(See Energy Level Diagrams for 5Li)
The excitation curve measured from Ed = 0.2 to 2.85 MeV shows a broad maximum at Ed = 0.45 ± 0.04 MeV (Eγ = 16.6 ± 0.2 MeV, σ = 50 ± 10 μb, Γγ = 11 ± 2 eV). Above this maximum, non-resonant capture is indicated by a slow rise of the cross section. The radiation appears to be isotropic to ± 10% at Ed = 0.58 MeV, consistent with s-wave capture (1954BL89). See also (1961TO1E).
(1964IM03) have searched for high-energy beta rays from 4Li in this reaction. With Ed = 0.5 to 2.3 MeV, upper limits of σ = 3 to 8 × 10-3 μb are obtained. Other searches for 4Li have been made by (1959AR61, 1959BA27, 1962TO12, 1964CL03). See also (1963KA28, 1964BE1L, 1964KI06, 1964KO1E, 1965DA1G). The astrophysical interest in 4Li is discussed by (1958FO1C, 1964BA1X, 1964BA2A, 1964PA1A).
Cross sections and angular distributions for reaction (a) from Ed = 35 keV to 10 MeV are given in (1957JA37). Below 100 keV the cross section follows the simple Gamow form: σ = (18.2 × 103/E)exp(-91E-1/2) b (E in keV) (1953JA1A, 1954AR02). The zero-energy cross section factor S0 = 6700 keV · b (1964PA1A). A pronounced resonance occurs at Ed = 430 keV of about 450 keV width. The peak cross section is given as 0.695 ± 0.014 b by (1952BO68, 1955KU03: see also (1953YA02, 1954FR01)). The resonance is closely fitted with the one-level dispersion formula using the parameters listed in Table 5.3 (in PDF or PS). See also (1963MA1N, 1964HU1C, 1964JE1B).
The angular distribution of protons is isotropic near resonance and shows froward peaking at higher energies. Differential cross sections have been measured at Ed = 5.9, 7.5, 10.4, 12.3 and 13.7 MeV (1960ST25), and Ed = 23.2 to 27.0 MeV (1964BI06). The similarity to 3H(d, n)4He is very close, and the angular distributions show pronounced direct interaction effects (1963BI08, 1964BI06). See also (1960BR1E).
The polarization of the protons has been studied as a function of Ed and θ for the range Ed = 3.0 to 12.0 MeV by (1963BR10), at Ed = 0.77 and 1.88 MeV by (1963VA1H), at Ed = 1.5, 2.1 and 2.6 MeV by (1964FA01), at Ed = 2 MeV by (1964VA1G), and at Ed = 8.3 MeV by (1965RO02). (1963BR10) report polarizations as high as 0.76, in good agreement with the mirror reaction. See also (1959GO1G, 1964MC1E, 1964SE1F, 1965BA15, 1965TA1J).
Proton groups have been reported corresponding to 4He excited states at Ex = 19.94 ± 0.02 MeV (Γ = 140 ± 25 keV) and 21.24 ± 0.2 MeV (Γ = 1.1 ± 0.2 MeV) (1965PA01: E(3He) = 31.8 MeV). At Ed = 6 to 10 MeV (1964YO03) report a forward-peaked group corresponding to Ex = 20.08 ± 0.05 MeV with Γ = 0.2 ± 0.05 MeV. See also (1960ST25, 1963YN02, 1965DO1H, 1965ME1D).
The triton spectrum (reaction (c)) has been studied at Ed = 11 MeV (1965TO01), 12 to 14 MeV (1965HE1A, 1965JA1D), 20 and 25 MeV (1964AR08) and 24 to 33 MeV (1963BI14, 1964CO1A). At small forward angles, a pronounced peak is observed at the high-energy end of the continuum, indicating a strong p - p final state interaction. See also (1964DO1F).
Differential cross sections for Ed = 0.4 to 3 MeV are plotted in (1957JA37), and for Ed = 5.6, 5.9, 8.3, 12.3 and 14.4 MeV are tabulated in (1960BR10). Measurements are also reported for Ed = 2 to 11 MeV (1965TO1E), 23.2 to 27.0 MeV (1964BI06) and 29 MeV (1962GA22). See also (1952AL36, 1959MC65, 1960BR19, 1960MC1E, 1963BI08).
In the range Ed = 380 to 570 keV (θc.m. = 65°) the scattering cross section is considerably below Rutherford scattering and is consistent with s-wave formation of a J = 3/2+ state. Above Ed = 2 MeV, the distributions are very similar to those reported in 3H(d, d)3H (1954BR05, 1960BR10). The angular distributions obtained by (1960BR10) are not symmetric around 90°. Two minima are observed around 90°: the central maximum shifts towards larger angles with increasing energy. (1965TO1E) report a broad state of 5Li with Ex = 20.0 ± 0.5 MeV, formed by d-wave deuterons (Jπ = 3/2+ or 5/2+). See also (1960BA1M, 1965GR1Q).
The ground-state group is observed in addition to continuum neutrons at E(3He) = 3.2 MeV: σ = 21 ± 4 mb, Q0 = 10.3 ± 0.2 MeV. The angular distributions indicate some direct interaction. This reaction appears to be an order of magnitude more intense than the mirror reaction 3H(3He, p)5He (1961BA40: but see (1963SM03)).
The spectrum of protons has been measured at E(3He) = 0.36 MeV (1954GO18), 4.9 MeV (1965AL1L), 3 to 18 MeV (1965BA1D, 1965BA1E). A pronounced peak corresponding to the formation of 5Lig.s. is observed, superposed on a continuum; analysis with final state interaction characterized by γ2 = 7 MeV, Eλ = 4.16 MeV yields a good fit to the data (1965BA1D). See also (1963BA53, 1964TO1D). At small forward angles the α-spectrum has a pronounced peak, indicating a strong p - p interaction (1964AR08, 1965TO01).
References for the principal measurements of cross sections and polarizations are listed in Table 5.5 (in PDF or PS), together with a selection of papers dealing with derived phase shifts and polarization. Measured cross sections, phase shifts and polarizations up to Ep = 11 MeV are tabulated by (1964BA08). In this range l = 0 and l = 1 phase shifts are well determined, l = 2 less well.
Semi-empirical phase shifts including l ≤ 2 and l ≤ 3 for Ep = 10 to 40 MeV have been calculated by (1958GA13). Although these phase shifts give a reasonably good account of observed differential cross sections (1957BR28, 1959BU98, 1959SA14), the observed polarization shows striking deviations beginning at Ep ≈ 29 MeV (1963CR09, 1963HW01, 1963WE11). At 40 MeV (1963SU03) find that complex phase shifts with l ≤ 3 provide a satisfactory fit; (1963GI1G) use real phase shifts with l ≤ 4.
In the region 0 to 11 MeV, the s-wave phase shift is satisfactorily accounted for by hard-sphere scattering with radius R = 2.5 fm. The course of the p-wave phase shifts is given by the Breit-Wigner dispersion formula with the following parameters, calculated with a radius R = 3.0 fm (1964BA08: see also (1952AD09, 1952DO30)):
No evidence is found for other resonance levels below Ex = 16.6 MeV (1959HI70, 1959SA14, 1964BA08). An anomaly at Ep = 23 MeV corresponding to 5Li*(16.6) is reported by (1963WE11). Model calculations of phase shifts are discussed by (1958GA13, 1958HO1B, 1959KE1A, 1959PI42, 1960BU1F, 1960HE15, 1962LA1E, 1962RO1F, 1964GI1E). See also (1959KE1A, 1960MC1D, 1960SI1C, 1963KA1G, 1964CR1B, 1964HO1F, 1965GI1E, 1965GR1U) and (1959AJ76).
Inelastic (p, p') spectra at 185 MeV give evidence of a peak near Q = -22.5 MeV (1958SE74, 1959HI70, 1962SA1E). At Ep = 55 MeV, (1964HA13, 1964HA1P, 1964HA49) report an inelastic group corresponding to 4He* = 22.4 ± 0.7 MeV, Γ = 1.7 ± 0.5 MeV. At Ep = 40 MeV two groups are reported corresponding to 4He* = 20.48 MeV, Γ ≈ 0.3 MeV, and 21.95 MeV, Γ ≈ several MeV (1965WI10).
Angular distributions for reaction (a) are reported at Ep = 27.9 MeV (1957WI22), 31 MeV (1953BE14, 1964BU16), 53 MeV (1964CA1B), 55 MeV (1964HA13, 1964HA1P, 1964HA49) and 94 MeV (1958SE74). The distributions are characterized by a strong forward peak and a secondary maximum. Analysis in terms of the momentum distribution of the picked-up neutron is discussed by (1958SE74). The 31 MeV data have been analyzed by DWBA: a quite satisfactory agreement in shape is obtained with large deuteron absorption. The observed distribution agrees well with that derived from the inverse reaction (1964BU16). See also (1956EI05) and (1963WE11). For reaction (b), see (1957WI22) and (1956EI05). For reaction (c), see (1956EI05, 1957WI22, 1958SE74, 1965RI1A, 1965TY1A).
Neutron spectra are reported for Ed = 7.9, 8.9 and 9.9 MeV (1962LE12), 13 MeV (1956BO1F, 1956BO43), and 18.6 MeV (1961RY01) and for Eα = 34.6 MeV (1961RY01). The spectra show two peaks superimposed on a continuous distribution, one at high energy, ascribed to formation of 5Lig.s. and one at low energy, corresponding to 5Heg.s.. The observed spectra are well fitted with resonance final state interaction of 4He + n, 4He + p, characterized by Eres = 1.0 and 2.1 MeV, respectively, γ2 = 12 MeV · fm, R = 2.6 fm. A broad distribution underlying the peaks is ascribed to direct breakup (1961RY01). See also 5He: 4He(d, p)5He and (1965NA1D, 1965NA1E).
At Ed = 1 MeV a broad ground state triton group is observed (Γc.m. = 2.0 MeV) (1958FR52). Angular distributions have been measured at Ed = 15 MeV (1959HA29, 1960HA14) and 20 MeV (1959VL24). They are characteristic of l = 1; θ2 = 0.24 (1959VL24), θ2 = 0.15 (1960HA14). The spectrum shape is analyzed in terms of p - α scattering parameters by (1960HA14). See also (1959KU1C) and 8Be.