A=5He (2002TI10)

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⁵He (2002TI10)

(See Energy Level Diagrams for ⁵He)

GENERAL: References to articles on general properties of ⁵He published since the previous review (1988AJ01) are grouped into categories and listed, along with brief descriptions of each item, in the General Tables for ⁵He located on our website at (nucldata.tunl.duke.edu/NuclData/General_Tables/5he.shtml).

See also 3 [Electromagnetic Transitions in A = 5-7] (in PDF or PS) and 5.1 [Table of Energy Levels] (in PDF or PS).

See also the A = 5 introductory discussion titled A = 5 resonance parameters.

1. ¹H(⁶He, np)⁵He Q_m = -1.771

The quasi-free neutron knockout reaction was studied with ⁶He beams produced by 115 MeV ¹⁵N primary beams (1997KOZV, 1997KO07). ⁵He was observed in the separation energy spectra. The ⁵He → ⁴He + n decay energy is reported to be consistent with the "known mass of ⁵He" and is given as 0.97 MeV.

2. ³H(d, γ)⁵He Q_m = 16.792

At low energies the reaction is dominated by a resonance at E_d = 107 keV; the mirror reaction shows resonance at E_d = 430 keV. The branching ratio Γ_γ₀/Γ_n integrated over the resonance from 0 to 275 keV is (5.6 ± 0.6) × 10^-5 (1986MO05), in very good agreement with the earlier value of (5.4 ± 1.3) × 10^-5 for E_d = 45 to 146 keV (1984CE08). Assuming Γ_n of ⁵He*(16.7) is 37 ± 5 keV (see reaction 8), then Γ_γ₀ = 2.1 ± 0.4 eV. (1986MO05) also report branching ratios up to E_d = 0.72 MeV and summarize the earlier work to 5 MeV. More recently, a measurement (1993KA01) at E_d = 100 keV of the ³H(d, γ)⁵He/³H(d, α)n ratio gave (1.2 ± 0.3) × 10^-4 which is larger than the results of (1986MO05) and (1984CE08) but includes contribution from decay to both the ground and first excited states.

Differential cross sections, vector- and tensor-analyzing powers were measured at E_d = 400 keV for ³H(d, γ)⁵He (1989RI04) and at E_d = 0.1, 0.45 and 8.6 MeV for ³H(d, γ) and ³He(d, γ) by (1994BA02). These results were compared with coupled channels resonating group model (CCRGM) calculations. See also the shell model description of the 3/2⁺ resonance presented in (1993KU02).

The ³H(d, γ)⁵He and ³He(d, γ)⁵Li reactions were used in a measurement (1991BA02) of the ground state widths of ⁵He and ⁵Li. The results were Γ_n = 1.36 ± 0.19 MeV in ⁵He and Γ_p = 2.44 ± 0.21 MeV for ⁵Li. These values lead to reduced widths for ⁵He and ⁵Li which are equal (within error). This is consistent with charge symmetry expectations. The ground-state widths given by the conventional R-matrix prescription in 5.2 (in PDF or PS) and 5.4 (in PDF or PS) are 0.963 MeV and 2.11 MeV for ⁵He and ⁵Li, respectively.

The data of (1991BA02) were used by (1996EF03) in a single-level R-matrix analysis to obtain values of the ground-state energies and widths of ⁵He and ⁵Li, close to those given by the extended R-matrix prescription in 5.1 (in PDF or PS) and 5.3 (in PDF or PS).

3. (a) ³H(d, n)⁴He Q_m = 17.58928 E_b = 16.79151
(b) ³H(d, 2n)³He Q_m = -2.98834
(c) ³H(d, pn)³H Q_m = -2.22457

The cross section for reaction (a) has been measured in the range E_t = 12.5 to 117 keV (1984JA08) [0.525(± 4.8%) mb to 3.739(± 1.4%) b] and in the range E_d = 79.913 to 115.901 keV (± 0.015 keV) (1987BR10) [3.849 to 4.734 b (± 1.6%)]. See also (1985FI1G; E_d = 13.8 to 114.3 keV). A strong resonance, σ (peak) = 4.88 b, appears at E_d = 105 keV: see 5.2 (in PDF or PS) in (1979AJ01) and (1987BR10). For a discussion of R-matrix analysis and evidence for a "shadow" pole, see (1987BR10, 1987HA20). See also (1987HA44, 1987MO1K). The related work of (1991BO23) uses a resonance coupled channels model to interpret the ⁵He (3/2⁺) resonance as a coupled channel pole associated predominantly with the d-t system. A later study by (1993CS02) uses a realistic dynamical microscopic reaction approach and reaches the same conclusion. A more recent analysis of cross section data for E_d = 8 - 116 keV is described in (1995LA33). Resonance parameters for the ⁵He 3/2⁺ second excited state were determined.

From E_d = 10 to 500 keV, the cross section is well fitted with the assumption of s-wave formation of a J^π = 3/2⁺ state. (See however the discussion below.) Measurements of cross sections and angular distributions for reaction (a) have been reported to E_d = 21 MeV and E_t = 20.0 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] as well as at 1.0, 1.5 and 2.0 MeV (1987LI07). Neutron yields from reaction (a) above have been measured at E_d = 140 - 300 keV (1989SH17). Measurements to determine the intensity of intermediate energy neutrons are described in (1989GA21). An absolute measurement of the polarization of 50 MeV neutrons at θ_lab = 29.7° was reported in (1991SA18).

A study of reaction (a) with polarized deuterons at E_d = 0.2 to 1.0 MeV indicates intervention of the s-wave, J^π = 1/2⁺ channel, as well as possible p-waves above E_d = 0.3 MeV. The polarization increases monotonically from 0.03 at E_d = 3 MeV to ≈ 0.5 at E_d = 6.5 MeV and then with a lower slope to 0.69 at E_d = 13 MeV. The change in the slope may be caused by excited states of ⁵He near 20 MeV. Comparison with the ³He(d, p)⁴He mirror reaction at corresponding cm energies shows excellent agreement between the polarization values in the two reactions up to E_d = 6 MeV, but then the proton polarization becomes ≈ 15% higher, converging back to the neutron values at E_d ≈ 12 - 13 MeV. This may be due to experimental factors. Vector polarization transfer coefficients, K_y^y'(0°) have been measured for E_d = 5 to 11 MeV (1985HOZU, 1986HO1E). For earlier polarization work see (1984AJ01).

An R-matrix formalism was used in a phase shift analysis of d + ³H below 1 MeV to obtain the contribution of ²S_1/2- and P-wave channels near the ⁵He (3/2⁺) resonance. See also the recent work (1997BA72) in which properties of the 3/2⁺ levels of ⁵He and ⁵Li are discussed in terms of conventional R-matrix parameters. The multichannel resonating group model has been used in a study (1990BL08) of partial wave contributions in this energy region.

Improved formulae for fusion cross sections and thermal reactivities utilizing new data and R-matrix techniques are presented in (1992BO47). See also (1989AB21, 1989SC1F, 1989SC19, 1989SC25, 1989SC41).

The ³H(d, n) reactivity in fusion reactors and screening-effect corrections needed for low energy data are discussed in (1989LA29).

(1987BR10) have derived astrophysical S-factors in the range E_d = 8.3 to 115.9 keV [S(0) = 11.71 ± 0.08 MeV · b], as well as reactivities. See (1984AJ01) for the earlier work, and (1985CA41, 1987VA36). Angular distributions of α particles were measured for E_d < 200 keV (1997BE59) and evidence for a D-wave contribution to the cross section in the vacinity of the 3/2⁺ s-wave resonance in ⁵He was reported. Thermonuclear reaction rates for this reaction calculated from evaluated data are presented in the compilation (1999AN35).

Reaction (b) has been studied for E_d = 10.9 to 83 MeV. A study of reaction (c) leads to the suggestion of a resonance at E_cm = 2.9 ± 0.3 MeV [E_x = 19.7 MeV], Γ_cm = 1.9 ± 0.2 MeV, consistent with J^π = 3/2^- [see 5.1 (in PDF or PS)]: see (1974AJ01, 1979AJ01). See also the references cited in (1988AJ01). For applications and developments in muon-catalyzed fusion see the references cited in (1988AJ01) and the General Table for ⁵He located on our website at (nucldata.tunl.duke.edu/NuclData/General_Tables/5he.shtml).

4. ³H(d, d)³H E_b = 16.792

The elastic scattering has been studied for E_d = 2.6 to 11.0 MeV: see (1984AJ01). For earlier measurements at other energies see (1966LA04). The excitation curves show an interference at E_x ≈ 19 MeV and a broad (Γ > 1 MeV) resonance corresponding to E_x = 20.0 ± 0.5 MeV, similar to that seen in ³He(d, d) [see ⁵Li]. Together with data from ³H(d, n)⁴He, this work favors an assignment D_3/2 or D_5/2 with a mixture of doublet and quartet components (channel spin 1/2 and 3/2) if only one state is involved [any appreciable doublet component would, however, be in conflict with results from ⁷Li(p, ³He)⁵He]. Measurements of differential cross section and analyzing power using polarized deuterons with E_d = 3.2 to 12.3 MeV show resonance-like behavior in the vector analyzing power near E_d = 5 MeV. The anomaly appears in the odd Legendre coefficients and is interpreted in terms of a (1/2, 3/2)^- excited state of ⁵He with E_x ≈ 19.7 MeV. Broad structure in the differential cross section near 6 MeV, principally in the even Legendre coefficients, corresponds to an even parity state ⁵He*(20.0). Elastic scattering data is also utilized in the S-matrix studies of the ⁵He (3/2⁺) resonance at E_x = 16.84 MeV (1988BE1U, 1991BO23, 1993CS02). (See reaction 3). See also the effective-range expansion and Coulomb renormalization for d + t and related systems (1991KA31, 1996PO26). For earlier references see (1979AJ01, 1988AJ01). For d-t correlations see (1987PO03). See also "Complex reactions" in the General section of (1988AJ01) and (1981PL1A, 1983HAYX, 1986BO01). See also (1997BA72) in which properties of the 3/2⁺ levels of ⁵He and ⁵Li are discussed in terms of conventional R-matrix parameters.

5. ³H(t, n)⁵He Q_m = 10.534

At E_t = 0.5 MeV, the reaction appears to proceed via three channels: (i) direct breakup into ⁴He + 2n, the three-body breakup shape being modified by the n-n interaction; (ii) sequential decay via ⁵He_g.s.; (iii) sequential decay via a broad excited state of ⁵He. The width of ⁵He_g.s. is estimated to be 0.74 ± 0.18 MeV. Some evidence is also shown for ⁵He* at E_x ≈ 2 MeV, Γ ≈ 2.4 MeV: see (1979AJ01). See also ⁶He and (1986BA73).

6. ³H(α, dα)n Q_m = -6.257

A kinematically complete experiment at E_α = 67.2 MeV has been reported by (2000GO35). They report observation of ⁵He excited states at E_x = 18.9, 19.9 and 20.7 MeV with widths of 0.3, 0.25 and 0.25 MeV, respectively.

7. ³He(t, p)⁵He Q_m = 11.298

Some evidence is reported at E_t = 22.25 MeV for a broad state of ⁵He at E_x ≈ 20 MeV, in addition to a sharp peak corresponding to ⁵He*(16.7): see (1979AJ01). See also ⁶Li.

8. ⁴He(n, n)⁴He E_b = -0.798

The coherent scattering length (thermal, bound) is 3.07 ± 0.02 fm, σ_s-bar = 0.76 ± 0.01 b. Total cross sections have been measured for E_n = 4 × 10^-4 eV to 150.9 MeV and at 10 GeV/c [see (1984AJ01)] and at E_n = 1.5 to 40 MeV (1983HA20).

The total cross section has a peak of 7.6 b at E_n = 1.15 ± 0.05 MeV, E_cm = 0.92 ± 0.04 MeV, with a width of about 1.2 MeV: see (1979AJ01). A second resonance is observed at E_n = 22.133 ± 0.010 MeV [σ_peak = 0.9 b] with a total width of 76 ± 12 keV and Γ_n = 37 ± 5 keV (1983HA20). Attempts to detect additional resonances in the total cross section have been unsuccessful: see (1979AJ01). For curves and tables of neutron cross sections see (1988MCZT, 1990NAZH, 1990SH1C).

The P_3/2 phase shift shows strong resonance behavior near 1 MeV, while the P_1/2 phase shift changes more slowly, indicating a broad P_1/2 level at several MeV excitation. (1966HO07) have constructed a set of phase shifts for E_n = 0 to 31 MeV, l = 0, 1, 2, 3, using largely p-α phase shifts. At the 3/2⁺ state the best fit to all data is given by E_res = 17.669 MeV ± 10 keV, γ_d² = 2.0 MeV ± 25%, γ_n² = 50 keV ± 20% (see 5.2 (in PDF or PS) in (1979AJ01)). See also (1997BA72) in which properties of the 3/2⁺ levels of ⁵He and ⁵Li are discussed in terms of conventional R-matrix parameters.

An R-function analysis of the ⁴He + n data below 21 MeV (including absolute neutron analyzing power measurement and accurate cross section measurements) has led to a set of phase shifts and analyzing powers which are based on the ⁴He + n data alone (rather than also including the ⁴He + p data). At a = 3.3 fm the values obtained for the P_1/2 and P_3/2 resonances are, respectively, E_cm = 1.97 and 0.77 MeV, Γ_cm = 5.22 and 0.64 MeV: see (1984AJ01). Angular distributions of A_y have been studied by (1984KL05, 1984KR23, 1986KL04) for E_n = 15 to 50 MeV: see also for phase-shift analysis and comparison with ⁴He(p, p).

The excitation energies and the spectroscopic factors for ⁵He states are obtained by (1985BA68) from 2-level R-matrix fits to the phase shifts, as functions of the channel radius. For a ≈ 5.1 fm a very broad state with J^π = 1/2⁺ is found to lie at E_x ≈ 7 MeV in both ⁵He and ⁵Li, in agreement with the shell-model calculation by (1984VA06). Broad 3/2⁺ and 5/2⁺ states then lie at ≈ 14 MeV and the 1/2^- state is at about 2.6 MeV. (1985BA68) suggest that the phase-shift analysis should be redone with values of a larger than those previously used (a ≈ 3 fm). See also references cited in (1988AJ01). In more recent work S-matrix studies of the low energy 3/2^- and 1/2^- states are described in (1997CS01, 1998CS02). See also the calculations of (1999AO01, 1999FI10).

Nucleon-α potentials have been derived from phase shifts by (1991CO05) and constructed from experimental data by the Marchenko inversion method as discussed in (1993HO09). The scattering amplitude in the vicinity of the ⁵He (3/2⁺) resonance is expressed in terms of the scattering length and the d-t effective range by (1994MU07). A study of the two-pole structure of the 3/2⁺ resonance is discussed in (1993CS02). See also the discussion of Pauli blocking in this reaction (1990AM07) and an application of an algebraic cluster approach to n-α scattering (1989US02).

9. ⁴He(p, π⁺)⁵He Q_m = -141.150

As reported in (1988AJ01), differential cross sections were measured at E_p = 201 MeV (1985LE19) and at E_p = 800 MeV (1984HO01; also A_y). See also (1987SO1C) and (1985GE06).

More recently differential cross sections and analyzing powers were measured at incident proton energies between 240 and 507 MeV, spanning the region of the Δ₁₂₃₂ resonance (1994FU06). These results were compared with the prediction of a microscopic (p, π⁺) model and with a phenomenological model. See (1994FA10).

10. (a) ⁴He(d, p)⁵He Q_m = -3.022
(b) ⁴He(d, pn)⁴He Q_m = -2.2246

A typical proton spectrum (reaction (a)) consists of a peak corresponding to the formation of the ground state of ⁵He, plus a continuum of protons ascribed to reaction (b). A study of the latter reaction shows evidence for sequential decay via ⁵He*(0, 16.7 ± 0.1 [Γ = 80 ± 30 keV]) and suggests some fine structure near E_x = 19 MeV [see also reactions 15 and 23]: see (1979AJ01). Differential cross sections and VAP have been measured for the ground state group at E_d = 5.4, 6.0, and 6.8 MeV (1985LU08) and at 6 to 11 MeV (1985OS02). Measurements of differential cross sections, analyzing powers, and polarization transfer coefficients at E_d = 56 MeV were reported in (1990YOZZ). At E_α = 28.3 MeV tensor polarization measurements involving the ground state transitions to ⁵He (and ⁵Li) deviate from theoretical predictions which assume charge symmetry (1985WI15). See also ⁶Li (1988PUZZ; E_d = 2.1 GeV) and other references cited in (1988AJ01).

Cross sections and transverse tensor analyzing powers for reaction (b) at E_d = 7 MeV were measured with kinematic conditions chosen to correspond to singlet deuteron production (1988GA14).

Theoretical studies relevant to reaction (b) include: a study of effects of the proton Coulomb field on α, n resonance peaks (1988KA38); comparisons of measured cross sections and polarization observables at E_d = 12, 17 MeV with a three-body model (1988SU12); a study of the influence of three-particle Coulomb dynamics on the cross section (1991AS02); a study of the effects of the internal structure of the α particle on the reaction (1990KU27); and a multiconfiguration resonating group study of the six-nucleon system (1991FU01, 1995FU16).

11. ⁴He(⁴He, ³He)⁵He Q_m = -21.375

Differential cross sections for this reaction to ⁵He_g.s. were measured at E(⁴He) = 118 MeV, and compared with DWBA predictions (1994WA06). Measurements of angular distributions at E_α = 158 and 200 MeV were reported by (1996ST25).

12. ⁴He(⁷Li, ⁶Li)⁵He Q_m = -8.048

A study of this reaction and of the ⁴He(⁷Li, ⁶He)⁵Li reaction at E(⁷Li) = 50 MeV, and of the ⁶Li(¹²C, ¹³N)⁵He and ⁶Li(¹³C, ¹⁴C)⁵Li reactions at E(C) = 90 MeV was reported by (1988WO10). Properties of the two lowest states of ⁵He and ⁵Li, from R-matrix parameters (a = 5.5 fm) are displayed in 5.2 (in PDF or PS) of (1988AJ01). As noted there, positive parity states are then predicted to lie at E_x ≈ 5 MeV (1/2⁺) and 12 MeV (3/2⁺, 5/2⁺) in ⁵He - ⁵Li (1988WO10). See also the analysis in (1988BA75).

13. (a) ⁶Li(γ, p)⁵He Q_m = -4.497
(b) ⁶Li(e, ep)⁵He Q_m = -4.497
(c) ⁶Li(π⁺, π⁺p)⁵He Q_m = -4.497
(d) ⁶Li(π^-, π^-p)⁵He Q_m = -4.497

At E_γ = 60 MeV, the proton spectrum shows two prominent peaks. In early work cited in (1979AJ01) these peaks are attributed to ⁵He*(0 + 4.0, 20 ± 2): see (1979AJ01). The (γ, p₀₊₁) cross section has been reported for E_γ = 34.5 to 98.8 MeV. A broad secondary structure is also observed (1988CA11). A review of photodisintegration data for energies up to E_γ = 50 MeV was presented in (1990VA16). More recently, measurements were made at E_γ = 60 MeV (1994RY01), at E_γ = 61, 77 MeV (1994NI04), and at E_γ = 59 - 75 MeV (1995DI01). In reaction (b) the missing energy spectrum shows strong peaks due to ⁵He*(0, 16.7) and possibly some strength in the region E_x = 5 - 15 MeV (1986LAZH). See also ⁶Li, and see the recent triple cross section measurements of (1999HO02). Reviews of (e, e'p) data are presented in (1990DE16, 1991VA05). See also (1989LA13, 1990DE06, 1990LA06). A microscopic cluster model used to interpret these experiments is discussed in (1990LO14). For reaction (c) at E_π⁺ = 130 and 150 MeV, ⁵He*(0, 16.7) are populated (1987HU02). Measurements at E_π⁺ = 500 MeV were made by (1998PA31) to search for Δ components. Reaction (d) was studied at GeV energies by (2000AB25) to deduce Fermi momentum distributions.

14. ⁶Li(n, d)⁵He Q_m = -2.272

Angular distributions of d₀ have been studied at E_n = 6.6 to 56.3 MeV. At E_n = 56.3 MeV angular distributions have also been obtained to ⁵He*(16.7) and, possibly, to two higher states: see (1979AJ01, 1984AJ01). Measured cross sections and analysis for E_n = 14.1 MeV are presented in (1989SHZS). See also (1986BOZG). A Multiconfiguration Resonating-Group Method calculation applied to this reaction is discussed in (1995FU16).

15. ⁶Li(p, 2p)⁵He Q_m = -4.497

At E_p = 100 MeV the population of ⁵He*(0, 16.7) and possibly of a broad structure at E_x ≈ 19 MeV is observed: momentum distributions for ⁵He*(0, 16.7) and angular correlation measurements are also reported. Measurements were reported at E_p = 47 and 70 MeV (1983VD03), 70 MeV (1983GO06), 392 MeV (1996KAZZ, 1997HA15, 1998NO04), and 1 GeV (1985BE30, 1985DO16, 2000MI17). See also (1984AJ01). Experimental and theoretical studies for E_p = 30 - 150 MeV were reviewed in (1987VD1A). See also (1987VD01). The influence of noncoplanarity on information obtained from these reactions was studied by (1990GO34).

16. ⁶Li(d, ³He)⁵He Q_m = 0.997

⁵He_g.s. has been observed at E_d = 14.5 MeV: see (1979AJ01).

17. ⁶Li(α, αp)⁵He Q_m = -4.497

At E_α = 140 MeV ⁵He*(0, 20.0) are populated: see (1984AJ01).

18. ⁶Li(⁶Li, ⁷Be)⁵He Q_m = 1.109

Angular distributions have been obtained at E(⁶Li) = 156 MeV to ⁵He_g.s.. Unresolved states at E_x = 16 - 20 MeV are also populated (1987MI34).

19. ⁶Li(¹²C, ¹³N)⁵He Q_m = -2.553

See reaction 12 and (1988WO10).

20. ⁷Li(γ, d)⁵He Q_m = -9.522

Cross sections and excitation functions were calculated by (1988DU04). Also see ⁷Li.

21. (a) ⁷Li(π⁺, 2p)⁵He Q_m = 128.606
(b) ⁷Li(π^-, 2n)⁵He Q_m = 127.041

Reaction (a) at E_π⁺ = 59.4 MeV involves ⁵He*(0, 4.) and a broad peak centered at E_x ≈ 21 MeV with Γ ≈ 4 MeV. It is not clear whether ⁵He*(16.7) is populated (1986RI01). See also (1979AJ01, 1984AJ01).

DWIA calculations of cross sections and analyzing powers for population of ⁵He_g.s.(3/2^-) are described in (1992KH04).

22. ⁷Li(n, t)⁵He Q_m = -3.265

The angular distribution of t₀ has been measured at E_n = 14.4 MeV: see (1979AJ01) and ⁸Li in (1988AJ01). See also (1986BOZG, 1989SHZS).

23. (a) ⁷Li(p, ³He)⁵He Q_m = -4.029
(b) ⁷Li(p, pd)⁵He Q_m = -9.522

At E_p = 43.7 MeV, angular distributions of the ³He groups to the ground state of ⁵He (Γ = 0.80 ± 0.04 MeV; L = 0 + 2) and to levels at 16.7 MeV (L = 1) and 19.9 ± 0.4 MeV (Γ = 2.7 MeV) have been studied. Since no transitions are observed in the ⁷Li(p, t)⁵Li reaction to the analog 20 MeV state in ⁵Li [see ⁵Li], the transition is presumably S-forbidden and the states in ⁵He - ⁵Li near 20 MeV are ⁴D_3/2 or ⁴D_5/2 [compare ³H(d, d)]. Particle-particle coincidence data have been obtained at E_p = 43.7 MeV. They suggest the existence of ⁵He*(20.0) with Γ = 3.0 ± 0.6 MeV and of a broad state at ≈ 25 MeV. No T = 3/2 states decaying via T = 1 states in ⁴He were observed: see (1979AJ01). Measurements of angular distributions at E_p = 29.1 - 44.6 MeV are reported in (1989BA88). In reaction (b) ⁵He*(0 + 4, 16.7, 25) appear to be involved at E_p = 670 MeV (1981ER10) while at 200 MeV some structure at E_x ≈ 20 MeV is reported in addition to the ground state (1986WA11).

24. (a) ⁷Li(d, α)⁵He Q_m = 14.325
(b) ⁷Li(d, n)⁴He⁴He Q_m = 15.1223

At E_d = 24 MeV, the α-particle spectrum from reaction (a) shows structures corresponding to the ground and 16.7 MeV states and to states at E_x ≈ 20.2 and 23.8 MeV with Γ ≈ 2 MeV and ≈ 1 MeV, respectively. Measurements of the α-particle energy spectra at E_d = 13.6 MeV were reported in (1993PAZP). An analysis of cross section data measured at E_d = 0 - 12 MeV is reported in (1997HAZX). Astrophysical S factors were measured at E_cm = 57 - 141 keV by (1997YA08). Measurements of the reaction rate at low energies for ⁷Li implanted in Pd foil were reported by (2000BAZO). Reaction (b) proceeds mainly via excited states of ⁸Be and ⁵He_g.s. and possibly as well ⁵He*(4.): see (1979AJ01). Measurements at E_d = 4.35 MeV have been reported by (2000MIZU). See also (1987WA21) and ⁸Be in (1988AJ01).

Measurements of σ(θ) at E_d = 6.8 MeV were reported in (1989AR04). Parameters of the resonance for the ⁵He state at E_x = 16.76 MeV were extracted. Analysis (1991AR10, 1993FA12) of coincidence measurements at E_d = 1.4, 2.1 and 2.5 MeV gave E_x = 4.1 ± 0.2 MeV, Γ = 2.9 ± 0.4 MeV for the ⁵He p_1/2 first excited state.

25. (a) ⁷Li(³He, pα)⁵He Q_m = 8.831
(b) ⁷Li(³He, ³He d)⁵He Q_m = -9.522

A kinematically complete experiment is reported at E(³He) = 120 MeV. The cross section for reaction (b) is an order of magnitude greater than that for reaction (a). The missing mass spectrum for the composite of both reactions suggests the population of several states of ⁵He, in addition to ⁵He*(0, 16.7, 20.0), including a state at 35.7 ± 0.4 MeV with a width of ≈ 2 MeV (1985FR01).

26. ⁸Li(p, α)⁵He Q_m = 14.516

Differential cross sections were measured at E_cm = 1.5 MeV with a ⁸Li beam, and the data were used to calculate thermonuclear reaction rates for ⁸Li destruction (1992BEZZ, 1992BE46).

27. (a) ⁹Be(p, pα)⁵He Q_m = -2.371
(b) ⁹Be(p, d³He)⁵He Q_m = -20.724

Both reactions have been studied at E_p = 26.0 to 101.5 MeV [see (1984AJ01)]. Reaction (a) was studied at E_p = 150.5 MeV (1985WA13) and at E_p = 200 MeV (1989NA10), who analyzed the data in terms of DWIA. Absolute spectroscopic factors were derived. See also (1985VD03). More recently, cross sections and polarization observables were measured at E_p = 296 MeV by (1996YOZZ, 1997YOZQ, 1998YO09). Alpha spectroscopic factors were deduced.

28. ⁹Be(d, ⁶Li)⁵He Q_m = -0.897

The angular distribution to ⁵He_g.s. has been measured at E_d = 13.6 MeV (1984SH1F). See also (1989VAZJ).

29. (a) ⁹Be(³He, ⁷Be)⁵He Q_m = -0.785
(b) ⁹Be(³He, α)⁴He⁴He Q_m = 19.0041

See (1984AJ01) and (1990MAYW). A coupled-channel model analysis of data at E_³He = 60 MeV is described in (1996RU13). For reaction (b) see ⁸Be in (1988AJ01) and (1987WA25).

30. ⁹Be(α, 2α)⁵He Q_m = -2.371

Measurements at E_α = 197 MeV of energy-sharing distributions were reported by (1994CO16). Spectroscopic factors were extracted. See (1984AJ01) for earlier work. Cross section measurements at E_α = 580 MeV with DWIA calculations are described in (1999NA05).

31. ⁹Be(⁷Li, ⁷Liα)⁵He Q_m = -2.371

This reaction was studied at E_⁷Li = 52 MeV (1998SO05, 1998SO26), and decay from ⁹Be excited state into the α + ⁵He channel was observed.

32. ⁹Be(¹⁸O, ²²Ne)⁵He Q_m = 7.296

Cross sections were measured and the mass excess was extracted by (1990BEYY).

33. ¹⁰B(n, ⁵He)⁶Li Q_m = -5.258

See ⁶Li.

34. ¹⁰B(d, ⁷Be)⁵He Q_m = -1.877

An angular distribution has been measured at E_d = 13.6 MeV involving ⁵He_g.s. and ⁷Be*(0.43) (1983DO10).

35. (a) ¹¹B(⁷Li, ¹³C)⁵He Q_m = 9.157
(b) ¹¹B(⁹Be, ¹⁵N)⁵He Q_m = 8.620

At E(¹¹B) = 88 MeV a broad structure is observed at E_x = 5.2 ± 0.3 MeV, Γ = 2.0 ± 0.5 MeV (1988BE34). For reaction (b) see (1990BEYX).

36. ¹²C(⁶He, ⁵He n)¹²C Q_m = -1.771

Peripheral fragmentation of 240 MeV/A ⁶He was studied by (1997CH24, 1997CH1P). It was found that one-neutron stripping to ⁵He is the dominant mechanism.