
^{11}C (1990AJ01)(See Energy Level Diagrams for ^{11}C) GENERAL: See also (1985AJ01) and Table 11.16 [Table of Energy Levels] (PDF or PS) here. Model calculations: (1988WO04) Special states: (1985SH24, 1986AN07, 1988KW02) Astrophysical Questions: (1987RA1D) Complex reactions involving ^{11}C:(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) Applications:(1985TA1D, 1986WE1E, 1987BO16, 1987HI1B, 1988FA1C, 1988HI1F, 1988VO1D, 1989TR1B, 1989WO1B) Pion and kaon capture and reactions(see also reactions 19, 20 and 27): (1984OH04, 1988AB05, 1988GIZU) Hypernuclei:(1984AS1D, 1984ZH1B, 1985GA1E, 1986DA1H, 1986DA1G) Other topics:(1985AN28, 1985SH24, 1985TA26, 1986HE01, 1988KW02) Groundstate properties of ^{11}C:(1984ZI04, 1985AN28, 1985HA18, 1985FA01, 1985ZI05, 1986GL1A, 1987FU06, 1987SA15, 1988VA03, 1988WA08, 1988WO04, 1989SA10)
Q = 34.26 mb (1978LEZA)
The half life of ^{11}C is 1223.1 ± 1.2 s. Log ft= 3.599 ± 0.002. The ratio of Kcapture to positron emission is (0.230^{+0.014}_{0.011})%. See (1980AJ01) for references. See also (1985AJ01) and (1987BO1Y).
At E(^{6}Li) = 4.1 MeV angular distributions have been obtained for the neutronsto ^{11}C*(2.00, 4.32, 4.80, 6.34 + 6.48, 6.90, 7.50). In addition, nγcoincidences via ^{11}C*(8.42) [and an 8.42 MeV γray] are reported. ^{11}C*(8.10) was not observed. The lifetimes, τ_{m}, for ^{11}C*(4.32, 6.90, 7.50) are < 140, < 69 and < 91 fs, respectively. See (1980AJ01) for references. For yields see ^{12}C and (1987DO05).
At E(^{7}Li) = 82 MeV no states of ^{11}C are populated (1987AL10).
At the resonances at E_{α} = 0.884 ± 0.008 and 1.376 ± 0.003 MeV [^{11}C*(8.106, 8.419)], ωγ = 0.331 ± 0.041 and 3.80 ± 0.57 eV, Γ_{γ} = 0.350 ± 0.056 and 3.1 ± 1.3 eV for these two states and Γ_{α} = 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(^{3}He) = 1.3 to 13 MeV: see (1980AJ01). The dominant Lvalues are 0 for ^{11}C*(0, 8.10), 1 for ^{11}C*(6.34, 7.50), 2 for ^{11}C*(2.00, 4.32, 4.80, 6.48, 8.42) and 3 for ^{11}C*(6.90). Neutron groups to T = 3/2 states have been reported at E_{x} = 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 ^{11}C levels up to E_{x} = 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 J^{π} = 1/2^{}, 5/2^{}, 3/2^{}, 1/2^{+}, 7/2^{}, 5/2^{+}, 3/2^{+} for ^{11}C*(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 ^{12}C and (1984SUZZ).
This reaction has been investigated for E_{p} = 0.07 to 17.0 MeV. Reported resonances are displayed in Table 11.19 (PDF or PS). Observed capture γrays are displayed in Table 11.17 (PDF or PS) [see also for τ_{m} measurements]. Capture measurementsfor E_{p} = 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 E_{p} = 10 and 560 keV) of which are swave resonances. Thermonuclear reaction rates for T = (0.01 → 5) × 10^{9} K are deduced from the results (1983WI09; see also for spectroscopic factors). The 90° yield of γ_{0} has been measured for E_{p} = 2.6 to 17 MeV and angular distributions have been obtained for E_{p} = 2.8 to 14 MeV. The excitation function is consistent with the giant resonance centered at E_{x} ≈ 16 MeV. In addition to weak structures at E_{p} = 4.75 MeV and 10.5 MeV, there are three major peaks at E_{p} = 4.1, 7.0 and 8.8 MeV (Γ = 1  2 MeV) [E_{x} = 12.4, 15.0, 16.7 MeV]. At ^{11}C*(12.4), the γ_{0} angular distribution is essentially isotropic: Γ_{ p}Γ_{γ}/Γ ≈ 200 eV, Γ_{γ} ≈ 5 keV (assuming Γ_{p} ≈ 10 keV). The E_{p} = 4.1 MeV resonance is probably part of the E1 giant resonance and is formed by swave capture. At the two higher resonances the angular distributions are characteristic of E1 giant resonances in light nuclei. The ^{10}B(p, γ_{1}) cross section is small for E_{p} = 2.6 to 17 MeV: see (1980AJ01). See also (1984YA1A, 1985CA41, 1988CA26; astrophysics).
The total (p, n) cross section has been measured to E_{p} = 10.6 MeV: broad maxima are observed at E_{p} = 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 ^{10}C_{g.s.} measured up to 12 MeV shows similar behavior to 8 MeV. At E_{p} ≈ 8 MeV, a sharp maximum is observed. The cross section for production of 3.35 MeV γrays (from ^{10}C*) does not appear to show structure for E_{p} = 8.5 to 12 MeV. For references see (1980AJ01). For n_{0} and n_{1} excitiation curves from E_{p} = 13.7 to 14.7 MeV see (1985SC08). See also (1984BA1R, 1984BA1U).
Below E_{p} = 0.7 MeV the scattering can be explained in terms of pure swave potential scattering but the possibility of a state near E_{p} = 0.27 MeV (E_{x} = 8.95 MeV) cannot be excluded. The elastic scattering then shows two conspicuous anomalies at E_{p} = 1.50 ± 0.02 MeV and at 2.18 MeV [E_{x} = 10.05 and 10.67 MeV] with J^{π} = 7/2^{+} and 9/2^{+}: see Table 11.19 (PDF or PS). At higher energies (to E_{p} = 10.5 MeV) a single broad resonance is reported at E_{p} ≈ 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 γ_{1} [from ^{10}B*(0.72)] rises monotonically from E_{p} = 1.5 to 4.1 MeV and then shows resonance behavior at E_{p} = 4.36 and 5.73 MeV: see Table 11.19 (PDF or PS). For E_{p} = 6 to 12 MeV, the cross section for γ_{1} shows several sharp maxima superposed on a broad maximum (Γ ≈ 2.5 MeV) at E_{p} ≈ 7.2 MeV. See however (1975AJ02). Yields of five other γrays involved in the decay of ^{10}B*(1.74, 2.16, 3.59, 5.18) have also been measured in the range E_{p} = 4 to 12 MeV [see (1975AJ02)]. Excitation curves for the p_{1}, p_{2} and p_{3} groups have been measured for E_{p} = 3.5 to 5.0 MeV. Possible resonances are observed in the p_{2} yield [to the T = 1 state ^{10}B*(1.74)] corresponding to the first T = 3/2 states at E_{x} = 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 p_{1} and p_{3}. Yield curves for inelastically scattered protons have also been measured at E_{p} = 5.0 to 16.4 MeV ( p_{1}, p_{2}, p_{3}), 6.6 to 16.4 MeV (p_{4}), 8.9 to 16.4 MeV (p_{5}) and 10.9 to 16.4 MeV (p to ^{10}B*(6.03)): the principal feature for all groups, except that to ^{10}B*(6.03), is a structure at E_{p} ≈ 7.5 MeV, Γ ≈ 4 MeV. In addition narrower structures are observed, including three at E_{p} = 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 E_{p} = 49.6 MeV for the deuterons to ^{9}B*(0, 2.36): see (1975AJ02). In reaction (b) two strong maxima are observed at E_{p} ≈ 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 E_{p} = 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 E_{p} = 75 keV to 3 MeV shows that the ^{7}Be 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 (α_{0}) αparticles exhibit broad resonances at E_{p} = 1.17, 1.53, 2.18, 3.0, 4.4, 5.1 and 6.3 MeV. Alpha particles to ^{7}Be*(0.43)[α_{1}] and 0.43 MeV γrays exhibit all but the 1.2 MeV resonance: see (1975AJ02). A broad maximum dominates the region from E_{p} = 4 MeV to about 7.5 MeV. A study of the yield of 0.43 MeV γrays for E_{p} = 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 E_{p} = 2.5 MeV is also reported. For references see (1980AJ01, 1985AJ01). See also ^{7}Be in (1988AJ01) and (1984YA1A, 1985CA41; astrophysics).
Table 11.20 (PDF or PS) presents the results obtained in this reaction and in the (^{3}He, d) reaction. Information on τ_{m} and on the γdecay of ^{11}C states is displayed in Table 11.17 (PDF or PS): see (1968AJ02, 1975AJ02) for references. See also (1986WE1E; applied) and ^{12}C.
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 ^{11}C*(8.66, 8.70) shows that these levels are the analogs, respectively, of ^{11}B*(9.19, 9.27) whose J^{π} are 7/2^{+} and 5/2^{+} [the ^{11}B states were studied in the (d, p) reaction]: Γ_{c.m.} are ≪ 9 keV and 15 ± 1 keV, respectively, for ^{11}C*(8.66, 8.70): see (1975AJ02) for references.
Angular distributions have been measured at E_{α} = 25.1 and 56 MeV [see (1980AJ01)] and at 24.8 and 30.1 MeV (1983VA28; t_{0}, t_{1}). See also (1984BE23; theor.)
Angular distributions of ^{6}He ions have been measured at E(^{7}Li) = 3.0 to 3.8 MeV and at 24 MeV [to ^{11}C*(0, 4.32, 6.48)]. ^{11}C*(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 E_{p} = 14.0, 14.3 and 14.6 MeV (1985SC08; n_{0}, n_{1}, n_{2}, n_{3}, (n_{4+5}), n_{6}, n_{7}), 15.8 and 18.6 MeV (1988KA30; n_{0}, n_{1}) and 16 to 26 MeV (1985GR09; n_{0}, n_{1}, n_{2}, n_{3}) [see also for a study of the GT matrix elements]. For 0° cross sections at E_{p} = 492 and 590 MeV see (1989RA09). See also ^{12}C, (1984BA1R, 1985GU1C), (1988CA26; astrophysics), (1984TAZS, 1986MU08, 1987RA32) and (1986HU06; theor.).
Angular distributions of t_{0} and t_{1} have been measured at E(^{3}He) = 10, 14, and 217 MeV [the latter also for the triton groups to ^{11}C*(4.3, 4.8, 6.48, 8.10] and at E(pol. ^{3}He) = 33 MeV. At E(^{3}He) = 26 MeV the known states of ^{11}C below E_{x} = 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 ^{11}C [and to ^{11}B states reached in the (γ, p) reaction] has been measured at E_{bs} = 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 positiveparity states with 6 < E_{x} < 8 MeV. In general the main contribution to the strength of the transitions to the various excited states of ^{11}B, ^{11}C lies in rather localized energy bands in ^{12}C which are a few MeV wide (1970ME17). See also reactions 24 and 25 in (1980AJ01), (1985AJ01), (1988HA01) in ^{12}C and (1985CA32, 1987GOZO, 1987GO37, 1987VA15; theor.).
^{11}C*(4.32)[5/2^{}] (and the analog state in ^{11}B) is surprisingly strongly populated for E_{π+} = 60 to 300 MeV: see (1980AJ01, 1985AJ01). For reaction (b) see ^{13}C in (1986AJ01). In reaction (c) at 1 GeV the separation energy between 6 and 13 MeV broad 1 p_{3/2} and 1 s_{1/2} groups is ≈ 17 MeV (1985BE30, 1985DO16). See also ^{12}C and (1984GO1F).
Angular distributions at E_{π+} = 49.3, 90 and 180 MeV have been obtained to ^{11}C*(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 ^{11}C. T = 3/2 states have been suggested at E_{x} = 12.5 ± 0.3 and 13.3 MeV: see (1985AJ01). See also (1982DO01).
Angular distributions have been measured for E_{p} = 19 to 800 MeV [see (1968AJ02, 1975AJ02, 1980AJ01, 1985AJ01) for references], at E_{pol. p} = 497 MeV (1984OH06; p_{0}; also A_{y}) and at E_{p} = 800 MeV (1984SM04; to ^{11}C*(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 ^{11}C*(8.4) and a state at 13.22 ± 0.25 MeV (Γ ≈ 2 MeV) are also reported (1984SM04). Earlier observed states of ^{11}C are displayed in Table 11.24 (PDF or PS) of (1980AJ01). See also ^{13}N in (1991AJ01), (1987CA20) and (1984RE14).
At E_{d} = 28 MeV the t_{0} angular distribution has been measured and a detailed comparison has been made with the results for the mirror reaction ^{12}C(d, ^{3}He)^{11}B. At E_{d} = 29 MeV the t_{0} angular distribution leads to spectroscopic factor C^{2}S = 2.82 or 3.97 depending on different sets of parameters for ^{11}C_{g.s.}. ^{11}C*(2.0, 4.32) are also populated. See also ^{14}N in (1986AJ01), (1980AJ01) for references, and (1984KO1M).
Angular distributions have been measured at many energies to E(^{3}He) = 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 E_{x} = 11.2, 12.4, 15.3, 23, and (28) MeV has also been suggested: see (1980AJ01). At E(^{3}He) = 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 S_{theor.}, 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 ^{11}C*(8.10) [3/2^{}] is predominantly a p_{3/2} hole state coupled to ^{12}C*(7.65) [0^{+}]: see (1980AJ01). Alphaγ correlations have been studied for E(^{3}He) = 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 γray (together with knowledge of the τ_{m}) fixes J^{π} = 1/2^{} for ^{11}C*(2.00). τ_{m} = 10.3 ± 0.7 fs for ^{11}C*(2.00). See also ^{12}N, and ^{15}O in (1986AJ01). Reaction (b) has been studied at E(^{3}He) = 75 MeV: transitions to ^{11}C*(0, 2.0, 4.3, 4.8, 6.3) are observed by looking at p, t angular correlations: see (1985AJ01). See also (1984BE1A; applied).
The angular distributions involving ^{7}Li_{g.s.} + ^{11}C_{g.s.} and ^{7}Li*_{0.48} + ^{11}C*_{2.00} have been studied at E(^{6}Li) = 36 MeV: see (1980AJ01). See also (1986GL1E).
At E(^{10}B) = 100 MeV, angular distributions have been measured involving ^{11}B_{g.s.} + ^{11}C_{g.s.}, ^{11}B_{g.s.} + ^{11}C_{2.00} and ^{11}C_{g.s.} + ^{11}B_{2.12}. Both ^{12}C(^{10}B, ^{11}B)^{11}C (with ^{11}B detected in the forward direction) and ^{12}C(^{10}B, ^{11}C)^{11}B (with ^{11}C detected in the forward direction) were measured. In each case, ^{11}B_{g.s.} + ^{11}C_{2.00} and ^{11}C_{g.s.} + ^{11}B_{2.12} were not resolved, but the authors argues that the (^{10}B, ^{11}B) case would have little contribution from ^{11}C_{g.s.} + ^{11}B_{2.12} (because of the spins of ^{10}B and ^{11}B_{2.12}), so that it essentially gives the ^{11}B_{g.s.} + ^{11}C_{2.00} angular distribution, and similarly for the other case. See (1985AJ01) and (1987OS1E; theor.)
Angular distributions involving ^{11}C_{g.s.} have been studied at E(^{12}C) = 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 ^{13}C*(3.68 + 3.85) + ^{11}C*(4.32) (1988WI09, 1989WI07). The results are in agreement with the predictions of the exact FRDWBA. Above ≈ 30 MeV/A the angleintegrated cross sections fall off with an approximately exponential shape (1988WI09).
At E_{π+} = 32 MeV angular distributions have been obtained for the deuterons to ^{11}C*(0, 6.48): see (1985AJ01).
At E_{p} = 43.7 to 50.5 MeV angular distributions of the tritons have been studied to ^{11}C*(0, 2.00, 4.32, 4.80, 6.48, 6.90, 7.50) and to a T = 3/2 state at E_{x} = 12.47 MeV [see Table 11.18 (PDF or PS)] whose J^{π} is determined to be 1/2^{} [it is thus the analog of ^{11}Be*(0.32)]. The state decays primarily by p → ^{10}B*(1.74). Alpha decay to ^{7}Be*_{g.s.+0.4} is also observed. Angular distributions have also been measured for E_{p} = 26.9 to 65 MeV [see (1980AJ01, 1985AJ01)]. At E_{p} = 46.7 MeV the T = 3/2 state is also observed by (1974BE20) who, in addition, report the population of states with E_{x} = 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 E_{p} = 5.0 to 44.3 MeV for the α_{0} and α_{1} groups: see (1975AJ02, 1980AJ01). For reaction (b) see (1986VDZY; E_{p} = 50 MeV; prelim.). See also (1984RE14, 1985HA1J), (1986MA1P, 1987HI1B; applied), (1988CA26; astrophysics) and (1986GO28; theor.).
See (1988SH1E; theor.).
This reaction has been studied at E(^{10}B) = 100 MeV; see (1980AJ01). See also (1987OS1E; theor.).
See (1987KW01, 1987KW03; theor.).
