(See Energy Level Diagrams for 9Be)
Pion capture and reactions:(ME67Q, MI67E, BA68B, ER68C, NO68A, WI68B, BU69B, CA69A, CH69E, KO69D, MO69H, BA70CC, BE70C, CA70M, ER70, GO70M, CA71, CA71I, FA71E, GO71P, MA71B, RE71I, SE71, AB72H, BE72J, BU72R, HU72, MA72A, SA72A, SE72E, BA73J, BA73N, DI73C, GA73A, HS73, HS73A, JA73I, NY73, OS73A, PE73B, SQ73, UL73).
Other topics:(CO65I, VO65A, CH66K, DO66E, HA66F, HE66D, WI66E, BA67JJ, CA67L, CH67K, MO67M, KO68K, GO68, GU69D, LE69A, CO70C, GR70K, KA70F, PA70F, PE70F, SA70C, DA71D, ER71B, AN72B, CA72P, CH72E, FR72F, HA72AA, LE72, PN72, RA72J, TA72E, TU72A, BA73HH, BE73S, CL73G, JU73B, KO73K, KU73D, MA73FF, RA73H).
The 0° differential cross section for reaction (a) increases monotonically between Et = 0.10 and 2.4 MeV (SE60E, VA61I, SE62A) except for a resonance at Et = 1.875 MeV (9Be* = 18.938). The excitation function for 8Li (reaction (b)) increases monotonically for Et = 0.275 to 1.000 MeV (CI72A). In the range Et = 2.0 to 6.8 MeV, a broad peak [Γ ~ 1.3 MeV] is observed at Et = 4.57 MeV [Ex = 20.73 MeV] (AB73D). For reactions (c) and (d) see (66LA04). For reaction (e) see (LA66A, BE67T). See also 5He, 7Li and 8Li.
For Ed = 0.1 to 1.1 MeV, a resonance in the yield of capture γ-rays is observed at Ed = 362 ± 3 keV (WO65), 361 ± 2 keV (IM65), corresponding to 9Be*(16.977) with Γcm < 0.47 keV. The small width of this state and its energy correspondence with 9Li*(2.69) argue for T = 3/2 (WO65). The angular distribution of the γ-rays to 9Be(0) is isotropic to within 7% (IM65). The branching ratios to 9Be*(0, 1.7, 2.4, 2.8, 3.1, 4.7) are 100/8.5 ± 4.3/10.6 ± 5.3/ - / < / = 4.5/9.6 ± 4.8 (IM65), 100/11.8 ± 0.6/3.3 ± 0.7/13.3 ± 4.2/ - /12.9 ± 1.3 (SC71M). The Ex and Γ of 9Be*(2.8, 4.7) are 2.82 and 1.7 MeV, and 4.64 and 0.95 MeV, respectively. The character of the decay suggests (1/2)- for the second T = 3/2 state [9Be*(16.98)] and is consistent with Jπ = (1/2)- for 9Be*(2.8) (SC71M). See also (SN68B).
The yield of neutrons has been measured for Ed = 0.2 to 4.8 MeV (BA52, SL57, IM65), 0.86 to 1.33 MeV by (NU69A), 3 to 8 MeV by (KE67K: yield of neutrons to 8Be*(16.6, 17.6, 18.1), at one MeV intervals) and 5 to 19 MeV by (WE73P). Polarization measurements have been reported by (MO71P, MO73I: Ed = 0.64 MeV; n0) and (TH70E: Ed = 2.5 to 3.7; n0, n1). See also (SE72C; theor.) and (66LA04). Resonances in the yield of neutrons are observed at Ed = 0.36, 0.68, 0.98 and (1.8) MeV: see Table 9.3 (in PDF or PS).
The yield of α-particles has been measured for Ed = 0.2 to 0.3 MeV by (MA64DD), 0.6 to 2.0 MeV by (FR71), 0.7 to 1.6 MeV (DE69R) and 0.7 to 3.0 MeV by (PA63E). The excitation function for reaction (b) shows resonances at Ed = 0.75 and 1.00 MeV (FR71), 0.78 and 1.08 MeV (DE69R), as well as a broad structure at Ed = 2.5 MeV (PA63E). Also reported are α-particles from reaction (a) associated with 8Be*(11.4, 16.6, 16.9); the α-particles from the decay of 8Be*(11.4) seems to show resonance behavior at Ed = 0.7, 1.0 and 1.75 MeV. It is not clear whether the α-particles corresponding to 8Be*(16.6) show resonance at Ed = 2.5 MeV or whether the 8Be*(16.9) α-particles are appearing at this point (PA63E).
A study of the BL coefficients of the angular distributions of the α0 group for Ed = 0.45 to 2.0 MeV and of the α-α angular correlation coefficient, together with a re-analysis of the (d, d0) data of (FO64B), lead to assignments of 3/2- and (3/2, 5/2)+ for 9Be*(17.30, 17.50). The analysis also requires a (3/2, 5/2)- state at lower excitation energy and a (3/2, 5/2)+ state at higher energy (DE72P). See also (MO73I) for an interpretation of results from reaction (a).
A kinematically complete study of reaction (c) at Ed = 1.0 MeV shows that the yield is dominated by sequential decay via 8Be*(2.9) and 5Heg.s.. There is evidence also for the involvement of 9Be*(17.50) [measurement of relative yield for Ed = 0.9 to 1.1 MeV]: J = 3/2 is suggested (HE73I). See also 5He, 8Be and (AS66, KE67K, VA67D, WI68I, HE73D). See also (NU66, PO66J, BE67T, WI67F, DA68O, DA71H, BR72, SU72C, DA73I).
The yield of 8Li has been measured for Ed = 0.4 to 4 MeV (BA52, BA54A, BE56G, KA60), for Ed = 0.62 to 1.97 MeV by (SC72L) and for Ed = 2.0 to 7.0 MeV by (AD73D): observed resonances are displayed in Table 9.3 (in PDF or PS). The yield of 0.98-MeV γ-rays [from 7Li(d, p)8Li*] rises monotonically from Ed = 1.9 to 3.3 MeV (CH62B).
The total cross section at the Ed = 0.77 MeV resonance is 202 ± 9 mb (SC72L). Earlier values were 176 ± 15 mb (KA60) and 211 ± 15 mb (PA66K). We adopt 205 ± 8 mb. This cross section is important since the 7Be(p, γ)8B data are normalized to it and the S-factor is of interest in relation to the solar neutrino problem: see (PA68G). See also 8Li.
The upper limit for the relative partial width for elastic scattering at Ed = 0.36 MeV (9Be* = 16.98), Γd0/Γγ is 400 (IM65).
The elastic scattering, at Ed = 0.4 to 1.8 MeV, shows a marked increase in cross section for Ed = 0.8 to 1.0 MeV [perhaps related to 9Be*(17.30) and a conspicuous anomaly at Ed = 1.0 MeV, due to p-wave deuterons [9Be*(17.50)] (FO64B) [and discussion in (DE72P) and in reaction 5]. The elastic scattering cross section (θcm = 162°) decreases monotonically for Ed = 10.0 to 12.0 MeV (BI71F). See also 7Li.
The cross section for reaction (a) rises from threshold to 95 mb at Ed = 2.4 MeV and then more slowly to ~ 165 mb at Ed = 4.1 MeV (MA55D). The t0 yield curve (θlab = 155°) decreases monotonically for Ed = 10.0 to 12.0 MeV (ZA71B). See also 6Li. For reaction (b) see 6He.
Observed proton groups are listed in Table 9.4 (in PDF or PS) (CO68D). See also Table 9.5 (in PDF or PS) in (66LA04) for a listing of the older work. Angular distributions have been measured for the protons to 9Be*(0, 1.7, 2.4, 3.1) at E(3He) = 0.90 to 1.10 MeV (ST71R: not to 9Be*(1.7)), 2.2 to 3.2 MeV (SA69I, LI72L) and at E(3He) = 10 MeV (DI70, DI70K), and for the group corresponding to 9Be*(14.39) at E(3He) = 10 MeV (AD71A). The characteristics of the neutron and γ-decays of 9Be states are displayed in Tables 9.5 (in PDF or PS) and 9.6 (in PDF or PS) (GR65F, LY65, CH66A, CO68E, KR68, AD71A, AD72A, MC72B). See also (MA64II, LI70R), (BA69GG), (SA68D, TA69Q, LK70, WE71R; theor.), 8Be and 10B.
At E(7Li) = 2.9 MeV α-particle groups are observed corresponding to 9Be*(0, 1.7, 2.4, 3.1, 11.9 ± 0.2 [Γ = 0.5 ± 0.1 MeV]) (ME64A). Angular distributions of the α0 group have been measured at E(7Li) = 3.78 to 5.95 MeV (KI67A). At E(6Li) = 26.0 MeV and E(7Li) = 30.3 MeV the excitation of 9Be*(0, 11.8, 13.8, 15.2, 17.8, 21.0) is reported (GL71). See also (CH67Q, DA68N, OG70) and (RO66F, RO66H, RO66Y, RO69J; theor.).
See (LK70; theor.).
9Li decays by β- emission with τ1/2 = 176 ± 2 msec to 9Be*(0, 2.43, 2.78): see 9Li and Table 9.7 (in PDF or PS). 9Be*(2.43, 2.78) are neutron unstable. The probability that 9Li decays to these two states is 0.35. The branching ratio for the 9Be*(2.43) --> 8Be(0) + n decay is (6.4 ± 1.2)%. 9Be*(2.78) decays mainly to 8Be(0) + n. The assignment Jπ = 1/2- to 9Be*(2.78) derives from the allowed nature of the 9Li decay, and the large value of θ2p [0.48 ± 0.06] which is in agreement with the shell-model prediction that the 1/2- state should decay mainly by p-wave neutron emission to 8Be(0): if Jπ = 3/2- this decay branch should be small (CH70, CH70W). See also (AL63F, SC65E, RO73T) and (MA69H) for a general discussion of the problems in identifying the parameters of the low-lying states of 9Be.
The photoneutron cross section has been measured from threshold to 320 MeV: see Table 9.6 (in PDF or PS) in (66LA04). A sharp peak occurs 6 keV above threshold (BE67I) [but see discussion in (BA68K)] with σmax = 1.6 mb. The cross section then decreases slowly to 1.2 mb at Eγ = 40 keV (BE67I). A satisfactory fit to the cross section is obtained with a one-level approximation of R-matrix theory (BA68K). Peaks in the cross section of (γ, xn) are reported corresponding to Ex = 2.43 ± 0.03, 3.00 ± 0.03, 19.00 ± 0.03, 21.50 ± 0.05 and 23.9 ± 0.1 MeV, and there is some indication also of structure at Ex = 9.1, 10.8, 12.8 and 14.8 MeV (HU73A). See also (CO66E, TH72I) and (66LA04) for references to earlier work.
The total absorption cross section has been measured for Eγ = 10 to 155 MeV by (AH72A, AH73)†. The integrated cross section for Eγ = 16 to 29 MeV is 53 MeV · mb (AH72A). (DO69I) report an integrated cross section of 156 ± 15 MeV · mb for Eγ = 10 to 29 MeV and resonant structure at Eγ = 11.8, (13.5), 14.8, (17.3), (19.5), 21.0, (23.0) and (25.0) MeV (DO69I). Fine structure is reported at Eγ = 20.47 ± 0.04 and 20.73 ± 0.04 MeV (TE64C). See also (WY65).
† We are deeply indebted to E.G. Fuller for his very helpful remarks on the 9Be + γ processes.
See (66LA04) for a discussion of the early evidence on 9Be levels from reaction (a). See also (TH66B, GL67B, AD68D, KA68K, KA71A, BU72C, CR72C), (SH67H) and (BO65R, MA65Y, BO67I, BO67W, BO68W, MA68Z, MA68JJ, PA68T, AU69C, SA70H, TA72E, SL73A; theor.).
The yield shows structure in the energy region corresponding to the 9Be levels at 17 - 19 MeV (CL62C) followed by the giant resonances at Eγ ~ 23 MeV (CL62C: σ = 2.64 ± 0.30 mb). (DE66B) report structure attributed to eleven states of 9Be with 18.2 < Ex < 32.2 MeV. Integrated cross sections have been obtained for each of these resonances, and over different energy intervals for protons leading to 8Li*(0 + 0.98, 2.26 + 3.21, 9.0, 17.0) (DE66B). Angular and energy distributions of photoprotons in various energy intervals have been studied by many groups: see (66LA04) and (VO66, AD68D). See also (KO65C, AN69G, AN71F, DO73K), (SH67H, CO73T) and (MA68JJ; theor.).
The integrated cross sections are reported to be 1.0 ± 0.5 MeV · mb (Eγ = 21 --> 33 MeV) for reaction (a) to 7Li*(0 + 0.4) and 0.6 ± 0.3 MeV · mb (Eγ = 25 --> 33 MeV) for reaction (b) to 6Li(0). The total integrated cross section for [(γ, p) + (γ, pn) + (γ, d) + (γ, t)] is given as 33 ± 3 MeV · mb by (DE66B), who also report resonances in the (γ, d) and (γ, t) cross sections corresponding to 9Be*(26.0 ± 0.2) and 9Be*(32.2 ± 0.3), respectively. See also (66LA04) and (VO66, AD68D, AN69G, AN71F, AN72C) for reaction (a) and (VO66, AN72I) for reaction (b). See also (MA68JJ; theor.).
< r2 >1/2 = 2.46 ± 0.11 fm, Q = 6.5+0.9-0.6 fm2, b = 1.5+0.3-0.2 fm [b = oscillator parameter] (BE73C);
< r2 >1/2 = 2.519 ± 0.012 fm, Q = 6.4 ± 2.4 fm2 ((JA72I) and K. de Jager, private communication to J.C. Bergstrom);
< r2 >1/2 = 2.43 ± 0.08 fm, Q = 3 fm2 (BE69CC).
The elastic scattering of electrons has been studied at Ee up to 700 MeV: see (66LA04), the references listed above, and (VA65H, RA66C, BE69V). Magnetic elastic scattering at θ = 180° gives indication of both M1 and M3 contributions [(GR65L, RA66C): see (KU68A)].
Inelastic scattering reveals a number of levels: Table 9.8 (in PDF or PS) displays the parameters of these states (BA60N, ED62A, NG63, NG65, CL66, AR67A, CL68A, VA68D, BE73C, SL73A). See also (66LA04) for a discussion of the earlier work.
Electron bremsstrahlung has been measured at Ee = 1.0 and 2.0 MeV by (RE68C). See also (PE66A), (GO68F) and (GR65O, NE65E, DE66D, KU66C, KA67E, ST67K, WA67A, WA67M, JA68N, KU68F, BO69D, BO69E, VI69, BE70Y, TI70B, GO71P, BL72G, BO72B, DR72A, OK73; theor.).
The neutron spectrum at En = 3.7 MeV is consistent with the excitation of 9Be*(0, 1.7, 2.4, 3.1) with subsequent neutron decay of the two higher states (HU57C, WA58B). About 1/2 of the inelastic processes involve 9Be*(2.4) for En = 2.6 to 6.0 MeV; that level decays only 12 ± 5% via 8Be(0) + n (MA59B). See Table 9.5 (in PDF or PS). At En = 14 MeV 9Be*(6.8) appears to be excited (JE63D). Angular distributions have been measured at En = 14 MeV (AN58, NA58, RO68O, RO69R; n0, n2). See also 10Be, (66LA04) and (BO65K, FR65B, GO65H, AM66B, BO66A, BO66S, BO67, DR70) and (WA69C; theor.).
The elastic scattering has been studied at many energies for Ep = 5 to 725 MeV: see (66LA04). More recent angular distribution measurements have been carried out at Ep = 2.009 to 2.099 MeV (SU71A; p0), 6.36 and 6.48 MeV (VA71K; p1), 13.0, 14.0, 15.0, 21.35 and 30.3 MeV (VO73D; p0, p2), 17.0, 21.0, 25.0, 29.1 (MO73E; p0, p2 and p to 9Be*(3.1)), 33.6 MeV (KU70G; p0), 46 MeV (VE67B, SA67H; p0, p2 and p to 9Be*(11.3, 14.4, 16.7, 17.5)), 49.75 MeV (MA71G, MA71Q; p0, p2 and p to 9Be*(6.4)), and 100 MeV (MA66LL, LI68K; p0, p2 and p to 9Be*(4.7, 6.8)). The elastic angular distributions show pronounced diffraction maxima characteristic of the optical model. See (MO73E) for a discussion of optical model parameters. (VO73D), in coupled channels analysis, find that a quadrupole-deformed optical model potential with a deformation parameter β = 1.1 [see also (SA67H)] provides an improved description of the elastic data and a good fit to the p2 data [to 9Be*(2.4)].
The structure corresponding to 9Be*(1.7) is asymmetric: the line shape peaks 25+15-11 keV above the threshold for 8Be + n (TU70B): see also the discussions in (SP60, JE71D) and in (66LA04). The energy of 9Be*(2.4) is given as 2433 ± 5 (BR51F), 2434 ± 5 (BO56F), 2432 ± 4 (GO55E), 2430 ± 5 keV (SP60). 9Be*(3.1) has a width of 250 ± 5 keV (SP60): Ex = 3.03 ± 0.03 MeV (BO56F), 3.04 ± 0.05 MeV (SP60), Jπ = 3/2+, 5/2+. Higher states are observed at Ex = 4.8 ± 0.2, 6.76 ± 0.06 [Jπ = 1/2+, 5/2+, 7/2+ (but see below), Γ = 1.2 ± 0.2 MeV], 7.94 ± 0.08 (Γ ~ 1 MeV), 11.3 ± 0.2 MeV (Γ ~ 1 MeV), 14.4 ± 0.3 (Γ ~ 1 MeV), 16.7 ± 0.3, 17.4 ± 0.3, 19.0 ± 0.4, 21.1 ± 0.5 and 22.4 ± 0.7 MeV [the five highest states are all broad] (BE56A, HA65). See also Table 9.8 (in PDF or PS) in (66LA04). (JA65N) reports for 9Be*(2.4, 6.8) B(E2(uparrow)) = 49 ± 6 and 24 ± 4 fm4 and Γ(E2(downarrow)) = 0.0025 and 0.10 eV, respectively. The strong population of 9Be*(2.4, 6.8) in this reaction is consitent with the assumption that they have Jπ = 5/2- and 7/2-, respectively, and are members of the ground state K = 3/2- band: see discussion in (66LA04). See also (MA66LL).
The summed proton spectrum (reaction (a)) shows two peaks with Q = -16.4 ± 0.3 and Q = -25.4 ± 0.5 MeV, corresponding to removal of a p-proton and an s-proton respectively, and a third peak of uncertain assignment with Q = -32.3 ± 0.6 MeV (probably due to unresolved states) (TY66: Ep = 460 MeV). See also (66LA04), (WA66I, PE68D), (BE65U, JA66, JA66G, BE67DD, JA67E, KO67Q, JA68, KO69M; theor.) and 8Li. For reaction (b) see (66LA04) and (KO73D). Reaction (c) is characterized by a sequential mechanism at low energies and by a quasi elastic scattering mechanism at higher energies. At Ep = 26.0, 35.0, 46.8 and 57 MeV the data are consistent with quasi free scattering of the incident protons by zero-momentum α-particle clusters in 9Be: the probability of finding such clusters at these four energies is determined to be 0.166, 0.099, 0.124 and 0.09, respectively (RO68L, QU70C, QU72). See also (TA67G, YA69, GO70F, WO73), (HO69BB, GA71I) and (HO73R; theor.).
Elastic scattering has been studied at many energies in the range Ed = 7.8 to 27.7 MeV: see (66LA04). Elastic angular distributions are also reported for Ed = 1.1 to 2.5 MeV (MA68S), 4.5 to 6.0 MeV (PO70B), 5.00 to 7.00 MeV (DJ71), 11.8 MeV (FI67E; also d2), 12.8 MeV (VA73C; d1), 13.6 MeV (VE68A, VE70B, MA72V), 14.35 MeV (NG66A; also d2), 15.0 MeV (AR69I), 15.8 MeV (CO66J; also d2) and 410 MeV (BU60J; forward angles). For optical model parameters see discussions in (CO66J, FI67E).
Inelastic deuteron groups have been observed to 9Be*(1.7, 2.4, 3.1, 4.7, 6.8): see (66LA04). (KR68) report Ex = 2431.9 ± 7.0 keV and 3040 ± 15 keV [Γ = 294 ± 20 keV]. See also (ST63B, VE69D, EL70F, ZW73; theor.) and 11B.
Angular distributions of elastically scattered 3He particles have been obtained at E(3He) = 4, 6, 8, 10, 15 and 18 MeV (PA69E), 6.0 and 8.0 MeV (EA67), 13.2, 20.4, 22.2 and 27.0 MeV (BU72N), 22.7 and 32.3 MeV (AR65A), and 217 MeV (WI73F). See also (BA70KK). For optical model parameters see discussions in (BU72N, WI73F). At E(3He) = 39.8 MeV inelastic 3He groups are observed to 9Be*(1.7, 2.4, 3.1, 4.7, 6.8, 14.4) (BA68KK, BA69F). See also (HO68F, PA68Q, HO69Y; theor.), (66LA04) and reaction 28 in 6Li.
Elastic scattering has been studied at many energies for Eα = 9.5 to 48 MeV: see (66LA04). Recent measurements of the angular distributions of α0 are reported at Eα = 8.76, 9.27 and 10.13 MeV (BR67J), 28.5 MeV (FU67I; also α2, and partial angular distributions for α1 and α3) and 104 MeV (HA69E, HA70Y, DE72B). See (DE72B) for a discussion of optical model parameters. The structure (5He + α) for 9Be is found to be much more probable than (6Li + t): the ratio of the spectroscopic factors is about 30 (DE72B).
Inelastic groups have been observed to 9Be*(1.7, 2.4, 3.1, 6.8, 11.3): see (66LA04). The angular distribution of the group corresponding to 9Be*(1.7) is consistent with Jπ = 1/2+ (LU64: Eα = 18.4 MeV). The angular distributions for α2 are consistent with l = 2 (Jπ = (1/2, 5/2, 7/2)- (SU58A: Eα = 48 MeV) and (FU67I: Eα = 28.5 MeV). Analysis based on the rotational model leads to a deformation coefficient β2 = 0.46 (BL59C), 0.34 ± 0.01 (GR64). See also (GR66H, GR66I, LI68G, WO70, DM72, RA72L).
The summed α-spectra from reaction (b) show a peak corresponding to quasi-elastic scattering leaving 5He in the ground state. The angular distribution peaks at the angle corresponding to a zero-momentum α-cluster. The probability of formation of such clusters is 7+13-5% (PI69C, PI70C: Eα = 55 MeV). See also (YA65, YA68D, DO69A, DO69B) and 5He. The reaction cross section has been measured at Eα = 42.8 and 49.2 MeV by (GU71C).
Elastic scattering angular distributions have been obtained at E(12C) = 12, 15, 18 and 21 MeV. The neutron spectroscopic factor for 9Be is 0.84 (BA70W).
Forward angular distributions have been obtained at Ed = 15.0 MeV for the tritions to 9Be*(0, 1.7, 2.4, 3.1). The ground state transition is well fitted by l = 1. The transition to 9Be*(1.7) [Γ ~ 165 ± 25 keV] is consistent with Jπ = 1/2+, that to 9Be*(2.4) is quite well fitted with l = 3 [Jπ = 5/2-], and that to 9Be*(3.1) [Γ = 280 ± 25 keV] is consistent with l = 2. No other narrow states are seen up to Ex = 5.5 MeV (AU70C).
A good fit to the angular distributions of the deuterons to 9Be*(0, 2.4) has been obtained at En = 14.4 MeV, using DWBA. The spectroscopic factors are in close agreement with shell-model predictions (VA65D). See also (GO66N), (WE66E, MI71K), (66LA04) and 11B in (75AJ02).
The summed proton spectrum at Ep = 460 MeV yields Q = -6.7 ± 0.5, -11.9 ± 0.5, -17.1 ± 0.6 (all l≠ 0) and Q = -30.5 ± 0.6 MeV (l = 0) (TY66). See also (BE65U, JA66, JA66G, JA67E, KO67T, JA68; theor.), 10B and (66LA04).
Angular distributions of the 3He groups corresponding to 9Be*(0, 2.4) have been measured at Ed = 11.8 MeV (BA66S, FI67E: Sexp = 0.76 and 0.66, respectively) and at 28 MeV [(IN71C); (GA68H: ground state only)]. The data are very similar, as predicted, to those obtained in the mirror reaction: see reaction 12 in 9B. See also (SY65, WA71, WA72).
At Et = 12.9 MeV α groups are observed to the ground state of 9Be and to excited states at Ex = 1.75 ± 0.03, 2.43, 3.02 ± 0.04 [Γ = 320 ± 60 keV], 11.27 ± 0.04 [Γ = 530 ± 70 keV], (14.4) [Γ ~ 800 keV], 14.39 and 16.67 MeV. The T = 3/2 state 9Be*(14.39) is very weakly populated [~ 5% of intensity of α2]. The angular distribution of the α2 group shows sharp forward and backward peaking. The α0 group is not peaked in the backward direction (AJ68A). A study at Et = 1.0 to 3.2 MeV finds Ex = 1.750 ± 0.025 MeV, Γ = 220 ± 8 keV. The angular distribution of the corresponding α-group has been determined at Et = 2.5 MeV (GE71).
The ground state angular distribution has been measured at E(14N) = 27.5 MeV (NE62B).
The angular distribution of the ground state group has been measured at En = 14.4 MeV (MI70E).
At Ep = 45 MeV angular distributions are reported for the 3He ions corresponding to 9Be*(0, 2.4, 11.8, 13.8, 14.39 [T = 3/2], 15.96 ± 0.04 [T = 1/2]). In addition one or more states may be located at 9Be*(15.13). It is suggested that 9Be*(11.8, 13.8, 15.96) are the Jπ = 3/2-; T = 1/2 analogs to 9B*(12.06, 14.01, 16.02) (HA71C). Angular distributions are also reported at Ep = 40 MeV (KA71D; α0, α2). The intensity of the group to 9Be*(3.1) is ~ 1% of the ground state group (KA71D). For reaction (b) see (BA64BB).
Alpha groups are reported corresponding to 9Be*(0, 1.7, 2.4, 3.1). The width of 9Be*(1.7): Γcm = 224 ± 25 keV (KA58A, PU66A). The energy of 9Be*(2.4) is 2422 ± 5 keV (VA51), 2431 ± 6 keV (EL54), 2424 ± 5 keV (BO56F). The 5/2+ state is at Ex = 3.02 ± 0.03 MeV (LE55D), 3.05 ± 0.03 MeV (BO56F): Γcm = 257 ± 25 keV (KA58A, PU66A).
The ratio of the γ-decay width to the total width, Γγ/Γ, of 9Be*(2.4) is (1.16 ± 0.14) x 10-4. Since Γγ is known from (e, e') [see Table 9.8 (in PDF or PS)], Γ = 1.03 ± 0.18 keV. For 9Be*(1.7), Γγ/Γ < / = 2.4 x 10-5 (PU66A).
Reaction (b), at Ed = 10.4 and 12.0 MeV, proceeds via 9Be*(2.4) and to some extent via 9Be*(3.1, 4.7) and possibly some higher excited states. The dominant decay of 9Be*(2.4) is to 5He(0) + α while 9Be*(3.1, 4.7) decay to 9Be(0) + n (RE71K). It should be noted, however, that the peaks corresponding to 9Be*(3.1) have a FWHM of ~ 1 MeV, which may imply that 9Be*(2.8) is involved (RE71K). See also 8Be, 13C in (76AJ04) and (66LA04).
Angular distributions of the α0 group have been measured at En = 14.1 MeV (HS69, KI69A), 13.9 and 15.6 MeV (BR68N), and 14.8 to 18.8 MeV (SA71K). (BR68N, HS69) also report the population of 9Be*(1.7, 2.4, 3.1). Reaction (b) at En = 13 to 18 MeV involves 9Be*(2.4) (MO66A). See also (MO65C, MI66M, BE68I, KA69V, LO69G, DO71J, FA71A), (CI66A, 66LA04), (EL67E, CH68L; theor.), 12C in (75AJ02), and 13C in (76AJ04).
See 13C in (76AJ04).
A partial angular distribution involving the transition to 6Li(0) + 9Be(0) has been measured at Ed = 14.6 MeV (DE66A).
The angular distribution involving the transition to 11C(0) + 9Be(0) has been measured at Eα = 42 MeV (RU72A).