(See Energy Level Diagrams for 7Be)
GENERAL: References to articles on general properties of 7Be published since the previous review (1988AJ01) are grouped into categories and listed, along with brief descriptions of each item, in the General Tables for 7Be located on our website at (nucldata.tunl.edu/NuclData/General_Tables/7be.shtml).
The interaction nuclear radius of 7Be is 2.22 ± 0.02 fm (1985TA18). [See also for derived nuclear matter, charge and neutron matter r.m.s. radii]. A measurement of the magnetic moment by (1998KAZN) gave a preliminary result μl = -1.398 ± 0.015 μN.
The ε-capture decay is complex: see reaction 33 in 7Li.
The capture cross sections have been measured for Eα = 0.250 to 5.80 MeV and at E(3He) = 19 to 26 MeV [see (1974AJ01, 1984AJ01)], at Ecm = 195 to 686 keV (1988HI06), and at Eα = 385 to 2728 keV (1984OS03) and 1225 keV (1984AL24). One of the main reasons for doing these measurements is to determine the astrophysical S(0) factor. The values of S(0) appear, on the average, to be higher if the experiment involves measurement of the 0.48 MeV γ following ε-capture rather than if it involves a direct measurement of the capture γ-rays. It is not entirely clear why this should be so. Contaminant production of 7Be may be involved: see (1988HI06) and e.g. (1984AL24, 1985FI1D, 1986LA22). Earlier measurements, sometimes re-calculated, are discussed by (1986LA22, 1987KA1R, 1988HI06). The latter adopt best values of S(0) = 0.51 ± 0.02 keV b [prompt γ-rays] and 0.58 ± 0.02 keV b [7Be activity] (1988HI06). See also (1984AL24, 1985FI1D, 1987KA1R, 1988BA86). More recently, (1993MO11) measured differential cross sections for 3He - α scattering for Elab(3He) < 3 MeV and obtained optical potentials which were used to calculate S(0) for the capture reaction. They obtained S(0) = 0.516 keV · b in agreement with (1988HI06). They also calculated the branching ratio for transition to the first excited state and ground state to be R = 0.43. Theoretical calculations are in general agreement with the experimental values. See (1988AJ01) for examples from some of the early work. Calculations of astrophysical S factors for the capture reaction are included in (1988BU17, 1988KA07, 1989CH37, 1989CH48, 1989KA18, 1995DU09, 1995LI07, 1997DU15, 2001NO04). Phase shifts and cross sections (Ecm < 5 MeV) were calculated in an extended two-cluster model by (2000CS06). Astrophysical S factors were deduced. See also the S-factor calculation of (2001CS03). The reaction rate at T = 300 K was calculated in (1989SC25). See also the related work of (1990SC16, 1990SC26). The reaction rate and the effects of electron screening on the solar neutrino flux has been calculated by (2000LI13). The reaction rate and a correction to the Gamow penetration factor were calculated by (1994KA02). See also the calculations described in (1998FI02, 1999BU10, 1999SH13, 2000BA09). As noted in (1988AJ01), the solar model calculations of (1982BA80) used S34[S(0)] = 0.52 ± 0.02 keV · b. It appears clear that the uncertainty in S34 is not of severe consequence to the solar neutrino problem [see, e.g. (1985FI1D)]. For other early astrophysical-related work see (1984AJ01, 1988AJ01). See also (1986LI04).
Elastic-scattering studies have been reported for E = 0.25 to 198.4 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at Eα = 56.3 to 95.5 MeV (1985NE08, 1986YA14). Analyzing power measurements have been carried out at E = 4.3 to 98 MeV [see (1979AJ01)] and at E(3He) = 55 to 95 MeV (1986YA14).
For l ≤ 4, only f-wave phase shifts show resonance structure for E(3He) < 18 MeV, corresponding to 7Be*(4.57, 6.73, 9.27): see 7.8 (in PDF or PS). No structure corresponding to 7Be*(7.21) (Jπ = 5/2-) is seen in the elastic data. The s-wave phase shift is somewhat greater than hard-sphere. The decay of 7Be*(9.27) (Jπ = 7/2-) to 6Lig.s. requires f-shell configuration admixture. An estimate of the yield of ground-state protons relative to those corresponding to 6Li*(2.19) yields γ2(p0)/γ2(p1) = (16+5-10)% (1967SP10). A phase-shift analysis (single-level R-matrix) has been carried out for E(3He) = 18 to 32 MeV: the p-wave phase shifts indicate a 1/2- state at Ex ≈ 16.7 MeV (Er = 26.4 MeV), with Γ = 6.5 MeV (1978LU05). An R-matrix and S-matrix analysis (1992ZU03) of elastic scattering at Eα(cm) = 11 - 41 MeV on a polarized 3He target gave evidence of broad 9/2+ and 11/2- resonances. The R-matrix center-of-mass resonance energies and widths for the 9/2+ and 11/2- resonances are Eres = 29.5 ± 1.0 MeV, Γ = 8.5 ± 2.5 MeV and Eres = 32.5 ± 1.5 MeV, Γ = 10.5 ± 3.0 MeV, respectively (see 7.9 (in PDF or PS)). See also the earlier analysis reported in (1989OS06). Differential cross sections were measured for E(3He) = 1 - 3 MeV by (1993MO11). The data together with other available data were analyzed, and the optical potentials obtained were used to calculate astrophysical S factors for the radiative capture reaction (see reaction 1).
The differential cross section for reaction (b) has been determined for E(3He) = 8 to 28 MeV [see (1979AJ01)] and at Eα = 22.2 to 26.5 MeV. Resonances are observed corresponding to 7Be*(7.21, 9.27) in the p0 yield, to 7Be*(9.27) in the p1 yield and to states at Ex ≈ 10 MeV (T = 1/2) and 11.0 MeV (T = 3/2) in the yield of 3.56 MeV γ-rays. The evidence for the latter derives mainly from interference arguments. There is also some evidence for an extremely broad Jπ = 1/2- structure at Ex ≥ 10 MeV [see also 6Li(p, p): reaction 6]: see 7.8 (in PDF or PS) and (1974AJ01, 1984AJ01). For α + 3He correlations see (1987PO03). See also the General Table for 7Be located on our website at (nucldata.tunl.edu/NuclData/General_Tables/7be.shtml). For elastic and inelastic inclusive scattering cross sections at pα = 7.0 GeV/c see (1984SA39, 1987BA13). See also (1984IW01; astrophys.).
References to early theoretical work on 3He + 4He reactions are given in (1988AJ01). More recent theoretical studies include: an RGM study of the d + 5He cluster configuration (1991FU02); a potential description of cluster channels (1993DU02); inversion of phase shifts and 7Be bound-state energies to obtain potentials (1994CO08); a calculation of 7Be charge form factors (1987RO24); microscopic cluster theory (1987TA06); Glauber amplitude expansion calculation of σ(θ) (1988CH16, 1990LI11); a calculation of scattering lengths and astrophysical S factors (1988CH47, 1989CH34); a study of potentials deduced from phase shifts (1995MA37); and a multiconfiguration RGM calculation of reaction cross sections (1995FU16).
Angular distributions have been reported at Eα = 61.5 to 158.2 MeV (1982GL01) and 198.4 MeV (1985WO11) for the transitions to 7Be*(0 + 0.43). Cross section measurements at Eα = 160, 280, 620 MeV are reported in (2001ME13). See also (2001AU06). Thermonuclear reaction rates for this reaction calculated from evaluated data are presented in the compilation (1999AN35).
At low energies (Ep = 0.2 to 1.2 MeV) gamma transitions to the ground (γ0) and to the 0.43 MeV (γ1) states have been observed. The yield shows no resonance and the branching ratio remains approximately constant at 61 ± 5% to the ground state and 39 ± 2% to 7Be*(0.43): see (1974AJ01, 1984AJ01). Angular distributions of γ0 and γ1 have been studied at Ep = 0.50, 0.80 and 1.00 MeV (1987TI05). At Ep = 44.4 MeV, 7Li*(4.57) is strongly populated (1985HA05). See also (1983OS04), (1983HA1B, 1984BO1C, 1985CA41; astrophys.) and (1985BL1B).
In other work, γ angular distributions and γ-to-charged-particle ratios were measured for Ep = 40 - 180 keV and used to deduce astrophysical S factors (1992CE02). See also the measurements at Ep = 30 - 180 keV of (1993BRZQ). Measurements of thick-target yields and analyzing power versus θ were made with 80 keV polarized beams and used to deduce relative s-p wave contributions and astrophysical S factors (1996LA10). The slope of the astrophysical S factor was deduced from measurements at Ep = 80, 95 and 110 keV (1999KEZY). See also the cross section measurements at Ep = 0.8 MeV of (2000SK02). A compilation and review of Coulomb dissociation experiments of astrophysical significance is presented in (1996RE16). Reaction rates for Ep < 2 MeV were analyzed by (1997NO04). The primordial 6Li component was deduced. A compilation of charged-particle induced thermonuclear reaction rates is presented in (1999AN35). Cross section measurements at Ep = 0.8 MeV are reported by (2000SK02).
The previous review (1988AJ01) notes that measurements of elastic angular distributions have been reported for Ep = 0.5 to 600 MeV: see (1966LA04, 1974AJ01) and 6Li. Two resonances are reported at Ep = 1.84 and 5 MeV in the elastic yield [7Be*(7.21, 9.9)]. The parameters of the lower resonance are shown in 7.4 (in PDF or PS). The 5-MeV resonance has Γ ≈ 1.8 MeV and appears to also be formed by p-waves: γ2p is then 3 ± 2 MeV fm. A weak rise near Ep = 8 to 9 MeV may indicate a further level, 7Be* ≈ 13 MeV. A broad resonance at Ep = 14 MeV has also been suggested. Polarization measurements have been carried out for Ep = 1.2 to 800 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at Ep = 4 to 10 MeV (1986BE1H; p0) and 25 and 35 MeV (1982ROZT, 1983PO1B, 1983POZX; p0, p1). A phase-shift analysis for Ep = 0.5 to 5.6 MeV shows that only 2S, 4S and 4P are involved. The 4P5/2 amplitude resonates at Ep = 1.8 MeV, and the broad resonance at 5 MeV can be reproduced equally well by either 4P3/2 or 4P1/2: tensor polarization measurements are necessary to distinguish between the two: see (1974AJ01).
In more recent work, cross sections and analyzing powers were measured at Ep = 1.6 - 10 MeV (1989HA17), at Ep = 200 MeV (1990GL04) and at Ep = 0.4 - 2.2 MeV (1995SK01). Parameters for the Ep(lab) = 1.8 MeV resonance were measured by (1995SK01) (see 7.10 (in PDF or PS)). The depolarization parameter was measured at Ep = 72 MeV (1994HE11).
The reaction cross section for formation of 6Li*(2.19) has been measured for Ep = 3.6 to 9.40 MeV: a broad resonance indicates the presence of a state with Ex ≈ 10 MeV, Γ = 1.8 MeV, Jπ = (3/2, 5/2)-, T = 1/2. The cross-section and angular distributions of p2 (6Li*(3.56)) for Ep = 4.26 to 9.40 MeV are analyzed in terms of two Jπ = 3/2- states at Ex ≈ 10 and 11 MeV: see reaction 3. The total cross section for formation of 6Li*(3.56) decreases slowly with energy for Ep = 24.3 to 46.4 MeV. The total reaction cross section has been measured for Ep = 25.0 to 48 MeV (1985CA36). Kyy spectra at Ep = 50, 65 and 80 MeV, θ = 3° - 20°, are reported by (1987SA46). For the inclusive cross section at Ep = 200 MeV [back angles] see (1984AV07). See also the measurement of cross sections and analyzing powers for excitation of 6Li*(2.18, 3.56) at Ep = 200 MeV (1990GL04). Theoretical work on this reaction published since the previous review (1988AJ01) includes: a folding-model calculation to deduce halo effects (1992GA27); self-consistent calculation with matter-cluster dynamic model (1992KA06); a potential description study with a supermultiplet symmetry approximation (1993DU09); a description with a microscopic effective interaction (1993KO44); a consistent folding-model description (1993PE13); a calculation for (p, p) and (p, p') with Glauber-Sitenko diffraction theory (1994ZH28, 1994ZH34); an analysis with phenomenological microscopic optical potentials (1995GA24); a consistent analysis of the analyzing power puzzle (1995KA03); a continuum-continuum coupling analysis (1995KA07); a fully-microscopic analysis at Ep = 200 MeV (1997DO01); an RGM study of a 5/2- resonance (1997IG04); a study of shell-model structures observed in proton and electron scattering (1997KA24); and a microscopic-model analysis for Ep = 65 MeV (1998DO16).
The yield of neutrons increases approximately monotonically from threshold to Ep = 14.3 MeV: see (1974AJ01). The transverse polarization transfer, DNN (0°), for the g.s. transition has been measured for Ep = 30 to 160 MeV: see (1984TA07, 1986TA1E) and 6Be. Analyzing-power measurements are reported at Ep = 50 and 80 MeV (1987SA46) and at 52.8 MeV (1988HE08) [Ky'y (0°) = -0.33 ± 0.04; also Kz'z]. See also (1986MC09; Ep = 800 MeV) and (1984BA1U, 1986RA21, 1986SA1Q). For more recent work see the discussion on this reaction under 6Be.
Thermonuclear reaction rates and the astrophysical S-factor have been derived from the low-energy (Ep < 0.7 MeV) cross section measurements: S(0) ≈ 3.1 MeV b: see (1974AJ01, 1979AJ01, 1984AJ01). At higher energies the cross section exhibits a broad, low maximum near Ep = 1 MeV and a pronounced resonance at Ep = 1.85 MeV (Γ < 0.5 MeV). No other structure is reported up to Ep = 5.6 MeV. Measurements between Ep = 0.4 and 3.4 MeV show that the polarizations are generally large and positive: see (1974AJ01).
Angular distributions have been reported for Ep = 0.15 to 45 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at 47.8, 53.5, 58.5 and 62.5 MeV (1984NE05). For other early work see references cited in (1988AJ01). More recently, measurements of analyzing power versus Ep for Ep = 180 - 280 keV were reported by (1991BU14). Tests of isotopic dependence of electron-screening effects on the astrophysical S factor were reported for Ecm = 10 - 1004 keV (1992EN01, 1992EN04). See also: an analysis of S-factor data for Ecm = 10 - 1000 keV (1992SO25); a study of atomic screening and other small effects in reaction rates (1997BA95); a study of screening effects for solid targets (1997BO12); an optical-model formulation and S factor calculation for E = 10 - 100 keV (1997KI02); a study of reaction rates and the primordial 6Li component (1997NO04); and a study of R-matrix parameterization for Ecm < 1 MeV (1998AN18). Thermonuclear reaction rates for this reaction calculated from evaluated data are presented in the compilation (1999AN35).
Angular distributions of the n0 and n1 groups have been measured at Ed = 0.20 to 15.25 MeV: see (1974AJ01, 1979AJ01). The n1 - γ correlations are isotropic, indicating Jπ = 1/2- for 7Be*(0.43). Broad maxima are observed in the ratio of low-energy to high-energy neutrons at Ed = 4.2 and 5.1 MeV [7Be*(6.5, 7.2), Γcm = 1.2 and 0.5 MeV, respectively]: see (1966LA04). See also 8Be in (1988AJ01) and (1988KO1C).
Measurements at E < 1 MeV and determination of the astrophysical S-factor as well as studies of the (d, n)/(d, p) ratio are described in (1993CZ01, 1997CZ04). Cross section measurements and S-factor determinations at Ed = 24 - 111 keV are reported in (2001HO23). A calculation of the (d, n)/(d, p) branching ratio and discussions of the rate of Coulomb-induced predissociation is presented in (1990KO26). Cross sections for E < 1 MeV were calculated and reaction rates were deduced by (2001VO02). Calculations of radiated power vs. plasma temperature in controlled fusion are described in (1999HA50). See also (1996BO27, 1997NO04).
The reaction was used by (1998NA14) to separate ΔS = 0 and ΔS = 1 transitions through coincidence measurements of γ-rays from the 7Be 0.43 MeV state.
Forward-angle differential cross sections have been measured at Eπ+ = 20 MeV (1987IR01; also at 155° and 166°), at 33.5, 41.1, 48.7 and 58.8 MeV (1985IR01, 1985IR02), 70 to 180 MeV [see (1984AJ01)] and from 300 to 550 MeV (1988RO03).
The excitation energy of 7Be*(0.43) is 429.20 ± 0.10 keV, τm = 192 ± 25 fsec: see (1979AJ01). Angular distributions of n0 and n1 have been reported at Ep = 1.9 to 119.8 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at 200, 300 and 400 MeV (1987WAZT; n0+1). 7Be*(4.55, 6.51, 7.19, 10.79) have also been populated: see (1974AJ01, 1979AJ01). The ratios of σ1/σ0 (7Be*(0.43)/7Beg.s.) have been measured at 24.8, 35 and 45 MeV and yield the ratio of spin-flip to non spin-flip strength |V0τ/Vτ|2 (1980AU02).
Cross section measurements related to neutron production targets and detector efficiency calibration include (1987TE04, 1988HE08, 1989AM03, 1989BY02, 1989GU13, 1990BR24, 1990DR10, 1990TA11, 1992AM03, 1992DA20, 1997TA03, 1998KA20, 1998MA49, 1999BA73, 1999NA02, 1999NA15). Measurements or analyses of Gamow-Teller transition strength are reported in (1987TA13, 1989RA09, 1990RA08, 1994SA43). See also (1987HE22, 1987OR02). An analysis of neutron spectra for Ep = 120, 160 MeV and deduction of Gamow-Teller matrix elements are described in (2001GO25). A compilation of analyzing-power data is presented in (1987TA22). For studies of quadrupole excitation see (1994RA23, 1994WA22) and (1995YA12). Application-related measurements are described in (1987RA23, 1988BO33, 1989CR05, 1995RI14, 1996BB13, 1996SH29, 1996TA23, 1997DE54, 1997UW01, 1997ZH35, 1999LE16, 1999NA02, 1999SA16, 1999SH16). See also the astrophysical-related analysis in (1989BU10). See also the analysis (1998IO03) of 647 and 800 MeV data, and the study of the isovector part of optical potentials for 35 MeV (p, n) data (1998JOZW, 2000JO17). For earlier work see (1988AJ01).
See (1987AL10; E(7Li) = 65 MeV).
Angular distributions of t0 and t1 have been measured at E(3He) = 3.0 to 4.0 MeV and at E(3He) = 33.3 MeV: see (1974AJ01, 1984AJ01). The width of 7Be*(4.57), Γcm = 175 ± 7 keV: see (1974AJ01). See also 10B in (1988AJ01).
This reaction has been studied at E(6Li) = 14, 25 and 35 MeV/A. 7Be*(0, 0.43) are strongly populated and 7Be*(4.57, 7.21) are also evident. At the highest energy the reaction mechanism is predominantly one-step (1986AN29, 1987WI09). See also 6He and references cited in (1988AJ01). See also reaction 12.
Neutron yields have been measured with backscattered laser photons (1999TOZZ).
Cross sections were measured at En = 28 - 68 MeV (1998DU06).
Angular distributions of tritons have been measured at Ep = 43.7 and 46 MeV [see (1979AJ01)] and at 50 and 72 MeV (1984ZA07; t0+1, t2). The 11-MeV state has Ex = 11.01 ± 0.04 MeV, Γ = 298 ± 25 keV, Jπ = 3/2-; T = 3/2 [the Jπ; T assignments are based on the similarity of the angular distribution to that in the (p, 3He) reaction to 7Li*(11.13)]: see (1979AJ01).
Angular distributions have been studied for Ep = 2.8 to 7.0 MeV [see (1974AJ01)] and for 18 to 45 MeV (1986HA27; α0, α1, α2; see for spectroscopic factors). Ex of 7Be*(0.43) = 428.89 ± 0.13 keV (1979RI12). See also 11C in (1985AJ01), (1983DO07) and (1988KOZL; applied).
More recently several studies at astrophysical energies have been reported. They include measurements of σ(θ) and σ(E) at Ep = 120 - 480 keV (1991YO04) and at Ep = 37 - 120 keV (1993KNZZ); measurements of electron screening corrections at Ecm = 17 - 134 keV and determination of S(E) (1993AN06); direct-model calculations of astrophysical reaction rates (1996RA14); and a calculation of small-effect corrections in fusion reactions (1997BA95). A calculation of 7Be level population intensities at Ep = 45 MeV is described in (1992KW01). For application-related measurements see (1990BO15, 1995RI14, 1995SJ01, 1999SA16).
Yields of fragments, observed in protons at Ep = 1 GeV incident on 12C, were measured by (2000ANZX). A calculation of spectroscopic amplitudes in an intermediate coupling model analysis is reported in (1987KW03). See also the discussion under 6Li.
Differential cross sections were measured at Ed = 78 MeV in a study of 5-nucleon simultaneous transfer (1996JA12). Spectroscopic amplitudes were calculated in an intermediate coupling model by (1987KW03). See (1995CH69) for a measurement of 12C(d, 7Be)7Li, and see 7Li in this review.
Angular distributions involving 7Be*(0, 0.43) have been reported at E(3He) = 25.5 to 70 MeV [see (1979AJ01, 1984AJ01)] and at E(3He) = 33.4 MeV (1986CL1B; also Ay). See also (1986RA15) and see discussions of 12C(3He, 7Be)8Be [reaction 44] under 8Be in (1988AJ01).
At Eα = 42 MeV, angular distributions have been measured involving 7Be*(0, 0.43) and 9Beg.s.: see (1974AJ01). Angular distributions have also been measured at Eα = 49.0 and 80.1 MeV (1984GO03). An angular distribution and DWBA analysis for 12C(α, 7Be)9Be is reported in (1991GL03).
Cross sections for 7Be produced by protons and neutrons at E = 10 - 10,000 MeV were analyzed (2000NA34) and atmospheric production rates were deduced.
7Be yields were measured with 250 - 1050 MeV bremsstrahlung photons on O, Al, Cr, Cl, CO targets (1998SH18).
Angular distributions have been reported at E(3He) = 25.5 to 70 MeV to 7Be*(0, 0.43) and to various states of 12C: see 12C in (1985AJ01). See also (1986BA89). A measurement of σ(θ) for 16O(3He, 7Be)12C at E(3He) = 41 MeV is reported in (1987RA37). See also the calculation for E(3He) = 60 MeV in (1995MA57).
Angular distributions have been studied at E(7Li) = 50 MeV involving 7Be*(0, 0.43) and various states of 16N (1984CO20, 1986CL03). See also 16N in (1986AJ04) and (1984BA53). A compilation and analysis of data for E(7Li) = 78 MeV is presented in (1989GA26).
Cross sections have been calculated for E(8B) = 25.8, 415 MeV (1999SH20).
Production cross sections for 7Be for protons with Ep = 0.66, 1.0 and 8.1 GeV incident on separated tin isotopes 112Sn, 118Sn, 120Sn and 124Sn were measured by an activation technique (1998DAZI).
Production cross sections were measured for Ep = 65 - 2600 MeV (2001GL05).
Yields of 7Be from photon-induced 232Th fission were measured by (1998KAZL).