
^{11}C (1980AJ01)(See Energy Level Diagrams for ^{11}C) GENERAL: See also (1975AJ02) and Table 11.19 [Table of Energy Levels] (in PDF or PS). Special levels: (1976IR1B). Astrophysical questions: (1976VI1A, 1977SC1D, 1977SI1D, 1978BU1B). Special reactions: (1975HU14, 1976BE1K, 1976BU16, 1976DI01, 1976HE1H, 1976LE1F, 1976SM07, 1977AR06, 1977AS03, 1977SC1G, 1978DI06, 1978GE1C, 1978HE1C, 1979KA07, 1979VI05). Muon and neutrino capture and reactions: (1975DO1F, 1976DO1G). Pion capture and reactions (See also reactions 25 and 26.): (1975BA66, 1975BH03, 1975HU13, 1975KA1G, 1975PA1D, 1975SC1N, 1975SI18, 1975ZI1B, 1976MI15, 1977BA2H, 1977LE1G, 1977MA1M, 1978AM01, 1978HI03, 1978MO01, 1978WA1B, 1979AN1J, 1979HU02). Applied topics: (1975AL1B, 1975CH1H, 1977MA1P, 1977WO1A, 1978LO1D, 1978TI1A, 1978WI1F, 1978WO1C, 1979AL1Q, 1979WI1G). Other topics: (1976IR1B, 1979BE1H). Ground state of ^{11}C: (1969SC34, 1974SHYR, 1975BE31, 1976DO1G, 1977KA07, 1977YO1D).
Q = 34.26 mb (1978LEZA).
The halflife of ^{11}C is 1223.1 ± 1.2 sec [mean of previously reported values (see (1975AJ02)); mainly based on τ_{1/2} = 1222.9 ± 1.2 sec (1975AZ01)]. See also (1975BE28). Log ft = 3.599 ± 0.002 (1975AZ01) based on E_{β+}(max) = 960 ± 1 keV (from Q_{m}). See also (1975AZ01). (1975BE28) measure E_{β+}(max) = 960.8 ± 2.6 keV. The ratio of Kcapture to positron emission is (0.230^{+0.014}_{0.011})% (1967CA09). See also (1975AJ02, 1977BA48, 1978RA2A) and (1975KR14, 1975WI1E, 1976BE1E, 1976DO1G, 1977RI08, 1977YO1D, 1977YO1E, 1979DE15; theor.).
At E(^{6}Li) = 4.1 MeV [reaction (a)] angular distributions have been obtained for the neutrons to ^{11}C*(2.00, 4.32, 4.80, 6.34 + 6.48, 6.90, 7.50). In addition, nγ coincidences via ^{11}C*(8.42) [and a 8.42 MeV γray] are reported. ^{11}C*(8.10) was not observed (1976BA53). The lifetimes, τ_{m}, for ^{11}C*(4.32, 6.90, 7.50) are < 140, < 69 and < 91 fsec, respectively. The upper limits for τ_{m} of ^{11}C*(6.34, 6.48) [which were unresolved] are 0.5 psec. The ground state transition from ^{11}C*(7.50) has E_{γ} = 7505 ± 8 keV (1969TH01). For reaction (b) see (1968AJ02). For reaction (c) see (1974CE06).
Reported neutron groups are listed in Table 11.16 (in PDF or PS) of (1968AJ02). Angular distributions have been studied in the range E(^{3}He) = 1.3 to 13 MeV: see (1975AJ02) and (1979OS10). The dominant Lvalues from the angular distributions reported by (1974FU11) 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 by (1971WA21) [E_{x} = 12.17 ± 0.05 and 12.55 ± 0.05 MeV] and by (1969BR30) [E_{x} = 12.5 ± 0.1, 13.7 ± 0.1 and 14.7 ± 0.1 MeV]: see Table 11.22 (in PDF or PS). Gamma branching ratios and multipolarities for ^{11}C levels up to E_{x} = 7.5 MeV have been studied by (1965OL03, 1965RO07): see Table 11.20 (in PDF or PS). Together with evidence from reactions 12 and 27 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, 1965RO07) and reaction 3 in (1968AJ02) for a summary of the evidence concerning these assignments. See also (1977ZA1B; applied), (1977OS08; theor.) and ^{12}C.
The thick target yield for this reaction has been measured for E_{p} = 0.27 to 3.0 MeV (1975PE1A): see also reaction 11. A broad resonance is reported at E_{p} = 1.15 MeV: see Table 11.22 (in PDF or PS). Capture γrays are observed corresponding to the ground state transition and to cascades via ^{11}C*(2.00, 4.32, 6.48): see Table 11.21 (in PDF or PS) (1961JA11). 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 (1970KU09). See also (1974LO1B, 1975AJ02), (1976RO1Q; astrophys.) and (1977YO1F; applied).
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 11.23 (in PDF or PS)) (1963EA01). 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 (1966SE03). See also ^{10}C in (1979AJ01).
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 11.22 (in PDF or PS) (1962OV02: E_{p} = 0.15 to 3.0 MeV). At higher energies (to E_{p} = 10.5 MeV) a single broad resonance is reported at E_{p} ≈ 5 MeV (1969WA11) while (1970BO17) suggest additional structure. Polarization measurements are reported at 30.3 MeV (1976DE15, 1977PH02): optical model parameters are derived. The depolarization parameter D has been measured for polarized protons with E_{p} = 26 MeV (1976BI1E) and 50 MeV (1970BA05). See also (1977SA1B) and (1975BL10; theor.).
The yield 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 (1962OP03: see Table 11.22 (in 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 (1966SE03). [The cross section below E_{p} = 10 MeV appears to be in error: see (1969WA23).] Yields of five other γrays involved in the decay of ^{10}B*(1.74, 2.16, 3.59, 5.18) have also been measured by (1966SE03) in the range E_{p} = 4 to 12 MeV. Yield curves for inelastically scattered protons have 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 (1969WA23). It had previously been suggested by (1966SE03) that the formation of T = 1 states was relatively suppressed in this reaction. (1969WA23) find that the isotopic spin effect disappears when a correction factor (2J_{f+1}) is included. 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 and 12.50 MeV [see Table 11.21 (in PDF or PS)]: these do not occur in the yield of p_{1} and p_{3} (1971WA21). See also (1976DE15), ^{10}B in (1979AJ01) and (1975AJ02).
Polarization measurements have been carried out at E_{p} = 49.6 MeV for the deuterons to ^{9}B*(0, 2.36) (1971SQ02). See also ^{9}B in (1979AJ01).
The groundstate yield shows slight maxima at energies similar to those in the (p, α) yield in the range E_{p} = 4 to 10 MeV. However, the angular distributions do not vary strongly over the region and it is suggested that a direct interaction mechanism dominates (1963JE01). (1966SE03) report two strong maxima at E_{p} ≈ 4.5 and 6.5 MeV. See also ^{8}Be in (1979AJ01).
The total cross section for this reaction has been measured for E_{p} = 60 to 180 keV by (1972SZ02): 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 has been measured by (1975PE1A): 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 11.22 (in 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 0.43MeV 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 (1966SE03). For spallation studies see (1976BO08, 1977AV01). See also (1976GRZR, 1976IN04) and (1976RO1Q; astrophys.).
Table 11.23 (in PDF or PS) presents the results obtained in this reaction and in the (^{3}He, d) reaction (1955MA76, 1963OV02, 1970BO34). Information on the γdecay of ^{11}C states has been summarized by (1965OL03) and is incorporated in Table 11.20 (in PDF or PS). For the earlier work see (1959AJ76, 1968AJ02 [particularly Table 11.20 (in PDF or PS)], 1975AJ02). See also (1972RE1C) and (1974LO1B).
Table 11.23 (in 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) (1973FO02). Singlet deuteron emission has been studied at E(^{3}He) = 8, 10 and 11 MeV by (1970BO07). For the earlier work see (1975AJ02).
Angular distributions have been measured at E_{α} = 25.1 MeV (1974DM01; t_{1}) and at 56 MeV (1969GA11; t_{0}). See also (1975AJ02).
See (1957NO17).
Angular distributions of ^{6}He ions have been measured at E(^{7}Li) = 3.0 to 3.8 MeV (1968ST12; to ^{11}C_{g.s.}) and at 24 MeV (1977KO27: to ^{11}C*(0, 4.32, 6.48)). ^{11}C*(2.0, 4.80, 8.42, 8.66 + 8.70) are also populated (1977KO27).
See (1975NA15, 1977MO1A), (1975AJ02) and ^{13}C in (1981AJ01).
See (1975NA15). See also ^{15}N in (1981AJ01) and (1977OK1D; theor.).
See (1968GA03).
Yields of ^{11}C have been measured from threshold to E_{γ} = 169 MeV (1976MI15; see it also for other references).
Neutron groups have been observed to ^{11}C*(0, 2.008, 4.320, 4.806, 6.330, 6.481) (± 20 keV) (1965OV01; E_{p} = 10.9 MeV). Angular distributions of the n_{0} group have been measured at many energies up to 49.5 MeV [see (1975AJ02)] and at E_{p} = 3.15 to 4.85 MeV (1978VA12). See also (1977ME1C) and ^{12}C.
Angular distributions of t_{0} and t_{1} have been measured at E(^{3}He) = 10 MeV (1967CR04), 14 MeV (1970NU02) and 217 MeV (1976WI05; also to ^{11}C*(4.3, 4.8, 6.48, 8.10)). The latter have been compared with microscopic calculations and calculations of twostep processes (1976WI05). 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 states, assumed to be T = 3/2, at E_{x} = 12.15, 12.57 and 13.92 MeV [see Table 11.21 (in PDF or PS)] and, possibly, 14.15 MeV (1971WA21).
See (1975AJ02).
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 positive parity 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 (1975SC05, 1979KI1H). For the (e, n) reaction see (1978KL03).
For reaction (a) see (1977KN04, 1978SH14). (1978MO01) report the strong population of the 5/2^{} state ^{11}C*(4.32) (and of the analog state in ^{11}B) for E_{π+} = 60 to 300 MeV. See also (1973HO43, 1979LI11) for reactions (b), reaction 54 in ^{11}B and the "GENERAL" section here. For reaction (c) see ^{13}C in (1981AJ01). For reaction (d) see (1976MCZP). See also (1975AJ02) and ^{12}C.
At E_{π+} = 49.3 MeV angular distributions have been obtained to ^{11}C*(0, 2.0 ± 0.2, 4.35 ± 0.2, 6.4 ± 0.2, 8.5 ± 0.2, 12.5 ± 0.3). At the same momentum transfer this reaction and the (p, d) reaction give similar intensities to the lowlying energy states of ^{11}C (1978AM01). See also (1979AN1K, 1979AN1M).
Angular distributions have been measured for E_{p} = 19 to 700 MeV [see (1968AJ02, 1975AJ02)] and recently at 65 MeV (1975RO27; see Table 11.24 (in PDF or PS)), 121.2 MeV (1976ANZP) and 650 and 800 MeV (1978IG1A, 1978WH1A, 1979BO1A). Observed states of ^{11}C are displayed in Table 11.24 (in PDF or PS). See also (1975AJ02, 1975BE1Q, 1975IG1A, 1977HA1P, 1977MO1F, 1978AZ02, 1978IG1B, 1978SH1F, 1979WH1A), (1977HA1N [in ^{13}N, (1981AJ01)], and (1975GE1H, 1975RO29, 1976GR1G, 1976SHZQ, 1976WA15, 1977KA07, 1977LU1A, 1978CO1J, 1978LU1B;; theor.).
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 (1968GA13, 1966DE1C). At E_{dbar} = 29 MeV the t_{0} angular distribution leads to spectroscopic factors 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 (1978CO13). See also ^{14}N in (1981AJ01), and (1975AJ02).
Angular distributions have been measured at many energies to E(^{3}He) = 217 MeV [see (1968AJ02, 1975AJ02) for the earlier results] and at 11.0 MeV (1978CU02: α_{0}, α_{1}), 18, 20 and 22 MeV (1977AD07: α_{0}, α_{1}), at E(pol. ^{3}He) = 33 MeV (1976KA23: α_{0}, α_{1}), and at E(^{3}He) = 35.6 MeV (1978FO13: see Table 11.25 (in PDF or PS)), 82.1 MeV (1976TA12: α_{0}, α_{1}, α_{2+3}, α_{4+5}) and at 217 MeV (1978VA05: α_{0}, α_{1}). See also (1976STYX: 60 MeV) and (1978CH1P: 132 MeV). At E(^{3}He) ≈ 217 MeV (1975GE16, 1978VA05) also report the population of unresolved lowlying states, as well as the excitation of states with E_{x} = 11.2, 12.4, 15.3, 23 and (28) MeV. See Table 11.25 (in PDF or PS) for a display of the results. At E(^{3}He) = 35.6 MeV (1978FO13) find 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^{+}] (1978FO13). Alphaγ correlations have been studied for E(^{3}He) = 4.7 to 12 MeV: see, in particular, (1968EA03). Their results are summarized in Table 11.20 (in PDF or PS) and are discussed in detail in reaction 22 of (1968AJ02). 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) (1968BL09). See also (1976RO1L, 1977MO1F) and ^{15}O in (1981AJ01).
At E(^{6}Li) = 36 MeV the angular distributions involving ^{7}Li_{g.s.}+^{11}C_{g.s.} and ^{7}Li*_{0.48} + ^{11}C*_{2.00} have been studied by (1973SC26).
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}) + (^{11}B_{g.s.} + ^{11}C_{2.00}) [unresolved], as well as unresolved groups involving the first few states of ^{11}B and ^{11}C (1975NA15, 1975VO05, 1976NA09). See also (1975AJ02).
The angular distribution involving the ground state transitions has been studied at E(^{12}C) = 114 MeV (1974AN36). See also (1979HEZX).
See (1967BI06, 1974AN36) and ^{15}N in (1981AJ01).
At E_{p} = 43.7 to 50.5 MeV (1968CO26, 1968FL02) and at E_{pbar} = 49.6 MeV (1974MA12) 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 11.21 (in 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 (1968CO26). Angular distributions have also been measured for E_{p} = 26.9 to 43.1 MeV (1975MI01: t_{0} → t_{3}). 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]. However, the T = 3/2 state at E_{x} = 12.16 MeV reported by (1971WA21) in reactions 4, 8 and 22 is not observed by (1974BE20). See also ^{14}N in (1981AJ01).
Angular distributions have been reported at a number of energies in the range E_{p} = 5.00 to 44.3 MeV for the α_{0} and α_{1} groups: see (1975AJ02) for the earlier work and (1974HU02: 9.0 to 12.0 MeV; α_{0}). See also ^{15}O in (1981AJ01), (1976IN01; astrophys.), (1975CH1H; applied) and (1975KU1L; theor.).
This reaction has been studied at E(^{10}B) = 100 MeV: see (1975NA15, 1976NA09) and ^{13}C in (1981AJ01).
See (1975AJ02).
At E_{d} = 80 MeV angular distributions involving ^{11}C*(0, 2.0, 4.3 + 4.8, 6.3 + 6.5 + 6.9) have been measured (1978OE1A).
At E_{α} = 42 MeV, the angular distribution involving the two ground state transitions has been measured (1972RU03).
