
^{11}C (1968AJ02)(See Energy Level Diagrams for ^{11}C) GENERAL: See Table 11.14 [Table of Energy Levels] (in PDF or PS). Shell model:(1956KU1A, 1957KU58, 1960TA1C, 1961KU1C, 1965FA1C). Collective model:(1966EL08). Groundstate properties:(1963BE36, 1964ST1B, 1967SH05). Other:(1962DY1A, 1964RE1B, 1967AU1B, 1967DE1V, 1967FA1A, 1967NE1D, 1967PO1J, 1968DI1B).
μ = ()1.027 ± 0.010 nm (1963KO1G, 1964HA46); J = 3/2 (1961SN01).
The mean value of reported halflives is 20.34 ± 0.04 min (see Table 11.15 (in PDF or PS)); ft = 3882. The ratio of Kcapture of positron emission is (0.19 ± 0.03)% (1957SC29), (0.230^{+0.014}_{0.011})% (1967CA09). See also (1965GA1D, 1966MI1F, 1967AM1H).
At E(^{6}Li) = 4.1 MeV, neutron groups have been observed to the first seven excited states and to the 8.42 MeV state. Associated γrays were used for the stop triggering of the timeofflight system. The group to the 8.4 MeV state had an intensity ≈ 10% of that to the highest bound state at E_{x} = 7.5 MeV suggesting a small Γ_{α} for the 8.42 MeV state (compare ^{12}C(^{3}He, α)^{11}C). No evidence for the γdecay of the 8.11 MeV state was found (1966BA2U). See also (1957NO17, 1960NO1A, 1962BE16, 1962BE24).
Reported neutron groups are listed in Table 11.16 (in PDF or PS)). Angular distributions and excitation functions have been studied in the range E(^{3}He) = 1.3 to 10 MeV by (1961DU1B, 1963DU12, 1963VA16, 1965DI06, 1965TO06, 1966AD1D: see (1966WE1B, 1968OK1D)). In the middle range of these energies, the reaction is dominated by direct interaction, but it is not clear whether twoparticle stripping or knockon processes are involved. Large back angle cross sections are unexplained by DWBA (1965TO06). At 10 MeV, the distributions are consistent with a predominant role for the twonucleon stripping process. The contribution of the knockon process appears to be small (1968OK1D). Gamma branching ratios and multipolarities for ^{11}C levels up to E_{x} = 7.5 MeV have been studied by (1965OL03, 1965RO07): see Table 11.17 (in PDF or PS)), ^{10}B(d, n)^{11}C and ^{12}C(^{3}He, αγ)^{11}C. The following remarks on individual levels derive largely from (1965OL03, 1965RO07): Transitions to ^{11}C_{g.s.} and (2.0) are predominantly E1, fixing the parity of ^{11}C*(7.51) as even and that of ^{11}C*(2.0) as odd. The transition to ^{11}C*(2.0) is not isotropic, so J ≠ 1/2; J^{π} = 3/2^{+} or 5/2^{+} are possible, but if ^{11}C*(2.0) is 1/2^{}, J^{π} = 5/2^{+} is eliminated (see also ^{12}C(^{3}He, α)^{11}C). The relatively large strength of the cascade transition is difficult to understand, and comparison with ^{11}B*(8.00) suggests some deviation from charge symmetry (1965OL03, 1965RO07). E_{x} = 6.91 MeV. The g.s transition is predominantly E1 so J^{π} ≤ 5/2^{+} (1965OL03). Branching ratios favor J = 3/2 or 5/2 (1965RO07): J = 5/2 from ^{12}C(^{3}He, α)^{11}C. The analogue is presumably ^{11}B*(7.30) (1965OL03). τ_{m} < 0.16 psec (1966WA10). E_{x} = 6.48 MeV. The E2 character of the g.s. transition indicates J^{π} ≤ 7/2^{}; J = 7/2 from ^{12}C(^{3}He, α)^{11}C. This level is weakly populated in ^{9}Be(^{3}He, n)^{11}C. The analogue is presumably ^{11}B*(6.74). τ_{m} < 0.25 psec (1966WA10). See also (1966GO12). E_{x} = 6.34 MeV. The g.s. transition is predominantly E1 so J^{π} ≤ 5/2^{+} (1965OL03). Relative transition strengths are consistent with J = 1/2 or 3/2 with the assumption that ^{11}B*(6.79) is the mirror level (1965RO07). τ_{m} < 0.11 psec (1966WA10). J^{π} = 1/2^{+} from ^{12}C(^{3}He, α)^{11}C. E_{x} = 4.79 MeV. Stripping results indicate odd parity, J ≤ 5/2^{} (1965TO06), consistent with the observed M1, E2 nature of the g.s. transition. The strength of the transition to ^{11}C*(2.0) argues against J > 5/2. J = 3/2 from ^{12}C(^{3}He, α)^{11}C. E_{x} = 4.31 MeV. The M1 g.s. transition indicates J^{π} ≤ 5/2^{}. J = 5/2 from ^{12}C(^{3}He, α)^{11}C. E_{x} = 2.00 MeV. The E1 transition from ^{11}C*(7.50) fixes the parity as odd, J^{π} ≤ 7/2^{}. J^{π} = 1/2^{} is fixed from ^{12}C(^{3}He, α)^{11}C. See also (1959LI1D, 1962SE1A, 1963MA1K, 1964BR13, 1966WA1C, 1967BA1E, 1967BO1D).
In the range E_{p} = 0.7 to 4.7 MeV, two broad resonances are reported at 1.14 and ≈ 4.4 MeV: see Table 11.18 (in PDF or PS)) (1954DA20, 1955BA22, 1956CH20, 1957HU79, 1962OP03). At the E_{p} = 1.14 MeV resonance (E_{x} = 9.73 MeV), capture γrays are observed corresponding to the direct groundstate transition (relative intensity 1.0 ± 0.2) and to cascades via the states at 6.48 (0.3), 4.31 (0.18 ± 0.02) and 2.00 MeV (0.05), with (2J + 1)Γ_{γ} = 10, 1.8 and 3 eV for the ground state transition and the cascades through the 6.48 and 4.31 MeV states, respectively (1961JA11). The 6.48 MeV state decays ≈ 1/3 of the time via a cascade through the 4.31 MeV state (1961JA11). The 4.31 MeV state goes by direct groundstate decay (> 98%) while the 4.79 MeV state decays in (15 ± 5%) of the cases via the 2.0 MeV state (E_{γ} = (2.72 ± 0.08) + (2.05 ± 0.08) MeV) (1961DO03). See Table 11.17 (in PDF or PS)).
E_{thresh.} = 4880.1 ± 2.0 keV; Q_{0} = 4432.8 ± 1.8 keV (1966FR09). This result is 44 keV lower than the value used by (1965MA54), and considerably more accurate. We adopt (M  A) ^{10}C = 15702.6 ± 2.0 keV for the present review. The total (p, n) cross section has been measured to E_{p} = 10.6 MeV by (1963EA01): 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 11.18 (in PDF or PS)). The cross section for formation of ^{10}C_{g.s.} measured up to E_{p} = 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 (1959AJ76, 1963VA1C, 1965VA23).
The elastic scattering shows two conspicuous anomalies, at E_{p} = 1.50 ± 0.02 MeV and at 2.18 MeV, corresponding to states at E_{x} = 10.06 and 10.68 MeV with J^{π} = 7/2^{+} and 9/2^{+} (see Tables 11.18 (in PDF or PS)) and 11.19 (in PDF or PS)). 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} = 0.270 MeV (E_{x} = 8.95 MeV) cannot be excluded (1960OV1A, 1962OV02: E_{p} = 0.15 to 3.0 MeV). (1962OV02) also report evidence for a state formed by swave protons near E_{p} = 2.8 MeV. On the other hand (1962AN11) who have studied scattering to E_{p} = 3.5 MeV interpret the data as indicating a resonance above E_{p} = 3.5 MeV. See also (1951BR10, 1961RO05, 1966JA1F).
The yield of 0.71 MeV radiation, from ^{10}B*, rises monotonically from E_{p} = 1.5 to 4.1 MeV (1952DA05, 1954DA20, 1957HU79, 1964BE31), and then shows resonance behavior at E_{p} = 4.35 ± 0.02 MeV and 5.73 ± 0.02 MeV (1962OP03: see Table 11.18 (in PDF or PS)). For E_{p} = 6 to 12 MeV, the cross section shows several sharp maxima superposed on a broad maximum (Γ ≈ 2.5 MeV) at E_{p} ≈ 7.2 MeV (1966SE03). (1966SE03) have also measured the yields of the 1.02 (^{10}B*(1.7) → ^{10}B*(0.7)), 1.43 (^{10}B*(2.1) → ^{10}B*(0.7) and ^{10}B*(3.6) → ^{10}B*(2.2)), 2.86 (^{10}B*(3.6) → ^{10}B*(0.7)) and 4.44 ^{10}B*(5.16) → ^{10}B*(0.7)) MeV gamma rays for E_{p} = 4 to 12 MeV. The yields of both the 2.15 and 3.58 MeV states of ^{10}B show a broad resonance, about 4 MeV wide, centered at E_{p} ≈ 8 MeV, with some fine structure superimposed. The yields of the 1.74 and 5.16 MeV states show this resonance weakly or not at all (this is also true of the neutrons in reaction 6). For the groups that show the broad resonance, the maximum cross sections vary from 20 to 160 mb and tend to increase with increasing Q. For the groups that do not show the broad resonance, the cross sections are all below 5 mb and reach their maxima in the 7  12 MeV region. The weak reactions are those in which the residual nucleus is left in a T = 1 state. This is explained in terms of an α + α + d + p character for the broad resonance. This suggests a significant (α + α + d) cluster structure for the ^{10}B ground state as well as for the first few lowlying states of ^{10}B (1966SE03, 1967WA1L).
See ^{9}B in (1966LA04).
The groundstate yield has been obtained for E_{p} = 4 to 10 MeV (θ = 50°, 90°). There are slight maxima at similar energies to those in the (p, α) yield. However, the angular distributions do not vary strongly over the region covered 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.
The parameters of observed resonances are displayed in Tables 11.18 (in PDF or PS)) and 11.19 (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 (1959AJ76, 1962OV02, 1964JE01). Alpha particles to the 0.43 MeV ^{7}Be state (α_{1}) and 0.43 MeV γrays exhibit all but the 1.2 MeV resonance (1959AJ76, 1962OP03, 1964BE31, 1964JE01, 1966SE03). Weak resonances are also reported at 2.32, 2.57 and 3.59 MeV (1964BE31). A broad maximum dominates the region from E_{p} = 4 MeV to about 7.5 MeV (1966SE03). See also discussion under reaction 6, and (1963VA1C).
Neutron spectra have been studied by (1959AJ76), (1952JO10, 1956CE1B, 1956CE73, 1956GR54, 1956MA83, 1957GR50, 1959NE1A, 1960MC1C, 1963OV02, 1965SI13) and others. Angular distributions, γ spectra and (nγ) correlations are reported by (1960FE13, 1960MC1C, 1960NE17, 1961JA12, 1962FR06, 1963BR1H, 1965OL03, 1966AD1D), (1966GO12, 1966RU01, 1966WE1B, 1967DI01) and (1959AJ76). The principal results are exhibited in Table 11.20 (in PDF or PS)). DWBA fits to the groundstate distribution are reported by (1967DI01: E_{d} = 5 to 7.6 MeV). At E_{d} = 7.6 and 9.0 MeV, the angular distributions corresponding to the first four levels match the PWBA l = 1 patterns moderately well, although the ^{11}C*(2.0) level is relatively weak (1956CE1B, 1956CE73: 7.6 MeV) and (1956MA83: 9 MeV). For E_{d} = 1 to 4 MeV, levels at E_{x} = 6.48, 8.43 and 8.66 MeV show good patterns; ^{11}C*(2.0, 4.3, 4.8, 6.34, 6.91) are quite weak (1960FE13, 1960NE17, 1965SI13: E_{d} = 5 to 8 MeV) and (1961JA12). The ^{11}C*(2.0) is believed to have J^{π} = 1/2^{} and is presumably formed by an exchange or spinflip mechanism (1963AU1A). In jj coupling, it is expected that only the levels (3/2)_{I}, (7/2)_{I} and (5/2)_{II} will show large stripping widths: these are presumably ^{11}C*(0, 6.48, 8.42) (1960BI08, 1960MA32, 1961JA12). Information on the gamma decay of levels up to ^{11}C*(7.50) has been summarized by (1965OL03) and is incorporated in Table 11.17 (in PDF or PS)). See also (1966GO12). Neutron threshold measurements indicate levels at 8.103, 8.426 and 8.656 MeV (1955MA76: ± 8 keV; based on Q_{m}). (1963OV02) has investigated this region with timeofflight techniques and finds that two levels exist near E_{x} = 8.7 MeV, at E_{x} = 8.657 and 8.702 MeV. A broad level is located at E_{x} = 10.69 MeV (Γ ≈ 200 keV) but no evidence is found for other levels reported above E_{x} = 8.7 MeV. The doublet appears to correspond to the sparticle doublet in ^{11}B*(9.19, 9.28) (1963OV02). See also (1959BR75, 1959BU1F, 1960FE01, 1963MO07, 1965MA1K, 1966GO1N, 1966RO1X, 1967SC1K) and ^{12}C.
See (1961RO21).
Angular distributions of the neutrons to the ground state of ^{11}C and to the first five excited states have been analyzed by stripping theory [(1961HI08: E(^{3}He) = 9.84 MeV) and (1965PA10: E(^{3}He) = 3.5 to 10 MeV)] and the excitation energies of nine states have been determined (1961HI08): see Table 11.21 (in PDF or PS)). See also (1959AL96, 1960FO01, 1960SP08, 1962BR10).
The tritons corresponding to the ground state have been observed at E_{α} = 43 MeV (1967DE1K).
For reaction (a) see (1957NO17). For reaction (b) see (1962NE01, 1963TO1E, 1966GA04).
Neutron groups have been observed to ^{11}C_{g.s.} and to the first excited states: see Table 11.21 (in PDF or PS)) (1965OV01). Angular distributions of the groundstate neutrons have been studied at many energies up to E_{p} = 18.5 MeV (1960HI04, 1961AL07, 1964AN1B, 1964SA1D, 1964ST1C, 1965WA04). See also (1956AJ22, 1961GO13, 1961TA12, 1963PA1E, 1964BA16, 1965VA23, 1966UN1A) and ^{12}C.
The groundstate tritons have been observed at E(^{3}He) = 4.8 to 5.0 MeV, dσ/dΩ ≈ 0.26 mb/sr (1965GO05). Angular distributions of t_{0} and t_{1} have been obtained at E(^{3}He) = 10 MeV (1967CR04).
See (1963FU05, 1967FI1E) and ^{12}C.
For reaction (a) see ^{13}C in (1970AJ04). For reaction (b) see ^{13}N in (1970AJ04) and (1962AU1A, 1962BA1A, 1962GU10, 1966PA08).
At E_{p} = 155 MeV, deuteron groups have been observed to the ground state and to excited states of ^{11}C at 2.0 ± 0.1, 4.9 ± 0.1 and (7.0 ± 0.2) MeV (1962RA01, 1963BA1R, 1963RA01, 1967BA2L). See also (1965DE1A, 1965KE02, 1965PU02, 1965VE1B). Angular distributions have been measured at E_{p} = 1920 MeV (1962WA31), 27.5 MeV (1967GL01), 30 MeV (1967CH15), 31.1 and 33.5 MeV (1967GR1M), 36 MeV (1965KE02), 40 MeV (1963KA26, 1966SH1A), 45 MeV (1966MA2B), 54.9 MeV (1968TA1P), and 60 MeV (1965IS06). For spectroscopic factors, see (1967BA2L). See also (1956SE1A, 1959GR1B, 1960RA12, 1961CL09, 1962BE1H, 1963CL07, 1963IS1B, 1963MA1J, 1964JA1C, 1964SH07, 1965GL1E, 1967HO1M, 1967TO1D).
Ten states of ^{11}C have been observed at E_{d} = 50 MeV. The angular distributions are identical with those seen in the mirror reaction ^{12}C(d, ^{3}He)^{11}B to analogue states (1966CH1K): see ^{11}B. At E_{d} = 28.5 MeV the (d, t) and (d, ^{3}He) cross sections to the ground states of the mirror nuclei ^{11}C and ^{11}B are equal (1966DE1C). See also (1959VL23, 1967FI1G), and ^{14}N in (1970AJ04).
Angular distributions of alpha particles to the ground state have been observed at E(^{3}He) = 1.8 to 5.4 MeV (1964KU05), 2.4 to 4.5 MeV (1963LU05), 4.8 to 5.9 MeV (1966BL01), 8.5 to 10.0 MeV (1966SC22), 6.0, 8.8, 9.4 and 10.1 MeV (1960HI07), 16 to 18 MeV (1967GR1L, 1967GR1N), 24.8 MeV (1967HA21), 26 to 33 MeV (1963PA1G), and 26 MeV (1966DA1H). The α_{1} distributions (to the 2 MeV state) have been investigated at E(^{3}He) = 4.2, 4.9, 5.6, 6.0, 8.8, 9.4, 10.1, 16 to 18 MeV (1960HI07, 1964KU05, 1966BL01, 1967GR1L, 1968GR1G). Angular distributions at the higher energies are consistent with l_{n} = 1 for both α_{0} and α_{1} (1960HI07). See also (1966SC22). The energy of the first excited state is E_{x} = 1.990 ± 0.010 (1959PO61), 2.000 ± 0.010 (1960HI07), 1.999 ± 0.004 MeV (1968EA03). See also (1961CA1D, 1962AG01, 1962CA29, 1962GA17, 1962WE1C, 1963PA15, 1964BE1K, 1965GR1R).). See also ^{15}O in (1970AJ04) and (1966HA1Q, 1967BR1N). Studies of αγ correlations have been carried out by (1965WA06: E(^{3}He) = 4.7 MeV), (1965NE06, 1965SC1D: E(^{3}He) = 5.1 MeV), (1967BL22: E(^{3}He) = 9 MeV), (1966GA19: E(^{3}He) = 10 MeV), and (1968EA03: E(^{3}He) = 6 to 12 MeV) with the following results (1968EA03) (see also ^{9}Be(^{3}He, n)^{11}C and Table 11.17 (in PDF or PS)): E_{x} = 8.42 MeV. This level is unbound Γ_{γ}/Γ = 0.2 ± 0.1. E_{x} = 8.11 MeV. Γ_{γ}/Γ < 0.04; J^{π} ≤ (5/2^{}) from ^{9}Be(^{3}He, n)^{11}C (Table 11.16 (in PDF or PS)). E_{x} = 7.51 MeV. For the groundstate transition, the αγ correlation permits J = 3/2 or 5/2. With the J = 5/2 assignment, an unreasonable M2 enhancement is required, therefore J^{π} = 3/2^{+} and x(≡ (L + 1)/L amplitude) = 0.04 ± 0.04 (1968EA03). The correlation in the cascade transition excludes J^{π} = 3/2^{} for ^{11}C*(2.0) and indicates J^{π} = 1/2^{}, x = 0.0 ± 0.03 (1968EA03). E_{x} = 6.91 MeV. The correlation analysis gives J = 5/2, x = 0.02 ± 0.03; J = 1/2 and 3/2 are eliminated. E_{x} = 6.48 MeV. Analysis of αγ correlation gives J = 7/2, x = 0.01 ± 0.06. E_{x} = 6.34 MeV. The cascade transition is via ^{11}C*(2.0) and not ^{11}C*(4.31). From ^{9}Be(^{3}He, n)^{11}C, J^{π} = 1/2^{+} or 3/2^{+}. For J^{π} = 3/2^{+} correlation analysis requires an excessive M2 admixture. The angular distribution of α's at E(^{3}He) = 11.0 MeV gives an l = 0 pattern: J^{π} = 1/2^{+}. E_{x} = 4.79 MeV. The decay is to ^{11}C_{g.s.} and (2.0). With J^{π} = 1/2^{} for ^{11}C*(2.0), the correlation analysis eliminates J^{π} = 5/2^{} and 1/2^{} and gives for J^{π} = 3/2^{}, x(g.s.) = (0.04 ± 0.04) or (3.28 ± 0.49), and x(4.8 → 2.0) = +(0.03 ± 0.05) or +(1.60 ± 0.12). See also (1966GA19, 1967BL22). E_{x} = 4.31 MeV. Analysis of angular correlations gives J = 5/2, x = 0.17 ± 0.03. See also (1966GA19, 1967BL22). E_{x} = 2.00 MeV. Stripping results give l_{n} = 1, J^{π} = 1/2^{} or 3/2^{}. The αγ correlation is isotropic (1965NE06, 1965WA06). The cascade from ^{11}C*(7.51) excludes J^{π} = 3/2^{}. See also (1967BL22).
At E_{p} = 43.7 MeV, a triton group was observed corresponding to a T = 3/2 state at E_{x} = 12.45 ± 0.08 MeV, Γ = 566 ± 60 keV, J^{π} = 1/2^{} (1966MA2N). See also (1968TA1V).
At E_{p} = 38 MeV angular distributions have been obtained for α_{0}, α_{1}, α_{2} + α_{3} (1968GA1N). See also (1961CL09, 1962MA1L, 1963BR14) and ^{15}O in (1970AJ04).
See (1955AJ61) and (1962BI09).
