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GENERAL: See also Table 18.4 [Table of Energy Levels] (in PDF or PS).

Theory: See (RE54C, EL55, EL55A, NE56D, GR57D, WA59).

1. 18F(β+)18O

Qm = 1.677

The positron end point is 635 ± 15 (BL49A), 649 ± 9 keV (RU51). The spectrum is simple (see (DR56A)). The half-life is 112 ± 1 min (BL49A), 111 ± 1 min (JA55), 110 ± 1 min (BE58G): log ft = 3.62. The fact that the β transition to the ground state of ¹⁸O is allowed indicates J = 1⁺ for ¹⁸F (assumed T = 0) (MO54). The ratio ε_K/β⁺ = 0.030 ± 0.002 (DR56A). See also (DZ56) and (RE58; theor.).

2. 12C(7Li, n)18F

Qm = 5.963

See (NO57A).

3. 14N(α, γ)18F

Qm = 4.421

Resonances have been observed at E_α = 1.53, 1.62, 2.35, and 2.88 MeV, corresponding to ¹⁸F*(5.61, 5.68, 6.25, and 6.651) (PR55, AL58, BR58, PH58): see Table 18.5 [Resonances in ¹⁴N + α] (in PDF or PS).

The 5.61 MeV state decays to the ¹⁸F ground state (16%), and to states at 1.08 MeV (41%) and 3.06 MeV (45%). Gamma rays with E_γ = 2.12 and 0.94 MeV are also observed (AL58): see Fig. 39 (Gamma-ray transitions in ¹⁸F). The radiative widths ωΓ_s to the ground state and ¹⁸F*(1.08) are 0.7 and 2.2 eV, respectively; all others amount to 3 eV (PR55). The branching ratios favor J = 1^-; T = 0 for ¹⁸F*(5.61) and T = 1 for ¹⁸F*(1.08 and 3.06). Angular distributions of the cascade γ-rays are consistent with J = 0⁺ and 2⁺ for the states at 1.08 and 3.06 MeV. Angular correlations rule out J = 0 for the 0.94 MeV state. The 3.06 MeV state shows a 25% ground-state branch and a 75% cascade through the 0.94 MeV level (AL58: see also (KU58C)). Delayed coincidence measurements on the γ-decay of the 0.94 MeV state show τ ≤ 5 x 10^-9 sec. This implies 1 ≤ J ≤ 3 when taken together with the results of the ¹⁶O(³He, pγ)¹⁸F reaction (BR58).

The 5.68 MeV state decays to the 1.08 MeV state (1.075 ± 0.010 MeV) with ωΓ_γ = 2.2 ± 0.3 eV. The ground-state transition is < 0.2 eV; others amount to about 2 eV (PR55). The strength of the transition 5.68 → 1.08 suggests dipole radiation, J(5.68) = 1; T = 0 (WA59).

The 6.25 MeV state decays mainly to ¹⁸F*(1.7): E_γ = 4.45 ± 0.05 MeV (ωΓ_γ = 7.9 ± 1.0 eV), and ¹⁸F*(0.94): E_γ = 5.30 ± 0.10 MeV (ωΓ_γ = 0.8 ± 0.15 eV). Transitions to the ground state and to levels at ~ 3 MeV have upper limits of 5% and 20%. The 1.7 MeV state decays through ¹⁸F*(1.05). The (6.25 → 1.7) and (1.05 → 0) γ-γ correlation is isotropic within 10%, consistent with J = 0⁺ for the 1.05 MeV state. The 1.7 MeV state is most likely to be 1^± or (2⁺), and is assumed to be T = 0 from the ¹⁸O level structure (compare ²⁰Ne(d, α)¹⁸F). The 6.25 MeV state is then 2^± or 3^- (PH58). If the 1.7 MeV state is 1⁺, J(6.25) is 2⁺ or 2^-; the strength of the transition (6.25 → 1.7) indicates T = 1 for ¹⁸F*(6.25) (WA59).

The 6.65 MeV state decays with E_γ = 5.80 ± 0.10 (7%), ωΓ_γ = 0.25 eV and 4.90 ± 0.05 MeV (70%), ωΓ_γ = 2.1 eV to the 0.94 and 1.70 MeV states, respectively. Transitions with relative intensity ~ 23% are also reported to states with E_x ~ 3 MeV (PH58). See also (BA58H, BR58E, HE58A) and ¹⁶O(³He, p)¹⁸F.

4. 14N(α, n)17F

Qm = -4.747

Eb = 4.421

See (FU38).

5. 14N(α, p)17O

Qm = -1.197

Eb = 4.421

Observed resonances are displayed in Table 18.5 [Resonances in ¹⁴N + α] (in PDF or PS) (HE53, HE58D, KA58C). Absolute cross sections are given by (HE58D) for E_α = 2.7 to 3.6 MeV. The yield of protons to ¹⁷O*(0.7) is at least a factor of 10 smaller than the ground-state yield. See also (MA54M, GR55) and (1952AJ38).

6. 14N(α, α)14N

Eb = 4.421

Observed anomalies in the elastic scattering are exhibited in Table 18.5 [Resonances in ¹⁴N + α] (in PDF or PS) (BR39, DE39A, HE53, HE58D, HE58E, KA58C). The indicated assignments to the narrow resonances at E_α = 2.35, 2.37, 2.77, 2.88, and 3.58 MeV are obtained from qualitative analysis of the excitation functions. The two broad resonances at E_α = 2.870 and 3.080 MeV have been analyzed in detail: both are formed with p-waves, J = 1^- and 2^-, respectively. For the former, Γ_α/Γ = 0.85. See also (KA58C). A broad anomaly at E_α = 3.7 MeV requires two levels, and possible admixture of higher l-values (HE58E, KA58C).

7. 15N(α, n)18F

Qm = -6.420

Not reported.

8. 16O(d, γ)18F

Qm = 7.538

At E_d = 1.7 MeV, the capture cross section is ~ 10 μb (BU55A). See also (SI54).

9. 16O(d, n)17F

Qm = -1.631

Eb = 7.538

Observed resonances in the forward yield of neutrons are displayed in Table 18.6 [Maxima in the yield of ¹⁶O + α reactions] (in PDF or PS) (MA55M). See also (1952AJ38) and (BU55A).

10. 16O(d, p)17O

Qm = 1.919

Eb = 7.538

The yield shows strong variations with energy, suggesting compound nucleus formation (HE48A, BE55E, ST55C, RO56A, VA56C): see Table 18.6 [Maxima in the yield of ¹⁶O + α reactions] (in PDF or PS). On the other hand, angular distribution measurements show strong stripping peaks for both p₀ and p₁, for E_d = 0.5 to 4.1 MeV (AL55F, BE55E, JU55A, ST55C, GR56, JU56C, KO56F, BA57F, JU57). See also ¹⁷O.

11. 16O(d, d)16O

Eb = 7.538

Observed maxima in the θ = 135° and 97° cross section are listed in Table 18.6 [Maxima in the yield of ¹⁶O + α reactions] (in PDF or PS) (BE56D). Structure in the yield of elastically scattered deuterons is also reported by (BA57F). See also (KH55, KH55A).

12. 16O(d, α)14N

Qm = 3.116

Eb = 7.538

Two resonances are reported for ground-state α-particles at E_d = 3.85 MeV, Γ = 35 keV, and 4.0 MeV, Γ = 100 keV (BA57F): see Table 18.6 [Maxima in the yield of ¹⁶O + α reactions] (in PDF or PS). Yield curves of the α₀, α₁ and α₂ groups are reported for E_d = 5.5 to 7.5 MeV by (BR56F). The α₁-group, leading to the T = 1, 2.31 MeV state of ¹⁴N, is greatly inhibited: the average intensity is only a few per cent of the average yield of the α₀ group. Broad resonances are observed in the yields of all three α groups. The resonances in the α₁-yield occur at ~ 6.2, 6.6, and 7.0 MeV; they are presumably due to predominantly T = 1 states at E_x ~ 13.0, 13.4, and 13.8 MeV (BR56F). At E_d = 7.2 MeV, the intensity ratio α₁/α₀ is 16% (θ = 35°), at 6.8 and 7.1 MeV, α₁/α₀ < 6%, and at 8.9 MeV, < 2% (DA58B). The observations are consistent with expected isobaric spin impurities in the states involved (BR56F). Angular distributions for α₀, α₂ may give evidence of compound nucleus effects (DA58B): see also ¹⁴N.

13. 16O(t, n)18F

Qm = 1.280

See (PO51, BA55I, SH56A).

14. 16O(3He, p)18F	Qm = 2.045
	Q0 = 2.052 ± 0.015 (HI59).

Seventeen proton groups corresponding to excited states of ¹⁸F from 0 to E_x = 4.36 MeV are reported by (HI59: E(³He) = 5.7 to 5.9 MeV): see Table 18.7 [Energy levels of ¹⁸F from ¹⁶O(³He, p)¹⁸F, ¹⁹F(³He, α)¹⁸F and ²⁰Ne(d, α)¹⁸F] (in PDF or PS). See also (KU58C). Angular distributions for the first five states, analyzed by direct interaction theory, indicate J = 1⁺, 2⁺ or 3⁺, 0⁺, (?), and 4⁺ or 5⁺ for ¹⁸F*(0, 0.94, 1.04, 1.08 and 1.13), respectively (HI59: tentative assignments). Gamma transitions to ¹⁸F(0) have been observed from the levels at 0.94, 1.04 and 1.08 MeV; the decay of the 1.13 MeV level has not been detected (KU58C). Proton-gamma coincidence techniques have been used to determine branching ratios and angular correlations involving ¹⁸F states at 0.94, 1.08, 1.7, 2.1, 2.5, and 3.07 MeV (KU58: see also (BU56)): see Fig. 39 (Gamma-ray transitions in ¹⁸F). All of these states show at least one anisotropic radiation except for ¹⁸F*(1.04 and 1.08), excluding J = 0 for all but these two ((KU58) and E. Almqvist, private communication).

The mean life of the 0.94 MeV state is ≤ 5 x 10^-9 sec, indicating J ≤ 3 (BR58). The polarization of the γ-radiation indicates positive parity for the state (LI58B). The strong transition from ¹⁸F*(3.07: T = 1) suggests T = 0. For the 1.04 MeV state, J = 0⁺ is indicated by the proton angular distributions (HI59); J = 0^-; T = 0 is suggested by the γ-branching (E. Almqvist, private communication). The 1.08 MeV state appears to have J = 0⁺; T = 1 (see ¹⁴N(α, γ)¹⁸F). The absence of the ground-state transition from ¹⁸F*(1.12) is consistent with its expected J = 5⁺ character. The 1.7 MeV state is fixed as J = 1⁺ from the present reaction and ¹⁹F(p, d)¹⁸F. For ¹⁸F*(2.1 and 2.54) assignments of J = 1, 2 and 1, 2, 3 are indicated by the branching ratios (E. Almqvist, private communication). See also (BR58D, BR58E).

15. 16O(α, pn)18F

Qm = -18.533

See (TE47).

16. 16O(6Li, α)18F

Qm = 6.067

See (NO57A).

17. 17O(p, γ)18F

Qm = 5.619

A resonance in the capture cross section may be indicated near 1.24 MeV (E_x = 6.79 MeV), σ ~ 1 mb (NI56).

18. 17O(p, α)14N

Qm = 1.197

Eb = 5.619

Resonances in the yield of ground state α-particles are displayed in Table 18.8 [Resonances in ¹⁷O(p, α₀)¹⁴N] (in PDF or PS) (AH57).

19. 17O(d, n)18F

Qm = 3.392

See ¹⁹F.

20. 17O(3He, d)18F

Qm = 0.125

Not reported.

21. 17O(α, t)18F

Qm = -14.194

Not reported.

22. 18O(p, n)18F	Qm = -2.450
	Ethresh. = 2.590 ± 0.004 (RI50E);
	Ethresh. = 2.584 ± 0.010 (MA56E);
	Ethresh. = 2.577 ± 0.008 (HI56C).

Slow neutron thresholds are reported corresponding to E_x = 960 ± 10, 1065 ± 15, and, possibly, 1245 ± 10 keV; no others appear with E_x < 1.65 MeV (NA56). Gamma rays are observed with E_γ = 940 ± 20 and 1040 ± 20 keV at E_p = 4.3 and 4.4 MeV: the 1040 keV γ-ray exhibits a Doppler shift (τ < 3 x 10^-13 sec, consistent with J = 0⁺), the 940 keV γ-ray does not, which is consistent with J = 3⁺, 5⁺. No γ-ray is observed from the 1245 keV state (NA56A, RO56B). See also ¹⁶O(³He, p)¹⁸F and ¹⁹F.

23. 18O(3He, t)18F

Qm = -1.685

See (KU53A).

24. 18Ne(β+)18F

Qm = 4.227

See ¹⁸Ne.

25. 19F(γ, n)18F

Qm = -10.414

See ¹⁹F.

26. 19F(n, 2n)18F

Qm = -10.414

See ²⁰F.

27. 19F(p, d)18F	Qm = -8.187
	Q0 = -8.12 ± 0.2 (RE56).

At E_p = 18 MeV, angular distributions have been measured to the ground state of ¹⁸F (RE56, BE58A) and to levels at 0.94, 1.05, 1.7, 3.4 and 4.1 MeV (BE58A). The results indicate J = 0⁺ or 1⁺ for the ground state (RE56), even parity for the 0.94, 1.04, 1.7 and 4.1 MeV states; probably assignments are stated to be 3⁺, 0⁺, 0⁺ and 2⁺, respectively, and odd parity, J ≤ 2 for the 3.4 MeV state (BE58A). The reduced width for the ground state reaction is θ² = 0.009 (RE56). According to (WA59), the distributions permit J = 0⁺ or 1⁺ for ¹⁸F*(1.7); J = 0 is excluded by the observed γ-decay to ¹⁸F*(1.04). See also ¹⁹F and (EL58A; theor.).

28. 19F(d, t)18F	Qm = -4.155
	Q0 = -4.17 ± 0.02 (EL57A).

At E_d = 8.9 MeV proton groups are observed to the ground state and to states at 0.94 ± 0.02 and 1.07 ± 0.02 MeV. The angular distributions are consistent with l_n = 0, 1 and 0, respectively (EL57A). The l_n = 1, odd parity assignment for the 0.94 MeV state is not in accord with other experiments (see, e.g., ¹⁶O(³He, p)¹⁸F and ¹⁹F(p, d)¹⁸F). See also (BO50D, SH51A).

29. 19F(3He, α)18F	Qm = 10.164
	Q0 = 10.162 ± 0.015 (HI59).

At E(³He) = 5.9 MeV, 41 α-particle groups have been observed, corresponding to the ground state of ¹⁸F and to excited states with E_x < 7.5 MeV (HI59): see Table 18.7 [Energy levels of ¹⁸F from ¹⁶O(³He, p)¹⁸F, ¹⁹F(³He, α)¹⁸F and ²⁰Ne(d, α)¹⁸F] (in PDF or PS).

30. 20Ne(n, t)18F

Qm = -14.802

Not reported.

31. 20Ne(p, 3He)18F

Qm = -15.567

Not reported.

32. 20Ne(d, α)18F	Qm = 2.784
	Q0 = 2.791 ± 0.009 (MI54B).

Observed alpha-particle groups are listed in Table 18.7 [Energy levels of ¹⁸F from ¹⁶O(³He, p)¹⁸F, ¹⁹F(³He, α)¹⁸F and ²⁰Ne(d, α)¹⁸F] (in PDF or PS) (MI51D).

33. 21Ne(p, α)18F

Qm = -1.746

Not reported.

34. 25Mg(p, 2α)18F

Qm = -11.636

See (CO54H).