
^{14}N (1959AJ76)(See the Energy Level Diagram for ^{14}N) GENERAL: See also Table 14.5 [Table of Energy Levels] (in PDF or PS). Theory: See (1955AD1A, 1955OT1B, 1956EL1B, 1956FR1A, 1957BA1H, 1957GR1D, 1957VI1A, 1958FA1A, 1958MA1K, 1958MO17, 1958SK1A, 1959WA16).
See (1957NO17).
Resonances are reported at E_{α} = 1.51, 1.64, 2.16, 2.26, 2.95, 4.53, 4.85, and 5.36 MeV: see Table 14.6 (in PDF or PS) (1953SH64, 1955SH46, 1956BO61, 1958MA1J, 1959GI47). Angular distributions have been measured at E_{α} = 1.51 and 2.16 MeV (1955SH46).
Observed resonances in the yields of γrays (from ^{13}C*) and of various proton groups are given in Table 14.6 (in PDF or PS). Studies of the angular distributions of protons (1953SH64), γray angular distributions, and (pγ) correlations (1954ST20) lead to the J^{π} assignments given in the table. Angular distributions of the protons at the E_{α} = 1.51 and 2.16 MeV resonances are identical with those of the neutrons at the same resonances. However, the reduced neutron width at E_{α} = 1.51 MeV is 5.7 ± 0.5 times the proton width, while at E_{α} = 2.16 MeV the ratio is near unity. It is suggested that strong isobaric spin mixing must occur for the E_{α} = 1.51 MeV state: ^{14}N*(12.70) (1955SH46: see also (1957BA1K, 1958MC63)).
Observed resonances are exhibited in Table 14.6 (in PDF or PS) (1953SH64).
See ^{10}B.
Evidence is reported for levels of ^{14}N at 0, 2.0, 3.15, 3.85 and 4.8 MeV (± 0.3 MeV) (1956QU1A). See also (1944PE1A, 1955BR1A) and (1955AJ61).
At E_{d} = 1.50 MeV, the cross section is less than 1 μb (1955AL16).
Resonances in the yields of protons and neutrons are displayed in Table 14.7 (in PDF or PS): see (1955MA76, 1956BO08, 1956KO26, 1956MC88, 1956VA17, 1957JA37, 1957SA01, 1958MC63). See also (1948BA02, 1949BO67, 1950PH1A, 1957DE22). Angular distributions of protons for E_{d} < 1 MeV are reported to be strongly influenced by stripping effects (1956JU1E, 1956KO26, 1956VA17, 1957JU1A); the same influence is seen for E_{d} > 2 MeV (1956MC88: see ^{13}C). In the region E_{d} = 0.8 to 1.7 MeV, however, (1957SA01) find no stripping contribution and analyze the observed distributions in terms of 5 resonances: see Table 14.7 (in PDF or PS). Although the J^{π} assignments listed are determined in part by choosing γ^{2}_{n} ≈ γ^{2}_{p}, neutron reduced widths seem generally to be nearly a factor of 10 low (1957SA01). A detailed analysis for the region E_{d} = 2.5 to 3 MeV has been made by (1958MC63). Both stripping and compound nucleus formations are involved. See also (1955AL1D, 1955AL1E). For E_{d} = 5 to 30 MeV, the course of the cross section indicates predominance of stripping over compound nucleus effects (1955WI43).
Reported resonances are given in Table 14.7 (in PDF or PS) (1956MC88, 1958MC63). A detailed analysis of the resonances at E_{d} = 2.502 and 2.735 MeV has been made by (1958MC63). See also (1954CA1C, 1956CA1J) and (1955AJ61).
The cross section rises from ≈ 0.1 mb at E_{d} = 16 MeV to ≈ 10 mb at 20 MeV. The magnitude of the cross section is indicative of the pickup character of the reaction (1955WI43).
See ^{10}B.
Not reported.
Proton groups have been observed corresponding to the first five states of ^{14}N. Angular distributions of the various proton groups have been measured for E(^{3}He) = 1.30 to 21 MeV (1957BR18: 1.30 to 2.66 MeV; p_{0}, p_{1}, p_{2}), (1958JO20: 2.0 to 5.0 MeV; p_{0}, p_{1}, p_{2}), (1958SW63: 6.05 MeV; p_{0}, p_{1}, p_{2}, p_{3+4}), and (1958WE1E: 21 MeV). At the lower energies, the distributions show both compound nucleus and direct interaction effects. At the higher energies, the forward peaking increases, and at 6.05 MeV the direct interaction character is well developed. The deexcitation of the 3.95 MeV state has been studied; the direct groundstate decay is (3.7 ± 0.6)% of the total (1956GO42, 1957BR18); see also (1958MO17) and ^{13}C(p, γ)^{14}N. The angular distribution of the 2.31 MeV γrays is spherically symmetric while that of the 1.64 MeV γray (from the 3.95 → 2.31 cascade transition) involves a 22% P_{2}(cosθ) term, consistent with J = 0^{+} and 1^{+} for the 2.31 and 3.95 MeV states respectively (1956GO42, 1957BR18). The polarization of the 1.64 MeV γray also indicates that the parity of these two states is the same (1958LI41). Since the J^{π} assignments permit M1 transitions for both the ground state and cascade transitions from the 3.95 MeV level, the ground state transition would be expected to dominate by a large factor. However, the M1 matrix element effectively cancels for ΔT = 0, T_{z} = 0 (1957VI1A, 1958MO17, 1959WA16). The E2 transition is estimated to be 0.9%: the observed value of 3.7% must be ascribed to collective enhancement (1956EL1B, 1957VI1A). See also ^{14}C(β^{})^{14}N and ^{15}O.
This reaction has been observed at E_{α} = 42 MeV. The deuteron angular distribution is similar to the αparticle distribution in the ^{14}N(d, α)^{12}C reaction at E_{d} = 20 MeV (1958BO71).
Resonances are observed at E_{p} = 0.45, 0.55, 1.16, 1.25, 1.47, 1.55, 1.75, 2.10, and 3.11 MeV; their parameters are displayed in Table 14.8 (in PDF or PS); see also (1957JA37). The decay schemes of various levels of ^{14}N, as derived from the γspectra in this and other reactions are exhibited in Energy Level Diagrams for ^{14}N ((1953CL39, 1953WO41, 1956LE28, 1957BR33, 1957WI27) and D. Hebbard, private communication). At E_{p} = 114 and 126 keV, the capture cross sections are, respectively, (5.1 ± 2.0) × 10^{3} μb and (8.2 ± 2.5) × 10^{3} μb (1957LA15). The 0.45 MeV resonance involves both ground state decay and ≈ 4 MeV cascade radiation with about equal radiative widths (D. Hebbard). The width of the E_{p} = 0.55 MeV resonance (E_{x} = 8.06 MeV) indicates swave formation (J = 0^{}, 1^{}) (1953WO41). The observed isotropy of the radiation supports this assignment (1949DE1A). The level is established as J = 1^{} from ^{13}C(p, p)^{13}C. (1957BR33) find a 1% anisotropy, indicating a dwave admixture of ≈ 6%, θ^{2}_{p}(d) = 0.45; see, however, (1959WA04). The γwidth for the groundstate radiation indicates an uninhibited E1 transition, and hence T = 1 for ^{14}N*(8.06) (1953CL39). The relative strength of the Tforbidden transition to ^{14}N*(2.3) is about 2% (1956LE28, 1956PI1B, 1957BR25, 1957WI27), indicating a strong T = 0 admixture in ^{14}N*(8.06). The fact that the 6.23 MeV state, J = (1^{}); T = 0 (see below) shows a similar contamination, suggests that these two states have a common parentage and contaminate each other (1957WI27): see, however, (1957BR25, 1957BR33, 1959WA04). The strength of the transition 8.06 → 5.69, Γ_{γ} ≈ 0.7 eV, suggests E1 radiation and hence J = 0^{+}, 1^{+}, 2^{+}; T = 0 for ^{14}N*(5.69). The further transition 5.69 → 2.3 rules out J = 0^{+}. J = 2^{+} is excluded by the strength of 8.62 → 5.69, Γ_{γ} = 0.7 eV (1956LE28, 1957WI27); see, however, (1957BR33). According to (1959WA04), the transition strength of 8.06 → 5.69 also admits M1, ΔT = 1, and hence J = 1^{}; T = 0 for ^{14}N*(5.69). The transition ^{14}N*(3.95) → g.s. is 5.5 ± 1.0 % of the cascade, 3.95 → 2.3 (1956LE28, 1956PI1B). See also (1954HI1B, 1956GR17) and ^{12}C(^{3}He, p)^{14}N. The narrow E_{p} = 1.16 MeV resonance, ^{14}N* = 8.62 MeV, J = 0^{+} (from ^{13}C(p, p)^{13}C) shows strong transitions to the ground state and to ^{14}N*(3.95, 5.69): hence T = 1 (1959WA16). The strength of transition to ^{14}N*(6.23) indicates E1 radiation, J = 1^{}; T = 0 for the 6.23 MeV state (1957WI27). However, the angular correlation in the cascade 8.62 → 6.23 → g.s. favors J = 1^{+} or 2^{+} for ^{14}N*(6.23) (1956GO1L, 1956GO39, 1957GA1B, 1957GO30). In this case, the transition strength still requires J = 1; T = 0 for ^{14}N*(6.23). The strong transition 8.62 → 3.95 requires dipole radiation and hence J = 1 for the latter (1959WA04). The E_{p} = 1.25 MeV resonance (E_{x} = 8.71 MeV, J = 0^{} from ^{13}C(p, p)^{13}C) is established as due to swaves by its width (1953WO41). Again the large γwidth is consistent with E1 radiation and T = 1 (1953WI1A). The γspectrum has been studied by (1957BR33) at E_{p} = 0.9 and 1.0 MeV, where the main effects should be due to the E_{p} = 1.25 MeV resonance: see, however, (1957JA37, 1959WA04). The results indicate relatively strong transitions to both the 4.9 and 5.7 MeV levels (see Energy Level Diagrams for ^{14}N) and would appear to exclude the assignments J = 0^{}, 1^{} respectively for these levels. An assignment J = 1^{+} to ^{14}N*(5.10) is suggested. At E_{p} = 1.4 MeV, (1959WA04) finds no evidence of transitions to the 5.10 MeV state. It is pointed out that some of the reported transitions may derive from the background or from other resonances. The angular distribution of the groundstate γrays at the E_{p} = 1.75 MeV resonance (^{14}N*(9.17)) indicates J = 1^{+}, 2^{+} or 2^{}; the relatively large γwidth, 13.3 eV, suggests an uninhibited E1 transition, J = 2^{}; T = 1 (1951DA1A, 1951DA1B, 1953WO41, 1956MA87). However, the polarization is consistent with M1 or E2 but not E1 (1958ST33); see also (1959WA16). The total width is < 400 eV (1956MA87), < 150 eV (1958PA1D), 75 ± 50 eV (1958BO71). The resonant energy is 1746.9 ± 0.8 (1956MA87), 1747.6 ± 0.9 keV (1958BO76). If the transition 9.17 → 6.44 is dipole (ωΓ_{γ} = 1.3 eV), and if J(9.17) is 2, the angular distribution requires J(6.44) = 3 (1953WO41) and T = 0 (1959WA16). See also (1958ME77). From elastic scattering work (see ^{13}C(p, p)^{13}C), the E_{p} = 1.47 MeV resonance, ^{14}N* = 8.90 MeV, has J = 2^{}, with 3^{} and 1^{} possible. The resonance at E_{p} = 2.11 MeV, ^{14}N* = 9.50 MeV has J = 3^{}, with 2^{} and 1^{} possible. A study of the gamma decay scheme and angular distributions confirms the assignments J = 2^{} (T = 1) and J = 3^{}; T = 1 for these two levels. For the latter, the channel spin mixture is (56 ± 14)%J_{c} = 0. Levels at ^{14}N* = 5.83 and 5.10 MeV are J = 3^{()} and J = 2. The mean lives for these two levels, determined by Doppler shift, are 0.5 < τ < 6.5 × 10^{13} sec, and τ > 3 × 10^{13} sec, respectively. The 7.02 MeV level probably has J = 2, while the 6.44 MeV level has J = 2, 3 or 4. Shellmodel assignments and the correlation with the levels of ^{14}C are discussed in some detail (1959WA04). See also (1956WI1G). At the E_{p} = 3.11 MeV resonance (E_{x} = 10.43 MeV), the angular distribution of groundstate γrays is 1  (0.40 ± 0.02)P_{2}(cosθ), indicating J = 2^{}, formed by dwaves with channel spin mixture σ(J_{c} = 0)/σ(J_{c} = 1) = 3/2, followed by E1 radiation, or J = 2^{+}, fwave formation, J_{c} = 1, M1 radiation. The relatively large gamma width, 17 eV, suggests E1 radiation and T = 1 (1957WI30). According to (1959WA16), however, the assignment J = 2^{+} (p or f) is equally satisfactory. The integrated cross section is 0.033 MeVmb, in good agreement with the corresponding value for ^{14}N(γ, p)^{13}C (1957WI30).
The elastic scattering has been studied for E_{p} = 0.15 to 0.75 MeV by (1957HE1C), for E_{p} = 0.45 to 1.60 MeV by (1954MI05) and for E_{p} = 1.5 to 3.4 MeV by (1957ZI09, 1958ZI17): see Table 14.8 (in PDF or PS). Assignments and level parameters for E_{p} < 2 MeV are based in part on a qualitative analysis of the elastic scattering and in part on ^{13}C(p, γ)^{14}N (1952SE01, 1953WO41, 1954MI05). Near the 0.55 MeV resonance, the cross sections of (1957HE1C) are about 10% lower than those of (1954MI05). A close fit to the theory is obtained from E_{p} = 0.12 to 0.65 MeV when the energy variation of Γ and E_{0} are taken into account (1957HE1C: see also (1956CH1E)). Above E_{p} = 2 MeV, the nonresonant background requires s, p and d waves. At the 9.51 MeV level, the channel spin mixture σ(1)/σ(0) = 2/3 corresponds to (5/2, 1/2) in jj coupling (1957ZI09, 1958ZI17): compare ^{14}N*(10.43) in ^{13}C(p, γ). The yield of γrays in reaction (b) has been measured for E_{p} = 3.6 to 5.0 MeV: the 3.1 MeV γyield shows broad resonances at E_{p} = 3.80, 4.1, and 4.14 MeV, while the 3.7 MeV γyield shows one strong resonance at E_{p} = 4.52 MeV (^{14}N*(11.1, 11.36, 11.39, 11.7)) (1957BA29, 1957CO1G).
Observed resonances are exhibited in Table 14.9 (in PDF or PS) (1950AD1A, 1951BL1A, 1953BA1C, 1957BA29). Absolute cross sections have been determined from threshold to 5 MeV by (1958MA1F, 1959GI47). The behavior at threshold appears to reflect the effect of a bound level, possibly that at E_{p} = 3.11 MeV. See also (1958BL55).
Observed neutron groups are exhibited in Table 14.10 (in PDF or PS) (1952BR1C, 1953BE1D, 1955BI1B, 1955GR1D). At E_{d} = 0.86 MeV the third excited state shows a strong, l = 0 stripping pattern (1955GR1D: see also (1955BI1B)). In the range E_{d} = 0.4 to 4.2 MeV, a single strong neutron threshold occurs at E_{d} = 0.422 ± 0.005 MeV (^{14}N*(5.685 ± 0.007)). The outgoing neutrons are likely to be pwave, and the incident deuterons swave (because of their low energy): the results are consistent with J = 1^{+} (1955MA76); see, however, (1959WA04). Observed γrays attributed to transitions in ^{14}N are shown in Table 14.11 (in PDF or PS) (1952TH24, 1955BE62, 1955MA36, 1958RA13). A study of the angular correlation of internal pairs indicates that the transition ^{14}N*(5.69) → g.s. is M1 or E2; of the two transitions (4.91 → g.s.) and (5.10 → g.s.), one is E1 and the other is E2 or M1 (1958CH1A). See also (1958GO81). See also (1955AU1A, 1956EL1B; theor.).
Not observed.
Not observed.
See ^{14}C.
Neutron thresholds have been observed at E_{p} = 671.5 ± 0.5 and 3149.6 ± 1.1 keV, corresponding to the ground state of ^{14}N and to an excited state at 2.3119 ± 0.0012 MeV (1956SA06). See also ^{15}N.
Not observed.
The cross section for neutron production, reactions (a) and (c), exhibits a maximum at E_{γ} = 22.5 MeV, Γ = 3.2 MeV, σ = 15.3 mb (1954FE16: see also (1951JO1B, 1957LI1A)). Below this maximum, there are less intense peaks in the cross section of reaction (a) at (≈ 10.8), ≈ 11.5, and ≈ 12.7 MeV. The latter two have widths of ≈ 0.3 and ≈ 1 MeV, respectively (1955CH1B). At E_{γ}(max) = 23 MeV, proton + recoil energies (reaction (b)) of 0.51, 1.63, and 2.92 MeV are observed, corresponding to the 8.06, 9.18, and 10.43 MeV levels of ^{14}N. Integrated cross sections of 0.6, 0.8, and 1.2 MeVmb respectively, are found, in good agreement with those obtained from the inverse reaction ^{13}C(p, γ)^{14}N (1956WR22). In a resonance absorption experiment, using γradiation from ^{13}C(p, γ)^{14}N at E_{p} = 1.76 MeV, ((1957HA1K) and private communication) find for the 9.17 MeV level of ^{14}N, Γ = 0.07 ± 0.02 keV, σ_{res} ≈ 6 b, (2J + 1)Γ_{γ} ≈ 48 eV. For the 8.06 MeV level, (1956GR17, 1958GR97) finds Γ_{γ} = 10.5 ± 6 eV (compare ^{13}C(p, γ)^{14}N). At E_{γ}(max) = 70 MeV, reaction (d) appears to proceed via a level at 8.2 MeV in ^{10}B (which then decays by proton emission) (1956LI05). See also (1950HO80, 1954BI04, 1955RA1E, 1955SA1F, 1955TI1A, 1956GO1G, 1956JO1C, BE57A, 1958CO1F, 1958JO1C, 1958RH1A) and (1955AJ61).
Elastic scattering of 14 MeV neutrons has been studied by (1952CO41, 1954SM97, 1956BU95). At E_{n} = 3.95 MeV, a 2.30 ± 0.05 MeV γray is observed (1956DA23). See also ^{15}N.
At E_{n} = 14 MeV, deuteron groups are observed leading to ^{13}C*(0, 3.7). The reduced width of ^{14}N(0) for separation into p + ^{13}C(0) is θ^{2}_{p0} = 0.025; for separation into p + ^{13}C*(3.7), θ^{2}_{p2} = 0.06. The ratio is consistent with ^{14}N(0) = ^{3}S_{1} but not with pure ^{3}D_{1}. On the other hand, the value of θ^{2}_{p0}, when suitably corrected, is consistent with a large amount of D character for ^{14}N(0). Upper limits for decomposition into ^{13}C*(3.09) or ^{13}C*(3.86) are θ^{2}_{p1} < 0.003 and θ^{2}_{p3} < 0.03 (1957CA07): see also ^{14}N(p, d)^{13}N.
Angular distributions measurements for groundstate deuterons at E_{p} = 18 MeV indicate l_{n} = 1. The peak cross section (18°, c.m.) is 5.0 ± 0.6 mb/sr, yielding a reduced width θ^{2} = 0.021 for ^{14}N(0). With appropriate correction, the reduced width is in qualitative agreement with that calculated form the independentparticle model and the result suggests that the ^{14}N ground state is largely D. Upper limits of 0.1 to 0.4 mb/sr are quoted for the transition to the first excited state of ^{13}N and are taken to indicate admixtures of p^{8}s^{2} or p^{8}sd in ^{14}N of a few per cent or less (1954ST1D, 1956ST1D). See also ^{14}N(n, d)^{13}C.
Elastic proton scattering has been studied at E_{p} = 9.5 MeV (1954FR38, 1957GI14), E_{p} = 9.8 MeV (1957HI56), 19.4 MeV (1956VA1B, 1957VA1B) and 20 MeV (1955CH1A). Analysis in terms of the optical model is not entirely satisfactory (1956BU95, 1957HI56). Elastic deuteron scattering has been studied at E_{d} = 8 MeV by (1952GI01). Observed inelastic proton and deuteron groups are shown in Table 14.12 (in PDF or PS) (1952AR29, 1953BO70, 1956BU16). At E_{p} = 9.5 MeV, the p_{1} group (to the 2.3 MeV first excited state) is surprisingly weak: < 1/6 of p_{2} (1954FR38). At E_{p} = 6.98 MeV, θ = 90°, the ratio of the intensities of the p_{1} and p_{2} groups to the p_{0} (elastic group) is 5 and 10 %, respectively. For deuterons, the ratio for the d_{2} group is 10%, while an upper limit of about 0.5% is set for the d_{1} group corresponding to the T = 1, 2.31 MeV state, as expected from the T selection rule (1953BO70). Angular distributions of the p_{0} and p_{2} groups have been studied at E_{p} = 9.5 MeV (1954FR38). See also (1956BA1G; theor.). At E_{p} = 96 and 185 MeV, inelastic groups with Q = 9.2, 17, and 21.5 MeV are reported (1958TY46: see also (1956ST30)). See also (1958MA1B, 1958TY49). Inelastic scattering of deuterons is also reported at E_{d} = 9 MeV by (1956GR37): the d_{2}, d_{3} and d_{4} groups are observed. For E_{p} = 3.9 to 4.9 MeV, the 2.3 MeV γradiation is isotropic, confirming the J = 0 assignment to the first excited state (1956BA34). The Doppler shift is very nearly the maximum possible, indicating a halflife less than 3.5 × 10^{13} sec (1955SH84), < 2 × 10^{13} sec (1955TH1A). See also ^{15}O.
At E_{α} = 21.5 MeV, inelastic alpha groups are reported to ^{14}N states at 3.95 ± 0.04, 5.12 ± 0.07, 5.79 ± 0.07, 6.47 ± 0.09, 7.02 ± 0.06, 7.94 ± 0.07, 8.45 ± 0.07 and 10.05 ± 0.07 MeV. Except for the 7.94 MeV level, which has recently been observed in ^{13}C(p, γ)^{14}N, the last three have not been reported in other reactions. The absence of the Q = 2.3 and Q = 8.06 MeV groups is consistent with their T = 1 assignment (1956MI17: see also (1956WA29)). At E_{α} = 31.5 MeV, the upper limit for the α_{1} group, corresponding to ^{14}N*(2.3), T = 1, is 6% of the α_{2} group (1956WA29).
The decay proceeds almost entirely to the J^{π} = 0^{+}; T = 1 state of ^{14}N at 2.3 MeV: see ^{14}O.
At E_{p} = 18.6 MeV, the transitions to the ground and first excited states of ^{14}N have been observed. The angular distributions of both groups are fitted by l_{n} = 1 pickup curves. The peak cross section for the ground state is about 7 times greater than that for the 2.31 MeV state (1957BE49, 1957SH1B). See also (1956FR1A; theor.).
Not reported.
Not reported.
Not reported.
Not reported.
Alphaparticle groups leading to ^{14}N levels at 0, 3.95, 5.01, and 5.70 MeV are reported by (1951AS1A); 0, 3.98 ± 0.04, 5.06 ± 0.05 MeV by (1951BU1A); 0, 3.9, and ≳ 5 MeV by (1953FR23); 0, 3.949 MeV by (1955BR1B). The group leading to ^{14}N*(2.3), T = 1, is ordinarily not observed; however, careful studies in the range E_{d} = 5.5 to 7.5 MeV (1956BR36) and E_{d} = 6.8 to 8.9 MeV (1958DA16) show a weak α_{1}group whose intensity shows marked resonance effects. The observed intensity is consistent with the expected isobaric spin impurity of the ^{16}O, ^{18}F*, and ^{14}N* states involved (1956BR36): see ^{18}F. Angular distributions of αgroups have been measured at E_{d} = 7.0 MeV (1956BR36; α_{0}, α_{1}, α_{2}), 6.8 and 8.9 MeV (1958DA16; α_{0}, α_{2}) and at 19 MeV (1953FR23; α_{0}). See also (1957EL1D; theor.) and (1953SP1A, 1956GR37).
See ^{18}F.
