(See Energy Level Diagrams for 5Li)
Model calculations: (1975KR1A).
Applied topics: (1975HU1A).
Ground state of 5Li: (1975BE31).
Excitation curves and angular distributions have been measured for Ed = 0.2 to 5 MeV and E(3He) = 2 to 26 MeV: see (1974AJ01).
A broad maximum in the cross section is observed at Ed = 0.45 ± 0.04 MeV [5Li*(16.66)]: σ = 50 ± 10 μb, Γγ = 11 ± 2 eV (1954BU06: γ0 + γ1); σγ0 = 21 ± 4 μb, Γγ0 = 5 ± 1 eV (1968BU09). The radiation at resonance is isotropic, consistent with s-wave capture: see (1954BU06, 1968BU09, 1968KR03). 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. The ratio of γ0 to γ1 is 1.00 ± 0.2 and 1.9 ± 0.4 at Ed = 480 and 1025 keV (1968BU09).
An excess in the cross section at higher bombarding energies is interpreted by (1972KI01) 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 3 and 7. 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 (1972KI01). (1970SC18) also report this state but find Ex = 19.7 ± 0.2 MeV [Γ = 5.0 MeV]: (2J + 1)Γγ0 = 1.32 keV (± 50%), suggesting E1 (if only one state is involved).
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, Γ ≈ 450 keV. The peak cross section is given as 695 ± 14 mb (1952BO68, 1955KU03): 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 and for Ed = 2.8 to 17.8 MeV: see (1974AJ01). 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)]. At Ed = 10.02 MeV differential cross sections have been measured at four angles to better than 3% (1974JA15). Polarization measurements have been carried out at many energies: see Table 5.6 (in PDF or PS) in (1974AJ01) and Table 5.4 (in PDF or PS) here.
Below Ed = 1.1 MeV, the polarization analyzing power of the reaction is minimally affected by p-wave contributions (less than a few percent). However, at Ed = 500 keV, the analyzing power is reduced by (12 ± 5)% by intervention of the s-wave Jπ = 1/2+ channel (1966BR02, 1967MC01, 1971LE27). Contour maps, Tab versus θ, Ed, for the vector and tensor analyzing powers are presented for Ed = 0 to 12 MeV by (1971GR47). Energy dependence of the angular distributions indicate resonance-like bevavior at Ex = 16.6, 17.5, 20.0, 20.9 and 22.4 MeV in 5Li (1971GR47). At Ed ≈ 6 MeV (1971KL02) find the angular distribution more complex than could be accounted for by a single 2D3/2 or 2D5/2 level at Ex ≈ 20 MeV [see 3He(d, d)]. For Ed(c.m.) = 7 to 18 MeV, differential cross sections fall monotonically with no indication of states of 5Li with 23.4 < Ex < 34, with Γ > 0.8 MeV and with appreciable widths for decay into 3He + d (1971KL02).
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 by (1977SL04) 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 (1974WA06, 1975WA31). At Ed-bar = 15 MeV (1976ME13) have measured the vector and the two tensor analyzing powers for reactions (b) and (c). (1974SC04, 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 FSI 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). See also (1975RU04) for reaction (c). See (1974AJ01) for the earlier work.
See also (1974TA1A, 1975GL08, 1976GO1B), (1974LA1C, 1974PR1B, 1975HE1C, 1975HU1A; applied topics), (1975SE07, 1975SE1D, 1975SE1E, 1976SE03, 1976SE1B, 1976SE1C, 1977SE09, 1977SE1C, 1978FI1E, 1978SL1B; reviews) and (1974AL01, 1974CH02, 1974DO10, 1974KE1B, 1975DO1B, 1975NE11, 1975YA12, 1977CH1D, 1977CO1B, 1978KO13, 1978SE01; theor.).
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 (1954BR05). 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 (1967TO02). [There is some evidence that there is more than one D-wave state in this Ex region: see reaction 3]. See also (1976AL22: Ed = 1.01 to 2.95 MeV). In the range Ed(c.m.) = 7 to 18 MeV differential cross sections show only a monotonic variation with energy. There is no evidence for any other resonances from Ex = 23 to 34 MeV (1972BA30, 1972KI02). Angular distributions have been measured at a number of energies from E(3He) = 18.7 to 44.1 MeV (1972KI02) and at E(3He) = 10.00 MeV (1974JA15; dσ/dΩ to ± 1%) and Ed = 39 MeV (1975RU04).
Polarization measurements have been reported for Ed = 4.0 to 12 MeV [see (1974AJ01)] and polarization analyzing powers have been studied at Ed-bar = 2.0 to 11.5 MeV (1975JE1A; abstract), Ed-bar = 3.73 to 11.89 MeV (1974OH05; pol. 3He; also spin correlation parameters), Ed = 5.35 to 9.2 MeV (1974LO06; polarization transfer coefficients), Ed-bar = 15 to 40 MeV (1976RO1C, 1976ROZM; vector analyzing powers) and E(pol. 3He) = 33 MeV (1977KA10).
Angular distributions have been measured at E(3He) = 2.0 to 5.5 MeV for n0 (Γg.s. = 2.03 ± 0.15 MeV) and at 3.5 to 5.5 MeV (partial distributions) for n1 to an excited state at Ex = 10.21 ± 0.28 MeV, Γ = 1.49 ± 0.61 MeV (1975AB11). At E(3He) = 14 to 26 MeV, the spectra show the n0 group and a broad resonance with Ex = 20.5 ± 0.8 MeV (1974CH15). Reaction (b) has been studied at E(3He) = 0.31 to 2.80 to attempt to detect a possible resonant energy dependence of the spin-singlet (T = 1) n-p FSI: a marked effect is not present (1975SC28). See also (1977DEYM) and 6Li.
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). At E(3He) = 13.6 MeV differential cross sections and polarizations have been measured for the p0 group (1976IR02). A deuteron cluster transfer process may be involved (1976AS05). At E(3He) = 43.7 and 53.0 MeV, the spectra show a prominent peak at the high energy end whose angular distributions exhibit a pronounced diffraction pattern (1967SL01, 1968MO10). Searches for three-proton enhancement (reaction (c)) have been unsuccessful: see (1974AJ01). See also (1976HE07; theor.).
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 the 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. (1977DO01) find that the reduced widths of the P-wave resonance states are nearly the same. See also (1974KR07: Ex = 2.3 ± 0.5 MeV, Γ = 9.0 ± 1.5 MeV for the P1/2 state). The D5/2, D3/2, F7/2 and F5/2 phase shift become greater than 1° at Ep ≈ 11, 13, 14 and 16 MeV, respectively (1977DO01). A contour plot of Ay is shown in (1973AR1N): the results are not significantly different from those of (1977DO01). The work of (1977DO01) relies heavily on the very accurate elastic scattering cross sections which they measured (better than 1%) and on the polarization measurements of (1977HA06) [absolute precision of ± 0.01]. It should be noted that Ay = 0.984 ± 0.005 at Epol. p = 11.93 MeV, θc.m. = 128.28° (1977HA06). For other phase-shift analyses, see (1976BR17) and (1974AJ01).
A resonance is observed at Ep = 23 MeV, corresponding to the known 3/2+ state at Ex = 16.7 MeV (1968AL1B, 1968DA04). An anomaly in the polarization is also observed at this energy (1966WE03, 1968DA04, 1972BA24). A further broad feature in the polarization excitation function (θ = 102°) is observed at Ep = 30 MeV (Ex = 22 MeV) (1972BA24). Cross sections for 23 < Ep < 45 MeV show no further evidence of excited states (1969BU10). An extensive phase-shift analysis, using complex phases with l ≤ 4 over the range Ep = 20 to 40 MeV has been made by (1972PL02), using mainly the polarization and differential cross-section data of (1972BA24). The D3/2 level is fit with R-matrix formalism, including background interference, with the following parameters: Ex = 16.68 MeV, γ2p = 122 keV, γ2d(l = 0) = 1.58 MeV (negative sign), γ2d(l = 2) = 1.58 MeV, θ2p = 0.014, θ2d = 0.765.
The Ep = 30 MeV structure is not reflected in anomalous behavior of any single phase shift. Strong absorption of even partial waves may indicate broad overlapping positive-parity levels, Jπ = 1/2+, 3/2+, 5/2+, 7/2+, of d + 3He character near Ex = 22 MeV, but there is no unambiguous identification of excited states other than the 3/2+ state in the p-α results (1972PL02). In an analysis of the data of (1971PL07) for Ep = 25 to 29 MeV, (1971RA27) report evidence for a 5/2+ level at Ex = 20 MeV [Γel/Γtotal = 0.15, Γtot = 8 MeV] and a 1/2+ level at Ex = 18 ± 1 MeV.
A recent analysis by (1975PL01) of the phase shifts below 50 MeV suggests a small D-state admixture to the dominant S-state configuration of 4Heg.s..
Total reaction cross sections have been measured at Ep = 18 to 48 MeV (1974SO06, 1976SO01) and at 0.87 and 2.1 GeV (1975JA1A). At an equivalent Ep of 1.05 GeV, the elastic distribution is characterized by a shallow first minimum (1977GE01) and is said to be in excellent agreement with the predictions of multiple-diffraction theory (1977WA06). Alpha-proton bremsstrahlung is observed at Ep = 7.0 to 12.0 MeV, at Eα = 20 MeV [see (1974AJ01)] and at Ep = 22, 40 and 45 MeV (1975AN18). Coherent single pion production has been studied at Ep = 18.6 GeV/c (1977BR1C). See also (1973BE1A, 1978GL1B), (1975IG1A, 1975RO1B, 1975TO1A, 1976GR1D, 1977BR1E, 1977RI1B, 1978BR1E, 1978IG1B), (1973GU1A, 1973HA1F, 1974BA34, 1974BA38, 1974CH02, 1974CH1E, 1974CI02, 1974DO10, 1974HA43, 1974JA1F, 1974LY02, 1974SA1G, 1974UL1A, 1974WA02, 1975AH07, 1975BA05, 1975BA1G, 1975BA76, 1975BL04, 1975CA05, 1975CO1A, 1975DU1A, 1975GR1C, 1975GU17, 1975KA1D, 1975NA07, 1975RU01, 1975RU07, 1975TA1A, 1975WA16, 1976AH1A, 1976AL1E, 1976AR12, 1976AU04, 1976CH1B, 1976DO1C, 1976DU06, 1976LE22, 1976LE1E, 1976NA04, 1976RU04, 1976SP1A, 1977AL06, 1977AR01, 1977CH1C, 1977DY01, 1977JA12, 1977KA1E, 1977KA1F, 1977KA1H, 1977LA1C, 1977LE1E, 1977PH01, 1977TH07, 1977TH09, 1977WA1C, 1977WA1E, 1977YO04, 1978CL1C, 1978HE2B, 1978LA02, 1978LE23, 1978MA37, 1978ME05, 1978YE1A, 1978YO1B; theor.).
Angular distributions of 3He ions (reaction (a)) have been measured for Ep = 27.9 to 155.4 MeV [see (1974AJ01)] and at Ep = 85 MeV (1974VO05), 275 to 500 MeV (1978CA05: back angles), 770 MeV (1976CO1C, 1977BA19) and at Eα = 3.98 GeV/c (1977BE34). The 85 MeV data are in agreement with DWBA at forward angles but the back angle behavior probably results from the need to include two-nucleon pickup in the analysis (1974VO05). The differential cross section is strongly backward peaked at Ep = 275 and 500 MeV and the differential cross section is similar in slope and magnitude to that for 3He(p, p), suggesting that deuteron exchange may be the major component of the reaction mechanism (1978CA05). The excitation function shows no indication of resonance for Ep = 38.5 to 44.6 MeV (1969BU10). Polarization measurements have been reported for Ep = 32 to 63 MeV [see (1974AJ01)] and at 45.04 and 52.34 MeV (1977SA1E) and 350, 400 and 500 MeV (1978CA05). At Eα = 6.85 GeV/c, the integrated cross section for 3He production (reactions (a) + (b)) is 24.1 ± 1.9 mb, suggesting an important component of 3He in 4He (1977BI05).
Reaction (b) and (c) have also been reported at Ep = 46.8 to 156 MeV [see (1974AJ01)]. The (p, 2p) reaction (reaction (c)) has also been studied at 350 and 500 MeV (1978EP1C, 1978KO1F) and 600 MeV (1969PE15), while both that reaction and reaction (d) have been studied at Ep = 156 MeV (1975FR14). See also (1973KR1A, 1978GL1B), (1977TE1A, 1978IG1B), (1976CO1B; astrophysics) and (1974BA34, 1974CH02, 1974CH29, 1974DO10, 1974HA36, 1974KA1D, 1974RO19, 1974YO01, 1975HA03, 1975KA1D, 1977CL1A, 1977KA1D, 1977KA1G, 1977RE1A, 1978BI1C, 1978RO06; theor.).
Reaction (b) has been studied at Ed = 14.2 MeV and at Eα = 18.0 to 42 MeV [see (1974AJ01)] and at Eα = 18 MeV (1978SA07) and 21.9 and 23.7 MeV (1974RA10). The data show that at 42 MeV, direct breakup, with quasi-free α-p scattering taking place and the n acting as a spectator, is at least as important a mechanism as the FSI in the 5Lig.s. (1968WA01). See also (1974HE21, 1976KO21, 1976LI1E, 1977BR25; theor.) and 6Li.
Angular distributions have been measured at Ep = 18.6 to 156 MeV [see (1974AJ01)] and at Ep = 185 MeV (1974KA28, 1976FA03). 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). See also (1978IG1A: 0.65 and 0.8 GeV).
Reaction (b) has been studied at Ep = 9 and 10 MeV, at 45 MeV [see (1974AJ01)] and 40, 45 and 50 MeV (1974BE46): the p-α FSI corresponding to 5Lig.s. is observed. See also (1975MI1A). For reaction (c) see (1977WA05). See also (1975ST1C, 1975VO04, 1978CH1G) and 6Li.
Angular distributions of the t0 group have been measured at Ed = 15 and 20 MeV: see (1974AJ01). For reaction (b) see (1977RO18: Ed = 0.47 MeV), (1974MI10, 1977MI13; Ed = 7.5 to 10.5 MeV) and (1975KO1A; theor.).
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 (1972BA30). In a kinematically complete experiment at E(3He) = 36 MeV the population of 5Li*(16.7, 20.2, 22.6) is reported (1976RAZW). The decay of the ground state has also been studied at E(3He) = 1.25 MeV (1974LI10) and at 1.47 to 1.75 MeV (1978GU15).
Cylindrical asymmetry observed in the breakup of 5Li(0) is attributed to the short lifetime of the 5Li intermediate state and to the memory retained by the proton of its localization at the time of formation of 5Li (1967RE03, 1968RE10). The first excited state of 5Li also appears to be involved (1972TH08, 1972TH1B): its parameters are given as Ex = 3.2 ± 0.2 MeV, Γ = 1.5 ± 0.5 MeV (1975GA14). See also (1975GL08, 1976STYX, 1977AR09) and 8Be.
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 20 in 5He] (1966CE05). Weak, broad states at Ex = 22.0 ± 0.5 MeV and 25.0 ± 0.5 MeV and possibly 34 MeV are reported by (1968MC02) in a coincidence experiment in which three- and four-particle breakup was analyzed. The t0 angular distribution has also been studied at Ep = 16.6 and 30.3 MeV: see (1974AJ01).
At E(3He) = 2.45 and 6.00 MeV the reaction proceeds in part via the first two states of 5Li (1966WA16).
Not observed: see (1972MA62).