|
![]() |
![]() |
![]()
13N (1959AJ76)(See the Energy Level Diagram for 13N) GENERAL: See also Table 13.9 [Table of Energy Levels] (in PDF or PS). Theory: See (1955LA1A, 1956DA1G, 1958FR1C, 1958HA1D, 1958SK1A).
Recent determinations of the half-life give 10.05 ± 0.03 min (1953CH34), 10.08 ± 0.04 min (1955WI43), 10.07 ± 0.06 min (1957NO17), 9.96 ± 0.03 min (1958AR15), 9.96 ± 0.03 min (1958DA09); see also (1957DE22). Eβ(max) = 1.202 ± 0.005 MeV (1950HO01), 1.185 ± 0.025 MeV (1954GR66), 1.190 ± 0.003 MeV (1958DA09). The positron spectrum shows no deviation from the allowed shape; it is concluded that the Fierz coefficient in the Fermi interaction is < 11%. Log ft = 3.66 (1957DA08, 1958DA09). The positron polarization has been studied by (1957BO65, 1957HA27). The results indicate that the positrons are completely polarized and hence that Fermi transitions as well as G-T transitions exhibit the maximum effect of parity nonconservation.
See (1957NO17).
At E(3He) = 2.54 MeV, the cross section for formation of the ground state is 5.2+2.1-1.6 mb. At E(3He) = 3.60 MeV, the differential cross section for formation of the ground state at θ = 0° is 0.73 ± 0.30 mb/sr (1957AJ71).
The yields of the protons to the ground and 4.4 MeV excited states of 12C have been measured for E(3He) = 1.3 to 5 MeV. Resonances are observed at 2.0, 3.7, 4.1 and 4.6 MeV, with widths of 0.5, 0.7, 0.12 and 0.15 MeV, respectively, corresponding to 13N*(23.2, 24.5, 24.8, 25.2). Angular distributions taken at six energies in the above range tend to be more asymmetric at the higher energies (1956SC01). See also (1956JO1B).
See 11C.
See 9B.
Measurements at Eα = 8 MeV with a proton recoil telescope and a neutron threshold detector are reported to indicate 13N states at 2.4 ± 0.3, 3.6 ± 0.3, (4.3 ± 0.3) and 5.0 ± 0.3 MeV (1956QU1A). See also (1957BA1K) and 14N.
Not reported.
Two resonances for capture radiation are reported, at Ep = 0.46 and 1.70 MeV (Table 13.10 (in PDF or PS)). The resonance at Ep = 1.75 MeV observed in 12C(p, p)12C does not appear in the γ-excitation curve (1951SE67). The displacement of the lower level (13N*(2.37), J = 1/2+) from its mirror in 13C*(3.09) is ascribed to the large reduced width (1951EH1A, 1952TH1D). The angular distribution of the ground-state radiation from the upper resonance (13N*(3.51), J = 3/2-) has the form W(θ) = 1 - 0.52cos2θ (1951DA1A, 1951DA1B). The capture cross section at low energy is of interest in connection with stellar energy generation. Measurements have been reported in the range Ep = 80 to 360 keV by (1950BA89, 1950HA78, 1957DE22, 1957LA15). At 80 keV, σ = (1.4 ± 0.4) × 10-5 μb; from 80 to 126 keV, the course of the cross section is reasonably well accounted for by extrapolation of the Ep = 0.46 MeV resonance (1957LA15: see also (1957DE22)). From Ep = 5 to 11 MeV, the cross section for formation of 13N changes only from 2.5 to 1.8 mb; this small change strongly indicates the predominance of direct capture in this region (1955CO57). According to (1956RE39), however, the 90° differential cross section for formation of 13N is < 1 μb/sr at Ep = 4.8 MeV. See also (1956CH1D). In the range Ep = 1.2 to 2.5 MeV, reaction (b) is observed, involving a γ-transition to the 2.37 MeV state. Excitation functions at θ = 0° and 90° indicate interference between p-wave resonant capture at Ep = 1.70 MeV, with Γγ = 0.04 eV, and direct p-wave capture (1954WO09). The angular distributions at Ep = 1.37 and 1.58 MeV have the form W(θ) = (0.02 ± 0.02) + sin2θ (1955HE1F).
See (1957ST1D, 1958TA03) and 12N.
See (1947CH1A, 1948MC1A, 1958WH34).
Elastic scattering studies indicate a number of pronounced resonances in the range Ep = 0 to 6 MeV: see Table 13.11 (in PDF or PS). The first five excited states correspond in character and approximately in reduced width to those of 13C: see 12C(d, p)13C and 12C(n, n)12C. The relatively large reduced widths of the first and third (s1/2 and d5/2) excited states indicate a single-particle character (1953JA1B). The small and roughly equal widths of 13N*(6.4, 6.9) suggest that they may comprise a doublet, built upon 12C*(4.4) + p (1956RE39: see also (1953BL1A, 1953MA1D, 1956SC29)). Angular distribution measurements above Ep = 10 MeV generally show direct interaction effects: see 12C. Some form of resonance structure may exist near 23 MeV (1955KI43). See also (1956KL55). The yields of 4.4 MeV gamma rays and inelastic protons from 12C*(4.4) show resonances at Ep = 5.39 and 5.93 MeV (1953MA1D, 1956BR27, 1957LI1B). Angular distributions of inelastic protons at Ep = 6.1 to 6.9 MeV do not fit direct interaction theory and suggest the effects of still higher compound nucleus levels (1956BR27). Polarization studies for Ep < 6 MeV are reported by (1956GA66, 1956SO1C, 1958WA1D): see also 12C. See also (1955DE50, 1956ER1A, 1956NI1B, 1957GL58; theor.) and (1957GO1D).
See 11C.
See 9B.
Neutron groups have been observed corresponding to excited states of 13N at 2.29 ± 0.12 (1949GR1A), 2.38 ± 0.05 MeV (1953MI10) and 3.48 ± 0.12 (1949GR1A), 3.74 ± 0.05 (1957GR1A), 3.53 ± 0.05 MeV (1953MI10). The angular distributions of the ground state group and the groups corresponding to the 2.37 and (3.51 ± 3.56) MeV states at Ed = 9.0 MeV are consistent with lp = 1, 0 and 2. The dimensionless reduced widths of the ground and (3.56) MeV states are respectively 0.056 and 0.19 (1957CA02: see also (1953MI10)). (1958MC63) finds that the reduced widths of the ground states of 13C and 13N are the same, 0.09 ± 0.035 (see also (1956BE1H, 1956CA1D, 1958KA16) and 12C(d, p)13C). In the range Ed = 2.8 to 3.7 MeV, a single neutron threshold is observed, at Ed = 3.09 ± 0.02 MeV, corresponding to 13N*(2.36 ± 0.02); the slow rise above threshold is attributed to p-wave neutron emission (1955MA76). Polarization of neutrons has been studied for Ed = 2.5 to 3.6 MeV by (1957HA1J). See also (1956BO1F, 1956BO43, 1956DE1D).
Not reported.
See also (1950RI59, 1955MA84, 1958BI1B) and 14N.
See (1952FR1A).
See 14N.
See 14N.
At Ed = 14.8 MeV, triton groups are observed corresponding to the states at 0, 2.37 and (3.51 ± 3.56) MeV. The cross section for the transition to the 2.37 MeV state is two orders of magnitude smaller than that for the ground state transition. Transitions to 13N*(2.37, 3.56) are shell-model forbidden (1957WA01).
Not reported.
Not reported.
See (1958WH34).
|
![]() |