(See Energy Level Diagrams for 11C)
Model calculations: (1988WO04)
Astrophysical Questions: (1987RA1D)
Complex reactions involving 11C:(1981AS04, 1985AR09, 1985HI1C, 1985MO08, 1986AV1B, 1986AV07, 1986BA3G, 1986HA1B, 1986HI1D, 1986UT01, 1987AR19, 1987BA38, 1987DE37, 1987NA01, 1987RI03, 1987SN01, 1987ST01, 1987YA16, 1988CA06, 1988KI05, 1988KI06, 1988SA19, 1988SM07, 1988VUZZ, 1989AR1G, 1989HA43, 1989SA10, 1989SE03, 1989YO02)
Q = 34.26 mb (1978LEZA)
At E(6Li) = 4.1 MeV angular distributions have been obtained for the neutronsto 11C*(2.00, 4.32, 4.80, 6.34 + 6.48, 6.90, 7.50). In addition, nγ-coincidences via 11C*(8.42) [and an 8.42 MeV γ-ray] are reported. 11C*(8.10) was not observed. The lifetimes, τm, for 11C*(4.32, 6.90, 7.50) are < 140, < 69 and < 91 fs, respectively. See (1980AJ01) for references. For yields see 12C and (1987DO05).
At E(7Li) = 82 MeV no states of 11C are populated (1987AL10).
At the resonances at Eα = 0.884 ± 0.008 and 1.376 ± 0.003 MeV [11C*(8.106, 8.419)], ωγ = 0.331 ± 0.041 and 3.80 ± 0.57 eV, Γγ = 0.350 ± 0.056 and 3.1 ± 1.3 eV for these two states and Γα = 6+12-2 and 12.6 ± 3.8 eV, respectively (1984HA13). See also (1983HA1B, 1984YA1A, 1985CA41, 1988BU01, 1988CA26; astrophysics).
Reported neutron groups are listed in Table 11.16 (PDF or PS) of (1968AJ02). Angular distributions have been studied in the range E(3He) = 1.3 to 13 MeV: see (1980AJ01). The dominant L-values are 0 for 11C*(0, 8.10), 1 for 11C*(6.34, 7.50), 2 for 11C*(2.00, 4.32, 4.80, 6.48, 8.42) and 3 for 11C*(6.90). Neutron groups to T = 3/2 states have been reported at Ex = 12.17 ± 0.05 [see, however, reaction 28], 12.55 ± 0.05 MeV and 14.7 ± 0.1 MeV: see Table 11.18 (PDF or PS).
Gamma branching ratios and multipolarities for 11C levels up to Ex = 7.5 MeV have been studied by (1965OL03): see Table 11.17 (PDF or PS). Together with evidence from reactions 12 and 21 they lead to assignments of Jπ = 1/2-, 5/2-, 3/2-, 1/2+, 7/2-, 5/2+, 3/2+ for 11C*(2.00, 4.32, 4.80, 6.34, 6.48, 6.90, 7.50): see (1965OL03) and reaction 3 in (1968AJ02) for a summary of the evidence concerning these assignments. See (1980AJ01) for references. See also 12C and (1984SUZZ).
This reaction has been investigated for Ep = 0.07 to 17.0 MeV. Reported resonances are displayed in Table 11.19 (PDF or PS). Observed capture γ-rays are displayed in Table 11.17 (PDF or PS) [see also for τm measurements]. Capture measurementsfor Ep = 0.07 to 2.20 MeV are consistent with five new resonances (see Tables 11.19 (PDF or PS) and 11.17 (PDF or PS)), the lowest two (at Ep = 10 and 560 keV) of which are s-wave resonances. Thermonuclear reaction rates for T = (0.01 → 5) x 109 K are deduced from the results (1983WI09; see also for spectroscopic factors).
The 90° yield of γ0 has been measured for Ep = 2.6 to 17 MeV and angular distributions have been obtained for Ep = 2.8 to 14 MeV. The excitation function is consistent with the giant resonance centered at Ex ~ 16 MeV. In addition to weak structures at Ep = 4.75 MeV and 10.5 MeV, there are three major peaks at Ep = 4.1, 7.0 and 8.8 MeV (Γ = 1 - 2 MeV) [Ex = 12.4, 15.0, 16.7 MeV]. At 11C*(12.4), the γ0 angular distribution is essentially isotropic: Γ pΓγ/Γ ~ 200 eV, Γγ ~ 5 keV (assuming Γp ~ 10 keV). The Ep = 4.1 MeV resonance is probably part of the E1 giant resonance and is formed by s-wave capture. At the two higher resonances the angular distributions are characteristic of E1 giant resonances in light nuclei. The 10B(p, γ1) cross section is small for Ep = 2.6 to 17 MeV: see (1980AJ01). See also (1984YA1A, 1985CA41, 1988CA26; astrophysics).
The total (p, n) cross section has been measured to Ep = 10.6 MeV: broad maxima are observed at Ep = 5.92 ± 0.02, 6.68 ± 0.04, 7.33 ± 0.05 and 7.60 ± 0.05 MeV (see Table 11.19 (PDF or PS). The cross section for formation of 10Cg.s. measured up to 12 MeV shows similar behavior to 8 MeV. At Ep ~ 8 MeV, a sharp maximum is observed. The cross section for production of 3.35 MeV γ-rays (from 10C*) does not appear to show structure for Ep = 8.5 to 12 MeV. For references see (1980AJ01). For n0 and n1 excitiation curves from Ep = 13.7 to 14.7 MeV see (1985SC08). See also (1984BA1R, 1984BA1U).
Below Ep = 0.7 MeV the scattering can be explained in terms of pure s-wave potential scattering but the possibility of a state near Ep = 0.27 MeV (Ex = 8.95 MeV) cannot be excluded. The elastic scattering then shows two conspicuous anomalies at Ep = 1.50 ± 0.02 MeV and at 2.18 MeV [Ex = 10.05 and 10.67 MeV] with Jπ = 7/2+ and 9/2+: see Table 11.19 (PDF or PS). At higher energies (to Ep = 10.5 MeV) a single broad resonance is reported at Ep ~ 5 MeV. Polarization measurements are reported at 30.3 MeV: optical model parameters have been derived. The depolarization parameter D has been measured for polarized protons at 26 and 50 MeV. For references see (1980AJ01, 1985AJ01). See also (1984BA1U) and (1986MU08).
The yield of γ1 [from 10B*(0.72)] rises monotonically from Ep = 1.5 to 4.1 MeV and then shows resonance behavior at Ep = 4.36 and 5.73 MeV: see Table 11.19 (PDF or PS). For Ep = 6 to 12 MeV, the cross section for γ1 shows several sharp maxima superposed on a broad maximum (Γ ~ 2.5 MeV) at Ep ~ 7.2 MeV. See however (1975AJ02). Yields of five other γ-rays involved in the decay of 10B*(1.74, 2.16, 3.59, 5.18) have also been measured in the range Ep = 4 to 12 MeV [see (1975AJ02)].
Excitation curves for the p1, p2 and p3 groups have been measured for Ep = 3.5 to 5.0 MeV. Possible resonances are observed in the p2 yield [to the T = 1 state 10B*(1.74)] corresponding to the first T = 3/2 states at Ex = 12.16 [see however reaction 28] and 12.50 MeV [see Table 11.18 (PDF or PS)]: these do not occur in the yield of p1 and p3. Yield curves for inelastically scattered protons have also been measured at Ep = 5.0 to 16.4 MeV ( p1, p2, p3), 6.6 to 16.4 MeV (p4), 8.9 to 16.4 MeV (p5) and 10.9 to 16.4 MeV (p to 10B*(6.03)): the principal feature for all groups, except that to 10B*(6.03), is a structure at Ep ~ 7.5 MeV, Γ ~ 4 MeV. In addition narrower structures are observed, including three at Ep = 5.75, 6.90 and 7.80 MeV ( ± 0.2 MeV) and widths of ~ 500 keV. For references see (1980AJ01, 1985AJ01).
Polarization measurements (reaction (a)) have been carried out at Ep = 49.6 MeV for the deuterons to 9B*(0, 2.36): see (1975AJ02). In reaction (b) two strong maxima are observed at Ep ~ 4.5 and 6.5 MeV: see Table 11.19 (PDF or PS). See also (1975AJ02).
The total cross section for this reaction has been measured for Ep = 60 to 180 keV: the extrapolated cross section at the Gamow energy, taken to be 19.1 keV, is ~ 10-12 b. The thick target yield for Ep = 75 keV to 3 MeV shows that the 7Be yield constitutes a potential problem if natural boron is used as fuel in CTR devices.
The parameters of observed resonances are displayed in Table 11.19 (PDF or PS). The ground state (α0) α-particles exhibit broad resonances at Ep = 1.17, 1.53, 2.18, 3.0, 4.4, 5.1 and 6.3 MeV. Alpha particles to 7Be*(0.43)[α1] and 0.43 MeV γ-rays exhibit all but the 1.2 MeV resonance: see (1975AJ02). A broad maximum dominates the region from Ep = 4 MeV to about 7.5 MeV. A study of the yield of 0.43 MeV γ-rays for Ep = 2.0 to 4.1 MeV suggests that the 3.0 MeV resonance, which is asymmetric, is due to two broad states. A weak structure at Ep = 2.5 MeV is also reported. For references see (1980AJ01, 1985AJ01). See also 7Be in (1988AJ01) and (1984YA1A, 1985CA41; astrophysics).
Table 11.20 (PDF or PS) presents the results obtained in this reaction and in the (3He, d) reaction. Information on τm and on the γ-decay of 11C states is displayed in Table 11.17 (PDF or PS): see (1968AJ02, 1975AJ02) for references. See also (1986WE1E; applied) and 12C.
Table 11.20 (PDF or PS) displays the information derived from this reaction and from the (d, n) reaction. The study of the angular distributions of the deuterons to 11C*(8.66, 8.70) shows that these levels are the analogs, respectively, of 11B*(9.19, 9.27) whose Jπ are 7/2+ and 5/2+ [the 11B states were studied in the (d, p) reaction]: Γc.m. are << 9 keV and 15 ± 1 keV, respectively, for 11C*(8.66, 8.70): see (1975AJ02) for references.
Angular distributions of 6He ions have been measured at E(7Li) = 3.0 to 3.8 MeV and at 24 MeV [to 11C*(0, 4.32, 6.48)]. 11C*(2.0, 4.80, 8.42, 8.66 + 8.70) are also populated: see (1980AJ01) for references.
Angular distributions have been measured at many energies up to 49.5 MeV [see (1980AJ01, 1985AJ01)] and at Ep = 14.0, 14.3 and 14.6 MeV (1985SC08; n0, n1, n2, n3, (n4+5), n6, n7), 15.8 and 18.6 MeV (1988KA30; n0, n1) and 16 to 26 MeV (1985GR09; n0, n1, n2, n3) [see also for a study of the GT matrix elements]. For 0° cross sections at Ep = 492 and 590 MeV see (1989RA09). See also 12C, (1984BA1R, 1985GU1C), (1988CA26; astrophysics), (1984TAZS, 1986MU08, 1987RA32) and (1986HU06; theor.).
Angular distributions of t0 and t1 have been measured at E(3He) = 10, 14, and 217 MeV [the latter also for the triton groups to 11C*(4.3, 4.8, 6.48, 8.10] and at E(pol. 3He) = 33 MeV. At E(3He) = 26 MeV the known states of 11C below Ex = 11 MeV are populated and triton groups are also observed to the possibly T = 3/2 states displayed in Table 11.18 (PDF or PS) as well as a state at 14.15 MeV. For references see (1980AJ01, 1985AJ01).
The fraction of transitions to the ground and to excited states of 11C [and to 11B states reached in the (γ, p) reaction] has been measured at Ebs = 24.5, 27, 33 and 42 MeV: the ground state is predominantly populated. The population of analog states in the (γ, n) and (γ, p) reactions are similar. And a significant decay strength is found to the positive-parity states with 6 < Ex < 8 MeV. In general the main contribution to the strength of the transitions to the various excited states of 11B, 11C lies in rather localized energy bands in 12C which are a few MeV wide (1970ME17). See also reactions 24 and 25 in (1980AJ01), (1985AJ01), (1988HA01) in 12C and (1985CA32, 1987GOZO, 1987GO37, 1987VA15; theor.).
11C*(4.32)[5/2-] (and the analog state in 11B) is surprisingly strongly populated for Eπ+ = 60 to 300 MeV: see (1980AJ01, 1985AJ01). For reaction (b) see 13C in (1986AJ01). In reaction (c) at 1 GeV the separation energy between 6 and 13 MeV broad 1 p3/2 and 1 s1/2 groups is ~ 17 MeV (1985BE30, 1985DO16). See also 12C and (1984GO1F).
Angular distributions at Eπ+ = 49.3, 90 and 180 MeV have been obtained to 11C*(0, 2.0, 4.3 + 4.8, 6.5, 8.5). At the same momentum transfer this reaction and the (p, d) reaction give similar intensities to the low lying states of 11C. T = 3/2 states have been suggested at Ex = 12.5 ± 0.3 and 13.3 MeV: see (1985AJ01). See also (1982DO01).
Angular distributions have been measured for Ep = 19 to 800 MeV [see (1968AJ02, 1975AJ02, 1980AJ01, 1985AJ01) for references], at Epol. p = 497 MeV (1984OH06; p0; also Ay) and at Ep = 800 MeV (1984SM04; to 11C*(0, 2.0, 4.3, 4.8, 6.5, 8.1, 8.66 + 8.70, 9.98 ± 0.2, 10.56 ± 0.2)). In the latter experiment 11C*(8.4) and a state at 13.22 ± 0.25 MeV (Γ ~ 2 MeV) are also reported (1984SM04). Earlier observed states of 11C are displayed in Table 11.24 (PDF or PS) of (1980AJ01). See also 13N in (1991AJ01), (1987CA20) and (1984RE14).
At Ed = 28 MeV the t0 angular distribution has been measured and a detailed comparison has been made with the results for the mirror reaction 12C(d, 3He)11B. At Ed = 29 MeV the t0 angular distribution leads to spectroscopic factor C2S = 2.82 or 3.97 depending on different sets of parameters for 11Cg.s.. 11C*(2.0, 4.32) are also populated. See also 14N in (1986AJ01), (1980AJ01) for references, and (1984KO1M).
Angular distributions have been measured at many energies to E(3He) = 217 MeV [see (1968AJ02, 1975AJ02, 1980AJ01, 1985AJ01) for references]. Observed states are displayed in Table 11.21 (PDF or PS). In addition the excitation of states at Ex = 11.2, 12.4, 15.3, 23, and (28) MeV has also been suggested: see (1980AJ01).
At E(3He) = 35.6 MeV one finds good fits by DWBA for strong l = 1 transitions, and reasonable agreement in the forward direction, as well as with Stheor., for weak l = 1 transitions. Transitions involving l = 0 or 2 (and 3) are weak and the agreement with theory is poor. It is suggested that 11C*(8.10) [3/2-] is predominantly a p3/2 hole state coupled to 12C*(7.65) [0+]: see (1980AJ01).
Alpha-γ correlations have been studied for E(3He) = 4.7 to 12 MeV. Their results are summarized in Table 11.17 (PDF or PS) and are discussed in detail in reaction 22 of (68AJ02). A measurement of the linear polarization of the 2.00 MeV γ-ray (together with knowledge of the τm) fixes Jπ = 1/2- for 11C*(2.00). τm = 10.3 ± 0.7 fs for 11C*(2.00). See also 12N, and 15O in (1986AJ01).
At E(10B) = 100 MeV, angular distributions have been measured involving 11Bg.s. + 11Cg.s., 11Bg.s. + 11C2.00 and 11Cg.s. + 11B2.12. Both 12C(10B, 11B)11C (with 11B detected in the forward direction) and 12C(10B, 11C)11B (with 11C detected in the forward direction) were measured. In each case, 11Bg.s. + 11C2.00 and 11Cg.s. + 11B2.12 were not resolved, but the authors argues that the (10B, 11B) case would have little contribution from 11Cg.s. + 11B2.12 (because of the spins of 10B and 11B2.12), so that it essentially gives the 11Bg.s. + 11C2.00 angular distribution, and similarly for the other case. See (1985AJ01) and (1987OS1E; theor.)
Angular distributions involving 11Cg.s. have been studied at E(12C) = 93.8 and 114 MeV [see (1980AJ01, 1985AJ01)], at 20 MeV/A (1985BO39) and at 25, 35, and 50 MeV/A (1988WI09, 1989WI07). The strongest peak observed is due to the unresolved 13C*(3.68 + 3.85) + 11C*(4.32) (1988WI09, 1989WI07). The results are in agreement with the predictions of the exact FRDWBA. Above ~ 30 MeV/A the angle-integrated cross sections fall off with an approximately exponential shape (1988WI09).
At Eπ+ = 32 MeV angular distributions have been obtained for the deuterons to 11C*(0, 6.48): see (1985AJ01).
At Ep = 43.7 to 50.5 MeV angular distributions of the tritons have been studied to 11C*(0, 2.00, 4.32, 4.80, 6.48, 6.90, 7.50) and to a T = 3/2 state at Ex = 12.47 MeV [see Table 11.18 (PDF or PS)] whose Jπ is determined to be 1/2- [it is thus the analog of 11Be*(0.32)]. The state decays primarily by p → 10B*(1.74). Alpha decay to 7Be*g.s.+0.4 is also observed. Angular distributions have also been measured for Ep = 26.9 to 65 MeV [see (1980AJ01, 1985AJ01)]. At Ep = 46.7 MeV the T = 3/2 state is also observed by (1974BE20) who, in addition, report the population of states with Ex = 11.03 ± 0.03, 13.33 ± 0.06, 13.90 ± 0.04 and 14.07 ± 0.04 MeV [Γ = 300 ± 60, 270 ± 80, 150 ± 50 and 135 ± 50 keV, respectively]. See also (1989AR1G).
Angular distributions have been reported at a number of energies in the range Ep = 5.0 to 44.3 MeV for the α0 and α1 groups: see (1975AJ02, 1980AJ01). For reaction (b) see (1986VDZY; Ep = 50 MeV; prelim.). See also (1984RE14, 1985HA1J), (1986MA1P, 1987HI1B; applied), (1988CA26; astrophysics) and (1986GO28; theor.).
See (1988SH1E; theor.).