
^{12}N (1990AJ01)(See Energy Level Diagrams for ^{12}N) GENERAL: See also (1985AJ01) and 12.22 [Table of Energy Levels] (in PDF or PS) here. Model calculations:(1984KA1H, 1984SA19). Astrophysical questions:(1985CA41, 1987RA1D, 1988CA26, 1988LE08, 1989KR1C). Applied work:(1987KU17, 1987MI24). Complex reactions involving ^{12}N:(1985NO1E, 1986GA1P, 1987BA1T, 1987RI03, 1988BE02, 1988LE08). Muon and neutrino capture and reactions:(1986DA1J, 1987KR1L, 1988AL1O, 1988BO1X, 1988FU08, 1988MI1H, 1988MI20, 1989DR1A, 1989KR1C, 1989MI1I). Pion capture and reactions:(1983AS01, 1984AS05, 1988HA12, 1988KIZW). Other topics:(1984KA1H, 1984SA19, 1985AN28, 1986YA1F). Groundstate properties of ^{12}N:(1985AN28, 1985NA1A, 1986GL1A, 1986HA1P, 1987VA26, 1988VA03).
The halflife of ^{12}N is 11.000 ± 0.016 ms: ^{12}N decays to ^{12}C*(0, 4.44, 7.65, 10.3, 12.71, 15.11): see 12.21 (in PDF or PS). Since the transitions to ^{12}C*(0, 4.4) are allowed the J^{π} of ^{12}N_{g.s.} is 1^{+}. For measurements of the angular distribution functions from aligned ^{12}N nuclei see (1986MI1P, 1986MI1T, 1987MI1P). See also (1985AJ01), (1986CA1P, 1986MI1Q, 1986MI1R, 1987MI20, 1987VA1P), (1985BA2L; applied), (1985GR1A, 1985MI1A) and (1984DU1E, 1985MO13, 1986KE1A, 1986KO2C, 1986TO1A, 1987DR1A, 1987SA1N, 1988AL1E, 1988SA12, 1989SA1H; theor.).
Observed neutron groups are displayed in Table 12.23 (in PDF or PS).
The total cross section has been measured from threshold to E_{e} = 360 MeV: see (1985AJ01).
Angular distributions have been studied at E_{p} = 30.5 to 200 MeV [see (1980AJ01, 1985AJ01)] and at 35 and 40 MeV (1987OH04; n_{0}, n_{1}, n_{2}; DWBA), at 160 MeV (1984GA11; n_{0}; also A_{y}; comparison with (p, p') to ^{12}C*(15.1)). The angular distribution to ^{12}N(4.2) [u?] is consistent with J^{π} = 2^{} predicted by theory. A structure at E_{x} ≈ 7.2 MeV is also observed. Unresolved angular distributions over the range E_{x} = 2  17 MeV (and θ = 5°  13°) are dominated by l = 1 transitions (1984GA11) [as would be expected at those angles]. (1987TA13, 1989RA09) discuss the relationships between the GT strength and the 0° differential cross section in this and other (p, n) reactions. At E_{ pol. p} = 65 MeV the spin transfer coefficient K^{y'}_{y} (0°) for pol. n_{0} + pol. n_{1} has been measured by (1984SA12). See also (1985AJ01), ^{13}N in (1991AJ01), (1984BA1R, 1988HIZX, 1988NI1C, 1988TAZY, 1989PRZZ), (1988LE08; astrophysics), (1985BA2L), (1984GA36, 1984TAZS, 1985SH1C, 1986GA1P, 1986LI1T, 1987EL08, 1987EL14, 1987LI29, 1987RA32) and (1984SA19, 1987BE1D, 1988HO09, 1988PI08, 1988UD03; theor.).
Observed triton groups are displayed in 12.23 (in PDF or PS). Angular distributions of inelastically scattered ^{3}He to ^{12}C*(15.11, 16.11, 16.58, 17.77, 19.57) have been compared with those of tritons to ^{12}N*(0, 0.96, 1.19, 2.42, 4.25). When the ^{3}He cross sections are corrected for phasespace and isospin factors the angular distributions are closely similar to those for the triton groups, strongly suggesting isobaric analogs: see (1980AJ01) for references. [If ^{12}C*(17.77) and ^{12}N*(2.42) are analogs, then the latter is a 0^{+} state.] Angular distributions have been reported at 81 MeV (1983ST10) [to many of the states shown in 12.23 (in PDF or PS)]. [Compare the ^{12}B and the ^{12}N level structure: it is clear that not all the analog states have been observed in ^{12}N.] Angular distributions have also been studied at E(^{3}He) = 0.6 to 2 GeV (1987BE25; to ^{12}N*(0 + 0.96, 4., 7.). ^{12}N*(4.) is assumed to be a 2^{} state while ^{12}N*(7.) corresponds to a group of 1^{} states. The reaction appears to be singlestep direct and is well described by DWIA (1987BE25). At E(^{3}He) = 197 MeV (θ = 0°) the spectrum shows ^{12}N*(0, 0.96), an ≈ 1 MeV wide state at 4.3 MeV (possibly 2^{}, 4^{}) and the GDR at ≈ 10 MeV (≈ 84% of the strength is 1^{}). No structure is observed between E_{x} = 15 and 70 MeV (1984TA11). The spectra of inelastically scattered ^{3}He ions (see ^{12}C) and of tritons have been studied at E(^{3}He) = 170 MeV. The triton spectrum has been compared with photoabsorption results. (1982TA05) conclude that the isovector GDR is preferentially excited in the (^{3}He, t) process while the (^{3}He, ^{3}He) process preferentially excites the isoscalar giant multipole resonances. Delta isobar excitation has been studied at 1.5, 2.0 and 2.3 GeV (1986CO03). See also (1988AB08), (1984AB06, 1988JA1F, 1989JAZY), (1984GA36, 1984GE1A, 1985RO1N, 1986EL1C, 1986GA1P, 1987EL08, 1987EL14, 1988RO17) and (1984CH1N, 1985JA13, 1987DM02, 1987GU07, 1988ES1A, 1988UD03; theor.).
At E(^{6}Li) = 25 and 35 MeV/A angular distributions have been studied to ^{12}N_{g.s.} (1987WI09). At the higher energy ^{12}N*(1.0) is also populated as is a broad structure near 4.25 MeV. At forward angles the cross section for the GT transition in this and in other (^{6}Li, ^{6}He) reactions is found to be proportional to the βdecay strength (1986AN29). See also (1984GL06) and (1987AU04, 1988AN06, 1988AU1E, 1989AU1B).
See ^{12}B.
At E(^{13}C) = 30 MeV/A ^{12}N*(0, 1.0) are populated but the dominant groups in the forward direction are broad structures at E_{x} = 4.2 and 7.5 MeV attributed to 2^{} and 1^{} states (1986VO02, 1988VO06).
See (1986BA16, 1986EL1C, 1986RO1Q).
At E_{p} = 51.9 MeV angular distributions of the tritons to ^{12}N*(0, 0.96) and of the ^{3}He ions to the analog T = 1 states [^{12}C*(15.11, 16.11)] have been measured. At E_{p} = 52.5 MeV the angular distribution to ^{12}N*(2.44) has been studied. See (1980AJ01) for references.
