(See Energy Level Diagrams for 7Li)
GENERAL: References to articles on general properties of 7Li published since the previous review (1988AJ01) are grouped into categories and listed, along with brief descriptions of each item, in the General Tables for 7Li located on our website at (www.tunl.duke.edu/NuclData/General_Tables/7li.shtml).
The interaction nuclear radius of 7Li is 2.23 ± 0.02 fm (1985TA18). [See also for derived nuclear matter, charge and neutron matter r.m.s. radii].
Gamma spectra were measured for 40 MeV/A 6He incident on a solid hydrogen target (2001SA37). The 7Li ground state and the 0.48 MeV first excited states were not resolved. Measurements of momentum spectra of fragments as well as gamma-ray intensity distributions are described in (2001SA37). See also (2001SAZS).
Excitation functions and angular distributions have been studied for Eα = 0.5 to 2.0 MeV. The cross section rises smoothly as expected for a direct capture process: see (1966LA04) and (1987BU18; γ0, γ1). Measurements of the astrophysical S-factor, S(E), and the branching ratio R for direct capture to the 478 keV state compared to direct capture to the ground state were reported by (1987SC18). They deduce S(0) = 0.14 ± 0.02 keV b, R = 0.32 ± 0.01. More recently, available data on 3H + α scattering were analyzed (1993MO11) in the optical model framework to predict S(0) = 0.10 keV b and branching ratio R = 0.43. Measurements of the cross sections and angular distributions in the energy range 50 ≤ E ≤ 1200 keV were reported by (1994BR25). They determined R ~ 0.45 at low energies in disagreement with (1987SC18). An extended two-cluster model study for Ecm < 5 MeV is described in (2000CS06). Effects of inclusion of the 6Li + n channel on the zero-energy cross section and astrophsyical S factor as well as the quadrupole moment are explored. A recent analysis by (1999BU10) estimated the uncertainties in Big Bang nucleosynthesis 7Li yields. For astrophysical calculations related to 3H(α, γ) see the General Table for 7Li located on our website at (www.tunl.duke.edu/NuclData/General_Tables/7li.shtml). See also references cited in (1988AJ01).
Thermonuclear reaction rates for this reaction calculated from evaluated data are presented in the compilation (1999AN35).
The cross section for this reaction has been measured for Eα = 11 to 18 MeV: the data show the effect of 7Li*(7.46) and indicate a broad resonance near Eα = 16.8 MeV [7Li*(9.6)]. The level parameters derived from this reaction and from reaction 4 are displayed in Table 7.3 (in PDF or PS). The yield of 6Li ions at 0° (lab) has also been measured for Eα = 11.310 to 11.930 MeV with 2 - 3% accuracy: the data were then reduced to obtain the cm differential cross sections at 0° and 180° for the inverse reaction in the energy region corresponding to formation of 7Li*(7.46): see (1979AJ01). See also the compilation of (1985CA41). A resonating group calculation of σ(E) from threshold to 20 MeV is reported in (1991FU02).
The excitation curves for the elastic scattering show the effects of 7Li*(4.63, 6.68, 7.46, 9.67). The derived level parameters are displayed in Table 7.3 (in PDF or PS). Angular distributions have been studied for Eα = 2.13 to 2.98 MeV and Et = 6.0 to 17 MeV [see (1979AJ01, 1984AJ01)] and at Eα = 56.3 to 95.5 MeV (1986YA1M; also Ay]. More recently, cross sections and angular distributions were measured at Eα = 27.2 MeV and described in an RGM method and in the phenomenological optical model. A polarization extremum (Ay = -1) occurs near Et = 11.1 MeV, θ = 95°: see (1984AJ01). For the breakup of 7Li into α + t in various processes see (1984AJ01) and (1984SH17, 1987FO08, 1987PO03) as well as the General Table for 7Li located on our website at (www.tunl.duke.edu/NuclData/General_Tables/7li.shtml). For cross sections determined from shell-model and R-matrix calculations see (1987KN04). Other calculations that have been reported include: phase shifts for Eα < 300 MeV and 7Li charge form factor (1987RO24); scattering lengths (1988CH47, 1989CH34); phase-shift and transmission coefficients with RGM (1991FU02); phase-shift and astrophysical S factors in a two-cluster model (1995DU09, 1997DU15); RGM phase shifts (1995MA37); and phase shifts versus E in a three-body cluster model (1996SH02).
For muon catalysis see references cited in (1988AJ01).
Angular distributions have been reported at Eα = 39.9 to 140 MeV [see (1979AJ01, 1984AJ01)] and at 61.5 to 158.2 MeV (1982GL01) and 198.4 MeV (1985WO11) for the transitions to 7Li*(0, 0.48). Cross sections for Eα = 159.3, 279.6 and 619.8 MeV were measured by (2001ME13) to enable calculation of the amount of 7Li produced in early-galaxy cosmic rays. See also (2001AU06). See (1982GL01, 1985WO11) for a discussion of 7Li production in the Big Bang. See also 8Be in (1988AJ01) and (1986KA26).
The thermal capture cross section is 38.5 ± 3.0 mb (1981MUZQ). Gamma rays are observed corresponding to transitions to 7Li*(0, 0.48) with branching ratios 62 ± 2% and 38 ± 2% (1985KO47). 7Li*(4.63, 6.68) are not populated [≤ 5%] (1985KO47). See (1979AJ01) for the earlier work. The decay of 7Li*(7.46) → 6Lig.s. + n in the interaction of 35 MeV/A 14N ions on Ag is reported by (1987BL13).
A recent study discussed in (1997NO04) analyzed reaction rates of 6Li(n, γ) and other reactions that bear on the possibility of observing primordial 6Li.
The real coherent scattering length is 2.0 ± 0.1 fm; the complex scattering lengths are b+ = (0.67 ± 0.14) - i(0.08 ± 0.01) fm, b- = (4.67 ± 0.17) - i(0.62 ± 0.02) fm; σfree = 0.70 ± 0.01 b (1983KO17). See also (1979GL12). (1983AL1E) report σs (below 10 keV) = 0.72 ± 0.02 b. See also (1981MUZQ). The total cross section has been measured from En = 4 eV to 49.6 MeV [see (1976GAYV, 1984AJ01)], at 0.6 to 80 keV (1982AL35) and at 0.08 to 3.0 MeV (1983KN1D).
A pronounced resonance occurs at En = 244.5 ± 1.0 keV [Ex = 7459.5 ± 1.0 keV] with a peak cross section of 11.2 ± 0.2 b (1982SM02): see Table 7.4 (in PDF or PS). No other clearly defined resonance is observed to En = 49.6 MeV although the total cross section exhibits a broad maximum at En ~ 4.5 MeV: see (1984AJ01). The analyzing power has been measured for En = 1.48 to 5 MeV [see (1984AJ01)] and 5 to 17 MeV (1986PF1A). Multi-level, multi-channel R-matrix analyses (1987KN04, 1983KN06) for En ≤ 8 MeV [using also data from other channels] include 13 normal and 14 non-normal parity states with Ex ≤ 17 MeV. [Only ten states have been seen directly in reaction or compound nucleus cross-section work.] Two positive-parity states provide an explanation for the anisotropy of the 6Li(n, α) work at low energies (1983KN06). For the results of an earlier R-matrix analysis see (1984AJ01).
The excitation function for 3.56 MeV γ-rays exhibits an anomaly, also seen in the (n, p) reaction (reaction 9). The data are well fitted assuming Eres = 3.50 and 4.60 MeV [Ex = 10.25 ± 0.10 and 11.19 ± 0.05 MeV], T = 1/2 and 3/2, Γcm = 1.40 ± 0.10 and 0.27 ± 0.05 MeV, respectively; both Jπ = 3/2-. However, (1979AJ01) notes that an R-matrix study of 4He(t, t), 6Li(n, n), and 6Li(n, α) data leads to the identification of a 3/2- state at Ex = 9.85 MeV, Γ = 1.2 MeV. See (1979AJ01) for a discussion of these and other unpublished data.
Differential cross sections for n0 and n1 were measured at En = 6.8 - 9.8 MeV and used with other data in an analysis to deduce σ(E) for En = 6 - 14 MeV (1987SC08). Elastic and inelastic scattering cross sections σ(θ) were measured for En = 24 MeV (1987HA25) and analyzed, along with existing proton scattering data to study neutron and proton transition densities. Elastic and inelastic scattering differential cross sections were measured at En = 11.5, 14.1 and 18.0 MeV (1998CH33) and used to determine a phenomenological optical model potential. A measurement of double-differential neutron emission cross sections for En = 11.5 and 18.0 MeV was reported by (1998IB02). Theoretical work includes: a calculation of coherent and incoherent thermal cross sections (1990GO26); RGM calculations of σ(θ) at En = 18 MeV (1992KA06); calculation of phase shifts and cross sections for En < 18 MeV using a potential description (1993DU09); a study of antisymmetry contribution to the nucleon-nucleon potentials (1995CO18); and a study of the applicability of optical-model potentials for nuclear data evaluations (1996CH33).
See also earlier references cited in (1988AJ01).
For reaction (a) see (1985CH37, 1986CH24). The excitation function for reaction (b), measured from threshold to En = 8.9 MeV, exhibits an anomaly at En = 4.6 MeV. The excitation function, at forward angles, of p0 is approximately constant for En = 4.4 to 7.25 MeV: see (1979AJ01). Measurements of particle spectra have been made at En = 198 MeV (1987HE22), En = 118 MeV (1987PO18, 1988HA12, 1998HA24). Studies of this reaction as a probe of Gamow-Teller strength are reported in (1988JA01, 1988WA24, 1992SO02). Measurements at En = 280 MeV were used in a test of isospin symmetry (1990MI10). Measurements at En = 0.88 GeV with polarized targets are reported in (1996BB27). Theoretical studies of this reaction include: a dynamical cluster model calculation for En = 280 MeV (1991DA08); a calculation of phase shifts for En = 6.77 MeV (1993DU09); a calculation with hyperspherical harmonics (1996DA31); and with a three-body cluster model for En = 50 MeV (1997DA01). See also (1997ER05, 1997VA06). The excitation function, at forward angles, of deuterons (reaction (c)) increases monotonically for En = 5.4 to 6.8 MeV: see (1979AJ01, 1988AJ01). A multiconfiguration resonating-group method calculation of σ(θ) for En = 12 MeV is described in (1995FU16).
The thermal cross section is 940 ± 4 b: see (1981MUZQ). See also (1985SW01). A resonance occurs at En = 241 ± 3 keV with σmax = 3.3 b: see (1984AJ01, 1986CA28). The resonance is formed by p-waves, Jπ = 5/2-, and has a large neutron width and a small α-width: see Table 7.4 (in PDF or PS). Above the resonance the cross section decreases monotonically to En = 18.2 MeV, except for a small bump near En ~ 1.8 MeV and an inflection near En = 3.5 MeV. For a description of R-matrix analyses which suggest the location of higher states of 7Li, see reaction 8 and (1984AJ01), as well as (1987KN04).
Angular distributions have been measured at many energies in the range En = 0.1 to 14.1 MeV [see (1979AJ01, 1984AJ01)] as well as from 35 eV to 325 keV (1983KN03) and 2.16 to 4.20, 7.1 and 13.7 MeV (1986BA32, 1986BA68). Polarization measurements have been reported for En = 0.2 to 2.4 MeV: the data suggest interference between s-waves and the p-wave resonance at 0.25 MeV. Interference between this 5/2- state and a broad 3/2- state 2 MeV higher also appears to contribute. At the higher energies Ay is close to +0.9 near 90° and varies slowly with En: see (1979AJ01). See also (1983VE10, 1984VE1A).
Measurements with polarized thermal neutrons for studying parity violation effects have been reported in (1990VE16, 1994GL07, 1996VE02). Reaction rates for E < 2 MeV were analyzed (1997NO04) in connection with the possibility of observing primordial 6Li. Calculations of tritium production in applications of this reaction are described in (1993FA01).
For a study of coincidences in the 6Li(n, αd)n reaction see (1986MI11). The triton production cross section at En = 14.92 MeV is 32 ± 3 mb (1985GO18). The total α-production cross section [which includes the (n, nd) process] at En = 14.95 MeV is 512 ± 26 mb (1986KN06).
See also the references cited in (1988AJ01).
At Ep = 600 MeV, the reaction preferentially excites 7Li*(4.63). Angular distributions have been obtained for the pions to 7Li*(0, 0.48, 4.63) at Ep = 600 and 800 MeV. 7Li*(11.24) [T = 3/2] is not observed: see (1984AJ01). Recently σ(θ) and Ay measurements were reported at Ep = 800 MeV (1987SO1C). See also (1985LE19). An analysis for Ep = 201 - 800 MeV utilizing a semi-phenomenological model is discussed in (1993AL05).
Angular distributions of proton groups have been studied for Ed = 0.12 to 15 MeV and at 698 MeV: see (1966LA04, 1974AJ01, 1979AJ01, 1984AJ01). Jπ of 7Li*(0.48) is 1/2-. The two higher states have Ex = 4630 ± 9 and 7464 ± 10 keV, Γcm = 93 ± 8 and 91 ± 8 keV. The breakup reactions involve 7Li*(4.63, 7.46) and possibly 7Li*(9.6) [Γ = 0.5 ± 0.1 MeV]: see (1979AJ01). See also 8Be in (1988AJ01) and (1988KO1C).
The (d, p)/(d, n) yield ratio for low deuteron energies (Ed < 1 MeV) has been studied. Calculations in (1990KO26) concluded that Coulomb-induced predissociation of the deuteron should influence the ratio by < 10%. Measurements in (1993CE02) found no evidence of an enhanced ratio for Ecm = 20 - 135 keV. The yield ratio was studied in experiments of (1993CZ01, 1997CZ04). This work explained the charge-symmetry violation in terms of a subthreshold 2+ state in 8Be. See also the instrumentation-related measurements of (1994YE09) and the thick-target gamma yield measurements of (2000EL08). Calculations involving conservation of channel spin are described in (1996MA36). This reaction was also discussed by (1997NO04) in connection with deduction of the primordial 6Li component. Calculations for energy balance in controlled fusion are described in (2000HA50). See also the compilation of charged-particle-induced thermonuclear reaction rates in (1999AN35).
The reaction was studied by (1999NA36) for E(7Li) = 65 MeV/A to compare the Gamow-Teller transition strengths to those deduced from β decay.
The total photoneutron cross section rises sharply from 10 MeV to reach a broad plateau at about 15 mb from 14 to 20 MeV, decreases more slowly to about 0.5 mb at 25 MeV and then decreases further to about 0.3 mb at Eγ = 30 MeV (monoenergetic photons): there are indications of weak structure through the entire region: see (1979AJ01), (1988DI02) and (1988AJ01). A study by (1986SI18) reported evidence for the excitation of 7Li*(7.46), as well as of states at Ex = 13.75 ± 0.03 and 14.65 ± 0.03 MeV with Γ ~ 500 and 700 keV [and integrated cross sections of ~ 0.14 and 0.17 MeV · mb], in addition to a major broad structure at 17 MeV. The integrated cross section to 23 MeV is 39 ± 4 MeV · mb for the n0 transition and 17 ± 4 MeV · mb for the n1 transition: together these account for 0.4 of the exchange augmented dipole sum of 7Li: see (1979AJ01). The integrated cross section for formation of 6Li*(3.56) is 4 ± 1 MeV · mb to 30 MeV and 11 ± 3 MeV · mb to 55 MeV: see (1984AJ01).
The total absorption cross section for natLi in the range 10 to 340 MeV shows a broad peak at ~ 30 MeV (σmax ~ 3 mb), a minimum centered at ~ 150 MeV at ~ 0.3 mb and a fairly smooth increase in cross section to ~ 3 mb at ~ 320 MeV: see (1984AJ01).
The cross section for the (γ, p) reaction (reaction (c)) shows a maximum at ~ 15.6 MeV with a width of ~ 4 MeV. It then decreases fairly smoothly to 27 MeV. The integrated cross section for 11 → 28 MeV is 13.2 ± 2.0 MeV · mb: see (1974AJ01, 1979AJ01, 1984AJ01). Differential cross sections for the (γ, n0 + n2) and (γ, p0) processes are reported by (1983SE07, 1985SE17; Eγ = 48 to 141 MeV). Photodisintegration cross sections in the giant resonant range were analyzed by (1987VA05). Analyses of photodisintegration data for reactions (a, b, c, d) at Eγ < 50 MeV (1990VA16) were used to deduce the role of cluster configuration. Reaction (e) has been studied in the giant resonance region with bremsstrahlung photons, Ebrem ≤ 30 MeV. Deuteron groups to 5Heg.s. and possibly to the first excited state are reported. States of 7Li with Ex = 25 - 30 MeV may be involved when Ebrem = 37 to 50 MeV is used: see (1979AJ01). At Eγ = 0.9 GeV, (1985RE1A) have studied π- emission with the population of 6Li*(2.19).
The cross section for reaction (f) at 90° displays a broad resonance at E ~ 7.7 MeV (Γ = 7.2 MeV) with an integrated cross section of 6.2 MeV mb, a plateau for 12 → 22 MeV (at ~ 0.6 the cross section at 7.7 MeV) and a gradual decrease to 48 MeV. The (γ, t) cross section integrated from threshold to 50 MeV is 8.1 MeV mb: see (1984AJ01), and (1986VO20). More recently, measurements of differential cross sections with linearly polarized photons (Eγ < 90 MeV) were reported (1995BU08). Angular distributions at Eγ = 6.4, 6.7, 8.5, 9.0 MeV have been measured by (1999LI02). Theoretical studies on this reaction include: a microscopic analysis for E < 70 MeV (1987BU04); an analysis in the giant resonance range (1987VA05); a cluster structure study (E < 50 MeV) (1990ZH19); and a calculation of photodisintegration observables for E < 90 MeV (1998KO17). For earlier work, see references cited in (1988AJ01).
The electric form factor measurements for Ee = 100 to 600 MeV are well accounted for by a simple harmonic-oscillator shell model with a quadrupole contribution described by an undeformed p-shell: rr.m.s. = 2.39 ± 0.03 fm, |Q| = 42 ± 2.5 mb. From results obtained for Ee = 24.14 to 97.19 MeV, rr.m.s. = 2.35 ± 0.10 fm (model independent), 2.29 ± 0.04 fm (shell model). A study of the ratio of the electric charge scattering from 6Li and from 7Li as a function of (momentum transfer)2 yields < r2 > 1/26/< r2 > 1/27 = 1.001 ± 0.008. The r.m.s. radius of the ground state magnetization density distribution, < r2 > 1/2M = 2.98 ± 0.05 fm. See (1979AJ01) for references. More recent theoretical studies include: a study by (1991BE40) which obtained vertex constants from an analysis of form factors; a shell-model calculation of large-basis space and mesonic effects (1992BO30); a calculation of form factors including meson exchange contributions (1992WA37); and a study of shell-model structures of low lying states (1997KA24).
Inelastic scattering studies show peaks corresponding to 7Li*(0.48, 4.63, 6.68, 7.46): see (1974AJ01) and Table 7.5 (in PDF or PS). Form factors for 7Li*(0, 0.48) have recently been studied at Ee = 80 to 680 MeV (1989LI09, 1990LI21). Theoretical work includes: a calculation by (1989TA31) of cross section and reduced transition matrix elements for oriented nuclei; a calculation for polarized electron and polarized targets (1990LE14); a shell model calculation in a (0 + 2)ℏω space (1990WO10); a study of spin modes (1991AR22); a microscopic cluster calculation (1991UN01); calculation of form factors including meson exchange contribution (1992BO30, 1992WA37); and a shell-model study of low lying states (1997KA24). For reaction (b) energy and angular distributions were measured at Ee = 203 MeV (1999SH25) to study spin-isospin flip giant resonances.
For reactions (c) and (d) a measurement of the momentum distribution and study of clustering effects was reported in (1989LA22). Calculations discussed in (2000LA17) were used to study correlations in the 7Li ground-state wave function. See also the PWIA calculation for polarized electrons and targets of (1993CA11). See also (1988BO05). For earlier work see the references cited in (1988AJ01).
7Li*(0, 0.48, 4.63, 6.68, 7.46, 9.67) have been populated in this reaction. Angular distributions have been measured at Eπ+ = 49.7 MeV and Eπ± = 143 and 164.4 MeV: see (1984AJ01). Total and partial cross sections have been obtained for Eπ± in the range 85 → 315 MeV [see (1984AJ01)] and at Eπ+ = 50 MeV (1983NA18). A measurement of inclusive analyzing power at Eπ = 134, 164, 194 MeV was reported by (1994ME01). A cluster-model calculation of quadrupole effects is described in (1994NO06). Calculations of pion scattering for Eπ = 100 - 240 MeV are described in (2001LE01). Nuclear transition densities predicted by Quantum Monte-Carlo calculations were used. The 7Li(π-, π-p) reaction was studied at 0.7 GeV/c by (2000AB25). For 7Li(π+, π-p), see (1998PA31). For the (π+, 2p) reaction see 5He (1986RI01). For studies of (π+, pd) and (π±, pn) see (1986WH01) and (1986YO06), respectively. For π+ induced fission of 7Li see (1983BA26). See also references in the General Table for 7Li located on our website at (www.tunl.duke.edu/NuclData/General_Tables/7li.shtml).
Angular distributions have been measured at En = 0.5 - 3 MeV (1991AL04), En = 1.5 to 18 MeV [see (1979AJ01, 1984AJ01)], En = 5.4, 6.0, 14.2 MeV (1985CH37; n0+1, n2), En = 6.82 - 9.80 MeV (1987SC08; n0+1), 7 to 14 MeV (1983DA22; n0), En = 11, 13 MeV (1988CH09), 8.0 and 24.0 MeV (1988HA25; n0 and n2 at 24 MeV), En = 9, 9.5, 10 MeV (1995HU17; n1) and at 14.7 MeV (1984SH01; n0+1). Double differential cross sections were measured at En = 11.5 and 18.0 MeV (1998IB02). Theoretical work includes: calculations of coherent and incoherent scattering for En = 0.0728 eV (1987VE02, 1990GO26); DWBA calculations of σ(θ) for inelastic excitation of 7Li*(0, 478 MeV) (1992HU05); multi-configuration RGM calculations, En = 9.58 - 12.2 MeV (1995FU16); and studies of optical model potentials for nuclear data evaluation, En < 200 MeV (1996CH33). Reaction (b) at En = 14.4 MeV proceeds primarily via 7Li*(4.63) although some involvement of 7Li*(6.68) may also occur: see (1979AJ01). Cross sections have been measured by activation methods at En = 14.7 MeV (1987ME18) and 7.9 - 10.5 MeV (1987QA01). See also the evaluation of tritium production cross section for E < 17 MeV (1990YU02). See also 8Li and references cited in (1988AJ01) and (1985CO18; applications).
Angular distributions of protons have been measured for Ep = 1.0 to 185 MeV [see (1974AJ01, 1984AJ01)] and at Ep = 1.89 to 2.59 MeV (1986SA1P; p0). Inelastic proton groups have been observed to 7Li*(0.48, 4.63, 6.68, 7.46, 9.6): see (1952AJ38, 1974AJ01). Double differential cross sections for the continuum are reported at Ep = 65 MeV and 85 MeV (1987TO06, 1989TO04). Measurements of differential cross sections and analyzing powers for p0, p1 and p2 for Ep = 200 MeV were used to deduce radial transition density differences (1991GL01). Cross sections for inelastic scattering to the 7Li Ex = 0.478 MeV level have been measured in application-related experiments for Ep = 2.2 - 3.8 MeV (1988BO37), 3.2 - 3.6 MeV (1990BO15), 2.5 - 3.5 MeV (1994MI21), 1.03 MeV (1994WI15), 0.7 - 3.2 MeV (1995RI14). See also (1999SA16).
For reaction (b) see (1984PA1B, 1985PA1B; 50 - 100 MeV) and (1985BE30, 1985DO16; 1 GeV). See also 6He and (1984AJ01). Cross section measurements at Ep = 70 MeV were used to distinguish contributions of 1p and 1s shell nucleons by (1988PA26, 1998SH33). Proton spectra and polarization measurements at Ep = 1 GeV are reported by (2000MI17). For reaction (c) see (1986WA11). For reaction (d) see (1985BE30) and 6Li. Reaction (d) has been studied at Ep = 200 MeV (1986WA11): the deuteron spectroscopic factor is close to unity and the results indicate that the deuteron cluster momentum distribution is characterized, at small momentum, by a FWHM of 140 MeV/c. For measurements at Ep = 70 MeV, see (1998SH33). Cross sections for the (p, pt) reaction (reaction (e)) are very small but are consistent with a spectroscopic factor of unity for t + 4He in 7Li (1986WA11). For reaction (f) recent measurements of cross sections and analyzing powers measured for Ep = 296 MeV were used to deduce alpha spectroscopic factor for 7Li (1998YO09). See also (1983GO06, 1985PA1C, 1985PA04). See also 5He and (1984AJ01).
See also 8Be in (1988AJ01), and references to earlier work cited in (1988AJ01). For early theoretical work on these reactions see references cited in (1988AJ01). More recent calculations include: threshold effects in elastic scattering for Ep = 1.35 - 3 MeV (1990GU22); differential cross section calculated at high energies with a geometric model (1990HU09); a potential description of 7Li(p, p) with Ep < 7 MeV (1992DU07); calculation with a microscopic effective interaction (1993KO44); a folding model description for Ep = 25 - 50 MeV (1993PE13); a microscopic three-cluster model calculation for Ecm = 0.5 - 25 MeV, σ(E), S factors (1994DE09); a fully microscopic analysis for Ep = 200 MeV (1997DO01); an analysis of Ep = 200 MeV data studying shell model structures of low lying 7Li levels (1997KA24); a microscopic analysis of elastic scattering at Ep = 25, 30 and 40 MeV (2000DE61), Ep = 65 MeV (1998DO16), and at 60 - 70 MeV (1998FUZP); a resonance optical-model calculation for Ep = 1 - 10 MeV (2000LA40); and a Glauber-Sitenko diffraction theory calculation for Ep = 0.16 - 1.04 GeV (2000ZH50). See also (2000ZH53). Reaction rate uncertainties for reaction (g) were analyzed by (1998FI02).
Angular distributions have been reported at E(3He) = 11 MeV to 44.0 MeV and at E(3He) = 33.3 MeV: see (1974AJ01, 1984AJ01). See also the compilation and analysis of differential cross sections for E(3He) = 24 MeV (1995MI16). The missing mass spectrum in reaction (b) at E(3He) = 120 MeV indicates, in addition to the unresolved group to 7Li*(0, 0.48), a small peak at Ex = 17.8 ± 0.5 MeV, possibly some structure between 30 and 40 MeV, a peak at 40.5 ± 0.5 MeV (Γ ~ 2 - 3 MeV) and possibly some structure at higher energies (1985FR01). Measurements of cross sections for yields of protons, deuterons, 4He, 3H and 3He from 93 MeV 3He on 7Li are reported by (1994DO32). For pion production see (1984BR22).
Angular distributions (reaction (a)) have been reported for Eα = 3.6 to 29.4 MeV [see (1974AJ01, 1984AJ01)] and at Eα = 35.3 MeV (1985DI08; α to 7Li*(0, 0.48, 4.63, 6.68, 7.46, 9.67); collective coupled channel analysis). See also (1987BU27). More recently, differential cross sections were measured at Eα = 50.5 MeV for inelastic scattering to 7Li*(0, 0.478, 4.63 MeV) by (1996BU06). The α, t cluster spectroscopic factor extracted for the 7Li ground state is Sαt = 1.03 ± 0.1. Measurements of target polarization in 7Li(α, α') to Ex = 4.63 MeV for Eα = 27.2 MeV were reported by (1991KO41). See also coupled-channels calculations for these data (1997DM02). Gamma emission yields for Eα = 0.7 - 3.2 MeV were measured for nuclear microprobe applications by (1995RI14).
Reaction (b) has been studied at Eα = 18 to 64.3 MeV [see (1974AJ01, 1984AJ01)] and at 27.2 MeV (1985KO29). 7Li*(4.63) is strongly involved in the sequential decay, as are possibly 7Li*(6.68, 7.46). Cross sections measured for Eα = 77 - 119 MeV were used to deduce triton momentum distributions for α + t states in 7Li by (1992WA09). An analysis is reported in (1996JA01). See also references cited in (1988AJ01).
Elastic and inelastic (7Li; Ex = 0.476 MeV) differential cross sections for reaction (a) have been reported for Eα = 9 - 40 MeV (1998PO03). See also 6Li. The elastic angular distribution (reaction (b)) has been studied for E(7Li) = 4.0 to 6.5 MeV [see (1974AJ01)] and 2.0 to 5.5 MeV (1983NO08). Elastic and inelastic (7Li; Ex = 0.476 MeV) cross sections for Eα = 8 - 17 MeV were measured and analyzed with an optical model (1993BA43, 1997PO03). For reaction (c) cross sections for E(11Li) = 300 MeV were calculated in connection with a study of nuclear matter compressibility (1998GR21).
Elastic angular distributions have been measured at E(7Li) = 34 MeV [see (1979AJ01)] and at 78 MeV (1986GLZV, 1986GLZU; also to 7Li*(4.63)). For the interaction cross section at 790 MeV/A see (1985TA18).
Angular distributions (reaction (a)) involving 7Li*(0, 0.48) have been studied at E(7Li) = 4.5 to 89 MeV [see (1975AJ02, 1979AJ01, 1984AJ01)] and at E(7Li) = 53.8 MeV and E(12C) = 92.3 MeV (1984VI02, 1986CO02; also to 7Li*(4.63)) and at E(7Li) = 131.8 MeV (1988KA09; 7Li*(0 + 0.48); and various states in 12C) as well as at E(7Li) = 21.1 MeV (1984MO06; elastic). See also (1986GLZU) and 12C in (1985AJ01, 1990AJ01). Breakup studies involving 7Li*(4.63) are reported at E(7Li) = 70 MeV (1986DAZP, 1986YOZU) and 132 MeV (1986SHZP). See also the measurement at E(12C) = 58.4 MeV reported by (1987PA12). The interaction cross section on carbon at 790 MeV/A has been measured by (1985TA18).
The elastic scattering in reaction (b) has been studied for E(7Li) = 4.5 to 34 MeV [see 13C in (1986AJ01)] and by (1987CO02, 1987CO16; 34 MeV; also to 7Li*(0.48)). For earlier work, see references cited in (1988AJ01).
Elastic angular distributions (reaction (a)) are reported at E(7Li) = 36 MeV [see (1981AJ01)] and E(14N) = 150 MeV (1986GO1H) while those for reaction (b) have been studied at E(7Li) = 28.8 MeV [see 15N in (1986AJ01)].
The elastic scattering has been studied from E(7Li) = 9.0 to 20 and at 68 MeV [see 16O in (1986AJ04)] as well as at E(7Li) = 50 MeV (1984CO20). For fusion cross sections and breakup studies see (1984MA28, 1986MA19, 1986SC28, 1988MA07). See also (1982GU21, 1988PR02).
Angular distributions have been studied at E(7Li) = 36, 68 and 89 MeV: see 20Ne in (1983AJ01).
The elastic scattering has been studied at E(7Li) = 89 MeV and at 27 MeV (reaction (b)): see (1984AJ01). A study of the breakup on 27Al is reported by (1986NAZV) and the interaction cross section at 790 MeV/A has been measured by (1985TA18). See also (1988OT01, 1988SA10).
Angular distributions involving 7Li*(0, 0.48) and various states of 28Si and 40Ca have been studied at E(7Li) = 45 MeV. The elastic scattering on 40Ca and 48Ca has been studied at E(7Li) = 28, 34 and 89 MeV [the latter also to 7Li*(0.48)]: see (1984AJ01). Angular distributions (reaction (b)) involving 7Li*(0, 0.48) have also been reported at E(7Li) = 34 MeV (1985SA25). See also (1985GO11, 1986SA1D, 1987SA1C).
The decay proceeds to the ground and 0.48 MeV states. The branching ratio to 7Li*(0.48) is 10.44 ± 0.04%, and the adopted half-life is 53.22 ± 0.06 d. Both transitions are superallowed: log ft = 3.32 and 3.55 for the decays to 7Li*(0, 0.48). See also (1979AJ01). The first excited state has Ex [from Eγ] = 477.612 ± 0.002 keV: see (1984AJ01). A recent investigation of the decay utilized a high efficiency BeO calorimeter developed for use in a 7Li solar neutrino experiment (1998GA08). The decay rate of BeOH2 was studied under pressures up to 441 kbar (2000LI21) and showed systematic dependences at the 1% level. A large change in the decay rate for 7Be implanted in Au and Al2O3 was observed by (1999RA12) indicating that the chemical environment affects the 7Be lifetime. A further decay study using 7Be in BeO, BeOH2 and Be2 + (OH2)4 molecular forms (1999HU20) found considerable variation (~ 1.5%) in the lifetime. Less significant effects of the chemical environment on the measured half-life have been measured by (1949SE20, 1953KR16, 1956BO36, 1970JO21, 1973HE27). The authors of (2000HU20) deduced a half-life value of 53.42 ± 0.01 d for 7Be in BeOH2. A systematic discussion of 7Be half-lives is included in the evaluation of R. Helmer (see Table 7.6 (in PDF or PS)). Helmer's evaluation produced a general-use value of the half-life, 53.22 ± 0.06 d, which is intended to be valid for Be and BeO samples and adequate for various chemical forms. In spite of more precise measurements of the 7Be lifetime that show these environmental effects, we presently adopt this value.
In related threshold investigations, the polarization of the internal bremsstrahlung has been calculated (1988ME06) as well as the effect of daughter atom ionization (1994RE18) and the fractional electron probablities (1998SC28). For earlier work, see references cited in (1988AJ01).
Total cross sections have been measured at En = 0.025 - 13.5 keV (1988KO03). The cross sections obtained for the 7Li ground and first excited states (Ex = 0.477 MeV) were 38400 ± 800 b and 420 ± 120 b, respectively. The astrophysical reaction rate NA < σν was calculated. Uncertainties in elemental abundances from primordial nucleosynthesis were deduced in (1998FI02).
The capture of stopped pions has been studied in a kinematically complete experiment: 7Li*(0, 0.48) are weakly populated. Two large peaks are attributed to the excitation of 7Li*(7.46, 10.25). The recoil momentum distributions corresponding to these peaks are rather similar and both indicate a strong L = 0 component: see (1979AJ01).
An angular distribution is reported at En = 14.6 MeV (1987ZA01; t0+1). See also (1979AJ01) and 10Be in (1988AJ01). Cross section measurements have also been reported for En = 12.9 - 19.6 MeV (1988LI05) and for En = 16 - 19.6 MeV with Hauser-Feshbach calculations (1990WO07).
At Ep = 43.7 MeV, angular distributions have been obtained for the 3He particles corresponding to 7Li*(0, 0.48, 4.63, 7.46). The 7.46-MeV state is strongly excited while the analog state in 7Be is not appreciably populated in the 9Be(p, t)7Be reaction (see reaction 21 in 7Be). The angular distribution indicates that the transition to 7Li*(7.46) involves both L = 0 and 2, with a somewhat dominant L = 0 character. The Jπ = 3/2-, T = 3/2 state is located at Ex = 11.28 ± 0.04 MeV, Γ = 260 ± 50 keV: see (1979AJ01). Reaction (b) at Ep = 58 MeV involved 7Li*(0, 0.48, 7.47) (1985DE17). See also (1987KA25).
Angular distributions have been measured for Ed = 0.4 to 27.5 MeV [see (1966LA04, 1974AJ01, 1979AJ01)] and at Ed = 2.0 to 2.8 MeV (1984AN16; α0, α1). A study at 11 MeV finds Γcm = 93 ± 25 and 80 ± 20 keV, respectively for 7Li*(4.63, 7.46). No evidence is found for the T = 3/2 state 7Li*(11.25). Differential cross sections measured at Ed = 67 - 75 MeV for excitation of 7Li*(0, 0.48, 4.63, 7.46) were used to deduce spectroscopic amplitudes (1989SZ02). Measurements of vector analyzing powers for 7Li*(0, 0.48) were reported by (1994LY02) for Ed = 1.3 - 3.1 MeV. Measurements at Ecm = 57 - 139 keV (1997YA02) and Ecm = 30 - 130 keV (1997YA08) were used to deduce astrophysical S-factors. Differential cross sections for Ed = 90 - 290 keV are reported in (2001OCZZ). Astrophysical S factors were deduced. See also (1999OCZZ). The previous review (1988AJ01) notes that in a kinematically complete study of reaction (b) at Ed = 26.3 MeV, 7Li*(4.6, 6.5 + 7.5, 9.4) are strongly excited. No sharp α-decaying states of 7Li are observed with 10 < Ex < 25 MeV. Parameters for 7Li*(9.7) are Ex = 9.36 ± 0.05 MeV, Γ = 0.8 ± 0.2 MeV: see (1979AJ01). [Ex = 6.75 ± 0.20 MeV, Γ = 0.87 ± 0.20 MeV (1986PA1E)]. A study of inclusive α-spectra at Ed = 50 MeV has been reported by (1987KA17) who suggest the involvement of a 7Li state at Ex = 18 ± 1 MeV, Γ = 5 ± 1 MeV. For reaction (b) see also (1987VA29). See also 11B in (1990AJ01) and (1988NE1A). In more recent studies of reaction (b), differential cross sections have been measured at Ed = 18 MeV (1988GO02, 1988GU20) and Ed = 7 MeV (1988SZ02). See also the measurements of σ(E) for Ed = 0.9 - 11.2 MeV (1994AB25), Ay(θ) for Ed = 1.3 - 3.1 MeV (1994LY02), σ(θ) at Ed = 3 - 11 MeV (1995AB41) and Ed = 8 - 50 MeV (1995GU22). Astrophysical S factors were determined in measurements at Ecm = 57 - 139 keV (1997YA02, 1997YA08).
Angular distributions involving 7Li*(0, 0.48) have been reported at E(6Li) = 32 MeV (1985CO09) and E(9Be) = 14 MeV (1985JA09). Reaction cross sections have been calculated by (2001BH02) for E(6Li) = 790 MeV/A.
Angular distributions of α0, α1 and of α2 at the higher energies have been measured from En = 2 keV to 14.4 MeV: see (1979AJ01, 1984AJ01). τm(0.48) = 102 ± 5 fsec (1985KO47). More recently measurements of the ground to excited-state transition ratio σ(n, α0)/σ(n, αγ) for En = 0.2 - 1.0 MeV were reported by (1991WE11). A relative measurement of the 10B(n, αγ)7Li cross section has been made (1993SC20) for En = 0.2 - 4.0 MeV. A study of P-odd effects (in the mixing of opposite-parity levels) in this reaction determined forward-backward asymmetries for the α0 and α1 groups (3.4 ± 6.7) x 10-7 and (-2.5 ± 1.6) x 10-7 respectively (1996VE02). Earlier work was reported in (1986ER05, 1994GL07). Measurement and analysis of the Doppler-broadened gamma line shapes produced in the (n, α, γ) reaction for the purpose of boron concentration determination are described in (1994SA72, 1998MA61). See also (1997SA70). For early polarization studies (involving both n and 10B) see (1986KO19) and 11B in (1990AJ01). See also (1986CO1M; applications). See also the more recent measurements and calculations of (1999VE03) and the measurement at thermal energies of (2000GO03). A calculation of α-γ correlation parameters and study of time-reversal invariance related features are described in (2000GA43).
Delayed α-particles have been observed in the β- decay of 11Be: they are due to the decay of 11B*(9.88) [Jπ = 3/2+]. This state decays by α-emission 87.4 ± 1.2% to the ground state of 7Li and 12.6 ± 1.2% to 7Li*(0.48) (1981AL03). See also 11Be and 11B in (1985AJ01).
Angular distributions have been measured at Eα = 27.2 to 29.0 MeV and at 65 MeV. At Eα = 65 and 72.5 MeV, 7Li*(0, 4.63) are very strongly populated while 7Li*(0.48, 6.68, 7.46) are weakly excited: see (1979AJ01, 1984AJ01).
Cross sections were measured at Eγ = 27 - 47 MeV with bremsstrahlung photons by (1998KO77).
Angular distributions involving 7Lig.s. and 7Beg.s. and 7Li*(0.48) + 7Be*(0.43) have been studied at Ed = 39.8 MeV [see (1979AJ01)] and at 78.0 MeV (1986JA03, 1986JA15). See also (1984NE1A) and (1987KW01, 1987KW03).
More recently differential cross sections at Ed = 78 MeV were measured in a study of five-nucleon transfer (1996JA12).
Angular distributions have been studied at Et = 38 MeV to 8Beg.s. and 7Li*(0, 0.48) (1986SIZS).
Angular distributions have been obtained at E(6Li) = 36 MeV for the transitions to 7Li*(0, 0.48): see (1979AJ01). See also (1986GL1E). More recently differential cross sections and polarization observables were measured at E(6Li) = 50 MeV in a study of mirror states in 7Li, 7Be (1997KE04).
The reaction was studied (1999NA36) at E(7Li) = 65 MeV/A, and Gamow-Teller transition strengths were compared to those deduced from β decay.
At En = 14.1 MeV, 7Li*(0, 0.48) are approximately equally populated: see (1979AJ01). Differential cross sections have been measured at En = 14.4 and 18.2 MeV involving 8Beg.s. and 7Li*(0 + 0.48, 4.63) (1986TU02).
Gamma ray intensities and photo production cross sections were measured fo En = 4 - 200 MeV by (2001NE09).
At Ed = 14.6 to 15.0 MeV, angular distributions have been measured for the transitions to 12Cg.s. + 7Li*(0, 0.48) [reaction (a)], 13Cg.s.+7Li*(0, 0.48) [reaction (b)] and 14Ng.s.+7Li*(0, 0.48) [reaction (c)]: see (1979AJ01). See also (1984AJ01).
A Coulomb breakup experiment reported by (2001TO07) used a 42 MeV 7Li beam incident on target of 27Al, 58Ni, 64Zn, 90Zr, 120Sn, 144Sm, 169Tm, 197Au and 208Pb. The spectra of breakup particles were studied and the astrophysical S factors, S(E) for 3H(α, γ)7Li, were deduced.
Measurements of charged particle multipolarity, angular distributions and rapidity distributions were reported in (2001AB25). 7Li cluster structure was deduced.
Elastic and inelastic cross sections and analyzing powers were measured at E(7Li) = 27 MeV to study the effect of electric dipole polarizability of 7Li (1998MA65).