 2n)7Be	Qm = -20.565

The photo-neutron cross section has been studied from threshold (E_γ = 1.664 ± 0.004 MeV: (1956CO56)) to 320 MeV: see Table 9.2 (in PDF or PS). A sharp peak, Γ < 50 keV, σ ≈ 100 mb, occurs at E_γ = 1.70 MeV (1956CO56). A further broad maximum appears at E_γ ≈ 10 MeV, followed by the giant resonance at 20 - 22 MeV (1953JO1B, 1953NA1A: see (1956CO59)). Measurements from 6 to 18 MeV show pronounced peaks at 11.3 and 13.3 MeV and a broad, low peak at 16 MeV, immediately preceding the giant resonance (1959SP1B). At E_γ = 6.1 MeV the main processes appear to involve ⁹Be(γ, n)⁸Be*(2.9) and ⁹Be(γ, α)⁵He (1954CA1A). Angular distributions for E_γ = 1.7 and 1.8 MeV are spherically symmetric; at E_γ = 2.76 MeV, W(θ) = 1.2 + sin²θ (1949HA1A: see also (1954NI1B, 1956FA30)).

Calculations of (1949GU1A) and (1956MA1M) envisage E1 transitions to p⁴s and p⁴d configurations, with levels at ≈ 1.8 and ≈ 5 MeV (assuming a fixed well depth). The angular distributions and general trend of the cross section are well accounted for, as is the ratio of σ(γ, n)/σ(e, e'n) (1958BA60: 6 to 17 MeV). (1956CO56) state, on the other hand, that the 1.70-MeV peak is to be attributed to an M1 transition.

See also (1954ER1B, 1955JO1B, 1958BA60, 1958CH31) and (1956CZ1B, 1956CZ1C, 1956DE1C, 1957KO1B; theor.).

The cross section for reaction (c) is < 1 mb at E_γ = 1.63 MeV (1952AL26, 1952AL30). For reaction (d) see (1957LO1A).

11. (a) 9Be(γ, p)8Li	Qm = -16.885
(b) 9Be(γ, np)7Li	Qm = -18.919

The yield has a broad maximum, Γ = 4.7 MeV, at E_γ = 22.2 MeV where σ = 2.72 mb (1953HA1A). The angular and energy distributions of photoprotons produced by bremsstrahlung with E_max = 25 to 80 MeV has been studied by (1956CO59, 1956KL19). The angular distributions can be accounted for by the direct interaction of γ-rays with individual nucleons (1956KL19). The energy distributions indicate that transitions to levels in the residual nucleus play an important part in the direct photo effect (1956KL19). (1956CO59) suggest, on the other hand, that the relatively large proportion of low-energy protons indicates predominance of a (γ, n) process, followed by proton emission from ⁸Be levels at high excitation. See also (1953HE1B, 1953NA1A, 1957CH24, 1958CH31, 1958PA1B, 1958ST1A, 1958WH35).

12. (a) 9Be(γ, d)7Li	Qm = -16.693
(b) 9Be(γ, t)6Li	Qm = -17.687
(c) 9Be(γ, α)5He	Qm = -2.529

See (1955AJ61), (1956CO59, 1958WH35) and ⁹Be(γ, n)⁸Be.

13. 9Be(e, e')9Be*

Elastic scattering has been studied at E_e = 125, 150 and 190 MeV (1953HO79, 1954MC45). An r.m.s. radius of (2.2 ± 0.2) × 10^-13 cm is obtained (1957HO1E: see also (1956HO93)). Inelastic peaks corresponding to levels at 2.54 and 6.96 MeV are reported by (1954MC45). Comparison of σ(γ, n) and σ(e, e'n) for E_e = 6 to 17 MeV indicates that the transitions are mainly E1 (1958BA60). See also (1957EH1A, 1958EH1A).

14. (a) 9Be(n, n)9Be
(b) 9Be(n, 2n)8Be	Qm = -1.667

The neutron spectrum observed when ⁹Be is bombarded with 3.7-MeV neutrons exhibits a structure which is consistent with the excitation of the known states at 0, 1.5, 2.4 and 3.1 MeV, with subsequent neutron emission from the latter two. It is concluded that the (n, 2n) process at this energy proceeds mainly via discrete states of ⁹Be (1957HU14, 1958WA05). At the same bombarding energy (1955FO1B) observe two discrete groups in coincidence, suggesting the process ⁹Be(n, n')⁹Be*(2.43) → n + ⁸Be: see, however, (1957BO83: ⁹Be(α, α')⁹Be*). Using monochromatic neutrons with E_n = 2.6 to 3.25 MeV, (1957FI52) finds a sharp threshold for (n, 2n) at E_n = 2.7 MeV, corresponding to excitation of ⁹Be*(2.43). On the other hand, (1958MA22) find evidence for (n, 2n) at E_n = 2.6 MeV, below the threshold for (n, n'); at E_n = 5 to 6 MeV, the spectra show neutrons from the direct (n, 2n) process. At E_n = 14 MeV, the cross section for production of ⁹Be* is 170 ± 30 mb; comparison with σ(n, 2n) = 530 ± 40 mb indicates that about 1/3 of the (n, 2n) processes proceed via ⁹Be*(2.4) (1958AN32). See also (1957RO57) and (1958BE1E; theor.).

A search for γ-transitions from the 1.8 and 2.4-MeV levels yields upper limits of 0.3 and 0.2 mb, respectively, for E_n = 2.56 MeV and 1.8 and 0.3 mb for E_n = 2.74 MeV (1956DA23).

Elastic and inelastic neutron angular distributions show forward peaking at E_n = 14 MeV (1958AN32, 1958NA09): see ¹⁰Be, (1958RE1A, 1958TO1A).

15. 9Be(p, p)9Be

Elastic scattering has been studied at E_p = 14.5, 20 and 31.5 MeV by (1956KI54), at 10 MeV by (1956RA32), at 12 MeV by (1958SU14), at 17 MeV by (1956DA03), at 31 MeV by (1953WRZZ, 1954FI35, 1956BE14): see also ¹⁰B. All angular distributions show pronounced diffraction maxima characteristic of the optical model. Analysis in terms of the diffuse-surface optical model is discussed by (1957ME21). See also (1956KL55, 1956SH1C).

Inelastic scattering is observed corresponding to levels at (1.8), 2.43, 3.1, 5.0, 6.8, 7.9, 11.3, (14.5), (17.5), (19.9) and (21.7) MeV: see Table 9.3 (in PDF or PS). It is not clear whether the structure observed near 1.8 MeV is properly to be attributed to a level at this energy or to a three-body breakup, modified by the proximity of the neutron threshold. If the former is correct, the level width is 0.15 MeV and J = 1/2⁺ (1955GO48, 1958SU14). If a three-body breakup is involved, some interaction between the neutron and the ⁸Be must be involved: (1956BO18) find a satisfactory fit to the observed shape with an s-wave scattering length of 20 × 10^-13 cm; see also (1958MI1C) and ¹¹B(d, α)⁹Be. It is suggested by (1956SU67, 1958SU14) that the observed structure is to be understood in terms of a heavy particle stripping process and it is conjectured that the 4.8-MeV level may reflect the same effect, involving ⁸Be*(2.9); see, however, (1958MI1C).

A continuous distribution of neutrons, observed for E_p > 4.5 MeV is attributed to formation of ⁹Be*(2.4) with subsequent breakup into n + ⁸Be*(2.9) (1959MA20). Breakup into (⁸Be + n) occurs in 12 ± 5 % of transitions (J.B. Marion, private communication).

The energy of the 2.4-MeV level is given as 2433 ± 5 (1951BR72), 2434 ± 5 (1956BO18), 2432 ± 4 keV (1955GO48); the width is ≤ 1 keV (1955GO48). Analysis of angular distributions at E_p = 12 MeV in terms of direct interaction plus compound nucleus formation indicate J = 1/2^- or 5/2^- (1958SU14). At E_p = 31 MeV, analysis indicates J = 1/2⁺, 3/2⁺ or 5/2⁺ (1956BE14: see, however, (1958SU14)). Results at E_p = 10 MeV are consistent with odd parity (1956RA32). See also ¹⁰B(n, d)⁹Be and (1952DA1B).

The 3.03 ± 0.03 MeV level has a width > 0.28 MeV; the Wigner limit then restricts l_n to 0 or 1, J ≤ 3/2 (1956BO18: see, however, ¹¹B(d, α)⁹Be). Angular distributions for the higher levels have been studied by (1956BE14); the resulting spin assignments are given in Table 9.3 (in PDF or PS). See also (1954FI35, 1955GR12, 1958TY46) and (1956BL1B; theor.).

16. 9Be(d, d')9Be*

Elastic scattering angular distributions have been studied at E_d = 24 MeV by (1958SU14). See also (1947GU1A, 1952EL01) and ¹¹B.

Inelastic groups are reported corresponding to levels at (1.7), 2.4, 3.01 ± 0.1 (Γ ≈ 0.3), 4.8 and 6.8 MeV (1955RA41, 1956GR37, 1958MI1C, 1958SU14). The structure at Q = -1.7 MeV may be accounted for as a three-body breakup with an s-wave (n - ⁸Be) interaction characterized by a scattering length of 20 × 10^-13 cm, or by a resonance of about single-particle width. In either case a J = 1/2⁺ level of ⁹Be is indicated near the binding energy (1955RA41, 1958MI1C: see also ¹¹B(d, α)⁹Be). The angular distribution of the Q = -2.43 MeV group has been studied at E_d = 15 MeV (1956HA90) and E_d = 24 MeV (1958SU14). Analysis by direct interaction theory yields l = 2, J = 1/2^-, 5/2^- or 7/2^- (1958SU14: see, however, (1956HA90)). See also (1956SU1A).

17. 9Be(α, α')9Be*

Elastic scattering has been studied at E_α = 48 MeV by (1958SU14).

Inelastic groups are observed corresponding to ⁹Be* = (1.8), 2.4, (3.1), 6.8 and 11.3 MeV (1955RA41, 1956FA02, 1958SU14). The group corresponding to the 1.8-MeV "level" has a peak at Q = -1.83 ± 0.03 MeV, Γ ≈ 200 keV. It is suggested, however, that just such a structure would be expected from a heavy particle stripping process in which the proton also escapes, preferentially with the maximum possible energy. In this case, the 4.8-MeV "level" might arise from a similar process, in which the final nucleus is now ⁸Be*(2.9). The angular distribution of the Q = -2.4 MeV group at E_α = 48 MeV indicates l = 2, J = 1/2^-, 5/2^- or 7/2^- (1958SU14). Measurement of the momentum and angular distributions of α-particles from the breakup of ⁹Be*(2.4) indicate that the decay proceeds mainly via ⁴He + ⁵He, or by direct three-body breakup. Gamma decay is < 1%, neutron emission to ⁸Be(0) is < 10% (1957BO83). See also (1956BL1B, 1958PI1B; theor.).

18. (a) 9Be(p, d)8Be	Qm = 0.560
(b) 9Be(d, t)8Be	Qm = 4.592

At E_p = 95 MeV, two groups of deuterons are observed from reaction (a), corresponding to ⁸Be_g.s. and to states near 17 MeV. It is suggested that these reflect the "snatching" of the loosely bound neutron or of one of the tightly bound "alpha-particle" neutrons, respectively. Angular distributions lend some support to the α-particle model of ⁹Be; the occurrence of high momenta for the tightly bound neutrons indicates the operation of strong short-range two-body forces (1956SE1A).

Angular distributions at E_p = 6.5 and 22 MeV, and at E_d = 7.7 MeV are analyzed in terms of pickup theory, using a square-well (n - ⁸Be) interaction to represent the ground state of ⁹Be (1955DA1D, 1955DA1E). See also ¹⁰B, ¹¹B.

19. (a) 10B(γ, p)9Be	Qm = -6.585
(b) 10B(γ, p)8Be + n	Qm = -8.251

For reaction (a) see (1956GO1F, 1956GO1G). For reaction (b) see ⁸Be and ¹⁰B.

20. 10B(n, d)9Be

Qm = -4.358

At E_n = 14.4 MeV, the ground state and the level at 2.43 MeV are observed. No other deuteron groups were detected below E_x ≈ 5.5 MeV. The angular distribution of the deuterons, analyzed by pickup theory, indicate odd parity, 1/2 < J ≤ 9/2 for both states (1954RI15). See also (1956FR18), (1955FR1F; theor.) and ¹¹B.

21. 10B(d, 3He)9Be

Qm = -1.091

Not observed.

22. 10B(t, α)9Be

Qm = 13.228

At E_t = 1 MeV, α-groups are observed corresponding to ⁹Be levels at 2.39 and 3.06 MeV (1955AL57).

23. 11B(n, t)9Be

Qm = -9.564

Not observed.

24. 11B(p, 3He)9Be

Qm = -10.329

Not observed.

25. 11B(d, α)9Be	Qm = 8.022
	Q0 = 8.015 ± 0.010 MeV (1956BO18).

Alpha-particle groups are reported to states at (1.75), 2.4 and 3.0 MeV. The structure corresponding to the 1.75-MeV state can be explained in terms of an (n - ⁸Be) interaction with a scattering length a of 20 × 10^-13 cm or in terms of a resonance near threshold, with θ² ≈ 1 (1956BO18, 1958MI1C). (1958KA31) find, on the other hand, that a value of a ≥ 80 × 10^-13 cm is required to fit their distribution and suggest that the (n - ⁸Be) interaction must be very near resonance on this model. The energy of the 2.4-MeV state is given as 2422 ± 5 keV by (1951VA08), 2431 ± 6 keV (1954EL10), 2424 ± 5 keV (1956BO18). The next state is located at 3.02 ± 0.03 (1955LE36), 3.05 ± 0.03 MeV (1956BO18). The width is ≈ 0.3 MeV (1956BO18), Γ_c.m. = 161 ± 15 keV (1958KA31). See also (1955HO48).

26. 12C(n, α)9Be

Qm = -5.709

At E_n = 14 MeV, the cross section to the ground state of ⁹Be is 80 ± 20 mb; that to the 2.43-MeV level, σ_2.43, is 10 ≤ σ_2.43 ≤ 210 mb (1955GR21).

27. 13C(γ, α)9Be

Qm = -10.654

See (1953MI31).