
^{14}C (1986AJ01)(See Energy Level Diagrams for ^{14}C) GENERAL: See also (1981AJ01) and Table 14.3 [Table of Energy Levels] (in PDF or PS) here. Nuclear models: (1982SA1U, 1983SH38, 1983VA31, 1984AS07, 1984SA37, 1984VA06). Special states: (1983GO1R, 1983GO1B, 1983VA31, 1984AS07, 1984GO1M, 1984SA37, 1984VA06, 1985WE02). Electromagnetic transitions and giant resonances: (1980RI06, 1982RI04, 1984AS07, 1984KU07, 1985WE02). Astrophysical questions: (1981GU1D, 1983RE1B). Applied work: (1979PE1B, 1979TA1B, 1980EL1B, 1980EL1C, 1980SH1Q, 1981FA1E, 1981LI1K, 1981SC1D, 1982ZA1C, 1983BR1Q, 1983DO1H, 1983DO1K, 1983FA1B, 1983FA1H, 1983GI1E, 1983JU1B, 1983KR1B, 1983KU1C, 1983LI1A, 1983NE1A, 1983RE1B, 1983SC1B, 1983SU1C, 1983TU1C, 1984AN1P, 1984AN1Q, 1984BE1H, 1984BI1E, 1984BO1T, 1984CU1A, 1984DO1B, 1984EL1B, 1984EL1C, 1984FA1G, 1984GI1K, 1984GI1L, 1984GI1M, 1984HE1G, 1984HE1B, 1984KA1R, 1984KL1E, 1984LI1R, 1984MO1T, 1984NA1R, 1984NE1C, 1984NE1E, 1984PO1L, 1984PO1C, 1984RU1C, 1984SP1B, 1984SU1B, 1984SU1J, 1984TA1P, 1984VA1D, 1984VO1J). Complex reactions involving ^{14}C: (1981ME13, 1981OL1C, 1981VO06, 1982LY1A, 1983CH23, 1983EN04, 1983FR17, 1983FR1A, 1983MA06, 1983OL1A, 1983SA06, 1983WI1A, 1984AL34, 1984BA1H, 1984GA38, 1984GR08, 1984HI1A, 1984HO23, 1984KU1K, 1985PR01, 1985PR1G, 1985SA02, 1985SH01, 1985SH07). Muon and neutrino capture and reactions (See also reaction 32): (1981GI08, 1981PH1C, 1982SC11, 1983GM1A, 1984KO1U). Pion and kaon capture and reactions (See also reactions also 15, also 25, also 33 and also 34.): (1980GO1M, 1981HAZU, 1981SEZR, 1981SI09, 1981WH01, 1982DE1K, 1982IN1A, 1982KA16, 1982MU09, 1982RE1M, 1982THZZ, 1983AS01, 1983GM1A, 1983KRZZ, 1983LI1G, 1983MA63, 1983PE14, 1983SE16, 1983TR1J, 1984AS05, 1984CO1V, 1984GR27, 1984MI15, 1984SE14, 1985ALZX, 1985DY1C, 1985GI1J, 1985LE05). Hypernuclei: (1981WA1J, 1982KA1D, 1982RA1L, 1983CH1T, 1983FE07, 1983MA63, 1984AS1D, 1984CH1G, 1984SH1J, 1985AH1A). Other topics: (1982NG01, 1983GO1R, 1984PO11, 1985BO1D). Ground state of ^{14}C: (1980WH03, 1981AV02, 1982NG01, 1983ANZQ, 1983VA31, 1984FR13, 1984WE04, 1985WE02).
The adopted value of the halflife is 5730 ± 40 y: see (1976AJ04). See also (1981KHZY). Using Q_{m}, log ft= 9.04 (1971GO40). For discussions of the lifetime of ^{14}C see (1959AJ76, 1970AJ04, 1976AJ04). See also (1981MA1P, 1983GO2C) and (1981PR1G, 1984HUZY; theor.).
These reactions have been studied with E(^{7}Li) to 6.5 MeV: see (1970AJ04) for the early references. For E(^{7}Li) = 2.3 to 5.8 MeV, the cross section for emission of α_{0}, α_{1} and α_{2+3+4} is found to increase monotonically with energy. There is a report of several broad structures in the 0° yield of α_{0} and α_{1} for E(^{7}Li) = 2 to 20 MeV: it is suggested that they are due to a forwarddirection cluster transfer process: see (1976AJ04) for references. The elastic scattering has been studied for E(^{7}Li) = 2.0 to 5.5 MeV by (1983NO08). See also (1983KAZF).
Observed proton groups are displayed in Table 14.6 (in PDF or PS). See also ^{15}N.
Angular distributions have been measured at E(^{7}Li) = 5.6 to 6.2 MeV for the deuterons to ^{14}C*(0, 6.09, 6.59 + 6.73, 6.90 + 7.01, 7.34, 8.32). Gamma rays with E_{γ} = 6094.5 ± 3.2, 6728.1 ± 1.4 and 7011.7 ± 5.2 keV have been reported. For τ_{m} and E_{γ} measurements see Table 14.4 (in PDF or PS) and 14.5 (in PDF or PS) (1981KO08) [see this reference for an extensive study of electromagnetic transitions in ^{14}C and ^{14}N].
See (1981AJ01).
For possible resonant structure in (a) see (1976AJ04). For reaction (b) see (1981AJ01) and see also (1983CE01).
Angular distributions of p_{0} have been measured at E_{α} = 1.43 to 25.1 MeV: see (1976AJ04, 1981AJ01) and at 31.2 MeV (1984KO1Q). See also ^{15}N.
Below E_{x} = 10.4 MeV, ^{14}C*(6.09, 6.73, 6.90 + 7.01, 7.34, 8.32, 9.78) are observed in both reactions at E(Li) = 34 MeV (1984CL08): the states observed at higher excitation energies are displayed in Table 14.7 (in PDF or PS). The intensities of the ^{3}He and α groups in the two reactions are significantly different. Comparison of the angular distributions in reaction (a) and in the analog reaction ^{11}B(^{6}Li, t)^{14}N, as well as other data, leads to the assignment of analog pairs: see reaction 10 in ^{14}N. It is suggested that ^{14}C*(11.73) and not ^{14}C*(11.67) is populated in the inelastic pion scattering (1984CL08). For earlier work on reaction (b) see (1976AJ04).
Observed proton groups are displayed in Table 14.8 (in PDF or PS). Angular distributions have been measured at E_{t} = 5.5 to 23 MeV. The (t, p) strength to the positive parity states of ^{14}C are well accounted for by a model of (sd)^{2} twoneutron states coupled to an inert ^{12}C core: see (1981AJ01). The amplitude of sdshell excitation in ^{14}C_{g.s.} is 0.35 ± 0.02 (1982FO01). The nuclear gyromagnetic ratio for ^{14}C*(6.73) is g = 0.272 ± 0.007 showing that the state is not of a pure (p^{3}_{1/2}d_{5/2}) configuration (1974AL07). For τ_{m} see Table 14.4 (in PDF or PS). See also ^{15}N.
At E_{α} = 65 MeV angular distributions have been measured to ^{14}C*(0, 6.73 ± 0.02(u), 8.40 ± 0.14, 10.69 ± 0.05, 11.69 ± 0.06(u), 14.84 ± 0.4) [groups known to be unresolved are labelled (u)]. The two most strongly populated states (or groups of states) are ^{14}C*(6.73, 10.69). J^{π} = 1^{} and (6^{+}, 5^{}) are favored for ^{14}C*(11.69, 14.84). For the latter 4^{+} is considered to be very unlikely (1980VA17). See also (1981AJ01) for the earlier work.
At E(^{10}B) = 100 MeV ^{14}C*(6.72, 10.74) are strongly populated and the angular distributions to these states are reported. ^{14}C*(15.0) is also observed (1978HA10).
At E(^{16}O) = 128 MeV angular distributions have been measured to ^{14}C*(0, 6.73, 10.74) [J^{π} = 0^{+}, 3^{}, 4^{+}] (1979PR07). See also (1981AJ01).
The thermal capture cross section is 1.37 ± 0.04 mb (1982MU14). The decay is primarily to ^{14}C*(0, 6.59) [(84.0 ± 2.3)%, (8.5 ± 0.5)%] with weaker branches to ^{14}C*(6.09, 6.90) [(2.5 ± 0.5)%, (4.9 ± 1)%]. Gamma rays with E_{γ} = 8173.92, 6092.4 ± 0.2, 2082.6 ± 0.3, 1586.8 ± 0.2, 1273.9 ± 0.2, 808.9 ± 0.2 and 495.4 ± 0.3 keV have been observed: E_{x} = 6093.8 ± 0.2, 6589.4 ± 0.2 and 6902.6 ± 0.2 keV are reported for ^{14}C*(6.09, 6.59, 6.90). A (d, p) spectroscopic factor of 0.060 ± 0.004 was deduced for ^{14}C*(6.59) (1982MU14). The neutron capture yield for E_{n} = 95 to 235 keV shows a resonance at E_{n} = 152 ± 1 keV, Γ_{lab} = 5 ± 1 keV, Γ_{γ} = 4.0 ± 1.6 eV: see Table 14.8 (in PDF or PS) in (1981AJ01). Angular distributions of cross sections and A_{y} and the 90° γ_{0} cross sections have been measured in the range E_{pol. n} = 5.6 to 17 MeV. M1 resonances are indicated at E_{n} ≈ 9.2 and 10.1 MeV (Γ ≈ 200 keV) [E_{x} = 16.7 and 17.5 MeV]. σ(E2) is less than 2% of the total capture cross section for E_{n} = 5.6 to 17 MeV (1985WR01). See also (1984SE16).
The coherent scattering length (thermal, bound) is 6.19 ± 0.09 fm, σ_{scatt} = 4.16 ± 0.13 b (1979KO26). [However F.C. Barker, private communication, has recalculated this value and finds σ_{scatt} = 4.84 b.] The difference in the boundstate scattering lengths, b^{+}  b^{} = 1.2 ± 0.2 fm (1979GL12). The free coherent scattering length a_{+} = 5.47 ± 0.09 fm (1982MU14). See also (1981MUZQ). The total cross section has been measured for E_{n} = 0.10 to 23 MeV: see also (1981AJ01). Elastic differential cross sections have been measured for E_{n} = 1.25 to 6.5 MeV (1981LA05), 4.55 to 8.25 MeV (1982REZY, 1982REZX; also n_{1 → 3}) and 10 to 18 MeV (1982DA05, 1983DA22). See also also ^{13}C, (1983GO1H) and (1985WE02; theor.). The results of an Rmatrix analysis based on σ_{T} and σ(θ) (elastic) measurements (1981LA05) are summarized in Table 14.9 (in PDF or PS).
At E_{p} = 185 MeV (1973DA37) and 200 MeV (1980HO20) the angular distributions of π^{+} and π^{} to the ground states of ^{14}C and ^{14}O are very different. The population of ^{14}C*(6.09, 6.73 + 6.90 + 7.01, 7.34, 8.32) is also reported; that to the first excited state is very strong (1980SO05). See also (1981AJ01), the "GENERAL" section here, (1982GRZY, 1983THZZ, 1984KOZU) and (1979ME2A, 1981AU1C).
Observed proton groups are displayed in Table 14.10 (in PDF or PS). Angular distributions have been measured at a number of energies up to E_{d} = 14.8 MeV [see (1981AJ01)] and at E_{d} = 17.7 MeV (1984PE24; DWBA, CCBA; see Table 14.10 (in PDF or PS)) and at E_{d} = 56 MeV (1984HA26; p_{0}; A_{y}). Gamma rays are exhibited in Table 14.5 (in PDF or PS): studies of these, of the angular distributions analyzed by DWBA, and of pγ correlations lead to the following J^{π} assignments [see (reaction 14 in 1970AJ04) for a full discussion of the evidence and a listing of the relevant references]. ^{14}C*(6.09) is 1^{} (decay is E1); ^{14}C*(6.59) is 0^{+} (internal pairs only); ^{14}C*(6.73) is 3^{} (γ_{0} is E3; l_{n} = 2); ^{14}C*(6.90) is 0^{} (no γ_{0}; 0.81 MeV cascade via 6.09 is predominantly dipole; γ_{0.8} + γ_{6.1} correlation is only consistent with J = 0, and plane polarization leads to negative parity); ^{14}C*(7.34) is 2^{} (strength of cascade decay and angular correlation results). See also ^{15}N.
At E(^{7}Li) = 34 MeV the angular distribution to ^{14}C_{g.s.} has been measured: see (1976AJ04). ^{14}C*(6.09, 6.73, 6.90, 7.01, 7.34, 10.47) are also populated at that energy (1984CL08).
At E(^{9}Be) = 28.8 MeV the angular distribution to ^{14}C_{g.s.} has been measured (1980BO21). See also (1984DA17).
At E(^{11}B) = 114 MeV ^{14}C_{g.s.} is weakly excited but ^{14}C*(6.73, 7.34) [J^{π} = 3^{} and 2^{}] are strongly populated: see (1976AJ04).
Elastic angular distributions have been studied at E(^{13}C) = 16 to 50 MeV (1983KO15). For yield measurements see (1983KO15, 1984BA31). See also (1981BR1P) and (1983KO16; theor.).
Angular distributions have been measured at E(^{17}O) = 29.8 and 32.3 MeV and E(^{18}O) = 31.0 MeV: see (1981AJ01). See also (1984AB1A; theor.).
^{14}B decays primarily to ^{14}C*(6.09, 6.73): see Table 14.2 (in PDF or PS). The halflife is 16.1 ± 1.2 msec.
A narrow resonance is observed in the (γ, n_{0}) reaction at E_{x} = 11.3 MeV with an integrated cross section of 1.65 ± 0.12 MeV · mb of which 0.62 ± 0.06 MeV · mb is due to the GDR tail. Nearly 100% of the photoneutron reaction proceeds to ^{13}C_{g.s.} below E_{x} ≈ 13 MeV. Above this energy (and below 28 MeV) about onehalf of the T_{<} GDR is in the g.s. channel. There are strong indications of E1  M1 interference at 11.3 MeV [for which J^{π} = 1^{+} is suggested]. There is no evidence for E2 excitation for 15 < E_{x} < 20 MeV (1985KU01).
The charge radius of ^{14}C, r_{rms} = 2.56 ± 0.05 fm (1973KL12). At E_{e} = 37  60 MeV (θ = 180°) inelastic groups are reported to ^{14}C*(7.01, 7.34, 8.32, 9.80, 10.5, 11.31 ± 0.02, 12.96, 14.67) with the 11.3 MeV state [1^{+}, Γ = 207 ± 13 keV, Γ_{γ0} = 6.8 ± 1.4 eV] dominant (1977CR02). At E_{e} = 196.3 MeV (θ = 180°) (1984PL02) find the dominant strength to be to 4^{} states at 11.7, 17.3 and 24.3 MeV [ ± 0.1 MeV]. The first two of these are T = 1 states reported in the (π, π) reaction below, the third is suggested to have T = 2. The M4 form factors account for 41% and 37% of the T = 1 and T = 2 singleparticle (e, e') cross section, respectively. The observed transitions to the T = 1 states exhaust 33  45% of the total isovector transition strength and 1  15% of the isoscalar transition strength. Magnetic electron scattering is most sensitive to isovector transitions. ^{14}C*(6.09, 6.7, 7.0, 8.32, 9.8, 10.5, 22.1) are also populated (1984PL02). See also (1983TR1J, 1984LI25) and (1983GM1A, 1984GO1J; theor.).
Elastic angular distributions have been measured at E_{π±} = 50 MeV (1983MIZY, 1984MI1M) and 65 and 80 MeV (1983BL11). At E_{π±} = 164 MeV π^{+} and π^{} spectra have been studied: angular distributions have been obtained to states at E_{x} = 6.7 ± 0.1, 11.7 ± 0.1, 15.2 ± 0.1, 17.3 ± 0.1 MeV with J^{π} = 3^{}, 4^{}, 4^{}, 4^{} (1985HO07). In addition a braod structure (Γ ≈ 1.7 MeV) is observed near 24.5 MeV. It may include a narrower peak at 24.4 MeV. ^{14}C*(7.01, 8.32) are also populated (1985HO07). ^{14}C*(6.1, 10.4, 12.6, 15.1) are also observed (1981HO14). See also reaction 8.
Elastic angular distributions have been studied for E_{p} = 19 to 27 MeV (1984BAZZ). See also ^{15}N. Angular distributions have also been studied at E_{d} = 19 to 27 MeV to ^{14}C*(6.09, 6.59, 6.73, 6.90, 7.01, 7.34, 8.32) (1985BAZZ). See also (1981AJ01) and (1985DI1B; theor.).
Elastic angular distributions have been measured at E(^{3}He) = 4.5 to 18 MeV: see (1976AJ04).
Elastic angular distributions have been studied at E_{α} = 22, 24 and 28 MeV [see (1976AJ04)] and at E_{α} = 35.5 MeV (1984PE24). At the latter energy many inelastic groups have also been studied: see Table 14.11 (in PDF or PS) and reaction 16 (1984PE24). See also (1984RA17), ^{18}O in (1987AJ02) and (1983WI12, 1984LA01; theor.).
See (1983AR11, 1983CU03) and ^{18}O in (1987AJ02).
The elastic scattering for reaction (a) has been studied at E(C) = 12, 15, 18 and 20 MeV, and at 15 MeV for reaction (b) [see (1976AJ04)] and at E(^{14}C) = 31 to 56 MeV for reaction (a) (1985KO04) and for reaction (c) at E(^{14}C) = 31.4, 35.4, 38.9, 47.9 and 55.9 MeV (1981DR01) and 31 to 56 MeV (1980KO23, 1985KO04). For yield and fusion studies see (1981HE08, 1985KO04, 1985RI1C) for reaction (a) and (1980KO23, 1981DR01, 1981FR23, 1985KO04) for reaction (c). (1981FR23, 1985KO04) have studied the yields of γrays from ^{14}C*(6.73) [J^{π} = 3^{}] for E(^{14}C) = 25 to 70 MeV. See also (1981BR1P, 1981HA1V, 1982CI1C, 1982FR1U, 1983BI13) and (1981AB1A, 1981HA18, 1981TA20, 1982AB1F, 1983BA38, 1983FR23; theor.).
The elastic scattering angular distributions have been measured at E(^{16}O) = 20, 25 and 30 MeV: see (1981AJ01). For excitation functions see (1981KO07, 1982HE07, 1983VO1B). See also (1981HA1V, 1982FR1U) and (1981HA18, 1983DU13, 1983FR23, 1984AB1F; theor.).
Observation of the γtransition has led to the determination of the capture rate to ^{14}C*(7.01) [J^{π} = 2^{+}]: the experimental value is four times smaller than that predicted by theory (1981GI08). See also the "GENERAL" section here.
The π^{+} production has been studied at E_{γ} = 173 MeV to ^{14}C_{g.s.}: the CohenKurath wave functions overestimate the data as much as a factor of 4 (1985RO05). See also (1984COZW) and the "GENERAL" section here.
Branching ratios have been measured for the capture of stopped pions to ^{14}C*(0, 7.0 ± 0.1, 8.3, 11.3, 20.0 ± 1.0). The total radiative capture branching is (2.1 ± 0.2)% [see (1981AJ01)]. See also the "GENERAL" section here.
The p_{0} angular distribution has been measured at E_{n} = 14 MeV: see (1981AJ01). At E_{n} = 60 MeV the strongest transitions are to ^{14}C*(7.0 + 8.3, 11.3, 15.4) and to the giant resonance peak, centered at ≈ 20.4 MeV, and angular distributions have been studied to these groups (1982NE04). See also (1984TU1D; search for supermassive CahnGlashow particles), (1981BR1L), (1983FI1L, 1983KH1F; applied) and (1983GM1A; theor.).
See (1981AJ01).
Groundstate angular distributions have been measured for E_{n} = 14.1  14.8 MeV: see (1976AJ04, 1981AJ01).
^{14}C states populated in this reaction are displayed in Table 14.9 (in PDF or PS) of (1976AJ04), together with l and C^{2}S values.
At E(^{6}Li) = 93 MeV ^{14}C*(0, 7.01, 8.32, 10.45) are populated, the first two of these strongly: see (1981AJ01).
Angular distributions are reported at E(^{18}O) = 28, 32 and 36.1 MeV: see (1981AJ01).
The groundstate reaction has been studied at E_{bs} = 24 and 32 MeV (1982BA03): see ^{18}O in (1983AJ01). See also (1981AJ01).
See (1984NE1A).
The groundstate angular distribution has been measured at E_{d} = 13.6 MeV by (1980GA27). See also (1984NE1A).
