
^{11}C (1975AJ02)(See Energy Level Diagrams for ^{11}C) GENERAL: See also (1968AJ02) and Table 11.20 [Table of Energy Levels] (in PDF or PS). Shell model: (1972LE1L, 1973HA49, 1973SA30, 1974ME19). Cluster and collective model: (1972LE1L). Special levels: (1969HA1G, 1969HA1F, 1972MS01, 1973SA30, 1974IR04). Electromagnetic transitions: (1967WA1C, 1969HA1F, 1969HA1G, 1969WA1C, 1973HA49, 1973SA30, 1974ME19). Astrophysical questions: (1970BA1M, 1972KO1E, 1973LA19). Special reactions: (1968BE1F, 1968HA1C, 1968MO1C, 1968NO07, 1969GA18, 1969HI1A, 1969YI1A, 1970KR1C, 1970MO38, 1971AR02, 1971BA16, 1971BI22, 1971EP02, 1973CO1V, 1973JO07, 1973LA19, 1973PH1B, 1973SK01, 1973VA12, 1973WE1N, 1974DI16, 1974HA61). Applied topics: (1974PE04). Pion capture and pion reactions: (1968DA1G, 1968NY1A, 1970LI1H, 1971BL02, 1971KA62, 1971NO08, 1972SE13, 1973AL1D, 1973AL1E, 1973AR1B, 1973CH20, 1973HO43, 1973JA1J (and a correlation (1974JA29)), 1974AM01, 1974MI11). Other topics: (1968BU1B, 1970SH1C, 1972AB14, 1972AN05, 1972CA37, 1972LE1L, 1973RO1R, 1974IR04). Ground state properties: (1967CO1D, 1967SH14, 1968PE16, 1968RO1E, 1969FU11, 1971TA1A, 1971ZO03, 1972LE1L, 1972VA36, 1973CO1P, 1973MA1K, 1973SA30, 1974ME19).
μ = ± 0.997 nm (1968SC18); μ = 0.964 ± 0.001 nm (1973CO1P); see also (1971SH26); Q = ± 0.0322 b (1968SC18).
The halflife of ^{11}C is 20.40 ± 0.04 min (1969AW02). [The weighted mean value of previously reported halflives is 20.34 ± 0.04 min: see Table 11.15 (in PDF or PS) in (1968AJ02).] log ft = 3.591 ± 0.002 (B. Zimmerman, private communication). Relativistic corrections to the log ft value are considered by (1970ST04). The ratio of Kcapture to positron emission is (0.230^{+0.014}_{0.011})% (1967CA09). See also (1957SC29, 1969BE09, 1970BE66, 1972CH1G, 1973HO43), (1968FI02) and (1969LE1D, 1969SU15, 1970DA21, 1970KO41, 1971VA1C, 1973EM1B, 1973MU1D, 1973WI04, 1973WI11, 1974LE1G, 1974ME19, 1974WI1M; 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, n  γ coincidences via ^{11}C*(8.43) [and a 8.43 MeV γray] are reported. ^{11}C*(8.10) was not observed (1967BA53). See also (1969GU1D). 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 10 MeV: see (1968AJ02) for the earlier references and (1969DE1F, 1971DE2C: E(^{3}He) = 4.0 MeV), (1969HO1F: 4.25 and 6.2 MeV), (1974FU11: 10.5 and 13.0 MeV). 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, 8.43) 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 11.21 (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^{+} and 3/2^{+}, respectively 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 (1973SU07), (1968NE1A, 1970EL17, 1970MA38) and ^{12}C.
A broad resonance is reported at E_{p} = 1.15 MeV: see Table 11.23 (in PDF or PS) (1956CH20, 1957HU79, 1967PA19). 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). See also (1961DO03). 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 (1973SU1E) and (1973HA1X, 1973SP02; theor.). The lifetimes of ^{11}C*(4.32, 6.49), τ_{m} < 20 fsec (1969ROZT; abstract).
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 (1973ZW1A; theor.) and ^{10}C in (1974AJ01).
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 Tables 11.23 (in PDF or PS) and 11.24 (in PDF or PS) (1960OV1A, 1962OV02: E_{p} = 0.15 to 3.0 MeV). The elastic scattering has also been studied recently by (1970BO17: E_{p} = 3 to 10.5 MeV), and (1969WA11: E_{p} = 5.0 to 13.4 MeV; optical model analyses). (1969WA11) report a single broad resonance at E_{p} ≈ 5 MeV, while (1970BO17) report seven resonances in the corresponding energy interval, in addition to resonances at E_{p} = 3.6 and 4.4 MeV. See also (1962AN11). The depolarization parameter D has been measured for polarized protons with E_{p} = 25 MeV (1974BI1F) and 50 MeV (1970BA05). See also (1970BE1B) and (1973ZW1A, 1974GU13; theor.).
The yield of γ_{1} [from ^{10}B*(0.72)] 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 and 5.73 MeV (1962OP03: see Table 11.23 (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) with 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 11.22 (in PDF or PS)]: these do not occur in the yield of p_{1} and p_{3} (1971WA21).
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 (1974AJ01).
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 (1974AJ01).
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 parameters of observed resonances are displayed in Tables 11.23 (in PDF or PS) and 11.24 (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 (see (1962OV02, 1964JE01) and (1959AJ76)). 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 (see (1962OP03, 1964BE31, 1964JE01, 1966SE03) and (1959AJ76)). 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 (1968HA1B), (1973ZW1A; theor.) and (1974PE1C; applied).
Angular distribution measurements have recently been reported at E_{d} = 0.5 to 0.8 MeV (1969CH04: n to ^{11}C*(6.35 + 6.49)), 5.8 MeV (1970BO34: see Table 11.25 (in PDF or PS)) and 11.8 MeV (1971MU18: n_{0}). See also (1969JO1F). For recent angular correlation measurements see (1972TH14, 1973PA1N). A great deal of work had previously been done on this reaction: see (1959AJ76, 1968AJ02 [particularly Table 11.20 (in PDF or PS)]) for a discussion of the earlier work. Information on the γdecay of ^{11}C states has been summarized by (1965OL03) and is incorporated in Table 11.21 (in PDF or PS). Table 11.25 (in PDF or PS) summarizes results obtained in this reaction and in the (^{3}He, d) reaction (1955MA76, 1963OV02, 1970BO34). See also (1967CO30, 1973BR24) and ^{12}C.
See (1961RO21).
Angular distributions have been measured recently at E(^{3}He) = 1.38 MeV (1970BE1F: d_{0}), 11.0 MeV (1970BO34: see Table 11.25 (in PDF or PS)), 18.0 MeV (1973FO02: deuterons to ^{11}C*(8.66, 8.70)) and 21.0 MeV (1970FO05, 1971CO07: see Table 11.25 (in PDF or PS)). Table 11.25 (in PDF or PS) displays also the spectroscopic factors 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, 9.28) 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).
Angular distributions have been measured at E_{α} = 46 MeV (1969FO1C; abstract; for tritons to ^{11}C states with E_{x} ≤ 8.1 MeV) and at 56 MeV (1968GA1C, 1969GA11; t_{0}).
See (1957NO17).
Angular distributions of ^{6}He ions corresponding to the transition to ^{11}C_{g.s.} have been measured at E(^{7}Li) = 3.0, 3.5 and 3.8 MeV (1968ST12). At E(^{7}Li) = 24 MeV, the population of ^{11}C*(0, 2.00, 4.32, 4.80, 6.34 + 6.48, 6.90, 7.50, 8.10, 8.43, 8.66) is reported (1974KO1G).
See (1968BU1B, 1969BR1D, 1970GO1B) and (1968AJ02).
See (1968OK06).
See (1968GA03).
Neutron groups have been observed to ^{11}C*(0, 2.008, 4.320, 4.806, 6.330, 6.481) (± 20 keV) (1965OV01). See also (1970CL01). Angular distributions of the n_{0} group have been measured at many energies up to E_{p} = 18.5 MeV [see (1968AJ02)] and at 30.5 and 49.5 MeV (1970CL01: also n_{1} and n_{2} + n_{3}). See also (1969MO32, 1973GO1V), (1969BA1N; astrophys. considerations) and ^{12}C.
Angular distributions of t_{0} and t_{1} have been measured at E(^{3}He) = 10 MeV (1967CR04) and 14 MeV (1970NU02). See also (1969OP1A, 1970OP1B). 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 11.22 (in PDF or PS)] and, possibly, 14.15 MeV (1971WA21). See also (1968BR23).
At E(^{6}Li) = 30 MeV, ^{6}He groups are observed corresponding to ^{11}C*(0, 2.00, 4.32, 4.80, 6.48, 6.90) and the angular distribution to ^{11}C_{g.s.} is reported (1972LE1P).
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 the discussion in (1973DI1C, 1973SP03). See also (1969DE12, 1973GL1C, 1974SC23), (1970MU1D, 1971BI01, 1973MS01, 1973MS02; theor.) and ^{12}C.
For reaction (a) see (1969BA1F; theor.) and ^{12}C. For reaction (b) see (1973HO43). See also (1970LI1H) and the "Pion capture and pion reactions" section in ^{12}C. For reaction (c) see ^{13}C. For reaction (d) see (1968DE22, 1968PA05, 1969PO01) and ^{12}C.
Angular distributions have been recently measured at E_{p} = 55 MeV (1974SH1N: d_{0}, d_{1}, d_{2+3}), 100 MeV (1968LE01, 1969LI01: d_{0}, d_{1}, d_{2+3}, d_{4+5+6}), 155.6 MeV (1969BA05: d to ^{11}C*(0, 2.0, 4.3, 4.8, 6.7, 8.0, 11.0)), 185 MeV (1971KA56: see Table 11.26 (in PDF or PS)) and 700 MeV (1973TH1A, 1974BA58: d_{0} → d_{4}, d_{6}). The broad peak at E_{x} = 15 ± 0.7 MeV and the weak [≈ 7 MeV broad] structure at E_{x} = 18  23 MeV reported by (1969BA05) are not observed by (1971KA56). See also (1969SU02, 1973FA10). For a listing of earlier angular distribution measurements [E_{p} = 19 to 60 MeV] see (1968AJ02). See also (1968TI1A, 1972RO1K, 1974KI1A) and (1968JA1D, 1969DO08, 1969TO1A, 1970BA1N, 1971LO28 [pion], 1971MC15, 1972ST33, 1973TA27, 1974IN07; theor.).
At E_{d} = 28 MeV the t_{0} angular distribution has been measured and a detailed comparison has been made with the results from the mirror reaction ^{12}C(d, ^{3}He)^{11}B (1966DE1C, 1968GA13). Angular distributions of the t_{0} group have also been measured at E_{d} = 20.0, 24.0 and 28.0 MeV by (1971IN1C; unpublished thesis): at the highest energy angular distributions of several triton groups to excited states of ^{11}C are also reported. See also (1971BO50; theor.) and (1968AJ02).
Angular distributions have been measured at many energies. Recent experiments are reported at E(^{3}He) = 9.5, 10.5 and 11.5 MeV (1970BO34), 13.9 MeV (1968OB01: α_{0} → α_{3}), 16, 17 and 18 MeV (1970GR08), 19.1, 27.1 and 35.7 MeV (1968AR12), 24 and 28 MeV (1973FU02), 24.0, 29.2, 34.7 and 39.6 MeV (1974YA10: α_{0}, α_{1}, α_{2}), 35.6 MeV (1970FO05: α_{0} and α to ^{11}C*(8.10, 8.43)), 42 MeV (1973SI11: α_{0} → α_{4}), 44.8 MeV (1966BA13: α_{0}) and 217 MeV (1974GE09: α_{0}, α_{1}, α_{2}, α_{3}). See Table 11.27 (in PDF or PS) for a display of the results and (1968AJ02) for a summary of the extensive earlier work. For discussions of the reaction mechanisms see, e.g. (1970BO34, 1973FU02). Alphaγ correlations have been studied for E(^{3}He) = 4.7 to 12 MeV: see, in particular, (1968EA03). Their results are summarized in Table 11.21 (in PDF or PS) and are discussed in detail in reaction 22 (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 (1970CA28, 1970JA1E), (1969DO08, 1972WE1F, 1974DO15; theor.) and ^{15}O in (1976AJ04).
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).
Reaction (a) has been observed at E(^{10}B) = 100 MeV: ^{11}C_{g.s.} is much more strongly populated than ^{11}C*(2.00) (1973YO1C, 1973YO1D). See also reaction 58 in ^{11}B (1974HA1V). The angular distribution involving the ground state transitions has been measured for reaction (b) at E(^{12}C) = 114 MeV (1974AN36).
See (1967BI06, 1974AN36). See also (1967VO1A, 1969BR1D, 1973SC1J) and ^{15}N in (1976AJ04).
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 11.22 (in PDF or PS)] whose J^{π} is determined to be 1/2^{} [it is thus the mirror of ^{11}Be*(0.32)] (1968CO26, 1968FL02). 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 (1969SC1F) and (1971KA04; theor.).
Angular distributions have been reported at E_{p} = 4.99 to 5.55 MeV (1969WE02: α_{0}), 6.0 to 9.0 MeV (1968SH11: α_{0}) and 7.53, 8.03, 9.54 and 10.54 MeV (1970ME30: α_{0}, α_{1}) and 20.5 to 44.3 MeV (1974PI05: α_{0}, α_{1}). See also (1972MA21), (1968AJ02) and ^{15}O in (1976AJ04).
See (1968AJ02).
See (1969HO1H).
At E_{α} = 42 MeV, the angular distribution involving the transition to ^{9}Be_{g.s.} + ^{11}C_{g.s.} has been measured (1972RU03).
