(See Energy Level Diagrams for 5Li)
GENERAL: References to articles on general properties of 5Li published since the previous review (1988AJ01) are grouped into categories and listed, along with brief descriptions of each item, in the General Tables for 5Li located on our website at (nucldata.tunl.duke.edu/NuclData/General_Tables/5li.shtml).
See also the A = 5 introductory discussion titled A = 5 resonance parameters.
Gamma rays were measured over a large dynamic range for Eα = 200 MeV (2000HO18). Both inclusive and exclusive (coincidence with either α particle, proton or both) measurements were performed. A pronounced contribution from capture into the unbound ground and first excited states of 5Li was observed. For the measured parameters of the 5Li resonances, see 5.5 (in PDF or PS).
Angular distributions and analyzing powers for polarized 3He on 2H at E3He = 22.5, 24, 27, 30, 33 MeV were measured and analyzed by (2000OK01). Based on the phase shifts, they report the following resonances identified with 5Li with excitation energies between 15 and 30 MeV: "(i) the well-established (1988AJ01) 4S3/2 state at 16.7 MeV; (ii) a broad 2S1/2 state around 19 MeV; (iii) quartet D states around 20 MeV, [5/2+ and 3/2+ assigned before (1988AJ01)]; (iv) two doublet P states (3/2-, 1/2-) around 25 MeV; and (v) at least one negative parity state around 29 MeV."
The results are compared with shell model calculations. See also reaction 5 below.
The previous review (1988AJ01) describes the earlier work as follows: "The ratio Γγ/Γpα has been determined for E(3He) = 63 to 150 keV [Ecm = 25 to 60 keV] by (1985CE13) by measuring simultaneously the γ-rays and the charged particles. Because of the large widths of the final states, γ0 and γ1 could not be resolved but the results are consistent with Ex = 3.0 ± 1.0 MeV for the excited state. Γγ0/Γpα is roughly constant for Ecm = 25 to 60 keV at (4.5 ± 1.2) × 10-5 and Γγ1/Γpα = (8 ± 3) × 10-5 at E(3He) = 150 keV (1985CE13)". For applications see (1985CE13, 1985CE16, 1988CE04, 1992LI32).
"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*(16.7)]. σγ0 = 21 ± 4 μb, Γγ0 = 5 ± 1 eV. The radiation at resonance is isotropic, consistent with s-wave capture. Study of γ0 and γ1 yields Γ = 2.6 ± 0.4 MeV for the ground-state width (but see below), and Ex = 7.5 ± 1.0 MeV, Γ = 6.6 ± 1.2 MeV for the 1/2- state: see (1979AJ01, 1988AJ01). 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. 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 (1979AJ01)". In more recent measurements at Ed = 8.6 MeV a ground state width Γp = 2.44 ± 0.21 MeV was extracted from the γ0 spectrum (1991BA02). An analysis of these data with single level R-matrix fits (1996EF03) gave values for the energies and widths of the ground states of 5Li and 5He. Cross section and analyzing power measurements in the 3/2+ fusion resonance region (Ed = 0.45 MeV) and Ed = 8.6 MeV were reported by (1991WEZZ, 1992BA04, 1994BA02, 1998WE07), and comparisons with the results of coupled-channels resonating group model calculations were discussed. See also the shell model description of the 3/2+ resonance discussed in (1993KU02). Potential model descriptions of this reaction are discussed in (1990NE14, 1992LI32, 1992NE03, 1995DU13). Analyzing power formulae derived in a model-independent way are presented in (1996TA09).
Measurements of high-energy (> 20 MeV) gamma ray production in the reaction are described in (1992PI04).
Excitation functions and angular distributions have been measured for Ecm = 6.95 to 171.3 keV, and values of S(E) have been deduced: S(0) = 6.3 ± 0.6 MeV · b (1987KR18). See also (1984AJ01, 1988AJ01). S-factors have been obtained down to Ecm = 5.88 keV. The effect on S of electron screening at low energies has been studied by (1988EN03, 1988SCZG, 1988SC1F). See also the calculations of (1989BE08, 1990BR12).
A pronounced resonance occurs at Ed = 430 keV, Γ ≈ 450 keV. The peak cross section is 695 ± 14 mb: see 5.2 (in PDF or PS) in (1979AJ01). The recent work of (1997BA72) discusses a description of the 3/2+ levels of 5Li and 5He in terms of conventional R-matrix parameters. Excitation functions for ground-state protons have also been reported for E(3He) = 0.39 to 2.15 MeV and 18.7 to 44.1 MeV and for Ed = 2.8 to 17.8 MeV [see (1979AJ01)]. Angular distributions have been measured for Ed = 0.25 to 27 MeV and E(3He) = 18.7 to 44.1 MeV [see 5.6 (in PDF or PS) in (1974AJ01) and the discussion in (1979AJ01)]. Resonance-like behavior has been suggested at Ex = 16.6, 17.5, 20.0, 20.9 and 22.4 MeV: see (1979AJ01).
In early work, tensor analyzing power measurements were reported for Ed = 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 Ed = 0 to 40 MeV.] Measurements of angular distributions and analyzing powers at E(3He) = 27 and 33 MeV have suggested the presence of a broad resonance(s) at Ex ≈ 28 MeV. Vector and tensor analyzing powers have been studied at Ed = 1.0 to 13.0 MeV (1986BI1C, 1986BIZP) and 18, 20 and 22 MeV (1986SA1L). See also (1986RO1J) and 5.6 (in PDF or PS) in (1974AJ01) and 5.4 (in PDF or PS) in (1979AJ01). In recent work of (1999GE19), angular distributions and complete sets of analyzing powers were measured at five energies between Ed = 60 and 641 keV. The data were included in an R-matrix analysis of the 5Li system (see 5.6 (in PDF or PS)). Multichannel resonating group model calculations for this reaction are presented in (1988GU07, 1990BL02, 1990BL08). A model-independent description of the d + 3He system near the low energy 3/2+ resonance using the effective range expansion is described in (1996PO26).
Differential cross sections for reaction (b) were measured at Ed = 23.08 MeV (1988BR27, 1990BR14). Triple differential cross sections and vector analyzing powers were measured at Ed = 17 MeV (1989AYZZ, 1990AYZW) and at E(3He) = 32.25 MeV (1988DA18, 1991DA06).
The d-3He fusion process in reactors is discussed in (1988DA26, 1988MI29, 1988MO36). Applications of the reaction in studying deuterium diffusion behavior in materials is discussed in (1989PA26, 1990QIZZ). See also (1990LE30, 1990WI1L).
It is suggested that at low energies [Ed = 2.2 to 6 MeV] reaction (c) 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]: see (1979AJ01). Other studies of the breakup have been reported at Ed = 23.08 MeV (1986BR1J; reaction (c)) and 60 MeV (1985OK03; reaction (d)). For the earlier work see (1984AJ01). See also other references cited in (1988AJ01). For a descriptive list of theoretical work on this reaction see the General Table for 5Li located on our website at (nucldata.tunl.duke.edu/NuclData/General_Tables/5li.shtml).
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, 4D5/2 is favored, if only one state is involved: see (1979AJ01). A phase-shift analysis 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]: see (1984AJ01). See also (1987KR18).
Angular distributions and analyzing powers have been measured at many energies to E = 44 MeV: see (1979AJ01, 1984AJ01) for the earlier work, (1982COZO, 1983COZR; Ed = 10 MeV) and (1987YAZJ; Ed = 29.5 MeV on polarized 3He). For d-3He correlations see (1987PO03). See also "Complex reactions" in the 5Li General section of (1988AJ01). The R-matrix formalism was used by (1990TR08) to calculate the S(1/2+)-wave cross section for d + 3He, using p + 4He cross section data and d + 3He analyzing power data from the 5Li(3/2+) region. See also the work of (1997BA72). A generalized potential model description of 3He + d scattering is discussed in (1991NE01). For earlier theoretical work see references cited in (1988AJ01).
The spectrum of protons at E(3He) = 3 to 18 MeV shows a pronounced peak corresponding to 5Lig.s. superposed on a continuum: see (1979AJ01). The angular distribution of p0 has been measured at E(3He) = 26 MeV (1983KI10; polarized target). See also 6Be and (1986OS1D).
The contribution of unbound 6Li nuclear states to deuteron spectra from this reaction was calculated by (1993GO16).
Differential cross sections and polarization measurements have been carried out at many energies: see (1966LA04, 1974AJ01, 1979AJ01, 1984AJ01) for the earlier work. More recent measurements were reported (1988AJ01) at Ep = 65 MeV (1986FU05; Ay), 100 MeV (1983NAZV, 1985GUZX; σ(θ), Ay) and 495 MeV (1988STZZ) and at Ep = 695, 793, 890, 991 MeV (1985VE13; σ(θ)) and 1 GeV (1985AL09; σ(θ)). Cross sections and Ay at Ep = 98.7 and 149.3 MeV for the continuum were reported by (1985WE06). In experimental work reported since the previous review (1988AJ01), differential cross sections were measured for Ep = 695, 793, 890, 991 MeV by (1989GR20) with phase shift analysis and at 607 MeV/c by (1991BA1V). Differential cross sections and analyzing powers at 71.9 MeV were measured (1989BU01) and combined with existing data for Ep = 30 - 65 MeV for a phase shift analysis. Measurements of analyzing power at Ep = 180 MeV were reported by (1990WEZY). Cross sections for the p + 4He interaction at GeV energies have been measured at 2.7 GeV/c (1993AB07), at 8.6 and 13.6 GeV/c (1989BR30, 1993GL09), and at √s (square root of s) = 31.5 GeV (1989AK05). For earlier work at very high energies, see references cited in (1988AJ01). The previous review (1988AJ01) summarizes the analyses reported prior to 1988 as follows:
"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. 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). (1986TH1C; prelim.) have measured Ay for 1.1 ≤ Ep ≤ 2.15 MeV: Ay = 1 for Ep = 1.89 MeV, θcm = 87.0°."
"A phase-shift analysis for Ep = 21.8 to 55 MeV is presented by (1978HO17) [see also 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 a measurement of the spin rotation parameter, R, at Ep = 500 MeV see (1983MO01). See also (1986SA1J; prelim.; Ep = 65 MeV)."
Theory and analyses reported since the previous review (1988AJ01) include: the S-matrix studies of resonances in the A = 5 system of (1998CS02); the S-matrix and R-matrix determination of the 3/2- and 5/2- states of 5Li of (1997CS01); and the study of the 3/2+ levels of 5Li on 5He based on conventional R-matrix parameters (1997BA72). See also the study of the cluster potential model (1997DU15), and the calculation of interaction potentials by inversion of scattering phase shifts (1996AL01). See also (1996CO20).
Other theoretical work reported since the previous review (1988AJ01) includes calculations for p-α potentials derived from phase shifts for Ep ≤ 23 MeV (1991CO05) and at Ep = 64.9 MeV (1989CO11). Multichannel resonating group calculations are presented in (1989KA39, 1990BL02). The resonating group method was applied in the region Ep = 50 - 120 MeV by (1993KA47). See also the dynamic microscopic model calculation reported by (1993CS02). Glauber theory calculations of cross sections at intermediate energies were reported by (1993MA47). Other theoretical work related to 4He + p scattering is included in the descriptive list in the General Table for 5Li located on our website at (nucldata.tunl.duke.edu/NuclData/General_Tables/5li.shtml).
In earlier work PNC effects were studied via the elastic scattering of 46 MeV longitudinally polarized protons on 4He: the longitudinal power Az = -(3.3 ± 0.9) × 10-7. This was obtained by measuring σ+ and σ- for the positive and negative helicity of the incident protons (1985LA01, 1986LA29): the conclusion reached by the authors from this, and all other experiments, is that there does not exist any evidence for a non-zero value of fπ, the weak isovector coupling constant. See also (1984AJ01) and (1986ADZT, 1986HA1Q, 1988NA18). For α + p correlations see (1987PO03).
In application-related work, a method for precise absolute calibration of polarization effects is applied to p-α scattering at Ep = 25.68 MeV by (1989CL04). Measurements of recoil cross sections for α particles on protons in connection with depth profiling were reported at E(3He) = 0.9 - 3.4 MeV (1989SZ04) and at E(3He) = 1.3 - 2.1 MeV (1988WA22).
As reported in (1988AJ01) angular distributions of deuterons and of 3He ions (reaction (a)) have been measured for Ep = 27.9 to 770 MeV and at Eα = 3.98 GeV/c [see (1979AJ01, 1984AJ01)]. Angular distributions and analyzing powers were measured at Ep = 100 MeV (1983NAZV), 200 and 400 MeV (1986AL01). Excitation functions are reported at several energies in the range Ep = 38.5 to 44.6 MeV and 200 to 500 MeV. Continuum yields and analyzing powers have been studied at Ep = 98.7 and 149.3 MeV by (1985WE06). For polarization measurements to 500 MeV see above and (1979AJ01, 1984AJ01, 1988BAZH). More recently, analyzing powers and differential cross sections were measured at Ep = 32, 40, 50 and 52.5 MeV by (1991SA17).
For reactions (b), (c) and (d) see (1974AJ01, 1979AJ01, 1984AJ01). The breakup of 4He via reaction (c) has been studied by (1986FU05): large values of Ay in the FSI region were reported. In more recent work on reactions (b), (c) and (d), quasi-free knockout of charged particles for 4He was studied at Ep = 100 MeV by (1990WH01). For astrophysics-related theoretical work see (1989GU28, 1990BI06). For breakup processes at high energies, including pion production, see (1988AJ01).
In early work, antiproton interactions with 4He were studied by (1984BA60, 1985BA76, 1987BA12, 1987BA47, 1987BA69). See also (1983FA16, 1984BA74, 1984FA14, 1986DO20, 1987NA23). More recently, the production rate of 1H, 2H, 3H in p-bar-4He annihilation was studied between 0 - 600 MeV/c by (1988BA62), the annihilation cross section near 45 MeV/c was measured (1989BA59), and the cross section for production of Λ hyperons and K0s mesons at 600 MeV/c was measured by (1989BA94).
Calculations for the knockout and annihilation reactions were presented by (1989NA16), and a study of the change of the branching ratio of channels for p-bar-4He annihilation in the nuclear medium is discussed in (1989NA16).
For reaction (a) see reaction 10 in 5He, (1985WI15) and (1987KAZL; Ed = 15 MeV; n0). Early work on reaction (b) reported in (1988AJ01) includes measurements at Ed = 12 to 17 MeV and at Eα = 18.0 to 140 MeV: see (1979AJ01, 1984AJ01), 6Li and (1985DO03, 1987KUZI).
More recently, measurements of cross sections and analyzing powers at Ed = 7 MeV were reported by (1988GA14). Comparison of data at Ed = 12 and 17 MeV with predictions of the three-body model are made by (1988SU12). The effects of the internal structure of the α particle in a three-body description of the d + α reaction are explored by (1990KU27). Multi-configuration resonating group calculations are discussed in (1991FU01, 1992FU10).
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 suggested to lie at Ex = 2.82 ± 0.35 MeV, Γ = 1.64 ± 0.25 MeV [reaction (b)]: see (1982NE09, 1986YA01). See also (1985NEZW).
Measurements were made at Eα = 120, 160 and 200 MeV (1998ST07). Differential cross sections were extracted from measured triton energy spectra. Line shapes of the 5Li ground state resonance was well reproduced by DWBA calculations.
Available experimental data at energies up to Eγ = 50 MeV are reviewed and analyzed (1990VA16) to explore cluster effects and final-state interactions.
In early work, differential cross sections have been measured at Tπ = 75 and 150 MeV for p0: see (1984AJ01). More recently cross section measurements at Eπ = 50, 100, 150 and 200 MeV were reported by (1992RA01). DWIA calculations presented in (1992KH04) provide predictions of cross sections at Tπ = 115, 165 and 255 MeV.
Angular distributions have been measured at Ep = 18.6 to 185 MeV. At the highest energy, 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). The first excited state of 5Li is also reported to be populated: see (1984AJ01).
Reaction (b) has been studied at Ep = 9 to 50 MeV: the p-α FSI corresponding to 5Lig.s. is observed [see (1979AJ01)]. See also (1983CA13, 1986NI1B). At 1 GeV (reaction (c)) the separation energy between 4 - 5 MeV broad 1p3/2 and 1s1/2 peaks is reported to be 17.7 ± 0.5 MeV (1985BE30, 1985DO16). See also (1985PA03; Ep = 70 MeV).
In early work, angular distributions of the t0 group were measured at Ed = 15 and 20 MeV: see (1979AJ01). More recently the production cross section for triton was measured by radiochemical methods (1997ABZY). Calculations of differential cross sections for Ed < 30 MeV are described in (1997HAZK, 1997HAZY). Reaction (b) has been studied at Ed = 0.12 to 10.5 MeV: see (1984AJ01). See also 8Be in (1988AJ01).
In early work reviewed in (1988AJ01) at E(3He) = 25.5 MeV, 5Li*(0, 16.7) and two broad peaks at Ex ≈ 19.8 and 22.7 MeV [Γcm = 2 and 1 MeV] are populated: see (1979AJ01). At E(3He) = 33.3 MeV angular distributions and analyzing powers have been studied for 5Li*(0, 16.7) [Γ ≈ 1.6 and ≈ 0.4 MeV]: see (1984AJ01). More recently, in experiments at E(3He) = 8, 11, 13 and 14 MeV (1989ARZI, 1990AR17), the 5Li state at Ex = 16.7 MeV was observed and the width measured to be Γ = 150 ± 40 keV.
In reaction (b) an analysis (1989AR20) of data at E(3He) = 2.5 MeV gave Γ = 1.55 ± 0.2 MeV for 5Lig.s.. Measurements at E(3He) = 1.6, 3.5, 7.0 and 9.0 (1992AR20) found the 5Lig.s. width consistent with (1988AJ01) and independent of 3He incident energy. Work reported for E(3He) = 1.6 MeV (1991AR25) and E(3He) = 7 and 9 MeV (1993AR12) determined that the ground state width is independent of detector angle. In early work reviewed in (1988AJ01) the parameters of the first excited state are deduced to be Ex = 5.0 ± 0.7 MeV, Γcm = 5.7 ± 0.7 MeV (1984AR17; E(3He) = 1.7 and 2.3 MeV), Ex = 5.8 ± 0.5 MeV, Γcm = 5.2 ± 0.5 MeV (1987FA1I; E(3He) = 1.65 MeV). More recently an experiment at E(3He) = 2.0 and 2.2 MeV (1992DA1K) found values in line with those measured at E(3He) = 1.65 and 1.7 MeV. Measurements at E(3He) = 11, 13 and 14 MeV reported by (1989AR08) determined parameters for Ex ≈ 18 MeV and found a level at Ex = 17.9 ± 0.4 MeV, Γ = 3.5 ± 0.8 MeV. Angular distributions of protons from the decay of 5Lig.s. are reported by (1988BU04; E(3He) = 1.5 MeV). See also references cited in (1988AJ01).
A recent theoretical study (1996FA05) of the properties of resonance scattering in two fragment systems calculates parameters for the Ex = 16.66 MeV states formed in reaction (b).
Angular distributions have been measured at E(6Li) = 156 MeV to 5Lig.s.. Unresolved states at Ex = 16 - 20 MeV are also populated (1987MI34).
At Ep = 43.7 MeV, a triton group is observed to 5Lig.s. (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 23 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). Measurements of angular distributions and differential cross sections at Ep = 29.1 and 35 MeV are reported in (1989BA88). See also (1988BAZH). For reaction (b) at Ep = 670 MeV see (1984AJ01). See also (1985NEZW).
A kinematically complete experiment is reported at E(3He) = 120 MeV. The missing mass spectrum shows the ground-state peak and a 4 MeV wide bump at Ex ≈ 34 MeV, and some slight indication of a small bump at 22.0 ± 0.5 MeV (1985FR01).
At Eα = 90 MeV differential cross sections have been measured for the transitions to 5Li g.s.+ 8Lig.s.: see (1984AJ01).