(See Energy Level Diagrams for 14N)
GENERAL: See Table 14.7 [Table of Energy Levels] (in PDF or PS).
Model calculations: (1957HU1C, 1959BA1F, 1959BR1E, 1959OT1A, 1959SK1A, 1960PA08, 1960TA1C, 1960WA12, 1961BA1F, 1961BA1E, 1961FR1C, 1961TR1B, 1962IN1C, 1962TA1E, 1962WE1C, 1963KU1B, 1963NA04, 1963SE19, 1963TR02, 1963WA15, 1964AM1D, 1964BR1L, 1964FE02, 1964LO1B, 1964MA1G, 1964NE1E, 1964ST1B, 1964UL1A, 1965CO25, 1965GL09, 1966BO1R, 1966HA18, 1966HA31, 1966HE1E, 1966MAZY, 1966MI1G, 1966WI1E, 1967CO32, 1967EV1C, 1967KU1E, 1967LI06, 1967PA05, 1967SO1A, 1968CO13, 1968DE13, 1968EI1C, 1968GO01, 1968HO1H, 1968KU1E, 1968NO1C, 1968RA10, 1968SO1B, 1968ZH05, 1969UL03, 1969VA1C).
General calculations and reviews: (1960PA08, 1962MA1P, 1963BL1B, 1963VL1A, 1964LI1B, 1964MC1C, 1964TH03, 1964YO1B, 1965BE1B, 1965GI1B, 1965KO1D, 1965MA1N, 1966DA1E, 1966MAZY, 1966WI1E, 1966ZA03, 1967BI06, 1968FR03, 1968GA03, 1968HI1H, 1968LA1J, 1968RI1H, 1968RO1C, 1969AT1A, 1969FR1E, 1969WA1F).
Electromagnetic transitions: (1959FA1C, 1959WA16, 1959WA04, 1960WA12, 1962MO1A, 1962UN1A, 1963KU03, 1964HE1F, 1965BI10, 1966HA31, 1966WA1E, 1967KU1E, 1967PO1J, 1967WA1C, 1968RO1C, 1969VA1C).
Meson interactions: (1967BA2H, 1967BA78, 1967BU1D, 1967FO1A, 1967KO1D, 1967MI1B, 1968BA2G, 1968BA1M, 1968BA48, 1968CH1F, 1968GO1T, 1968KO1C, 1968NO1A, 1968RI1H, 1968TA1C, 1968WI1B, 1968ZU1A, 1969CH1C, 1969MO1E, 1969SA1L, 1969WU1A).
Spallation: (1965ZH1A, 1967AU1B).
Ground state: J = 1; μ = +0.40361 nm (1964LI14).
See also (1959KA07, 1960PA08, 1961BR13, 1962BA1K, 1962HE1A, 1966MA1P, 1967SH05, 1967SH14, 1968PE16, 1968RO1C, 1969AL04, 1969FU11, 1969VA1C, 1969WU1A).
Gamma rays due to the 3.95 → 2.31, 4.91 → 0, 6.21 → 2.31 and 6.44 → 0 transitions have been observed in these reactions and in reactions 6 and 19: Eγ = 1631.3 ± 1.3, 4913.8 ± 3.0, 3883.0 ± 1.9 and 6443.7 ± 1.8 keV, respectively. τm = 0.62 ± 0.08 psec for 14N*(6.44) [see also Table 14.12 (in PDF or PS)] (1969TH01). For reaction (b), see also (1957NO17).
Resonances are reported at Eα = 1.507 ± 0.004 MeV (1961BA22) and at 1.64, 2.16, 2.26, 2.95, 4.53, 4.85 and 5.36 MeV: see Table 14.8 (in PDF or PS) (1953SH64, 1955SH46, 1956BO61, 1959GI47). See also (1969ED1C).
Observed resonances in the yield of 3.09, 3.68, 3.85 and 0.17 [3.85 → 3.68] MeV γ-rays and of various proton groups are displayed in Table 14.8 (in PDF or PS) (1953SH64, 1954ST20, 1969GA01). Excitation functions have also been measured for Eα = 4.5 to 10 MeV (1969ED1C), 12.4 to 16 MeV (1967IV1B; p0) and 9.5 to 26 MeV (1966SP08). See also (1959AJ76).
Observed resonances below Eα = 2 MeV are exhibited in Table 14.8 (in PDF or PS) (1953SH64). Excitation curves have also been determined for Eα = 3.2 to 3.8 MeV (1960ON01), Eα = 12 to 24 MeV (d0) and 18 to 25 MeV (d1) (1967AL16). Clear resonance structure is not observed at these higher energies. See also (ED69D).
The yield of 0.72 MeV γ-rays has been measured for Eα = 2.1 to 3.5 MeV: observed resonances are shown in Table 14.8 (in PDF or PS) (1969GA01).
At E(6Li) = 5 MeV, deuteron groups are observed to the ground state of 14N and to excited states at 3.95, 4.91, 5.10, 5.69, 5.83, 6.23, 6.44, 7.03, 7.97, 8.47, 9.00, 9.13, 9.41, 9.71, 10.09, 10.43 and 11.06 MeV.
The T = 1 state at 10.43 MeV is populated weakly ((1966MC05) and private communication). See also (1963MO1B, 1969CO1D). Branching ratios for the γ-decay of 14N states have been measured: see Table 14.9 (in PDF or PS) (1966CA07). See also reaction 1 (1969TH02). See also (1964CA18, 1965CA05, 1967CA1D), (1966BR1G) and (1965RO1M, 1966RO1E, 1968TA1N).
Triton groups corresponding to a number of 14N states have been observed at E(7Li) = 5 MeV: see (1966MC05) and reaction 6. The angular distribution of the ground state tritons has been measured at E(7Li) = 4.5 MeV by (1963MO1B). See also (1965CA05, 1967CA1D) and (1966RO1E).
The capture γ-rays (reaction (a)) havre been studied for E(3He) = 1 to 3 MeV. The differential cross section (at 90°) for the γ0 transition increases rapidly with energy from ≈ 0.002 μb/sr at 1 MeV to ≈ 0.5 μb/sr at 3.0 MeV. At the latter energy Iγ/Iγ0 ≈ 0.22 ± 0.08. There is some evidence also for transitions to higher excited states of 14N (1965PU1B).
The excitation function at 0° in the range E(3He) = 1.5 to 5.6 MeV for neutrons corresponding to 13Ng.s. (reaction (b)) shows a broad peak at E(3He) = 4.15 MeV which may indicate the existence of a 14N state at Ex ≈ 24.0 MeV, Γ ≈ 1 MeV (1966DI04). The excitation function for reaction (b) has also been measured for E(3He) = 6 to 18 MeV (1967HA20). See also (1964DI1C, 1965BR42).
Yield curves for protons (reaction (c)) have been measured for E(3He) = 3.0 to 5.5 MeV (p0, p1, p1 + p2 + p3): they are rather featureless (1959HO01). This is also true for the ground state deuterons of reaction (d) in the same energy interval (1959HO01). Yield curves for reaction (e) have been measured for E(3He) = 6 to 18 MeV (1967HA20) and 10 to 30 MeV (1965BR42). See also 13C, and 11C and 12C in (1968AJ02). For reaction (f), see (1968PA1Y).
The excitation functions of α-particle groups (α0, α1, α2, α3) (reaction (g)) have been measured for E(3He) = 2.2 to 5.5 MeV. No significant resonance behavior is seen except for the α2 group which, in the 15° excitation function, exhibits a resonance at E(3He) = 4 MeV, Γ ≈ 1 MeV (1965FO06). See also 10B in (1966LA04). The excitation function for the reaction 11B(3He, 6Lig.s.)8Beg.s. has been measured for E(3He) = 1.4 to 5.8 MeV: no pronounced compound nucleus effects are observed (1967YO02, 1967YO1C).
Angular distributions have been measured for Eα = 2.4 to 3.7 MeV (1966MA04; n0), 3.4 to 3.7 MeV (1966MA04; n1), 2.1 to 5.4 MeV (1962CA05; n0) and 13.5 and 13.9 MeV (1962KJ03; n0, n2). See also (1959HE1B) and (1959AJ76).
At E(6Li) = 4.5 MeV, the angular distributions of the triton groups to 14N*(0, 2.31, 3.95) have been measured (1963MO1B). See also (1965CA05).
The capture cross section is reported to be ≈ 0.6 ± 0.2 μb at Ed = 1 MeV (1961KN03): at Ed = 1.5 MeV it is < 1 μb (1955AL16).
Resonances in the yields of neutrons and protons are displayed in Table 14.10 (in PDF or PS). Recent measurements of the yields of neutrons and protons are listed in Table 14.11 (in PDF or PS). See also (1965WI11, 1968CO04, 1969RO1R) and (1959AJ76).
Angular distributions of neutrons and protons have been reported at many of the energies listed in Table 14.11 (in PDF or PS). Except at very low energies, direct interaction is the predominant mechanism although resonances are observed for the first few MeV (see Table 14.10 (in PDF or PS)) and fluctuations persist to 12 MeV (1963EV04). See also (1955WI43), (1959AJ76), 13C and 13N. At Ed = 2.50 MeV (14N* = 12.41) the (d, p3γ) angular correlation is undistorted. This is an example of a resonant direct reaction due to a single-particle state (1966KA05).
Polarization measurements are summarized in Table 14.12 (in PDF or PS). See also (1968BA2R, 1968BA47; theor.) (reaction (a)), and (1959AL08, 1962GR10, 1963BE1M, 1966SK1A, 1967GR1L; exp.), (1967CI1A, 1967KH1A, 1968BA2R, 1968BA47, 1969PE1N, 1969PE1L; theor.) (reaction (b)). See also the reviews by (1961GO1K, 1963HA1G, 1966DA1B, 1966MI1E).
For reaction (a) see also (1959BR75, 1966WY01, 1967SC43, 1967WY02; exp.) and (1961MA1E, 1964CA1F, 1967HO1K, 1968NO1C; theor.). For reaction (b) see also (1963GE03, 1967AU05, 1967MO1P, 1967TI1A, 1968NO1C, 1969PE09). For a discussion of sequential decay, see (1963PI04) and 13C and 13N.
Reported resonances are displayed in Table 14.10 (in PDF or PS). Recent measurements of yields of scattered deuterons are listed in Table 14.11 (in PDF or PS). See also (1961CI08, 1962GR10, 1963GE03, 1965BA1W, 1967AU05, 1968BA2P, 1968GO1N), and (1965SA1H, 1966BA60, 1967HO1K, 1969IW1D). See also 12C in (1968AJ02) and (1959AJ76).
Polarization measurements are summarized in Table 14.12 (in PDF or PS). See also (1963ZA1B, 1965CA05, 1967RU1A; theor.).
The cross section rises from ≈ 0.1 mb at Ed = 16 MeV to ≈ 10 mb at 20 MeV (1955WI43). See also 11C in (1968AJ02).
Excitation functions have been measured for Ed = 5 to 29 MeV: see Table 14.11 (in PDF or PS).
Resonant structure has been reported by (1966PA1J) and (1968JA09): see Table 14.10 (in PDF or PS). Angular distributions have been measured at many of the above energies and analyzed by DWBA: see (1968KL06, 1969YA1C) and 10B in (1966LA04). See also (1963PE07, 1967HO1K).
The yield of the α2 group (to 10B*(1.74) [Jπ = 0+; T = 1] is typically < 1% of the intensity of the groups to the neighboring T = 0 states in the range Ed = 9 to 12.5 MeV. This is partly due to isospin conservation and partly to the Jπ selection rule involved in this transition. When the latter effect is calculated and the corresponding factor removed, the intensities of the T = 1 α2-groups range from ≈ 10% of the intensities of the T = 0 α-groups at Ed = 9 MeV to ≈ 1-2% at Ed = 11 MeV. Above Ed = 11.5 MeV, the yield of the α2 group increases slightly indicating perhaps a direct-interaction mechanism involving isospin mixing at the surface of the nucleus (1966ME09). [See, however, below). The mixing might also occur through Coulomb excitation during the d-capture or the α-emission (1966ME09). Some fluctuations in the cross sections, with widths of a few hundred keV, are observed at forward and backward angles. Ericson fluctuations may be involved (1966ME09). The data of (1966ME09) have been interpreted as indicating an intermediate structure resonance corresponding to Ex ≈ 18 MeV, Γ ≈ 2 MeV [Jπ = 3-], whose doorway state is a single-particle cluster resonance in either, or both, the entrance or exit channels (1968NO1C). However, (1969SM03) find that the broad structure reported by (1966ME09) at Ed ≈ 13 MeV can be resolved into at least three separate peaks, in contradiction to the predictions of (1968NO1C). Both the angular distributions and the excitation functions can be interpreted in terms of a few resonant states of 14N [l = 4 and 5 account for most of the cross section at Ed ≈ 12.5 MeV], without introducing any large direct reaction amplitudes (1969SM03). See also (1968NO1C).
Angular distributions of the n0, n1 and n2 groups have been measured at Et = 1.7 MeV (1966MA2G). At E(12C) = 12 to 20 MeV, the lifetimes of 14N*(5.11, 5.83) have been determined using recoil distance method: τm(5.11) = 12.4 ± 1.4 psec, τm(5.83) = 18 ± 2 psec: see Tables 14.9 (in PDF or PS) and 14.13 (in PDF or PS). The 5.11 → 0 transition is enhanced by 2.2 ± 0.7 W.u. The allowed M2 5.11 → 2.31 transition has |M|2 = 0.83 ± 0.14 W.u. while the isospin forbidden part of the 5.11 → 0 transition has |M|2 = (3.3 ± 1.3) × 10-3 W.u. (1968AL12). See also (1966AL11).
Many proton groups have been observed: see Table 14.14 (in PDF or PS). At E(3He) = 20 MeV angular distributions of the protons corresponding to states with 0 < Ex < 12.6 MeV have been measured by (1968MA29) and analyzed using the distorted-wave calculations of (1965GL09) and spin-independent interaction potential. L-values have been assigned and are displayed in Table 14.14 (in PDF or PS).
It is pointed out that in this reaction unnatural parity states of T = 1 are not allowed: the proton groups corresponding to the 0- 8.80-MeV state and the 2- 9.51-MeV state, both of which are T = 1, are not observed (1967MA1G, 1968MA29). Angular distributions have also been obtained at many other energies: see (1965GR1R: 1 - 1.8 MeV; p0, p1, p2), (1963LU01, 1963LU1F, 1964LU1B: 2.3 - 3 MeV; p2), (1964KU05: 2.5 - 4.9 MeV; p0 → p9), (1969HA49: 3.0 - 9.2 MeV; p0, p1: 3.0 - 11 MeV; p2 → p4: 5.1 - 11 MeV; p5 → p9), (1967CL1C: 3.5 MeV; p0 → p8), (1966BL01: 5.1 MeV; p2 → p6), (1968LA19: 5.3 - 5.5 MeV; p1, p2, p3, p5), (1965FU16: 6.6 - 10.7 MeV), (1960PR12: 13.9 MeV; p0, p1, p2), (1969HO23: 15 MeV: 0 < Ex < 12.8 MeV), (HO66, 1967FO1E: 15 MeV), (1968MA46: 25.3 MeV: 0 < Ex < 9.5 MeV) and (1959AJ76) for a listing of the earlier work. See also 15O. The parity of 14N*(6.44) is even from angular distribution measurements of protons and γ-rays at the E(3He) = 2.99 MeV resonance (1964KU05).
The γ decay of many states has been studied: Table 14.9 (in PDF or PS) displays observed branching ratios and radiative widths (1964WA09, 1965NE06, 1965RI02, 1965WA06, 1966GO15, 1967CH19, 1967GA12, 1967OL02, GA69J, 1969HA49). A very accurate value of the excitation energy of 14N*(5.11) is derived from Eγ: Ex = 5.10587 ± 0.00018 MeV (1967CH19). p-γ angular correlations have been measured at many energies. The results demand J = 0 or 1 for 14N*(4.91) and J = 2 for 14N*(5.11). The ground state transition for the latter contains E1, M2 and E3 components (1959WA04, 1965BL04, 1965NE06, 1966GO15), J = 2 for 14N*(7.03) and the angular correlation of the 2.51 MeV γ-ray (8.96 → 6.44) indicates J ≤ 5 for 14N*(8.96) (1967BL22). Jπ = 5+ (1967GA12). See also (1963LU01, 1963LU1F, 1964LU1B) and Table 14.9 (in PDF or PS). Polarization measurements lead to Jπ = 0-, 1- for 14N*(4.91) and odd parity for 14N*(5.11, 5.83) (1963BE33, 1968BL09). The parity of 14N*(6.21) is even (1964WA09). An analysis of elastic 3He, the angular distribution of the protons to 14N*(6.44) and of the subsequent ground state γ-rays at E(3He) = 2.99 MeV (15O*(14.46)) leads to even parity for 14N*(6.44) (1964KU05). The angular correlation of internal pairs is consistent with E2 radiation (1964WA09) for the 6.44 → 0 transition.
Measurements of mean lifetimes are displayed in Table 14.13 (in PDF or PS) (1964BE12, 1965LO07, 1966LI07, 1967LI04, 1969GA16, 1970GA09). See also (1963BE33).
See also (1959AL96, 1959FA1A, 1959HI69, 1960HA31, 1961CE02, 1967BE2G, 1967FO1E, 1967OG1A, 1969BA1Z, 1969GO11, 1969HA2D) and (1959EL43, 1960EL1C, 1960NE1A, 1962EL1C, 1967HA1T, 1969BO1G, 1969LI1D; theor.).
Angular distributions of deuterons corresponding to various states of 14N (see Table 14.15 (in PDF or PS)) have been measured at Eα = 42 to 53 MeV (1959BO40, 1960HA32, 1962CE01, 1962HA40, 1965PE03, 1967ZA01 ). See (1962CE01, 1963GL1C, 1965GL09) for discussions of the analysis. The known T = 1 states are not excited in this reaction: see Table 14.15 (in PDF or PS) and (1960HA32, 1965PE03, 1967ZA01, 1968NO1C). [It should be noted that in addition to isospin conservation, angular momentum and parity considerations would also inhibit the excitation of the Jπ = 0+; T = 1 2.31-MeV state; see, e.g., (1960HA32).] No evidence is seen at Eα = 42 MeV for deuterons in the Jπ = 0+; T = 1 singlet state leading to the excitation of the 2.31-MeV state: d-bar1/d0 = 5 × 10-3 (1967CR1G, 1969BR1N). The deuteron spectrum is dominated by very strong groups corresponding to the (d5/2)2, Jπ = 5+, state at 8.96 MeV, and to a state at 15.1 MeV (1962HA40, 1966RI04).
Comparison of the angular distribution of ground state deuterons (Eα = 41.7 MeV) with that of the ground state alphas from the 14N(d, α)12C reaction (Ed = 20 MeV) leads to an upper limit of 3% for the time reversal non-conserving fraction of the Hamiltonian (1959BO40, 1959HE1C).
See also (1964NA1E, 1965PE17, 1966BR1G, 1967OG1A) and (1961EL1A, 1968ZE1B; theor.).
At E(6Li) = 20 MeV, α-groups corresponding to most of the T = 0 states with Ex < 12.7 MeV are reported. See Table 14.15 (in PDF or PS). The spectrum is dominated by the α-group corresponding to the 5+ state at 9.0 MeV (1968ME10). See also (1962HO06, 1967DZ01). The α1 group to the Jπ = 0+; T = 1 state at 2.31 MeV has been observed. Its intensity ( < 3% of α0) decreases sharply from E(6Li) = 4 to 5.5 MeV, while the intensities of the α0 and α2 groups (to T = 0 states) increase rapidly. It is suggested that broad levels at the higher excitation energies corrrespond to such short lifetimes that the Coulomb forces do not have enough time to change the relative amountss of various isospin components in the compound nucleus wave function (1965CA06). See also (1962HO06, 1967DZ01).
Angular distributions of α-particles have been reported for E(6Li) = 2.0 and 2.4 MeV (1966BE07; α0, α2), 3.0 MeV (1963BA08; α0), 3.2 to 4.0 MeV (1962HO06; α0, α1, α2), 4.0 to 5.5 MeV (1965CA06; α1), 4.5 to 5.5 MeV (1966HE05; α0, α2) and 20 MeV (1968ME10: see Table 14.15 (in PDF or PS)).
Doppler-shift attenuation measurements have led to the determination of τm for the 6.44 MeV state: (0.63 ± 0.08) psec (1969TH01): see Table 14.13 (in PDF or PS) and reaction 1. See also Table 14.9 (in PDF or PS).
See also (1960SH01, 1960SH05, 1961MA1K, 1961MA33, 1962LI08, 1963OL1B, 1964CA18, 1967CH34, 1967OG1A, 1968DA20) and (1962IN1C, 1963TA1B, 1966RO1E, 1966RO1F, 1968HO1J, 1968RO1D; theor.).
At E(11B) = 115 MeV, the 9Be spectrum is dominated by groups corresponding to the 14N 5+ state at Ex = 8.96 MeV, the 4+ state at Ex = 12.79 MeV and to the 6- state at Ex = 15.10 MeV, the levels also strongly populated in the 12C(α, d)14N reaction (see reaction 18) (1966PO1E, 1967PO1E) and private communication). Groups to 14N*(0, 3.95, 5.83, 6.44, 10.81) are also reported (J.E. Poth, private communication). See also (1967VO1A). The angular distributions of the two strong groups are smoothly varying, exponential functions of angle, and have been fitted, in terms of a surface-diffuseness parameter, using a diffraction model (1965SA07). See also (1965DA1E, 1965GR1F) and (1964FL1D, 1964NA1E, 1967OG1A, 1968RO1D, 1969RO1G, 1969BR1D). For reaction (a), see (1969RO1G).
At E(14N) = 28 MeV, excitation of 14N*(0, 3.95, 4.91, 5.11) and some higher states is reported. The total cross section for excitation of the T = 1 state at Ex = 2.31 MeV is < 60 μb (1961HA04). See also (1968HU1H, 1969BR1D, 1969HE06).
Observed resonances are displayed in Table 14.16 (in PDF or PS). The decay schemes of various levels of 14N, as derived from the γ-spectra in this and other reactions are exhibited in Table 14.9 (in PDF or PS) (1953WO41, 1959WA04, 1960HE14, 1960RO13, 1960RO23, 1963PR03, 1963RO17, 1964RO03, 1965DE19, 1967RI1D, 1968BL1E, 1968RI1R).
The low-energy capture cross-section yields an extrapolated σ-factor at Ep = 25 keV (cm), S0 = 6.0 ± 0.8 keV · b (1960HE14). See also (1963BR14, 1964FO1A, 1966BA2P, 1967FO1B). The capture cross section rises from (7.7 ± 1.8) × 10-10 b at Ep = 100 keV to (9.8 ± 1.2) × 10-9 b at Ep = 140 keV (1961HE02).
Direct radiative capture of protons into the lowest three odd-parity states 14N*(4.91, 5.11, 5.69, 5.83) has been studied by (1964TR04). See also (1963RO17).
The angular distribution of the γ-rays at the Ep = 0.45 MeV resonance (14N* = 7.97 MeV) is consistent with Jπ = 2- (1960HE14). The width of the Ep = 0.55 MeV resonance and the isotropy of the γ-rays (1949DE1A, 1953WO41) indicate s-wave formation of 14N*(8.06): Jπ = 1- from 13C(p, p)13C. The decay properties of this state (see Table 14.9 (in PDF or PS)) show that the ground state transition is an uninhibited E1 transition, and thus that 14N*(8.06) has T = 1 (1953CL39) but with a strong T = 0 admixture [as shown by a 2% (8.06 → 2.31) transition] (1956LE28, 1957BR25, 1957WI27). The strong transition 8.06 → 5.69 admits either E1, ΔT = 1 or M1, ΔT = 1. Since the transition 5.69 → 2.31 is observed, 14N*(5.69) cannot have Jπ = 0+, and 2+ is excluded by the strength of the 8.62 → 5.69 transition. It appears then that 14N*(5.69) has J = 1: see (1956LE28, 1957WI27, 1959WA04).
Anomalies in the capture cross section ("midget resonances") are observed at Ep = 1.01, 1.52 and 1.70 MeV: see Table 14.16 (in PDF or PS). The predominant γ-decay at the first resonance, 14N*(8.49), is to the 5.10 MeV state. The angular distribution of the γ-rays and ωΓγ are consistent with Jπ = 4-; T = 0 for 14N*(8.49). The γ-decay of the second state, 14N*(8.96), is predominantly to the 6.44 MeV state: it's Jπ = 5+. The third state decays primarily to the ground state: the angular distribution of the γ-rays is consistent with Jπ = 2-; T = 0 for 14N*(9.13) (1965DE19).
The narrow Ep = 1.16 MeV resonance, 14N*(8.62) [J = 0+ from 13C(p, p)13C] shows strong transitions to 14N*(0, 3.95, 5.69): hence T = 1 (1959WA16). The strong transition 8.62 → 3.95 requires dipole radiation and hence J = 1 for the latter (1959WA04) while the strength of the transition 8.62 → 6.21 and the angular correlation in the cascade 8.62 → 6.21 → g.s. is consistent with Jπ = 1+; T = 0 for 14N*(6.21): see (1956GO1L, 1956GO39, 1957GA1B, 1957GO30, 1957WI27, 1959GA05).
The Ep = 1.25 MeV resonance, 14N*(8.80) [Jπ = 0- from 13C(p, p)13C] has a large γ-width consistent with E1 radiation and T = 1 (1953WI1A). At Ep = 1.47 MeV, the plane polarization of 0.73 MeV γ-rays (from 5.83 → 5.11) suggests odd parity for both these states (1962RO21).
Angular correlation and angular distributions of γ-rays at the Ep = 1.75 MeV resonance, 14N*(9.17), indicates J = 2+ for that state, J = 3 for 14N*(6.44) and J = 2 for 14N*(7.03) (1959RO54, 1959WA04, 1960RO13, 1960RO23, 1963PR03). The angular distribution of the 2.73 MeV γ-rays (9.17 → 6.44) suggests odd parity for 14N*(6.44) (1961SE03, 1963PR03).
Marked variations are observed in the (cosθ) term at Ep = 2.75 and 2.90 MeV [14N*(10.09) and (10.23)] (1960RO23). The angular distribution of the γ-rays from the 10.23 → 2.31 transition (Ep = 2.88 MeV resonance) is consistent with Jπ = 1+, assuming a single state at 10.23 MeV: M2(M1) leads to a T = 0 assignment (1963RO17). At the Ep = 3.11 MeV resonance [14N*(10.43)], the angular distribution of ground state γ-rays is consistent with J = 2 (1959WA16, 1960RO23): the similar decay characteristics of 14N*(10.43) and of the Jπ = 2+; T = 1 state at Ex = 9.17 MeV suggest that the 10.43 MeV state is in fact also a Jπ = 2+; T = 1 level (1964RO03).
The yield of γ0 for Ep > 3.5 MeV shows a steady rise marked at first by pronounced resonances and then by broad structures most of which are related to levels seen in the inverse reaction (14N(γ, p)13C). The γ1 yield (to 14N*(2.31)) is on the average only about a third the γ0 yield with roughly constant cross section for Ep = 7 to 18 MeV. Only weak structure is observed (1967RI1D, 1968BL1E, 1968RI1R): see Table 14.16 (in PDF or PS).
See also (1959WA02, 1962WA1C), (1965FA1E, 1965MA1H; theor.) and (1959AJ76).
The elastic scattering has been studied for Ep = 0.14 to 0.75 MeV (1960HE14), 0.45 to 1.60 MeV (1954MI05), 1.0 to 2.6 MeV (1966LA03), 1.5 to 3.4 MeV (1957ZI09, 1958ZI17), 2.6 to 5.0 MeV (1961KA04), 5 to 8.1 MeV (1965BA1W), and 7 to 11 MeV (1966SH1H): parameters of resonances observed in this reaction and in the 13C(p, γ)14N reaction are displayed in Table 14.16 (in PDF or PS). Angular distributions of elastically scattered protons have been measured at many of these energies.
The yield of γ-rays in reaction (b) has been measured for Ep = 3.6 to 5.0 MeV: the 3.1 MeV γ-yield shows broad resonances at Ep = 3.80, 4.1, 4.14 and 4.60 MeV while the 3.7 MeV γ-yield shows one resonance at Ep = 4.52 MeV (14N* = 11.07, 11.30, 11.39, 11.82 and 11.75 MeV, respectively) (1960BA35, 1961BA09): see Table 14.16 (in PDF or PS). The angular distribution of inelastic protons to 13C*(3.68) at the Ep = 4.52 MeV resoance leads to the assignment Jπ = 1+ for 14N*(11.75) (1961BA09). The excitation functions for proton groups to 13C*(3.09, 3.68, 3.85) have been measured for Ep = 5 to 11 MeV (1965BA1W, 1966SH1H). See also (1962BE04).
Polarization measurements for elastically scattered protons are reported at Ed = 7 MeV by (1969GU02) and at Ep = 14.5 MeV by (1962RO20, 1965RO22, 1966RO1B, 1966RO1R). At Ep = 32.9 MeV, the polarization and asymmetry in the elastic scattering have been compared. They are equal to within 1%, and there is therefore no evidence for violation of time reversal invariance for strong interactions, at least for that part of the force which flips the spin of the proton (1968GR1K, 1969MA2D).
See also (1962WA1C, 1963GE03, 1964FO02, 1967AR1D), (1967HO1L, 1969WA11), (1964PF1A, 1966AM1B; theor.) and (1959AJ76).
The yield of neutrons has been measured from threshold to Ep = 13.7 MeV: see (1959AJ76) and (1959BR06, 1960BA35, 1961DA09, 1961WO03, 1966DI03). Observed resonances are displayed in Table 14.17 (in PDF or PS). Angular distributions have been measured at many energies: over much of the energy range (below Ep = 10 MeV) there is pronounced backward peaking with a secondary maximum near 50° and no forward peak (1961DA09). The polarization of neutrons corresponding to 13Ng.s. has been studied for Ep = 6.9 to 12.3 MeV (1964WA1G, 1965WA02). See also (1962BE04, 1964CA1F, 1965VA23, 1969BA1N) and 13N.
The yield of ground state deuterons has been determined for Ep = 5 to 11 MeV (1965BA1W, 1966SH1H). See also (1962BE04). A polarization measurement at Ep = 7 MeV is reported by (1969GU02). See also (1968TA1V) and 12C in (1968AJ02).
Alpha-particle yields have been measured for Ep = 7 to 12 MeV (1963PE07, 1964FO02, 1966SH1H).
Observed neutron groups are exhibited in Table 14.18 (in PDF or PS). Recent angular distribution measurements are reported by (1969CH04: 0.5 to 0.8 MeV; n3), (1961JA09: 1.2 MeV; n0 → n6), (1961ZD01, 1964WI03: 1.3 to 2.5 MeV; n0, n1, n2), (1963BE05: 3.9 MeV; n0, n1, n2, n3 + n4), (1966FU10, 1966SI02, 1967FU04: 5.5 and 6 MeV; many groups), (1968CO24: 7 to 12 MeV; n0, n1, n2), and (1969VE1D: 11.8 MeV; n0, n1, n2). See also (1960VA11, 1962SH19, 1963DE19). Comparison of relative spectroscopic factors here and in the 13C(3He, d)14N reaction [see Table 14.19 (in PDF or PS)] shows smaller values for the T = 1 state [14N*(2.31)] in this reaction than in the (3He, d) reaction (1966SI02, 1967FU04). Simple DWBA calculations would suggest that the factors would be the same in both proton pickup reactions. However, the dependence of the cross section magnitude on the T of the final state [the t · T term] appears to be energy dependent: see Table 14.19 (in PDF or PS) (1968CO24). See also (1967LE1F).
In the range Ed = 0.4 to 4.2 MeV, a single strong neutron threshold occurs at Ed = 0.422 ± 0.005 MeV (14N* = 5.691 ± 0.006) (1955MA76). See also (1965MA1K).
Observed γ-rays attributed to transitions in 14N are shown in Table 14.20 (in PDF or PS) (1952TH24, 1955BE62, 1955MA36, 1958RA13, 1966AL10). The decay of 14N*(5.69) is via 14N*(2.31) [63 ± 2%] and directly to 14Ng.s. [37 ± 2%]. τm [14N*(4.91)]<0.5 psec (1963AL21) [see also Tables 14.9 (in PDF or PS) and 14.13 (in PDF or PS)]. The angular correlation of internal pairs conclusively establish the parities of 14N*(4.91, 5.10, 5.69) as odd (1964WA05).
See also (1959CH28, 1959GO78, 1966EV1B), (1959NE1B, 1960AB02, 1964BA1G, 1966BA2R, 1966ST1L, 1967BA2J; theor.) and (1959AJ76). See also 15N.
Angular distributions have been obtained at E(3He) = 13 and 17 MeV (1966SI02: 14N*(0, 2.31, 3.95)), 15 MeV (1966HO15, 1969HO23: 14N*(0 → 9.17)), 17.8 MeV (1966EC1B: 14N*(0, 2.31, 3.95)) and 22 MeV (1969MA1R: 14N*(0, 2.31)). Relative spectroscopic factors for the first three states have been compared with those obtained in the 13C(d, n)14N reaction (1966HO15, 1966SI02): see reaction 30 and Table 14.19 (in PDF or PS). See also (1967LE1F). Spectroscopic factors for the higher states have also been obtained by (1966HO15), from a DWBA analysis. l-values for the observed groups are in agreement with those obtained by (1966FU10) in the (d, n) reaction: see Table 14.18 (in PDF or PS). See also (1965HE01, 1967BA1D).
Angular distributions have been obtained at Eα = 46 MeV of the tritons corresponding to the first seven states of 14N: the data are consistent with the assumption of a direct interaction in which a proton is transferred from the incident α-particle (1969FO1C).
At E(11B) = 113.5 MeV, 10Be groups are observed corresponding to 14N*(5.69 + 5.83), (8.80 + 8.91) and possibly to 14N*(12.2). The two lower transitions correspond to the addition of s1/2 and d5/2 protons to the 13C target core. States which were not excited would have required the excitation of the target core in addition to the transfer of a nucleon (1967PO13). See also (1969BR1D).
Neutron thresholds have been observed at Ep = 671.5 ± 0.5 and 3149.6 ± 1.1 keV (1956SA06) and at Ep = 4910 ± 8 keV (1960BA34) corresponding to the ground state of 14N and to excited states at 2.3119 ± 0.0012 and 3.952 ± 0.008 MeV. Angular distributions of the neutrons corresponding to 14N*(0, 2.31, 3.95) have been obtained for Ep = 6 to 14 MeV. At the highest energies these have been analyzed by using finite range DWBA, taking into account various isospin and spin factors. The ground state transition is not inhibited, whereas the 14C β-decay is. This requires spin-flip mechanisms such as a tensor interaction or particle exchange (1967WO05). See also (1969MA1G). Angular distributions are also reported at Ep = 20 and 30 MeV (1969SA1M; n0, n1, n2). See also 15N.
At E(3He) = 44.8 MeV, triton groups are observed corresponding to all he known levels of 14N with Ex < 7.1 MeV. Triton groups were also seen to unresolved states with Ex = 8.0 - 9.5 MeV, to 14N*(10.43) and to excited states with Ex = 12.49 ± 0.04, 12.83 ± 0.05 and 13.70 ± 0.04 MeV. Angular distributions were obtained for nine of the triton groups and analyzed using a local two-body interaction with an arbitrary spin-isospin exchange mixture. Dominant L = 0 transitions are found to 14N*(2.31, 3.95, 13.7), L = 1 to 14N*(5.11), L = 2 to 14N*(0, 7.03, 10.43) and L = 3 to 14N*(5.83) (1967BA13, 1968BA1E, 1969BA06). See also (1969MA1G) and reaction 45.
The total absorption over the range Eγ = 9 to 31 MeV is dominated by a single peak at 22.5 MeV [estimated σ ≈ 29 mb, Γ ≈ 2 - 3 MeV] and appreciable strength extending beyond 30 MeV. The cross section cannot be accounted solely by the (γ, n) and (γ, p0) processes: particle unstable excited states of 13C, 13N are believed involved (1969BE92). Over the interval Eγ = 20.0 to 20.5 MeV, the average cross section is 10.5 ± 4 mb (1959CA1C, 1960CA09). See also (1968CO13). The cross section for neutron production, reactions (a) and (d), exhibits maximum at Eγ = 22.5 MeV, Γ = 3.2 MeV, σ = 15.3 mb (1954FE16) [Γ = 3.8 MeV, σ = 14.5 mb (1960FA06)]. The cross section for reaction (a) shows a maxima at Eγ = 11.7, 13.2, 15.2, 19.5 and 22.8 MeV (1960KI02). [The peak cross sections for the two highest energy maxima are ≈ 1.8 and 2.8 mb, respectively; the widths are ≈ 2 - 3 MeV, estimated from the published curve.] Breaks in the (γ, n) activation curve are reported at Eγ = 11.07 MeV (1960GE06) and 11.49, 11.61, 12.39, 12.92, 13.28, 13.87, 14.62, 15.25, 16.35, 18.05 and 19.10 MeV (1959MU08, 1960MU02: ± 50 keV). See also (1959FU1A, 1960BA15, 1960KO05, 1960SA09, 1962GO1E, 1962KO23, 1963CO1D, 1963FU06, 1970LO1A).
Studies of reaction (b) indicate the involvement of 14N*(8.06, 9.17, 10.43) (1956WR22, 1960WA17) as well as of 14N states with Ex = 11.8, 13.0 and 15.2 MeV (1960WA17). See also (1959FU1A, 1960BA15, 1960KO05, 1962GO1E, 1962KO23, 1963FI1B, 1964ED01, 1964KO1D). For reaction (c), see (1964ED01). For reaction (d) see also (1959RE1A, 1960BA15, 1962GO1E, 1962KO23, 1963KO1B, 1964KO1D).
For reactions (e), (f) and (g) see (1956LI05, 1958MA1A, 1960BA15, 1960KO05, 1962GO1E, 1962MO16, 1964ED01, 1964TO1B). See also (1959AJ76).
Resonant absorption measurements give Γ = 72 ± 10 eV (1965LU05), 77 ± 12 eV (1959HA11) for 14N*(9.17): ωΓγ = 14.5 ± 2 eV consistent with dipole radiation (1959HA11). (1966SW01) finds Ex = 7.029 ± 0.006 MeV for 14N*(7.03). The angular distribution of the scattered radiation is consistent with J = 2. Assuming that 14N*(7.03) decays entirely to the ground state [actually 98%: see Table 14.13 (in PDF or PS)], τm = 5.4 ± 0.5 fsec (1966SW01). The mean lifetime for 14N*(2.31) is 77 ± 18 fsec (1961SW01), 97 ± 30 fsec (1964BO22). For 14N*(8.06), (1956GR17, 1958GR97) finds Γγ = 10.5 ± 6 eV. See Tables 14.9 (in PDF or PS), 14.13 (in PDF or PS) and 14.21 (in PDF or PS).
An elastic scattering study shows a broad (several MeV wide) maximum centered around Eγ = 24 MeV and indicates a secondary maximum around 30 MeV (1967LO1B).
The r.m.s. radius of 14N at Ee = 400 MeV is 2.58 ± 0.05 fm (1968DA1Q). See also (1964BI04). See also (1959ME24). Measurements of magnetic form factors at Ee = 100 to 180 MeV favor jj-coupling for 14Ng.s. (1966RA29).
Inelastic scattering (θ = 180°) gives evidence for the excitation of 14N*(8.91, 9.17, 10.43): the ground state Γγ are given in Table 14.21 (in PDF or PS) (1962ED02, 1963BA19, 1966KO08, 1968CL05). In addition (1968CL05) report the excitation of a state with Ex = 11.01 ± 0.07 MeV and (1966KO08) report structure at Ex = 11.7 and 12.7 MeV. Partial Γγ [for cascade transitions of 14N*(9.17, 10.43)] have been obtained by (1968CL05) and are shown in Table 14.9 (in PDF or PS). See also (1963GO04). Inelastic scattering is also reported to 14N*(2.3, 3.95, 5.1, 5.85, 7.05, 8.0) (1964BI09). See also (1964BI04). See (1962BA1D) for a general discussion. See also (1958CA1B, 1960PA08, 1963GU1A, 1967KA1A, 1969VI02).
Angular distributions of elastically and inelastically scattered neutrons are displayed in Table 14.23 (in PDF or PS). See also (1959AJ76) and 15N.
Observed gamma rays are displayed in Table 14.23 (in PDF or PS) (1969DI1B, 1969NY1A). See also (1959HA13, 1968CO1W). Lifetime measurements are reported in Table 14.22 (in PDF or PS) (1969NY1A).
See also 15N, (1961AS1B, 1963MO04, 1963OP1A, 1964EN1B, 1964MO1D, 1964PE20, 1965VA1K, 1966MO1C) and (1965JO07, 1965TA07, 1968CA1A, 1969WA11).
Angular distributions of elastically and inelastically scattered protons have been measured and analyzed at a number of energies: see Table 14.23 (in PDF or PS). See also 15O and (1968OD1B). Observed inelastic proton groups are shown in Table 14.24 (in PDF or PS). The proton groups corresponding to 14N*(7.40, 7.60) reported by (1956BU16) are spurious: see (1964DO03, 1964EA04). See also (1963BR14, 1966ME1L). (1965DE21) reports the excitation of 14N states with Ex = 11.2 ± 0.2 and 12.8 ± 0.4 MeV, and the measurement of the angular distribution of the protons from the decay of 14N*(11.2). See also (1957HO34, 1961CL09, 1969CU1D) and (1962KA1E, 1962WA1D, 1965TA07, 1969MA1G, 1969WA11). See also (1959AJ76) and (1960WA12).
Reaction (b) at Ep = 19 MeV proceeds at least in part through an intermediate state in 14N at Ex ≈ 11.2 MeV (1965DE21). See also (1961CL09, 1965RI1A, 1966TY01) and (1965BE1E, 1965DE1P, 1967JA1E, 1967KO1P, 1969KO1J; theor.) and 13C. For reaction (c) see (1961CL09) and (1964BA1P, 1966JA1A; theor.).
Angular distributions of elastically and inelastically scattered deuterons have been obtained at a number of energies: see Table 14.23 (in PDF or PS). See also 16O in (1971AJ02). Inelastic deuteron groups are displayed in Table 14.24 (in PDF or PS). The deuteron group to the 0+; T = 1 state at Ex = 2.31 MeV is isospin forbidden: its intensity is 1 - 3% of the deuteron group to 14N*(3.95) for Ed = 7.7 to 10.2 MeV (1968DU1E). See also (1953BO70). The deuteron group to the T = 1 state 14N*(8.06) is also not seen: see Table 14.24 (in PDF or PS). See also general discussions in (1960WA12, 1966BR1G, 1968NO1C). See also (1968ME1E, 1969CU08).
Angular distributions of elastically and inelastically scattered 3He particles have been determined by (1962SE13, 1964SE05, 1965AR1E, 1969BA06): see Table 14.23 (in PDF or PS). See also (1967KN1B).
At E(3He) = 44.6 MeV, twelve 3He groups are reported corresponding to states in 14N: see Table 14.24 (in PDF or PS) (1969BA06). The angular distributions were analyzed using a local two-body interaction with an arbitrary spin-isospin exchange mixture. A comparison of the cross sections of the reactions 14N(3He, t)14Og.s., 14N(3He, 3He')14N*(2.31) and 14C(3He, t)14Ng.s. [which all correspond to transitions between identical initial and final states] shows that they are roughly equal, as would be expected fron charge independence, once detailed-balance, isospin coupling and phase-space correactions have been applied (1969BA06). See also (1968HO1C, 1968LE1G, 1969RA1B).
Angular distributions of elastically and inelastically scattered α-particles have been measured for Eα = 11 to 104 MeV: see Table 14.23 (in PDF or PS). The intensity of the isospin-forbidden α1 group to 14N*(2.31) is low. The highest intensities reported are 0.18 of the α0 group and 0.4 of the α2 group for Eα = 11.4 to 12.7 MeV (1966CH1E). Generally the intensity of the α1 group is much smaller than that, typically a few percent of the α0 or α2 group: see (1959AJ76, 1966HA19): see also Table 14.23 (in PDF or PS).
Reduced transition probabilities are reported by (1966HA19): B(E2)↓/e2 = 6.5 and 3.3 fm4, respectively for 14N*(3.95, 7.03); B(E3)↓/e2 = 40 and 60 fm6, for 14N*(5.11, 5.83). See also (1962HA40, 1962JO14, 1963MI1C, 1969BA06), (1968FA1A), (1960WA12), (1968NO1C, 1968RA1C; theor.) and 18F in (1972AJ02).
At Eα = 22.9 MeV, reaction (b) to 13Cg.s. appears to involve twelve states of 14N with Ex = 8.4 to 13.2 MeV, while reaction (c) proceeds via five states with Ex = 11.5 to 12.9 MeV (1969BA17). See also (1967BE30, 1968KU1C).
See (1961NE04, 1962SM02, 1964KU1D).
See (1962SM02, 1968JA1N) and (1967BR1M, 1969VO1E).
The decay proceeds almost entirely to the Jπ = 0+; T = 1 state of 14N at 2.31 MeV: see 14O. Measurement of the γ-ray energy from the decay of 14N*(2.31) leads to Ex = 2.31287 ± 0.00010 MeV for this state (1968FR08), 2.31289 ± 0.00010 MeV (1967CH19). The spectrum shape for the transition to 14Ng.s. differs markedly from the statistical shape. τm for 14N*(2.31) extracted from these data is 33 ± 3 fsec (1966SI05): see, however, Table 14.13 (in PDF or PS).
Angular distributions have been obtained for the deuterons corresponding to 14N*(0, 2.31, 3.95) (1961BE12: Ep = 18.6 MeV) and to 14N*(0 - 8.06, 8.62, 8.91, 8.96+8.98, 9.17 - 10.43, 10.81, 11.04, 11.24 + 11.30, 11.39 - 11.66, 11.75 + 11.81, 11.95, 12.23 + 12.29, 12.50, 12.61, 12.79 + 12.83, 13.16 + 13.23, 13.72) (1969SN04: Ep = 39.8 MeV). Spectroscopic factors were extracted by DWBA analysis of the ln = 1 pickup angular distributions. Γ = 210 ± 30 keV for 14N*(13.75). Weak deuteron groups to 14N states at Ex = 6.70, 7.40 and 7.60 MeV are reported [see, however, reaction 54] (1969SN04).
At E(3He) = 2.8 MeV, α-particle groups are observed to 14N states at Ex = 3.95, 4.91, 5.113 ± 0.008, 5.691 ± 0.008, 5.832 ± 0.008, 6.048 ± 0.012 [see, however, (1969HO23)], 6.224 ± 0.012, 6.436 ± 0.012, 7.032 ± 0.010, 7.97 and 8.06 MeV (1962CL12, 1962CL1D). The previously reported states at Ex = 6.70, 7.40 and 7.60 MeV are unobserved (1962CL12, 1969HO23). Angular distributions have been obtained at E(3He) = 2.8 MeV (1962CL12: to 14N*(3.95, 5.69, 5.83)), 15 MeV (1969HO23: to 14N*(0 - 8.91, 9.17 - 9.70) and 39.8 MeV (1966BA13: to 14N*(0, 2.31, 3.95, 7.03, 9.17, 10.43) and to a state at Ex = 13.72 ± 0.04 MeV). See also (1965SE01).
At Ep = 40 MeV, angular distributions have been measured for the 3He particles corresponding to 14N*(0, 2.31, 3.95) (1966BR1X, 1966HO1F). The excitation of 14N*(7.03, 9.17) is also reported (1965PE17). At Ep = 43.7 MeV, a comparison has been made between the angular distributions of the 3He particles to 14N*(2.31) and the tritons (from the 16O(p, t)14O reaction) to 14Og.s.. As would be expected from charge independence, the shape of the distributions and the cross sections are approximately the same to the two analog states: σ(p, t)/σ(p, 3He) = 1.12/1 (1964CE02).
Angular distribution of α-particles have been measured at many energies: see Table 14.25 (in PDF or PS). See also (1959FI30).
Alpha particle groups have been seen corresponding to most known states of 14N with Ex ≤ 11.51 MeV (in some cases, the identification of the groups is inconclusive), with the exception of previously reported states at Ex = 6.05, 6.70, 7.40 and 7.60 MeV (1968JO07: Ed = 5 to 9 MeV). See also (1965IS04). The yield of the isospin-forbidden α1 group [to 14N*(2.31)] has been studied for Ed = 3 to 15 MeV. The intensity of the α1 group, relative to the α0 and α2 groups [to the T = 0 states of 14N*(0, 3.95)] depends on the deuteron energy and on the angle of observation [the isospin impurity in the compound nucleus is a function of the excitation energy in 18F and of J] (1969JO09). Studies of the α1 yield have also been conducted for Ed = 5.5 to 7.5 MeV (1956BR36) and 6.8 to 8.9 MeV (1958DA16). For further discussions, see (1963CE02, 1966BR1G, 1968NO1C, 1969NO1B, 1969NO1C). See also (1960HU10, 1961PE09, 1961YA08, 1963JA03, 1963YA1B) and 18F in (1972AJ02).
Preliminary results on the absolute cross sections of this reaction and its inverse [14N(α, d)16O] are in agreement, to ± 0.56%, with the principle of detailed balance (1967TH1E, 1968TH1J, 1969PL1C).
See also (1961TE02, 1963DO1B, 1963VA1E, 1964RI1C, 1966BE1E, 1966JA05, 1966KL1E, 1968KO24), (1960EL1E, 1961BA1J, 1961JA1H, 1964HO1E, 1966ME1E, 1967JO1H; theor.) and (1959AJ76).
See 18F in (1972AJ02).