(See Energy Level Diagrams for 5Li)
Reactions involving antiprotons:(1981YA1B).
Excitation curves and angular distributions have been measured for Ed = 0.2 to 5 MeV and E(3He) = 2 to 26 MeV. A broad maximum in the cross section is observed at Ed = 0.45 ± 0.04 MeV [5Li*(16.66)]. σγ0 = 21 ± 4 μb, Γγ0 = 5 ± 1 eV. The radiation at resonance is isotropic, consistent with s-wave capture. Study of γ0 and γ1 yield Γ = 2.6 ± 0.4 MeV for the ground-state width, and Ex = 7.5 ± 1.0 MeV, Γ = 6.6 ± 1.2 MeV for the 1/2- state: see (1974AJ01).
An excess in the cross section at higher bombarding energies is interpreted as being due to a state at Ex ≈ 18 MeV: even parity is deduced from the relative intensity of γ0 and γ1. It is presumed to be the 1/2+ state reported in reactions 2 and 6. A broad peak is also observed at Ex ≈ 20.7 MeV in the γ0 cross section. The cross section for γ1 is ≈ 0. The observations are consistent with Jπ = 5/2+: angular distributions appear to require at least one other state with significant strength near 19 MeV: see (1974AJ01).
Below 100 keV the cross section follows the simple Gamow form: σ = (18.2 × 103/E) exp (-91E-1/2) b (E in keV). The zero-energy cross-section factor S0 = 6700 kev · b. [However (1981JA1F) suggest that the cross section below 100 keV may be in error by as much as 50%.] A pronounced resonance occurs at Ed = 430 keV, Γ ≈ 450 keV. The peak cross section is 695 ± 14 mb: see Table 5.2 (in PDF or PS). Excitation functions for ground-state protons have also been reported for E(3He) = 0.39 to 1.46 MeV and 18.7 to 44.1 MeV, for Ed = 2.8 to 17.8 MeV [see (1974AJ01)], and at E(3He) = 0.20 to 2.15 MeV (1980MO03). Angular distributions have been measured for Ed = 0.25 to 27 MeV and E(3He) = 18.7 to 44.1 MeV [see Table 5.6 (in PDF or PS) in (1974AJ01, and (1979AJ01]. Resonance-like behavior is suggested at Ex = 16.6, 17.5, 20.0, 20.9 and 22.4 MeV: see (1979AJ01).
Tensor analyzing power measurements are reported for Epol. d = 0.48 to 6.64 MeV (1980DR01). [See, however, (1980GR14) for a discussion of the (1980DR01) results and for a summary of T20(0°) for Epol. d = 0 to 40 MeV]. (1981RO13) report measurements of angular distributions, of σt and of the VAP for Epol. d = 14.6 to 39.9 MeV: the results are consistent with the presence of an f-wave 7/2- state and suggest the importance of d-wave amplitudes. Measurements of angular distributions and analyzing powers at E(pol. 3He) = 27 and 33 MeV suggest the presence of a broad resonance(s) at Ex ≈ 28 MeV (1979OK03). For other recent polarization studies see (1980ST1A) and (1979BUZO, 1981CL1B, 1981DE1G, 1981DE2E, 1981WOZX, 1982COZO; all preliminary). The earlier polarization work is summarized in Tables 5.6 (in PDF or PS) (1974AJ01) and 5.4 (in PDF or PS) (1979AJ01).
Reactions (b), (c) and (d) have been studied at Ed = 22.3 and 35 MeV and at E(3He) = 30, 33.5 and 52.5 MeV and analyzed with a PWIA: Fourier transforms of the wave functions were obtained. At E(3He) = 35.9 MeV, the spectra in reactions (b) and (c) are dominated by the nucleon-nucleon FSI: the results were fitted with a fully antisymmetrized PWBA and with DWBA. Polarization measurements for reactions (b) and (c) are reported at Epol. d = 15 MeV (1976ME13) and at E(pol. 3He) = 33 MeV (1980OK04). (1976SC26) have studied the excitation function for reaction (c) for Ed = 2.2 to 6 MeV in a kinematically complete experiment. They have extracted the p + t FST going via 4He*(20.1) [Jπ = 0+] and suggest that the reaction goes primarily via a Jπ = 3/2-, T = 1/2 state of 5Li located 0.8 ± 0.2 MeV above threshold [i.e. Ex = 18.9 ± 0.2 MeV]. This suggests that the attraction of a p3/2 nucleon to 4He*(0+) is stronger than is the attraction of such a nucleon to 4Heg.s. (1976SC26). (1981FU11) have studied the deuteron breakup (reactions (b), (c), (d)) at E(3He) = 89.4 and 118.9 MeV.
In the range Ed = 380 to 570 keV, the scattering cross section is consistent with s-wave formation of the Jπ = 3/2+ state at 16.66 MeV. The excitation curves for Ed = 1.96 to 10.99 MeV show a broad resonance (Γ > 1 MeV) corresponding to Ex = 20.0 ± 0.5 MeV. From the behavior of the angular distributions an assignment of 2D3/2 or (2D, 4D)5/2 is favored, if only one state is involved: see (1979AJ01). A phase-shift analysis by (1980JE01) of the angular distribution and VAP data below 5 MeV suggests several MeV broad states [2P3/2, 4D7/2, 4D5/2, 4D3/2 and, possibly, 4D1/2].
Angular distributions and analyzing powers have been measured at many energies to E = 44 MeV: see (1979AJ01) for the earlier work, (1979JE02: Epol. d = 1.5 to 11.5 MeV; σ(θ) and VAP, T20(θ), T21(θ), T22(θ)) and (1981RO13: Epol. d = 14.6 to 40 MeV; σ(θ), σt and VAP). See also (1983BR1E) and (1978TA1A, 1979SE04, 1980ZE1D, 1981SA1N; theor.).
The spectrum of protons shows a pronounced peak at E(3He) = 3 to 18 MeV corresponding to 5Lig.s. superposed on a continuum: see (1974AJ01). Searches for three-proton enhancement (reaction (c)) have been unsuccessful: see (1974AJ01). See also (1979AJ01) and 6Be.
Differential cross sections and polarization measurements have been carried out at many energies: see Tables 5.5 (in PDF or PS) in (1966LA04), 5.7 (in PDF or PS) in (1974AJ01) and 5.5 (in PDF or PS) in (1979AJ01). Recent studies include those of (1978HO17; Ep = 21.85 to 47.65 MeV), (1983RI01; Epol. p = 28.8, 29.77 and 30.40 MeV), (1979IM01; Epol. p = 45.0, 52.3, 59.6 and 64.9 MeV), (1980MO09; Epol. p = 200, 350 and 500 MeV), (1979GR08; Epol. p = 222, 325 and 518 MeV; analyzing powers at θlab = 15°), (1982VE03; Ep = 992 MeV) and (1979CO01; Epol. p = 0.56, 0.80, 1.03, 1.24, 1.73 GeV). See also (1981KH1C, 1981RO1J). For work at GeV energies (to Ec.m. = 88 GeV) see (1978BR1V, 1978DU15, 1978NA13, 1979VA1L, 1980AB1C, 1982BE1X, 1982FA1B).
Phase shifts below Ep = 18 MeV have been determined by (1977DO01) based on all the available cross-section and polarization measurements, using an R-matrix analysis program. The P3/2 phase shift shows a pronounced resonance corresponding to 5Lig.s. while P1/2 shift changes slowly over a range of several MeV, suggesting that the first excited state is very broad and located 5 - 10 MeV above the ground state. The reduced widths of the P-wave resonance states are nearly the same. The D5/2, D3/2, F7/2 and F5/2 phase shifts become greater than 1° at Ep ≈ 11, 13, 14 and 16 MeV, respectively (1977DO01).
A phase-shift analysis for Ep = 21.8 to 55 MeV is presented by (1978HO17) [see also for analyzing power contour diagram for Ep = 20 to 65 MeV]. A striking anomaly is seen in the analyzing power at Ep = 23 MeV and the 2D3/2 phase shift clearly shows the 3/2+ state at Ex = 16.7 MeV [see also (1979AJ01)]. The other phase shifts 2S1/2, 2P3/2, 2P1/2, 2D5/2, 2F7/2, 2F5/2, 2G9/2 and 2G7/2 are smooth functions of energy. Both the 2P3/2 and 2P1/2 inelastic parameters show a somewhat anomalous behavior at Ep ≈ 30 MeV: the absorption first increases then decreases to stay rather constant at Ep > 40 MeV. These results are consistent with broad and overlapping states with Jπ = 1/2- and 3/2- at Ex ≈ 22 MeV. There is very little splitting of the real parts of the F-wave phase shifts up to 40 MeV. There is some indication (from the 2G7/2 phase shifts) of a 7/2+ level around Ep = 29 MeV [Ex ≈ 21 MeV]. The G-waves are necessary to fit the detailed shape of the angular distributions for Ep = 20 to 55 MeV (1978HO17). For a contour diagram of the analyzing power for Ep = 130 to 1800 MeV see (1980MO09). For the earlier work see (1979AJ01). See also (1982FR11; theor.).
(1982HE1C) have studied parity non-conservation (PNC) by comparing the cross sections σ+ and σ- (positive and negative helicities) for longitudinally polarized 46 MeV protons. The longitudinal polarizing power Az = (0.3 ± 1.3) × 10-7 [see (1982HE1C) for a discussion of the weak pion-nucleon coupling constant].
A search for γ-ray transitions within the broad ground state of 5Li has been unsuccessful (1983SC10; Ep = 1.5 to 7.0 MeV). For a measurement of the spin rotation parameter R at Ep = 500 MeV see (1983MO01). For total cross-section measurements see (1979SC07; 224 → 563 MeV), (1981KH1C; 992 MeV) and (1978JA16; 0.87 and 2.1 GeV/nucleon). See also (1980FA08; inelastic interactions at Eα = 1.74 and 2.57 GeV).
See also (1977BO40, 1982BE1T), (1982GO1A), (1978AL1G, 1978BR1A, 1980CA1A, 1980LE19, 1981IG1A, 1982FA1F, 1982IG2A, 1983YO01) and (1978AH03, 1978AU11, 1978GR1G, 1978GR1H, 1978HA2F, 1978HE2A, 1978LE2E, 1978MA2M, 1979AL12, 1979AR02, 1979AR06, 1979DY07, 1979GH01, 1979KA17, 1979KOZV, 1979LE1T, 1979LU1A, 1979SA09, 1979SA35, 1979SH1V, 1979WI1B, 1980AR08, 1980AU09, 1980DM1A, 1980DY1A, 1980FU1G, 1980GO1K, 1980LA20, 1980PE1K, 1980RO1L, 1980VI01, 1980WA06, 1981AU07, 1981FE02, 1981FR20, 1981GU1F, 1981KH07, 1981LY1B, 1981NI1E, 1981RO1G, 1981SH04, 1981TE01, 1981VA1L, 1981ZH03, 1982AV02, 1982AZ01, 1982FR14, 1982PA25, 1982PR1E, 1982PR1F, 1982PR1G, 1982WA1H, 1983SA1H, 1983SH12, 1983VI1D; theor.).
Angular distributions of 3He ions (reaction (a)) have been measured for Ep = 27.9 to 770 MeV and at Eα = 3.98 GeV/c [see (1979AJ01)] and at Ep = 200 and 400 MeV (1981LI1B). Excitation functions are reported at Ep = 38.5 to 44.6 MeV [see (1979AJ01)] and 200 to 500 MeV (1978KA2A). For polarization measurements to 500 MeV see (1979AJ01) and (1981LI1B, 1982SA05, 1983RI01). At Epol. p = 50 MeV the analyzing power angular distributions for this reaction and for 4He(pol. n, d) are the same, which is expected from charge symmetry (1982SA05; also measurements at Epol. p = 32, 40 and 52.5 MeV). See also (1982KA21). For reaction (b) see (1974AJ01).
Reaction (c) has been studied at Ep = 250, 350 and 500 MeV: energy-sharing spectra, coplanar symmetric angular distributions and quasi-free angular distributions have been obtained. The results are in good agreement with DWIA calculations dor q ≲ 150 MeV/c but a spin-orbit term has to be included in the optical potential used to generate the DW for larger recoil momenta (1982VA01, 1980EP01). For polarization measurements at Epol. p = 250 and 500 MeV see (1982MA19). See (1979AJ01) for the earlier work. For inclusive scattering at Ep = 500 MeV see (1981RO1J). For breakup processes see (1980WE1C, 1981AL1J). See also (1980MC1C, 1982DA1K), (1977GO1V; applications) and (1978BA1C, 1978BL1C, 1978TA1A, 1979KA19, 1979MI1K, 1979SH21, 1979TE07, 1980DM1A, 1981FE02, 1981TE01, 1982LE28; theor.).
Reaction (b) has been studied at Ed = 14.2 MeV and at Eα = 18.0 to 42 MeV [see (1979AJ01)] and at Epol. d = 12 and 17 MeV (1983SL01) and Eα = 28.3 MeV (1979AN24, 1981BE1G) and 140 MeV (1982LA14). 5Lig.s. is formed. Tensor moments are derived by (1979AN24, 1981BE1G). See also (1978NA12, 1980KO04; theor.) and reaction 5 in 6Li.
At Eα = 26.3 MeV, 5Lig.s. is reported to have a width of 1.9 ± 0.25 MeV, while the first excited state is reported at Ex = 2.82 ± 0.35 MeV, Γ = 1.64 ± 0.25 MeV (1982NE09) [reaction (b)]. See also (1979KU08; theor.) and (1979AJ01).
Differential cross sections have been measured at Eπ = 75 and 150 MeV for the transition to 5Lig.s. (1980KA11).
Angular distributions have been measured at Ep = 18.6 to 156 MeV [see (1974AJ01)] and at Ep = 185 MeV (1976FA03, 1974KA28). In the latter experiment the spectra are characterized by a broad, asymmetric peak corresponding to 5Lig.s., a narrow peak [5Li*(16.7)] and a broad peak at Ex ≈ 20 MeV. DWBA analysis leads to C2S = 0.64 and 0.57 for 5Li*(0, 16.7) (1976FA03). The first excited state of 5Li is reported to be populated by (1969BA05; Ep = 156 MeV).
Angular distributions of the t0 group have been measured at Ed = 15 and 20 MeV: see (1974AJ01). Reaction (b) has been studied at Ed = 0.47 MeV and 7.5 to 10.5 MeV [see (1979AJ01)] and at Ed = 117 to 772 keV (1979HO04; differential cross sections and energy spectra). See also 8Be.
At E(3He) = 25.5 MeV, the spectra show 5Li*(0, 16.7) and two broad peaks at Ex ≈ 19.8 and 22.7 MeV with Γc.m. = 2 and 1 MeV, respectively. At E(pol. 3He) = 33.3 MeV, angular distributions and analyzing powers have been studied for 5Li*(0, 16.7) [Γ ≈ 1.6 and ≈ 0.4 MeV] (1981BA38). In reaction (b) the Ex and Γ of the first excited state are reported to be 7.5 MeV and 5 ± 1 MeV, respectively (1982LA20). See also (1979AJ01), (1981DU1F; theor.) and 8Be.
At Eπ = 65 MeV, 5Li*(0, 16.7) are populated (1982DO01).
At Ep = 43.7 MeV, a triton group is observed to 5Li(0) (Γ = 1.55 ± 0.15 MeV): the angular distribution is consistent with a substantial mixing of L = 0 and 2 transfer. There is some evidence also for a very broad excited state between Ex = 2 and 5 MeV. 5Li*(16.7, 20.0) were not observed. The formation of 5Li*(16.7) (4S3/2) would be S-forbidden: the absence of 5Li*(20.0) would indicate that this state(s) is also of quartet character [see reaction 19 in 5He]. Weak, broad states at Ex = 22.0 ± 0.5 MeV and 25.0 ± 0.5 MeV and possibly 34 MeV are reported in a coincidence experiment in which three- and four-particle breakup was analyzed: see (1979AJ01). For reaction (b) at Ep = 670 MeV see (1979AL11). See also (1980CA13).
At Eα = 90 MeV differential cross sections have been measured for the tranisitions to 5Lg.s. + 8Lig.s. (1981DA03).
See (1982DO1E; Ed = 13.6 MeV).
See (1982DO1F; Eα = 27.2 MeV).