
^{12}N (2017KE05)(See 12.44 (in PDF or PS) and Energy Level Diagrams for ^{12}N and Isobar Diagram)
Q = +9.8 ± 0.9 mb (1998MI10). <(r^{matter}_{rms})^{2}>^{1/2} = 2.40  2.50 fm; i.e., see (2006WA18, 2010LI18). An analysis of the T = 1 states of ^{12}B, ^{12}C and ^{12}N with J^{π} = 1^{+}, 2^{+} and 0^{+} using the quadratic form of the IMME is reported in (1998BR09). A similar report is given in (2013LA29) which also included the 2^{} and 1^{} states. See also (2009BA41, 2014MA56).
The halflife of ^{12}N is 11.000 ± 0.016 ms (1978AL01); see also T_{1/2} = 10.95 ± 0.05 ms (1963FI05), 11.43 ± 0.05 ms (1958VE20), 11.0 ± 0.1 ms (1963PE10), 11.1 ± 0.2 ms (1962PO02) and 11.2 ± 0.4 ms (1959FA03). ^{12}N decays to ^{12}C*(0, 4.44, 7.65, 10.3, 12.71, 15.11): see 12.42 (in PDF or PS). See (2015MO10) for discussion of the β and neutrino spectra shapes. Since the transitions to ^{12}C*(0, 4.4) are allowed, the J^{π} of ^{12}N_{g.s.} is 1^{+}. Measurement of the magnetic quadrupole moment, via βNMR techniques, yields Q = +9.8 ± 0.9 mb (1998MI10). See also (1998MI20). Measurements of βγ correlations in aligned ^{12}N (and ^{12}B) nuclei can provide information on conservation of vector currents without secondclass currents (1985MI1A, 1985GR1A, 1995GO34: reviews) and (1978BR18, 1979MA31, 1987MI20, 1990CA10, 1993MI32, 1994MO23, 1995KO28, 1998MA27, 1999MI04, 2002MI01, 2003SM02). Analysis of modern experiments yields the axial charge, y = 4.90 ± 0.10 (2002MI01), which is consistent with an inmedium renormalization of hadron masses; the data implies an inmedium nuclear mass reduction of (16 ± 4)%. The longitudinal polarization of positrons emitted from polarized ^{12}N is analyzed and sets a lower limit M(W gauge boson) ≥ 310 GeV/c (1996AL23, 1998SE04, 2001TH18) for the right handed guage boson contributing to electroweak interaction; these results are consistent with the standard model. Limits on the Gparity irregular induced tensor coefficient, f_{T}, in the weak nucleon axial vector current are found as 2Mf_{T}/f_{A} = 0.15 ± 0.12 (stat.) ± 0.05 (theory) from analysis of βray angular distributions from spin aligned ^{12}N and ^{12}B ions (1998MI14, 1999MI41, 2000MI11, 2002MI03, 2002MI36, 2002MI49, 2003MI24). See also (1991LI32, 1998MA27, 2013MI10) for ^{12}N polarization methods.
The E_{x}(^{12}N) = 8.7 to 9.9 MeV region of the ^{8}B(α, p) reaction was studied in inverse kinematics by impinging E(^{11}C) = 98 to 110 MeV beams on 720 μg/cm^{2} CH_{2} targets (ΔE ≈ 100 keV) and detecting the α+^{8}B reaction products (2004RE31). The cross sections for the complementary reaction, deduced via the Detailed Balance equation, increase steadily from about 50 nb to 20 mb with only a slight enhancement of near 9.1 MeV. This cross section, which is relevant to the astrophysical hot ppchain, is roughly two orders of magnitude larger than previously expected. See also (1990DE21).
Indirect studies of the astrophysically important ^{11}C(p, γ) reaction were carried out by analyzing angular dependent cross sections for the ^{2}H(^{11}C, ^{12}N_{g.s.}) reaction at (θ_{cm} ≤ 33.8°) and E(^{11}C) = 9.8 MeV (2003LI51, 2005LI40, 2006LI62), and at (10.9° ≤ θ_{cm} ≤ 72°) and E(^{11}C) = 150 MeV (2011LE25). While the earlier measurement confirmed the dominant mechanism is direct capture to the ground state, their results (ANC = 2.86 ± 0.91 fm^{1}) are limited by low statistics. The later measurement found the ANC as (C^{12}N_{eff})^{2} = 1.83 ± 0.27 fm^{1}, and in calculations where they folded in resonant capture to the first and second excited states and interference contributions they obtained the astrophysical Sfactor(0) = 0.097 ± 0.020 keV ⋅ b, which is significantly higher than theoretical predictions. Analogous to determination of the ^{2}H(^{11}C, n) ANC, the ^{2}H(^{11}B, p) θ ≤ 160° angular distribution data from (1967SC29, 1974FI1D, 2001LI45) were analyzed in (2007GU01) to determine the ^{12}B*(0, 0.95, 1.67) → ^{11}B + n ANCs; then by charge symmetry the corresponding ^{12}N → ^{11}C + p ANC values were deduced. In addition to determining astrophysical Sfactors for capture to the ground, first and second excited states, Γ_{p} = 0.91 ± 0.29 keV and 99 ± 20 keV were deduced for ^{12}N*(0.95, 1.19), respectively. See also (2005SH39, 2005TI07, 2005TI14, 2012OK02).
The ^{12}N total reaction and interaction cross sections were measured on ^{9}Be, ^{nat}C and ^{27}Al at E(^{12}N) = 730 MeV/A (1995OZ01) and on ^{nat}Si at E(^{12}N) = 20 to 42 MeV/A (2006WA18) and E(^{12}N) = 34.9 MeV/A (2010LI18). The cross sections were analyzed in Glauber models to deduce matter radii of R^{matter}_{rms} ≈ 2.40  2.50 fm. Spectroscopic factors to ^{11}C*(0, 2.0, 4.32, 4.80) are calculated and compared with the data in (2006WA18). See also (2001OZ04).
An E(^{13}O) = 30.3 MeV/A beam, produced via the ^{1}H(^{14}N, ^{13}O) reaction, impinged on a ^{9}Be target where 1n and 1p knockout reactions populated ^{12}N and ^{12}O (2012JA11). Excited ^{12}N decayed into ^{11}C + p and ^{10}B + 2p. In (2012JA11), kinematic reconstruction of the relative energies found evidence for ^{12}N states at E_{x} = 968 ± 10 keV [^{11}C + p] and E_{x} = 12196 ± 29 keV (Γ < 110 keV: J^{π} = 0^{+}) and ≈ 14200 keV [^{10}B + 2p]. A followup analysis (2013SO11) focused on ^{13}O and ^{12}N events involving the ^{12}N second excited state; E_{x} = 1.179 ± 0.017 MeV and Γ = 55 ± 20 keV were deduced for this J^{π} = 2^{} resonance that decays 100% via ^{11}C + p. In (2012JA11), the ^{12}N*(12196) state is interpreted as the IAS of ^{12}O_{g.s.}, and a comparison using the IMME formula finds the T = 2 quintet for A = 12 can be fit with a quadratic form. See also ^{12}O reaction 1.
The ^{11}C(p, γ) reaction is part of the hot pp chain (1989WI24), which can produce CNO seed nuclei earlier than the tripleα process; see discussion in (1990DE21, 2006LI62, 2011LE25). At present there are no direct measurements of the capture cross section, which is expected to be determined by direct capture and resonant capture to ^{12}N*(0.96[2^{+}], 1.19[2^{}]). Estimates of Γ_{γ} = 2.59 meV and 1.91 meV were deduced in (1989WI24) by analogy with ^{12}B*(2^{+}) and from systematics given in (1979EN05), respectively. Subsequent experimental (i.e. see reaction 19) and theoretical (1990DE21, 1999DE03, 2003TI01) analysis suggests Γ_{γ}(2^{}) ≫ 2 meV leading to a much higher reaction rate than estimated in (1989WI24). See also (1993TI01, 2010HU11). The ^{11}C + p elastic scattering in thick target inverse kinematics (TTIK) has been used to provide important data for the capture reaction. An E(^{11}C) = 3.5 MeV/A beam was stopped in a thick (CH_{2})_{n} target, and scattered protons were detected at θ_{lab} < 5°; using the p and ^{11}C stopping powers in the CH_{2} target the ^{11}C + p excitation function was reconstructed from the observed proton energy spectrum. The ^{12}N*(1.2, 1.8, 2.4, 3.1, 3.6) levels are observed in the excitation spectrum, and J^{π} = 3^{} and (2)^{+} are deduced for ^{12}N*(3.1, 3.6) (2003KU36, 2003TE01, 2003TE09, 2003TE12). TTIK was also employed to probe the E_{x} = 2 to 11 MeV region (2006PE21); at E(^{11}C) = 73.8 and 125 MeV, elastically scattered protons from a CH_{2} target were detected at θ_{lab} = 0°, 5°, 10° and 15°, and at 99.8 MeV, protons elastically scattered in a CH_{4} gas filled chamber were detected at θ_{lab} = 0°, 11.5°, 12.5° and 16.5°. 12.45 (in PDF or PS) displays ^{12}N levels deduced from Rmatrix analysis of the (2006PE21) excitation function that relied on known ^{12}N and ^{12}B levels. See also discussion in (2016HO14).
Parameters for observed neutron groups, mainly from (1974FU11: E(^{3}He) = 12.5 and 13 MeV) are displayed in 12.46 (in PDF or PS). Angular distributions have been studied at E(^{3}He) = 2.5 and 3.6, 2.4, 2.75 and 2.94, and 4.0 and 5.8 MeV: see references in (1968AJ02), and at E(^{3}He) = 11, and 12.5 and 13 MeV: see references in (1975AJ02).
States at E_{x} ≈ 0, 1 and 4 MeV are populated in photopion production (1979PA06); see also (1976BE39: E_{brem} = 170 MeV), (1983SC11: E_{brem} = 190 MeV), and (1976WA07: E_{brem} = 250 MeV). At higher energies cross sections in the Δ resonance region were studied with (1974BO47: E_{brem} = 345 MeV), (1979BO23: E_{brem} = 360 MeV), (1974EP02: E_{brem} = 375 MeV), (1982AR06: E_{brem} = 390 MeV), (1982TO10, 1985TO14: E_{brem} = 400 MeV), (1990AN26: E_{brem} = 450 MeV); (1977BA60, 1978BA50: E_{brem} = 850 MeV), (1973GO44: E_{brem} = 1200 MeV), and (1980AL25: E_{brem} = 4.5 GeV); see a review in (1988KA41). The reaction mechanism for ^{12}C(γ, π^{0}π^{}) is investigated at E_{brem} = 400 to 460 MeV in (2002ME22); see also (2003ME32, 2003RO20, 2003VI09, 2003VI11, 2004MU17).
The q^{2}dependence of the weak axial vector form factor, F_{A}(q^{2}), was deduced from the decay electron energy spectrum; analysis indicates F_{A}(q^{2} = 0) = 0.73^{+0.11}_{0.10}, which compares well with F_{A}(q^{2} = 0) = 0.711 deduced from βdecay (1994BO41: KARMEN Collaboration). Neutrino beams produced via π^{+} → μ^{+} + ν_{μ} followed by μ^{+} → e^{+} + ν_{e} + ν̄_{μ}; (E(ν_{e}) ≈ 26 to 50 MeV) have been used to measure the flux averaged cross section for Charge Current interactions (CC); present results, which are important for systematics in neutrino oscillation experiments, are summarized in 12.47 (in PDF or PS). The first measurement, E225 (1990AL09, 1992KR05), was carried out at LAMPF and produced cross section values for the exclusive ^{12}C(ν_{e}, e^{})^{12}N_{g.s.} reaction (identified by a scattered electron in coincidence with the β^{+} from ^{12}N decay) and inclusive ^{12}C(ν_{e}, e^{})[^{12}N_{g.s.}+^{12}N*] reaction; the cross sections are often evaluated to deduce the ^{12}C(ν_{e}, e^{})^{12}N* yields. Later efforts by the KARMEN collaboration (1992BO11, 1993BO12, 1994BO34, 1994BO41, 1994KR14, 1996KL07, 1998AR04, 2008EI01) and LSND collaboration (1997AT02, 2001AU09) have produced results in reasonable agreement. See an overview in (2003KO50). In general, theoretical estimates of the reaction cross sections are in good agreement with measured values and have been carried out using QRPA/CRPA models (1992KO07, 1996KO32, 1997AU05, 1998IM02, 1999KO24, 2000VO13, 2001AU05, 2001VO18, 2002JA03, 2005BO44, 2005KR06, 2008PA06, 2010CH05, 2011SA04), Shell models (2000VO13, 2001AU05, 2001VO18, 2002AU01, 2003HA17, 2012SU15) and other approaches (1996EN06, 1996KO03, 2003HA44, 2004SA67, 2013PA06, 2013SO15, 2016GA35). The role of neutrino interactions for nucleosynthesis in supernovae explosions is discussed in (2006SU15, 2007SU08, 2008PA05, 2009CH49, 2013PA06).
A beam of ν_{μ} from inflight decay of π^{+} was used to determine the flux averaged cross sections for populating ^{12}N ground and excited states (2002AU03: LSND Collaboration). Detectors searching for neutrino oscillations are mainly mineral oil (carbon) based scintillators, and hence cross sections on ^{12}C for neutrinos from pion decay are vital for data analysis. For these measurements, the neutrino beam energy spectrum extended to slightly above 250 MeV so reactions occurred for E_{ν} = 150 (threshold) to 250 MeV. The exclusive cross section to ^{12}N_{g.s.}, which requires the coincidence of a μ^{} with a delayed β^{+} from ^{12}N decay, is σ = (5.6 ± 0.8 (stat.) ± 1.0 (sys.)) × 10^{41} cm^{2}, while the inclusive cross sections, which required only detection of the emitted μ^{}, is σ = (10.6 ± 0.3 (stat.) ± 1.8 (sys.)) × 10^{40} cm^{2}. The ^{12}N(ν_{μ}, μ^{})^{12}N* cross section is roughly 200 times greater than the ν_{e} induced reaction. See prior results from the collaboration in (1997AT03). Note: an earlier LAMPF measurement had significantly fewer events (1992KO18) and was incompatible with the LSND results. See also (2003KO50). Theoretical analyses of the cross sections have been carried out using QRPA/CRPA models (1996KO32, 1997AU05, 2001JA12, 2005BO44, 2005KR06, 2006CO15, 2006CO16, 2008PA06, 2011SA04), shell models (1999HA32, 2002AU01) and other approaches (2004ME12, 2004SA67, 2006JA04, 2006VA09, 2011KI06, 2014KI06, 2016PA43, 2016VA08). Special attention has been focused on the reaction channel populating ^{12}N*; this contribution to the reaction cross section is generally over predicted by roughly a factor of two (1995KO40, 1995UM02, 1996EN06, 1996KO03, 1997KO04, 1998IM02, 1999KO24, 2000HA17, 2000VO13, 2001AU05, 2001VO18, 2002JA03, 2003HA17). The scaling and superscaling approaches for relating the relativistic (e, e') and (ν_{μ}, μ^{}) cross sections provide a reasonable description and are examined for energies up to the quasielastic scattering and Δresonance regions in (2003HA44, 2005AM09, 2005CA54, 2006BA17, 2006BA62, 2006CA22, 2008IV01, 2009AN06, 2015AM02, 2015PA35, 2016IV03).
States populated in ^{12}C(p, n) are displayed in 12.48 (in PDF or PS). At E_{p} = 135 MeV, J^{π} values are deduced from a DWIA analysis of θ = 0°  45° angular distributions (1996AN08); see earlier measurements and analysis at E_{p} = 30.5 and 49.5 MeV (1970CL01) and at 160 MeV (1984GA11). At E_{pol. p} = 197 and 295 MeV cross sections, angular distributions, and spin observables were measured (1996SA11). The peak at E_{x} = 4.5 MeV is consistent with a J^{π} = 2^{} assignment, but at E_{x} = 7.5 MeV the strength is inconsistent with the predicted J^{π} = 1^{} because the sign of D_{NN} is negative; it should be positive. Contributions from additional states are suggested to explain the negative D_{NN}(0) (1996SA11). Unresolved angular distributions over the range E_{x} = 2 to 17 MeV (and θ = 5°13°) are dominated by l = 1 transitions (1984GA11). Angular distributions have also been studied at E_{p} = 35 and 40 MeV (1987OH04: n_{0}, n_{1}, n_{2}; DWBA), 61.8 and 119.8 MeV (1979GO16, 1980AN05: n_{0}, n_{1}) , 99.1 MeV (1980KN02: n_{0}, n_{1}), 120, 160 and 200 MeV (1981RA12: n_{0}, n_{1}) [the spinisospin term of the effective interaction appears to be almost energy independent over the latter energy interval], and at 144 MeV (1980MO10: n_{0}). See also (1994GA49, 2010AD18). The backward angle scattering distribution for n_{0} measured at E_{p} = 200 MeV was found to be five times larger than expected (1996YU02). At E_{p} = 647 and 800 MeV, the spectra show a narrow high energy peak and a broad bump at lower energies associated with pion production (1976CA17). The θ = 0° (L = 0) cross sections to ^{12}N_{g.s.} at E_{p} = 61.8 and 119.8 MeV (1979GO16, 1980AN05), 280 MeV (1990MI10), 160, 200 and 795 MeV (2001PR02), 492 MeV(1989RA09) have been compared with the GamowTeller transition strengths and to the strengths for population of the ^{12}C*(15.11) (1982AN08) and ^{12}B_{g.s.} members of the T = 1 isospin triad (1990MI10). See also (1980AN05, 2002DM01). In (1987TA13) analysis of the θ = 0° (L = 0) cross sections measured for GT transitions over a broad range of targets yielded a straightforward relationship between the cross section and B(GT). See also (1989RA09). A systematic analysis of ^{1219}C(p, n) reactions is given in (2016TA07). At E_{pol. p} = 160 and 186 MeV spin observables were measured for θ_{lab} = 0° to 50°; prominent peaks at ^{12}N*(0, 0.96, 1.2, 4.5, 7) were evaluated via multipole decomposition analysis (1993YA11, 1994RA23, 1995YA12). At E_{p} = 296 MeV, cross sections and polarization transfer observables were analyzed up to E_{x} ≈ 10 MeV; the E_{x} ≈ 7 MeV group is dominated by J^{π} = 2^{} strength and a strong spinflip strength is found in the continuum (2008DO02). See also (2007WA40: E_{pol. p} = 296 MeV) and (2005WA36). The polarization transfer coefficients, D_{NN}(0°), were measured at E_{pol. p} = 295 MeV (1995WA16), the large negative values measured for E_{x} up to 50 MeV suggest a stronger spinflip strength than what has been observed at lower bombarding energies. Results at E_{pol. p} = 318 and 494 (1993ME06) indicate that medium modified effective NN interactions play a role. See also measurements at E_{pol. p} = 50 and 72 MeV (1991LI32), E_{p} = 296 MeV (2008DO02), 12.49 (in PDF or PS), and analysis in (1998HI02, 1999AN32, 2000KI03). Cross sections and analyzing powers have been measured for quasifree neutron knockout (1994WA22: E_{pol. p} = 186 MeV, 1991TA13: E_{p} = 494 and 795 MeV, 1993HI01: E_{pol. p} = 290 and 420 MeV) and are found to be similar to those for free NN scattering (1993HI01). See also (1992WA19, 1993DE33, 1999NA43). Measurements on the spinlongitudinal and spintransverse strength functions are given in (1984TA07: E_{p} = 160 MeV, 2002HA14: E_{pol. p} = 197 MeV, 2004WA14: E_{p} = 345 MeV, 1999WA08: E_{pol. p} = 346 MeV, 1993CH13, 1994TA24: E_{pol. p} = 495 MeV, 1994PR08, 1995PR04: E_{pol. p} = 495 and 795 MeV). See discussion in (1993HO04, 1993SA30, 1994DE29, 1994HO15, 1994HO18, 1994IC04, 1995DE44, 1996GA20, 1999YO02, 2001KA19, 2002IC02, 2002NA17). 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 (1987LI29, 1987RA32). Evidence for pionic and ρmesonic correlation effects is deduced from analysis of polarization transfer coefficients measured at E_{p} = 296 MeV (2009DO12). See also (1994DM03, 1994HE06, 1996OS02, 1996PR03, 1998DO15, 1998IO03, 2002DA20, 2002IC02, 2002TO07, 2016DE06).
Measurements of the ^{12}C(^{3}He, t) reaction are summarized in 12.50 (in PDF or PS). Observed triton groups are displayed in 12.46 (in PDF or PS). The ^{12}N*(0, 0.96, 1.19, 2.42, 4.25) triton group angular distributions (corrected for phasespace and isospin factors) are similar to those of inelastically scattered ^{3}He to ^{12}C*(15.11, 16.11, 16.58, 17.77, 19.57) strongly suggesting isobaric analogs (1969BA06, 1970AR05, 1976CE02, 1982TA05). Following this suggestion, if ^{12}C*(17.77) and ^{12}N*(2.42) are analogs, then the latter is a 0^{+} state (1976CE02). Relatively narrow levels at ^{12}N*(4.25, 5.32, 6.10, 7.13) are reported in ^{10}B(^{3}He, n), while broader levels at ^{12}N*(4.15, 5.23) are observed in this reaction; it is therefore suggested that the selectivity is greater in the (^{3}He, n) reaction and that (^{3}He, t) populates unresolved states (1976MA15). More states are observed in ^{12}B than in ^{12}N, indicating that some analog states are missing. With the possible exception of the relatively narrow states, ^{12}N*(9.42, 9.90), the other reported groups with E_{x} > 6 MeV may be due to unresolved groups (1976MA15). See also (1975GO1L, 1978TA1M). At θ ≈ 0° the GamowTeller and spinflip ΔL = 1 resonances are strongly populated; cross sections have been measured (1991JA04: E = 76, 200 MeV), (1994AK02: 450 MeV), (2007ZE06: 420 MeV). The J^{π} = 1^{+}, 2^{+}, 2^{}, 0^{+}, 2^{}, 3^{}, 1^{} values are deduced for ^{12}N*(0, 960, 1190, 2439, 4250, 5348, 7130), respectively (1991JA04). A broad study of the B(GT) systematics finds σ_{GT} = 109/A^{0.65}, where the GT unit cross section, σ_{GT}, is related to the known B(GT) values from βdecay and the dσ/dΩ_{cm} cross section for zero momentum transfer (2011PE12). In (1994AK02, 1994HA40, 1998IN02, 1998HA43: 450 MeV) proton decay from excited ^{12}N states was measured in coincidence with σ(E_{t}, θ = 0°); ^{12}N*(4.16, 6.0, 9.9) were correlated with p_{0}decay to the ^{11}C J^{π} = 3/2^{} ground state, while ^{12}N*(7.4, 8.4, 9.9) were correlated with p_{1}decay to ^{11}C*( 2.0[J^{π} = 1/2^{}]). Preliminary analysis indicates J^{π} = (2^{}), (1^{}) and (0^{}) for ^{12}N*(6.4, 7.4, 9.9) respectively. Angular distributions have been reported to many states. ^{12}N*(4, 7.1) are reached via an l = 1 transfer (1983EL05). At 81 MeV, (1983ST10) carried out a DWBA analysis for states up to E_{x} = 7.4 MeV. 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^{}) (1984TA11). ^{12}N*(4.) is assumed to be the analog of the J^{π} = 2^{} isovector magnetic dipole state while ^{12}N*(7.) corresponds to a group of states with J^{π} = 1^{} strength that is the analog of the GDR (1991GR03). The ^{12}N and ^{12}B spindipole resonances, populated via ^{12}C(^{3}He, t)^{12}N and ^{12}C(d, ^{2}He)^{12}B reactions, are compared and discussed in (1998IN02). The spectra of inelastically scattered ^{3}He ions (see ^{12}C) and of tritons have been studied at E(^{3}He) = 170 MeV (1982TA05). The triton spectrum has been compared with photoabsorption results (1984TA11, 1991GR03, 1998IN02). (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. No structure is observed between E_{x} = 15 and 70 MeV (1984TA11). Analysis of data in the quasielastic scattering energy region (1987BE25) is given in (1996GA20, 1992WA19, 1996KE04). At E(^{3}He) = 0.6 to 2.3 GeV the reaction appears to be singlestep direct and is well described by DWIA (1987BE25). Delta isobar excitations have been studied at 1.5, 2.0 and 2.3 GeV (1986CO03) and at 4.4 to 10.8 GeV/c (1984AB06, 1988AB08). In later studies (1991HE12, 1992HE08, 1993RO09) π^{+} + protons were detected following decay of the Δ, and the width of the resonance was evaluated. The Δ excitation peak observed in the ^{12}C(^{3}He, t)^{12}N reaction is shifted from that found in the ^{12}C(d, ^{2}He)^{12}B reaction, see discussion in (1984GA36, 1984GE1A, 1985RO1N, 1986EL1C, 1986GA1P, 1987EL08, 1987EL14, 1988RO17). See also (1990AR05, 1990DE49, 1990GA19, 1991DE31, 1993DM01, 1993FE10, 1993OS03, 1994DM03, 1994HE06, 1994OS02, 1994SN01, 1994UD01, 2002DA20). Measurements and discussion on D_{nn}(0°) ≈ 1/3, the spin transfer coefficient, are given in (1994DM03, 1998KI10, 2000KI03).
At E_{π±} = 165 MeV, excitation of the ^{12}N and ^{12}B isovector analog giant E1 resonances, built on ^{12}C_{g.s.}, is observed (1994HA41). Earlier studies of (π^{±}, π^{0}) evaluated the A and isospin dependence of the cross section to investigate the Δnucleus interaction (1983AS01, 1984AS05, 1987OS05, 1990BE41, 1990IM02).
Angular distributions have been studied to ^{12}N_{g.s.} at E(^{6}Li) = 84, 150 and 210 MeV (1987WI09), E(^{6}Li) = 93 MeV (1984GL06), E(^{6}Li) = 100 MeV (1994LA10), E(^{6}Li) = 156 MeV (1990MO13, 1993SC02) and E(^{6}Li) = 210 MeV (1986AN29). At bombarding energies up to 210 MeV the reaction mechanism is dominated by twostep processes, but it is suggested that one step processes will dominate above 300 MeV (1987WI09). At the higher beam energies ^{12}N*(1.0) is also populated as is a broad structure near 4.25 MeV. The forward angle cross sections for the GT transitions are found to be proportional to the βdecay strength for ^{12}C and other targets (1986AN29). Proton angular distributions (p_{0}, p_{1} and p_{2+3}) of groups near ^{12}N*(4.2, 5.35, 6.4, 7.4, 9.5, 12) were analyzed via Legendre polynomial fits (1993SC02) to deduce spin information; the results are consistent with the accepted spin values, with the exception of the E_{x} = 6.4 MeV resonance, where J > 3 is required while prior studies indicate J^{π} = 1^{}.
The E_{x} = 0, 0.96 MeV states of ^{12}N and ^{12}B are populated in ^{12}C(^{12}C, ^{12}B) reactions at E(^{12}C) = 70 MeV (1986WI05, 1991AN12). Since only the ^{12}N_{g.s.} is bound, emphasis is typically placed on the ^{12}C(^{12}C, ^{12}N) reaction, which isolates ^{12}B excited states. See further discussion in ^{12}B reaction 35 ^{12}C(^{12}C, ^{12}N). Coherent pion production was measured using the ^{12}C(^{12}C, ^{12}Nπ^{+}) reaction at 1.1 GeV/A (2005BO22).
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 J^{π} = 2^{} (SFGDR) and 1^{} (GDR) states (1986VO02, 1988VO06). See analysis of the groundstate charge exchange reaction in (1999MA18).
At E_{p} = 38 MeV triton groups are reported to states up to E_{x} = 7.3 MeV (2015CH50); see 12.51 (in PDF or PS); see also discussion in (2016HO14). At E_{p} = 43.7 MeV, triton groups are observed to ^{12}N_{g.s.} and to the first excited state: E_{x} = 0.963 ± 0.030 MeV (1967CE1B: private communication). 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 (1976YO03). At E_{p} = 52.5 MeV the angular distribution to ^{12}N*(2.42) is consistent with J^{π} = 0^{+} (1976CE02). The atomic mass excess of ^{12}N, 17338 ± 1 keV, is derived from this reaction in (1976NO1J).
Angular distributions for ^{14}N(^{11}C, ^{12}N) were measured at E(^{11}C) = 110 MeV (2001TR04, 2002GA11, 2002GA44, 2003TA02) in order to determine the ^{12}N → ^{11}C + p ANC, which is related to the nonresonant ^{11}C(p, γ) reaction rate. The value (C_{peff}^{12N})^{2} = (C_{p1/2}^{12N})^{2} + (C_{p3/2}^{12N})^{2} = 1.73 ± 0.25 fm^{1} was deduced, implying a significantly larger astrophysical Sfactor than previously deduced. See also (2003KR14, 2003TR09, 2005TI07, 2005TI14, 2006MU15, 2012OK02) and reaction ^{11}C(p, γ).
At E(^{12}N) = 65.5 MeV/A the Coulomb dissociation of ^{12}N was measured on a ^{208}Pb target and the photobreakup excitation function was deduced from the kinematic reconstruction of the p + ^{11}C momenta (1995LE27). Analysis indicates Γ_{γ} = 6.0^{+7.0}_{3.5} meV for ^{12}N*(1.19) and C^{2}S = 0.40 ± 0.25 for the direct capture spectroscopic factor. See measurements at E(^{12}N) = 77 MeV/A in (2004MIZW) and (2005TY02). See also discussion in (2015MU08).
