(See the Energy Level Diagram for 15N)
Reported resonances are listed in Table 15.3 [Resonances in 11B + α] (in PDF or PS) (1954BE08, 1954TR09, 1955SH46, 1956BO61, 1958HA1B: see also (1950HO80)). Some absolute cross sections are given by (1956BO61). See also 14N.
Reported resonances are listed in Table 15.3 [Resonances in 11B + α] (in PDF or PS) (1955SH46, 1958LE23, 1959LE28). Angular distributions of the ground state protons have been measured at 150 energies in the range Eα = 2 to 4 MeV. The assignment J = 5/2+ to 15N*(12.50) agrees with an independent determination in 14N(n, n)14N (1958LE23). Partial widths for several resonances are listed by (1959LE28). See also 14C.
Proton groups have been observed corresponding to the ground state of 15N and to 15N*(5.4, 6.5) and to other unresolved excited states up to Ex ≈ 13.5 MeV (1951BU1D, 1951BU1E, 1957SH1C). Angular distributions have been studied at Eα = 30.5 MeV (1957HU1E) and 41.5 MeV (1957SH1C). They all show strong anisotropic structure typical of direct interaction. The ground state angular distribution is qualitatively similar to that of the inverse reaction. An excellent fit is obtained to the data > 30° under the assumption l (triton) = 1, R = 5.10 × 10-13 cm (1957SH1B, 1957SH1C: see also (1957BU52)).
Observed resonances are displayed in Table 15.4 [Resonances in 13C + d] (in PDF or PS) (1941BE1A, 1950CU13, 1953KO42, 1956MA46). Angular distributions have been measured at a number of energies in the range Ed = 0.3 to 2.8 MeV (1953KO42, 1956KO26, 1956MA46, 1956VA17). At most energies some stripping contribution is observed, although compound nucleus formation appears to be quite important for Ed < 3 MeV (1956MA46). There is some disagreement on absolute cross sections; see (1953KO42, 1956MA46, 1956VA17, 1957HO63). See also 14C.
Observed resonances are listed in Table 15.4 [Resonances in 13C + d] (in PDF or PS). Angular distributions and absolute cross sections are reported. Analysis of the narrow Eα = 2.2 MeV resonance suggests that it is formed by ld = 3 or 4 (1956MA35). See also 11B.
Proton groups have been observed corresponding to the ground state of 15N and to the levels at 5.3 MeV (unresolved) and 6.3 MeV; E(3He) to 4.5 MeV. Angular distributions show strong forward and backward peaking, roughly symmetric about 90°, and may indicate either compound nucleus formation or exchange stripping (1956SC01, 1957IL01, 1957JO1B). See also (1957BR18) and 16O.
Resonances for capture γ-radiation are listed in Tables 15.5 [Low-Energy 14C(p, γ)15N Resonances] (in PDF or PS) and 15.6 [Resonances in 14C(p, γ0)15N and 14C(p, n)14N] (in PDF or PS). The energies of the first four resonances (Table 15.5 [Low-Energy 14C(p, γ)15N Resonances] (in PDF or PS)) agree well with level energies derived from 14N(d, p)15N (1958HE48, 1959HE1D); corresponding values given by (1955BA44) are 8 to 10 keV higher. Quoted limits on lp in Table 15.5 [Low-Energy 14C(p, γ)15N Resonances] (in PDF or PS) are based on estimates of Γp. The assignment 3/2+ to 15N*(10.71) is based on 14C(p, p)14C (1958HE48, 1959HE1D); the assignment 3/2- gives a more satisfactory account of the p, γ0 angular distribution both for this level and for 15N*(10.81) (1955BA44); J = 3/2+ is, however, not excluded for either (1957BA18). Combination of 15N*(10.81) and 15N*(9.84) permits a good account of the low energy (n, n) and (n, γ) cross sections (1959HE1D). The thermal (n, p) cross section can be ascribed to the Ep = 1.5 MeV resonance (15N*(11.61)) (1955BA44: see also 14N(n, γ)15N).
Strong interference effects in the (p, γ) yield curve indicate that the Ep = 1.31 and 1.50 MeV states have the same Jπ (the former is given as 1/2+ from 14N(n, n)14N) and that the Ep = 1.16 MeV state has opposite (odd) parity: J = 1/2-, 3/2-; J = 1/2- is favored by σ(n, n).
The Ep = 1.66 MeV state has even parity. Assignments for these four levels indicated in Table 15.6 [Resonances in 14C(p, γ0)15N and 14C(p, n)14N] (in PDF or PS) are consistent with the 14C(p, n)14N results (1955BA44: see also (1953KA1A)). The state at Ep = 1.50 MeV probably has T = 3/2 and corresponds to 15Cg.s. (1955BA44, 1956BA16: see 14C(p, n)14N). See also (1954SP1B, 1956FE1C).
Elastic scattering has been studied for Ep = 340 to 690 keV. At the Ep = 527 keV resonance (see Table 15.5 [Low-Energy 14C(p, γ)15N Resonances] (in PDF or PS)), the scattering is consistent with d-wave formation of a J = 3/2+ state, Γp = 0.2 keV. No anomalies are observed at Ep = 351 or 635 keV (1958HE48, 1959HE1D).
Resonances reported by (1951RO16, 1953KA1A, 1954BA1C, 1955BA44, 1956SA06) are listed in Table 15.6 [Resonances in 14C(p, γ0)15N and 14C(p, n)14N] (in PDF or PS): see also (1959GI47). Neutron distributions are essentially isotropic at the Ep = 1.16, 1.31 and 1.50 MeV resonances and agree with the assignments derived from 14C(p, γ)15N and 14N(n, n)14N; the distribution at Ep = 1.67 MeV favors J = 3/2. At Ep = 1.79 MeV, the distributions favor 5/2-, but 3/2- is not excluded (1955BA44: see also (1953KA1A)); a computation of the cross section favors J = 3/2 (1956SA06). At Ep = 1.88 MeV, the angular distribution is consistent with the J = 1/2- assignment from 14N(n, n)14N and at Ep = 2.02 MeV the appearance of a P4(cos θ) term supports the assignment J = 5/2, excluding J = 5/2+ (1955BA44: compare Table 15.7 [Gamma Radiation from 14N(n, γ)15N] (in PDF or PS)). Parities of this and the next two states disagree with 14N(n, n)14N results. The Ep = 2.27 MeV state has J = 3/2 or 5/2; the σnn clearly indicates the latter (1955BA44, 1956SA06).
For 15N*(11.61) (Ep = 1.50 MeV), the proton reduced width indicates a single-particle level, while the neutron reduced width is only 10-3. This behavior is taken to indicate that the level has T = 3/2 and corresponds to 15Cg.s.; the predicted energy from M(15C) is 15N*(11.7 to 11.9 MeV) (1955BA44, 1956BA16).
The thermal cross section is 80 ± 20 mb (1957BA18). Observed γ-rays are given in Table 15.7 [Gamma Radiation from 14N(n, γ)15N] (in PDF or PS) together with the 15N levels with which they are presumed to be associated. The decay scheme is in good accord with that derived from 14N(d, p)15N (1957BA18). It does not appear that any of the known levels in this region can account for the large thermal cross section. The J = 1/2+; T = 3/2 level at 15N*(11.61) gives the same capture radiation spectrum and accounts very well for the thermal 14N(n, p)14C cross section, but contributes only 0.4 mb to σnγ. The required level is presumably to be found below the neutron threshold, 15N*(10.2 to 10.7 MeV), and should have a large neutron and a small proton width, =1/2+ or 3/2+, and Γγ0 = 1 eV (1955BA44): compare 14C(p, γ) (1959HE1D). See also (1958RA13).
The coherent scattering cross section is 11.0 ± 0.5 b; the total scattering cross section is 11.4 ± 0.5 b (bound atoms, epithermal neutrons: see (1958HU18)). The large thermal scattering reflects a nearby bound level (1949ME51). The approximate equality of the two values indicates that the scattering has little spin dependence (1955FO27). See (1959HE1D).
Resonances in the range En = 0.4 to 2.3 MeV are listed in Table 15.8 [Resonances in 14N + n] (in PDF or PS) (1951JO23, 1952HI12, 1955FO27, 1955HU1B, 1957HU1D, 1958HU18). Angular distributions at and between these resonances have been studied by (1950BA1C, 1955FO27). The potential s-wave phase shift approximately fits hard-sphere scattering (R = 3.7 × 10-13 cm) for En < 1.3 MeV: from 1.3 to 1.7 MeV, an abrupt increase (negative) appears, which may be associated with a shape resonance. The p-wave phase shift is somewhat smaller than the hard-sphere value; the d-wave shift is < 3° (1955FO27: En < 2.0 MeV).
The narrow En = 430 keV resonance is formed by ln ≥ 1; the proton width is very small, and the level has not been detected in 14C + p. The En = 495 keV resonance appears strongly in 14N(n, p)14C and 14C(p, n)14N, but not in elastic scattering. The two resonances at En = 639 and 998 keV are s-wave, assigned J = 1/2+ and 3/2+, respectively from σmax - σmin (1951JO23, 1952HI12). According to (1956FE1C) an additional broad J = 1/2+ level is located in this region (14C(p, n)14N; Ep = 1.5 MeV: 14N* = 11.61 MeV), presumably the first T = 3/2 state. This level has not appeared in 14N(n, n)14N; see e.g. (1955FO27). The En = 1120 keV resonance is given as J = 3/2 or 5/2 from cross sections; the angular distributions favor 3/2- (1955FO27). The narrow 1188 keV resonance does not appear in (14C + p) (1956SA06). Aside from the J = 1/2- resonance at En = 1211 keV, the remaining Jπ assignments disagree with those derived from 14C + p (compare (1955FO27) and (1955BA44)). For the En = 2250 keV resonance, (1955FO27) find J = 3/2-, while (1953ME1B) report J = 1/2-. From En = 1.8 to 4.0 MeV, there is evidence for considerable structure in the cross section curve, but little agreement as to the exact location of the levels involved. (1953ME1B) list 14 maxima in the total cross section for En = 1.9 to 3.6 MeV. Angular distributions have been studied by (1954HU1B) for energies between 3.2 and 3.9 MeV. The observed distributions can be accounted for by seven levels in the range 2.5 to 4.4 MeV with J = 3/2+ to 7/2+ (1954SP1C, 1954SP1D). See also (1955AJ61, 1956BE98, 1956FL1B, 1957HU1D).
The thermal cross section is 1.75 ± 0.05 b (1958HU18). A major portion of this cross section can be ascribed to 15N*(11.61) (1955BA44). Resonances reported by (1950JO57) occur at En = 495, 640, (993), and 1415 keV; parameters are listed in Table 15.8 [Resonances in 14N + n] (in PDF or PS) (1955HU1B, 1958HU18). Many additional levels have been reported through analysis of particle groups induced by continuous neutron spectra: see (1952AJ38, 1953GI1B, 1957BE71).
Proton groups corresponding to levels of 15N are listed in Table 15.9 [15N Levels from 14N(d, p)15N] (in PDF or PS). The Jπ assignments are based on stripping analysis of angular distributions (1950MA65, 1952GI01, 1954SP01, 1955SH28, 1956DO41, 1956GR37, 1957WA01). A detailed comparison of the experimental observations with shell-model calculations is made by (1957HA1E: see also (1957WA01)). Angular distributions have also been studied by (1954EB02, 1954JO1F, 1956VA17, 1958BO18). The ratio of the reduced widths of the ground states of 15N and 15O is 1.71 (1956CA1D: Ed = 9 MeV).
Observed gamma rays are listed in Table 15.10 [Gamma Rays from 14N(d, p)15N] (in PDF or PS) (1955BE81, 1958RA13). The observation of a 10.81 MeV γ-ray indicates a small proton width for the 15N level; it is suggested that this level may account for the large (n, γ) cross section (1958RA13). According to (1955BA44, 1958HE48), however, the γ-spectra are quite different: see Tables 15.5 [Low-Energy 14C(p, γ)15N Resonances] (in PDF or PS) and 15.7 (in PDF or PS). A 1.88 MeV γ-ray is reported by (1954TH1B), attributed to 15N*(7.16 → 5.2). A p-γ correlation experiment suggests that the 5.3 MeV radiation is dipole (1954ST1C). The relative intensities of the 7.31 MeV γ-ray and of the 15O 6.81 MeV radiation have been determined at several energies by (1955BE1G). See (1956EL1B, 1956FR1A, 1957HA1E, 1957SH1B; theor.).
With bremsstrahlung of Emax = 18.7 and 24.6 MeV, photoprotons corresponding to the ground state and excited states of 14C are observed. Peaks in the yield appear at Eγ = 11.6, ≈ 15, ≈ 18.6 MeV, in addition to the giant resonance at ≈ 20 MeV. The first peak corresponds to excitation of 15N* (J = 1/2+; T = 3/2): the angular distribution is consistent with isotropic emission. At 15 MeV, the distribution indicates dipole absorption, while the giant resonance shows a predominantly sin2θ distribution (1958RH1A, 1958RH30).
At Ep = 185 MeV, the summed proton spectrum shows two peaks, corresponding to ejection of p1/2 and p3/2 protons with binding energies of ≈ 12 and ≈ 19 MeV, respectively. The separation is consistent with the interpretation of 15N*(6.3) as a state with a hole in the p3/2 shell (1958MA1B, 1958TY49).