(See Energy Level Diagrams for 14C)
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 14C: (1981ME13, 1981OL1C, 1981VO06, 1982LY1A, 1983CH23, 1983EN04, 1983FR17, 1983FR1A, 1983MA06, 1983OL1A, 1983SA06, 1983WI1A, 1984AL34, 1984BA1H, 1984GA38, 1984GR08, 1984HI1A, 1984HO23, 1984KU1K, 1985PR01, 1985PR1G, 1985SA02, 1985SH01, 1985SH07).
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).
The adopted value of the half-life is 5730 ± 40 y: see (1976AJ04). See also (1981KHZY). Using Qm, log ft= 9.04 (1971GO40). For discussions of the lifetime of 14C see (1959AJ76, 1970AJ04, 1976AJ04). See also (1981MA1P, 1983GO2C) and (1981PR1G, 1984HUZY; theor.).
These reactions have been studied with E(7Li) to 6.5 MeV: see (1970AJ04) for the early references. For E(7Li) = 2.3 to 5.8 MeV, the cross section for emission of α0, α1 and α2+3+4 is found to increase monotonically with energy. There is a report of several broad structures in the 0° yield of α0 and α1 for E(7Li) = 2 to 20 MeV: it is suggested that they are due to a forward-direction cluster transfer process: see (1976AJ04) for references. The elastic scattering has been studied for E(7Li) = 2.0 to 5.5 MeV by (1983NO08). See also (1983KAZF).
Angular distributions have been measured at E(7Li) = 5.6 to 6.2 MeV for the deuterons to 14C*(0, 6.09, 6.59 + 6.73, 6.90 + 7.01, 7.34, 8.32). Gamma rays with Eγ = 6094.5 ± 3.2, 6728.1 ± 1.4 and 7011.7 ± 5.2 keV have been reported. For τm and Eγ 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 14C and 14N].
Below Ex = 10.4 MeV, 14C*(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 3He and α groups in the two reactions are significantly different. Comparison of the angular distributions in reaction (a) and in the analog reaction 11B(6Li, t)14N, as well as other data, leads to the assignment of analog pairs: see reaction 10 in 14N. It is suggested that 14C*(11.73) and not 14C*(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 Et = 5.5 to 23 MeV. The (t, p) strength to the positive parity states of 14C are well accounted for by a model of (sd)2 two-neutron states coupled to an inert 12C core: see (1981AJ01). The amplitude of sd-shell excitation in 14Cg.s. is 0.35 ± 0.02 (1982FO01). The nuclear gyromagnetic ratio for 14C*(6.73) is |g| = 0.272 ± 0.007 showing that the state is not of a pure (p-31/2d5/2) configuration (1974AL07). For τm see Table 14.4 (in PDF or PS). See also 15N.
At Eα = 65 MeV angular distributions have been measured to 14C*(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 14C*(6.73, 10.69). Jπ = 1- and (6+, 5-) are favored for 14C*(11.69, 14.84). For the latter 4+ is considered to be very unlikely (1980VA17). See also (1981AJ01) for the earlier work.
At E(10B) = 100 MeV 14C*(6.72, 10.74) are strongly populated and the angular distributions to these states are reported. 14C*(15.0) is also observed (1978HA10).
The thermal capture cross section is 1.37 ± 0.04 mb (1982MU14). The decay is primarily to 14C*(0, 6.59) [(84.0 ± 2.3)%, (8.5 ± 0.5)%] with weaker branches to 14C*(6.09, 6.90) [(2.5 ± 0.5)%, (4.9 ± 1)%]. Gamma rays with Eγ = 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: Ex = 6093.8 ± 0.2, 6589.4 ± 0.2 and 6902.6 ± 0.2 keV are reported for 14C*(6.09, 6.59, 6.90). A (d, p) spectroscopic factor of 0.060 ± 0.004 was deduced for 14C*(6.59) (1982MU14). The neutron capture yield for En = 95 to 235 keV shows a resonance at En = 152 ± 1 keV, Γlab = 5 ± 1 keV, Γγ = 4.0 ± 1.6 eV: see Table 14.8 (in PDF or PS) in (1981AJ01). Angular distributions of cross sections and Ay and the 90° γ0 cross sections have been measured in the range Epol. n = 5.6 to 17 MeV. M1 resonances are indicated at En ≈ 9.2 and 10.1 MeV (Γ ≈ 200 keV) [Ex = 16.7 and 17.5 MeV]. σ(E2) is less than 2% of the total capture cross section for En = 5.6 to 17 MeV (1985WR01). See also (1984SE16).
The coherent scattering length (thermal, bound) is 6.19 ± 0.09 fm, σscatt = 4.16 ± 0.13 b (1979KO26). [However F.C. Barker, private communication, has recalculated this value and finds σscatt = 4.84 b.] The difference in the bound-state 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 En = 0.10 to 23 MeV: see also (1981AJ01). Elastic differential cross sections have been measured for En = 1.25 to 6.5 MeV (1981LA05), 4.55 to 8.25 MeV (1982REZY, 1982REZX; also n1 → 3) and 10 to 18 MeV (1982DA05, 1983DA22). See also also 13C, (1983GO1H) and (1985WE02; theor.).
At Ep = 185 MeV (1973DA37) and 200 MeV (1980HO20) the angular distributions of π+ and π- to the ground states of 14C and 14O are very different. The population of 14C*(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 Ed = 14.8 MeV [see (1981AJ01)] and at Ed = 17.7 MeV (1984PE24; DWBA, CCBA; see Table 14.10 (in PDF or PS)) and at Ed = 56 MeV (1984HA26; p0; Ay).
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 Jπ assignments [see (reaction 14 in 1970AJ04) for a full discussion of the evidence and a listing of the relevant references]. 14C*(6.09) is 1- (decay is E1); 14C*(6.59) is 0+ (internal pairs only); 14C*(6.73) is 3- (γ0 is E3; ln = 2); 14C*(6.90) is 0- (no γ0; 0.81 MeV cascade via 6.09 is predominantly dipole; γ0.8 + γ6.1 correlation is only consistent with J = 0, and plane polarization leads to negative parity); 14C*(7.34) is 2- (strength of cascade decay and angular correlation results). See also 15N.
At E(11B) = 114 MeV 14Cg.s. is weakly excited but 14C*(6.73, 7.34) [Jπ = 3- and 2-] are strongly populated: see (1976AJ04).
A narrow resonance is observed in the (γ, n0) reaction at Ex = 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 13Cg.s. below Ex ≈ 13 MeV. Above this energy (and below 28 MeV) about one-half of the T< GDR is in the g.s. channel. There are strong indications of E1 - M1 interference at 11.3 MeV [for which Jπ = 1+ is suggested]. There is no evidence for E2 excitation for 15 < Ex < 20 MeV (1985KU01).
The charge radius of 14C, rrms = 2.56 ± 0.05 fm (1973KL12). At Ee = 37 - 60 MeV (θ = 180°) inelastic groups are reported to 14C*(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, Γγ0 = 6.8 ± 1.4 eV] dominant (1977CR02). At Ee = 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 single-particle (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. 14C*(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 Eπ± = 50 MeV (1983MIZY, 1984MI1M) and 65 and 80 MeV (1983BL11). At Eπ± = 164 MeV π+ and π- spectra have been studied: angular distributions have been obtained to states at Ex = 6.7 ± 0.1, 11.7 ± 0.1, 15.2 ± 0.1, 17.3 ± 0.1 MeV with Jπ = 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. 14C*(7.01, 8.32) are also populated (1985HO07). 14C*(6.1, 10.4, 12.6, 15.1) are also observed (1981HO14). See also reaction 8.
Elastic angular distributions have been studied for Ep = 19 to 27 MeV (1984BAZZ). See also 15N. Angular distributions have also been studied at Ed = 19 to 27 MeV to 14C*(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(3He) = 4.5 to 18 MeV: see (1976AJ04).
Elastic angular distributions have been studied at Eα = 22, 24 and 28 MeV [see (1976AJ04)] and at Eα = 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), 18O in (1987AJ02) and (1983WI12, 1984LA01; theor.).
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(14C) = 31 to 56 MeV for reaction (a) (1985KO04) and for reaction (c) at E(14C) = 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 γ-rays from 14C*(6.73) [Jπ = 3-] for E(14C) = 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(16O) = 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 γ-transition has led to the determination of the capture rate to 14C*(7.01) [Jπ = 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 Eγ = 173 MeV to 14Cg.s.: the Cohen-Kurath 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 14C*(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 p0 angular distribution has been measured at En = 14 MeV: see (1981AJ01). At En = 60 MeV the strongest transitions are to 14C*(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 Cahn-Glashow particles), (1981BR1L), (1983FI1L, 1983KH1F; applied) and (1983GM1A; theor.).
At E(6Li) = 93 MeV 14C*(0, 7.01, 8.32, 10.45) are populated, the first two of these strongly: see (1981AJ01).
Angular distributions are reported at E(18O) = 28, 32 and 36.1 MeV: see (1981AJ01).