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USNDP

19Ne (1995TI07)


(See Energy Level Diagrams for 19Ne)

GENERAL: See Table 3 preview 3 [Electromagnetic Transitions in A = 18-19] (in PDF or PS), Table 19.26 preview 19.26 [General Table] (in PDF or PS), Table 19.27 preview 19.27 [Table of Energy Levels] (in PDF or PS) and Table 19.28 preview 19.28 [Radiative decays in 19Ne] (in PDF or PS).

μg.s. = -1.88542 (8) nm (1982MA39)
μ0.239 = -0.740 (8) nm (1978LEZA)

1. 19Ne(β+)19F Qm = 3.238

We adopt the half-life of 19Ne suggested by (1983AD03): 17.34 ± 0.09 s. See also (1978AJ03). The decay is principally to 19Fg.s.: see Table 19.29 preview 19.29 (in PDF or PS). The 19Ne decay to 19F*(0.11) [Jπ = 1/2+ → 1/2-] proceeds by vector and axial vector weak currents, with the former making a negligible contribution. The measured decay rates are roughly an order of magnitude smaller than predicted using the 0ℏω + 1ℏω shell model (1981AD05, 1983AD03). Decay of polarized 19Ne is consistent with time-reversal invariance: see (1987AJ02, 1988SE11, 1993CA1K). See also (1988BR1D, 1988SA12, 1989SA55, 1991NA05, 1991SAZX, 1992HE12, 1992SE08, 1993SE1B).

2. 15O(α, γ)19Ne Qm = 3.529

(1986LA07) have recalculated the 15O(α, γ) direct capture rate at stellar energies. (1990MA05) have measured the branching ratios Γαtotal for Ecm = 850, 1020, 1071, 1183 and 1563 keV resonances in 15O + α. The strengths of these resonances were determined (see Table 19.30 preview 19.30 (in PDF or PS)) and the reaction rate for temperatures between 7 × 108 and 3 × 109 K was determined to differ from theoretical calculations (1986LA07, 1988CA26) by no more than 20%. See also (1988BU01, 1988TR1C). A recent measurement by (1995MA28) determined Γα for Ex = 4.033 keV and hence the resonant rate for 15O(α, γ) at astrophysical energies.

3. (a) 16O(3He, γ)19Ne Qm = -3.196 Eb = 8.443
(b) 16O(3He, n)18Ne Qm = -11.420
(c) 16O(3He, p)18F Qm = 2.032
(d) 16O(3He, d)17F Qm = -4.894
(e) 16O(3He, 3He')16O
(f) 16O(3He, α)15O Qm = 4.914
(g) 16O(3He, 7Be)12C Qm = -5.576

Excitation functions at 90° for γ0-2, γ3-5 and γ6 [reaction (a)] have been measured for E(3He) = 3 to 19 MeV (1983WA05): see Table 19.31 preview 19.31 (in PDF or PS) for a listing of the resonances reported in this and in the other channels. See also (1983AJ01, 1987AJ02) and (1990AB14, 1991SU17, 1992CO08).

4. 16O(α, n)19Ne Qm = -12.134

Gamma transitions have been observed from the first six excited states of 19Ne: see Table 19.25 preview 19.25 (in PDF or PS) in (1978AJ03) and Table 19.28 preview 19.28 (in PDF or PS) here. Angular distributions of many neutron groups have been studied at Eα = 41 MeV: see (1983AJ01).

5. 16O(6Li, t)19Ne Qm = -7.352

This reaction and the mirror reaction 16O(6Li, 3He)19Fhave been studied at E(6Li) = 24, 35, 36, and 46 MeV: see (1978AJ03, 1983AJ01). Table 19.16 preview 19.16 (in PDF or PS) displays the analog states observed in the two reactions. In addition triton groups are reported to states with Ex = 6.08, 6.28, 6.85, 7.21, 8.08, 8.45, 8.94, 9.81, 10.01, 11.08, 11.24, 11.40, 12.56 [all ± 0.02], 13.1, 13.22, 14.18, 14.44, 14.78 [remaining, ± 0.3] MeV. See also (1983CU02) and the preliminary report in (1992ROZZ).

6. 16O(10B, 7Li)19Ne Qm = -9.345

This as well as the analog reaction [16O(10B, 7Be)19F] have been studied at E(10B) = 100 MeV. On the basis of similar yields and Ex, and in addition to the low-lying analogs, it is suggested that the following pairs of states are analogs in 19F - (19Ne): 8.98 (8.94), 11.33 (11.09), 12.79 (12.48), 14.15 (14.17), 14.99 (14.61) and 15.54 (15.40) [ ± 100 keV]; however, problems of energy resolution are evident. See (1983AJ01) for references on this and on other heavy-ion induced reactions.

7. 16O(12C, 9Be)19Ne Qm = -17.836

This 3He stripping reaction was studied at E(12C) = 480 MeV (1988KR11). The ground state, 0.2 MeV doublet and 1.5 MeV multiplet were weakly populated. High spin states at 2.8 MeV (9/2+) and 4.64 MeV (13/2+) were strongly populated and were inferred to belong to the (sd)3, 2N + L, g.s. band with ((1d5/2)22s1/2)9/2+ and (1d5/2)313/2+ configurations. Levels at 8.9, 9.88 and 10.41 MeV were inferred to have spin parities of 11/2-, 11/2+, and 13/2+. A 17/2- spin parity was proposed for the strongly populated 12.3 MeV level.

8. 17O(3He, n)19Ne Qm = 4.300

Neutron-γ coincidence measurements lead to the determination of excitation energies [Ex = 4032.9 ± 2.4, 4140 ± 4, 4197.1 ± 2.4, 4379.1 ± 2.2, 4549 ± 4, 4605 ± 5, 4635 ± 4 and (5097 ± 10) keV], τm and branching ratios (see Table 19.28 preview 19.28 (in PDF or PS)). On the basis of these it is suggested that 19Ne*(4.14, 4.20) are the analogs of 19F*(4.03, 4.00) [Jπ = 9/2-, 7/2-] and that 19Ne*(4.55, 4.60) are the analogs of 19F*(4.556, 4.550) Jπ = 5/2+, 3/2-]. There is no evidence for a reported state at Ex = 4.78 MeV: see (1978AJ03).

9. 18O(p, π-)19Ne Qm = -134.812

This reaction (at Ep = 201 MeV) selectively populates stretched 2p-1h states, in particular 19Ne*(4.64) [Jπ = 13/2+] and a structure near 10 MeV. Angular distributions and Ay are reported for 19Ne*(0, 2.80, 4.6) (1986KE04). See also (1987AJ02) and (1990KU1H).

10. 19F(p, n)19Ne Qm = -4.020

For a review of threshold measurements see (1972AJ02, 1976FR13). Measurements of the total cross section from threshold (Ep = 4.24 MeV) to Ep = 28 MeV are reported by (1990WA10). Excited states of 19Ne determined from γ-spectra are displayed in Table 19.25 preview 19.25 (in PDF or PS) of (1978AJ03). Branching ratio and τm measurements are summarized in Table 19.28 preview 19.28 (in PDF or PS) here. For the g-factor of 19Ne*(0.24) see Table 19.27 preview 19.27 (in PDF or PS). Angular distributions have been measured at Ep = 160 MeV to 19Ne*(0[0], 1.54[(0 + 2)], 5.4[0], 6.2[(0 + 1)], 7.1[(0 + 1)], 7.7[(0 + 1)], 8.60[(0)], 10.2[(1)], 11.0 [0], 12.1) (1984RA22; [transferred angular momentum in brackets] also forward-angle σ(θ) at Ep = 120 MeV). Spin-transfer coefficients were measured at Ep = 120, 160 MeV by (1990HUZY). See also 20Ne in (1987AJ02) and (1987TA13, 1989RA1G).

11. 19F(3He, t)19Ne Qm = -3.257

Angular distributions have been obtained for the triton groups to 19Ne*(0.24, 1.54, 2.79) at E(3He) = 26 MeV: see (1978AJ03). 19Ne levels at Ex = 7.060/7.088, 7.500, 7.531 and 7.620 MeV were measured to obtain Γpα branching ratios (0.58 ± 0.08, 2.7 ± 0.9, 0.29 ± 0.09, and 0.34 ± 0.05, respectively) for determination of possible HCNO breakout reactions 18F(p, γ)19Ne and 18F(p, α)15O(α, γ)19Ne (1993UTZZ).

12. (a) 20Ne(n, 2n)19Ne Qm = -16.864
(b) 20Ne → 19Ne + n

Theoretical calculations of neutron-induced reaction cross sections on 20Ne in the energy range 1 - 30 MeV were performed (1991RE10). The shape and magnitude of the neutron yield from the breakup of 20Ne [reaction (b)] was calculated in the high-energy region using diffraction theory of processes of fragmentation of complex nuclei.

13. 20Ne(3He, α)19Ne Qm = 3.713

Alpha groups have been observed to 19Ne states with Ex < 10.6 MeV: see Table 19.27 preview 19.27 (in PDF or PS) and Table 19.32 preview 19.32 (in PDF or PS). Angular distributions have been measured for E(3He) = 10 to 35 MeV: see (1972AJ02). DWBA analysis of the strongest transitions leads to the l and Jπ values shown in Table 19.32 preview 19.32 (in PDF or PS). 19Ne*(0, 0.24, 1.54, 2.79) are identified as members of the Kπ = 1/2+ rotational band [with 19Ne*(4.38) as the 7/2+ member] and 19Ne*(0.28, 1.51, 1.62) with the Kπ = 1/2- band. Candidates for the 7/2- and 9/2- members of the Kπ = 1/2- band are thought to be 19Ne*(4.15, 4.20). Possible matching of other 19Ne states with those in 19F is also discussed: see (1972AJ02). For lifetime and radiative decay measurements see Table 19.28 preview 19.28 (in PDF or PS). See also (1987AJ02) and see (1989MC1C) for use of this reaction for observing parity-violating effects.

14. 21Ne(p, t)19Ne Qm = 15.144

At Ep = 40 MeV the angular distributions to 19Ne*(0.24, 4.03, 5.09) are well described by L = 2, 0 and 4, respectively. 19Ne*(4.03), Jπ = 3/2+, has a dominant 5p-2h configuration. 19Ne*(5.09) has positive parity and the data are consistent with J = 5/2. At Ep = 45 MeV the triton group to a state with Ex = 7.620 ± 0.025 MeV has an angular distribution [L = 0] which is similar to that for 19F*(7.66); both are thought to be the analogs of the (Jπ; T) = (3/2+; 3/2) 0.096 MeV first excited state of 19O. The ground state of 19O has Jπ = 5/2+; L for the analog state should be 2. 19Ne*(0, 2.79) are also populated: see (1978AJ03, 1983AJ01).