(See Energy Level Diagrams for 5Li)
General reviews: (1966DE1E).
Special reactions: (1971CH31).
Excitation curves and angular distributions have been measured for Ed = 0.2 to 2.85 MeV (1954BL89), Ed = 0.2 to 1.2 MeV (1968BU09), Ed = 1 to 5 and E(3He) = 2 to 5.5 MeV (1968KR03), E(3He) = 2 to 26 MeV (1972KI01), E(3He) = 2.3 to 11.2 MeV (1968DE14) and E(3He) = 3.7 to 12 MeV (1970SC18).
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). See also (1968KR03). 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). See also (1971WA08; theor.).
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). See also (1970CA1K, 1972PL02). Excitation functions for gorund state protons have also been reported by (1966NE1A: E(3He) = 0.39 to 1.46 MeV), (1971GR47: Ed = 2.8 to 11.5 MeV), (1972BA30: Ed = 9.4 to 17.8 MeV) and (1972KI02: E(3He) = 18.7 to 44.1 MeV). Angular distribution and polarization measurements are summarized in Table 5.6 (in PDF or PS). 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). See also (1971RO35, 1972SI1F, 1973OH02). (1971LE13) have evaluated matrix elements for l = 1 at Ed = 0.43 MeV. Vector polarization effects at Ed > 1 MeV disagree with the predictions of stripping theory (1966BR02). See also (1971ZA1C). Contour maps, Tab vs. θ, Ed for the vector and tensor analyzing powers are presented for Ed = 0 to 12 MeV by (1971GR47). See also (1971KL02, 1973CL13). Energy dependence of the angular distributions indicate resonance-like behavior at Ex = 16.6, 17.5, 20.0, 20.9 and 22.4 MeV in 5Li (1971GR47). See also (1972SE09, 1973CL13). 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(cm) = 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 (1972KI02). See also (1972BA30). The analyzing power for 3He polarization has been studied by (1971HA02, 1971HU1B, 1971LE13, 1971LE27): see (1971ST1J). For a discussion of excitation of 4He excited states in reaction (a) see (1973FI04).
Reaction (b) has been studied at Ed = 10.92 MeV (1972NI02), 11.0 MeV (1970LA10, 1970LA1K), E(3He) = 16.5 MeV (1971LI04), 18 MeV (1965ZU02), 18.0 and 24.0 MeV (1970AS02), E(3He) = 27 MeV (1971WA18, 1973WA13) and Ed = 27.5 MeV (1973CH05). See also (1966LA04). The spectra show the influence of neutron-proton final state interaction. Sequential decay via excited states of 4He is also reported: see (1970AS02, 1972NI02) and (1973FI04).
Reaction (c) has been investigated at Ed = 10.9 MeV (1972NI02), 11 MeV (1965TO01, 1970LA10, 1970LA1K), 15.2 and 20.2 MeV (1967NE1B, 1968NE1D), E(3He) = 16.5 MeV (1971LI04), 18 MeV (1965ZU02), 18.0 and 24.0 MeV (1970AS02), 19.9 MeV (1971GR12), Ed = 20.7 MeV (1970WA15), 24 to 33 MeV (1963BI14, 1964CO1A), 29.8 MeV (1970SL1A), E(3He) = 27 MeV (1971WA18, 1973WA13), 30 MeV (1973TR1H), Ed = 39.1 MeV (1971RU07, 1971RU1E), Ed = 36 MeV and E(3He) = 53 MeV (1967MO08, 1967MO1E, 1968MO10) and at Ed = 83 MeV (1972BA32). See also (1972SC1R, 1973SL03). The triton spectra are characterized by p-p final state interaction and by sequential decay via 4He*, as in reaction (b). (1970LA10, 1970LA1K) have analyzed the data of (1968MO10) using all first order interactions, in PWBA. The calculations indicate that complex exchange processes cannot be ignored, and that estimates of the nucleon-nucleon scattering length from such experiments are highly ambiguous (1970LA10, 1970LA1K).
Under kinematic conditions such that two outgoing particles have small relative kinetic energy, a DWBA analysis with two-body interactions has some success in accounting for spectral shapes: see (1967HE1B, 1971CH31, 1971WA18, 1972WA22, 1973WA13, 1973SL03). Reaction (d) has been studied at E(3He) = 26.8 MeV (1972WA22).
See also (1965DA05, 1967ME14, 1967RO07, 1968FI1D, 1968GO1N, 1968HO1D, 1969ME1B, 1971FO1J, 1970HO1L, 1970RO1L, 1970WI1G, 1971AL1B, 1971WA18, 1972RO1M, 1974PR1D), (1968TO1F, 1971BA1U, 1971HA2G, 1972OH1D) and (1965DU1A, 1965HE1A, 1966BA1J, 1966CS1A, 1966DE1D, 1966DU1A, 1967DE1G, 1968DE1K, 1968HA1F, 1968TA1J, 1969HE1K, 1969SE1B, 1970BR1L, 1970KH03, 1970PO1A, 1971DE20, 1971HA1L, 1971KH03, 1971SE1G, 1972OT05, 1973GA1H, 1973GR1L, 1973LI19; 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 [see, however, 7Li(p, t)5Li] (1967TO02). [There is some evidence that there is more than one D-wave state in this Ex region: see reaction 3]. See also (1969DA1F, 1972AL1P). In the range Ed(cm) = 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). See also (1970WI1G). Angular distributions have been measured at a number of energies from E(3He) = 18.7 to 44.1 MeV (1972KI02). Polarization measurements are reported for Ed = 4.0 to 11.5 MeV (1972KO07), 4 to 12 MeV (1973BA2P), 4.78 to 11.88 MeV (1970HA1M, 1971HA02), 5.7, 7.1, 8.4 and 9.4 MeV (1973LO1D), 6, 8 and 10 MeV (1969PL01), 9.9 and 11.9 MeV (1970WA32) and 10 and 12 MeV (1971DO1C). Strong variations of the angular distributions for all components of the analyzing power are observed between Ed = 4.0 and 8.0 MeV: it is suggested that one or more positive parity states are involved (18.8 < Ex < 21.2 MeV). At higher energies potential scattering is the dominant mode (1972KO07). See also (1971BA1U, 1971ST1J) and (1966BA1J, 1966BA1M, 1967HE1B, 1970BR1L, 1970HE1D, 1971HA1L, 1972TA1E, 1973CH27, 1974CH02; theor.).
The spectrum of protons shows a pronounced peak corresponding to 5Lig.s. superposed on a continuum (1965BA1D, 1965BA1E, 1972DE46: E(3He) = 3 to 18 MeV): the 5Li breaks up with a strong angular asymmetry (1968BA1N). The α-spectra E(3He) = 6.9, 7.9, 9.1 MeV) have been analyzed in terms of final state interactions including both p-p and p-α interactions (1972DE46). 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). See also (1965ZU02, 1966NE1A, 1966BL02, 1967MO1E, 1968BL06) and (1973LI1M; theor.). A search for a three-proton enhancement (reaction (c)) was unsuccessful at E(3He) = 44 MeV (1968TO01) and 53 MeV (1968MO10). See also (1966LA04).
Phase shifts below Ep = 3.2 MeV have been determined by (1967BR03) based on polarization measurements of (1967BR02) and available differential cross sections. The results are in essential agreement with earlier phase shifts of (1949CR1A) but are considerably more precise. In this range, the s-wave phase shift is that of a hard sphere with R = 2.48 fm; d-wave shifts are zero. 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: see (1959AJ76, 1966LA04) for reviews of earlier results.
From Ep = 3 to 18 MeV (1971SC04) have analyzed available polarization and differential cross section data to produce a set of phase shifts constrained to an analytic (effective range expansion) energy dependence. d- and f-wave phase shifts are positive and become of some importance above 8 MeV. A polarization contour plot is presented for Ep = 1 to 18 MeV (1971SC04). See also (1968MO26, 1971AR20, 1973AR1N). An R-matrix (single level plus background) formalism is used by (1972ST01). For P1/2 and P3/2 the resonance energies are given by ER = 8.10 and 2.06 MeV and the reduced widths γ2 = 12.30 and 8.02 MeV, respectively (1972ST01). See also (1973NI1B).
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 a range Ep = 20 to 40 MeV was made by (1972PL02), using mainly 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 umambiguous identification of excited states other than the 3/2+ state in the p-α results (1972PL02). In an alaysis of 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.
Other phase-shift analyses are reported by (1971AR20, 1973AR1N: 0 to 23 MeV), (1972ST01: 0.3 to 20 MeV), (1967BR02, 1967BR03: 0.9 to 3.2 MeV), (1966WE03: 14.3 to 31.0 MeV), (1967DA08: 29, 40, 48 MeV) and (1969PE01: 63, 70, 80 and 94 MeV). See also (1968PL02, 1973AR1P, 1973HO1U).
Alpha-proton bremsstrahlung is observed at Ep = 7.0 to 12.0 MeV (1971WO07, 1972WO1E), and at Eα = 20 MeV (1967BO1B). See also (1972AN1P). Cross section measurements have also been carried out at Ep = 23.4 to 48.5 MeV (1973DA1N, 1973DA1P), 180 to 560 MeV (1972SC1M) and at 1 GeV (1967IG1A). For inelastic scattering to excited states of 4He, see (1973FI04). For pion production, see (1972GU1D).
See also (1965JA1B, 1965KU13, 1966BL1B, 1967AU1A, 1967CA1E, 1968KO1F, 1968PA1J, 1969KO1M, 1970LI06, 1970RO1M, 1973CO1Y, 1973EK1A), (1966BA1K, 1966HA1F, 1966RO1B, 1970BO1P, 1971HA2G, 1971ST1J) and (1965HO1A, 1965HO1B, 1966RA1B, 1966TO04, 1967BA1F, 1967BA1G, 1967CZ1A, 1967SA1C, 1967TA1B, 1968BA1K, 1968CH35, 1968FR1F, 1968GL1A, 1968SA1B, 1968SC1D, 1968SE1A, 1968TA1E, 1968BA1U, 1969CO1E, 1969CR1A, 1969GE1A, 1969HE15, 1969LE03, 1968TH1C, 1970BA1F, 1970HE1D, 1970KU1C, 1970RE1A, 1970SA01, 1970TH1D, 1971BA1Y, 1971BA61, 1971BA74, 1971FE10, 1971HA1L, 1971IK01, 1971KR1A, 1971LO24, 1971MU1H, 1971PI04, 1971PL06, 1971RA15, 1971TH09, 1972BB19, 1972GR06, 1972IK01, 1972TH06, 1973AD01, 1973CL01, 1973FE1H, 1973LA14, 1973LY02, 1973PL02, 1973SA09, 1973UL1C, 1973YO1F, 1974CH02; theor.).
Angular distributions of 3He ions (reaction (a)) have been measured at Ep = 27.9 MeV (1957WI22), 31 MeV (1953BE14, 1964BU1B), 46.8 MeV (1969RO1L, 1969RO24), 49.5 MeV (1969HA16, 1970HA36), 53 MeV (1964CA1B), 55 MeV (1964HA13, 1964HA1P, 1964HA49), 94 MeV (1958SE74) and 155.4 MeV (1967BE35, 1970BE49). See also (1973VO1M). The excitation function shows no indication of resonances for Ep = 38.5 to 44.6 MeV (1969BU10). Polarization measurements have been carried out at Ep = 32, 40, 50 and 52.5 MeV (1973SA1W) and 55 and 63 MeV (1966BO1A). At Ep = 141 MeV the total reaction cross section (not including elastic scattering) is 79.5 ± 2.0 mb (1972NI04).
Reactions (b) and (c) have been studied at Ep = 46.8 MeV (1969RO1L, 1969RO24, 1970RO17, 1970SA01), 49.5 MeV (1969HA16, 1970HA36) and 156 MeV (1967BE35, 1970BE49). See also (1973KI1L, 1973RO1Z). Angular distributions have been measured in the region of the final state interactions. The t and 3He spectra show peaks due to sequential reaction processes via continuum resonance states in 4He: see (1973FI04). See also (1967AU1A, 1968PA1J) and (1969DO1G, 1969NA1F, 1973HA46, 1973JU02; theor.). For 4He(p, 2N + χπ) see (1965KU1C).
Reaction (b) has been studied at Ed = 14.2 MeV (1967FU1D), Eα = 29.2 MeV (1968TA11), 38.8 MeV (1971LE02), 42 MeV (1967WA08, 1968WA01) and at Eα = 18.0 and 24.0 MeV (1970AS02). See also (1971CH1T). The data indicate 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 final state interaction in the 5Li ground state (1967WA08, 1968WA01): see 5He. See also (1967NA1D, 1969NA09, 1972NA1D; theor.) and (1966LA04) for the earlier references.
Deuteron groups are observed to 5Li*(0, 16.7). Angular distributions have been measured at Ep = 18.6 MeV (1955LI09; d0), 33.6 MeV (1967KU10, 1970KU1D; d0, d2), 100 MeV (1969LI02; d0) and 156 MeV (1968BE72, 1969BA05, 1969TO1A; d0, d2). See (1969TO1A) for spectroscopic factors. In addition, the excitation of a state with Ex = 3.72 ± 0.10, Γ = 6.3 ± 0.5 MeV is reported by (1966SE1C). [See, however, (1967KU10, 1970KU1D)]. (1969BA05) confirm the population of the first excited state. See also (1966SE1C, 1972AZ03) and (1968JA1D; 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 Γcm = 2 and 1 MeV, respectively (1972BA30).
Cylindrical asymmetry observed in the breakup of 5Li(0) is attributed to the short lifetime of the 5Li imtermediate 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). See also (1964MA57, 1966LO10, 1967HO1C, 1968VI03, 1969VI05, 1970GA1G), (1966LA04), (1970DE41, 1972TH04; theor.) 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 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] (1966CE05). See also (1966BA1L, 1967PO1C). 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 3- and 4-particle breakup was analyzed. The t0 angular distribution has also been studied at Ep = 16.6 MeV (1965OG03) and 30.3 MeV (1969DE04).
For reaction (b) see (1967JO1C).
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).