A=18F (1978AJ03)

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¹⁸F (1978AJ03)

(See Energy Level Diagrams for ¹⁸F)

GENERAL: See also (1972AJ02) and Table 18.10 [Table of Energy Levels] (in PDF or PS).

Shell model: (1970FL1A, 1970SA1M, 1972EN03, 1972LE13, 1972PR08, 1973BA1Q, 1973CO03, 1973LA1D, 1973MA1K, 1973MC06, 1973SM1C, 1973VA05, 1974LO04, 1974WA17, 1975BA81, 1975GO1B, 1975SA1F, 1976DE13, 1976SA35, 1976SZ1A, 1977HA33, 1977HO1F, 1977SH11, 1977VA1E).

Cluster, collective and deformed models: (1971LIZI, 1972NE1B, 1975GO08, 1975SA1F, 1976SA35, 1977HO1F).

Electromagnetic transitions: (1970SI1J, 1972BE1E, 1972EN03, 1972EV03, 1972LO1D, 1973HA1N, 1973MI1C, 1974LO04, 1974MC1F, 1975GA03, 1976SA35, 1976SH04, 1977BR03, 1977HO1F, 1977SA13).

Special states: (1972EN03, 1972GA18, 1972HI17, 1972HO13, 1972LE13, 1972RA08, 1972YO1B, 1973BA1Q, 1973JO03, 1973KN1C, 1973KO42, 1973MC06, 1973MI1C, 1973VA05, 1974BO22, 1974KI1B, 1975BA81, 1975GA03, 1975LO1G, 1976BO1T, 1976DE13, 1976PR07, 1976SA35, 1976SZ1A, 1977HA33, 1977SA05, 1977SH11, 1977VA1E).

Astrophysical questions: (1974DE1M).

Muon and pion induced capture and reactions: (1972PL04, 1973CH20, 1973HO43, 1974LI1D, 1974LI1N, 1975KA1G).

Other topics: (1970SI1J, 1972BA23, 1972BA25, 1972CA37, 1972GO17, 1972HO13, 1972KU1C, 1972NA11, 1972PR08, 1972RA08, 1973BE35, 1973CO03, 1973GO1H, 1973JO03, 1973KO42, 1973KR16, 1973PA1F, 1973RA05, 1973VA05, 1974CO1E, 1974BO22, 1974GA36, 1974KI1B, 1974KI1C, 1974RE03, 1974SA05, 1974SH1G, 1974WA17, 1974ZU1A, 1975BA2F, 1975BA81, 1975BL1F, 1975GO1B, 1975GO08, 1975HE1H, 1975LO1G, 1975SH01, 1975SH1H, 1976BA2G, 1976BO1T, 1976PA03, 1976PR07, 1977GO1T, 1977SA05, 1977SH11, 1977SH13, 1977SO11, 1977VA1E).

Complex reactions involving ¹⁸F: (1971BI22, 1971OG03, 1972PU1B, 1973DI05, 1973VA12, 1973WI15, 1974DI16, 1974HA61, 1974KA22, 1974OL06, 1974RA11, 1975DI03, 1975NO10, 1975VO09, 1976BE1K, 1976LE1F, 1977AR06).

Applied topics: (1973WE1N, 1975AL1B, 1976GU20, 1977DE1X, 1977PA1K).

Ground and 1.12 MeV states of ¹⁸F: (1970SI1J, 1971SH26, 1971TA1A, 1972NA05, 1972VA36, 1972YO1B, 1973MC06, 1973MI1C, 1973SU1B, 1974MC1F, 1974RE03, 1974SH1G, 1974SHYR, 1976CH1T, 1976PA03, 1977BR03).

Q_1.12 = (1.33 ± 0.08)Q(¹⁷F_g.s.) = 0.13 ± 0.03 b (1974MI21); see also (1977AJ02);

μ_1.12 = +2.85 nm (1976FU06).

1. ¹⁸F(β⁺)¹⁸O

Q_m = 1.6555

The positron decay is entirely to the ground state of ¹⁸O [J^π = 0⁺, T = 1]; the half-life is 109.77 ± 0.05 min [see Table 18.11 (in PDF or PS) in (1972AJ02)]; log ft = 3.554. The fact that the β⁺ transition to ¹⁸O_g.s. is allowed indicates J^π = 1⁺ for ¹⁸F_g.s.. The ratio ε_K/β⁺ = 0.030 ± 0.002 (1956DR38). See also (1972AJ02), (1973HO43), (1975RO20; astrophys. questions) and (1972WI28, 1972WI1C, 1973EM1B, 1973LA03, 1973WI11, 1974LE1G, 1974WI1L, 1975HA45, 1975KR14, 1975WI1E, 1977AZ02, 1977BA48, 1977KU1E; theor.).

2. (a) ¹²C(⁶Li, n)¹⁷F Q_m = 4.064 E_b = 13.215
(b) ¹²C(⁶Li, p)¹⁷O Q_m = 7.608
(c) ¹²C(⁶Li, d)¹⁶O Q_m = 5.6885
(d) ¹²C(⁶Li, t)¹⁵O Q_m = -3.718
(e) ¹²C(⁶Li, α)¹⁴N Q_m = 8.7989
(f) ¹²C(⁶Li, ⁶Li)¹²C

Cross section measurements have been carried out in the range E(⁶Li) = 1.9 to 35.2 MeV: see Table 18.12 (in PDF or PS) in (1972AJ02) for a listing of the earlier work and (1977LE1N: 5 - 9.2 MeV; d₀, d₁₊₂), (1975SO1E: 9.0 - 14.0 MeV; α₀, α₁, α₂, unpublished), (1973BA53: 19.2 - 24 MeV; d₃, d₄) and (1973WH03: 32.5 - 35.2 MeV; α to first nine T = 0 states in ¹⁴N and ⁶Li elastic). See also (1972PO07) and (1977ME1F; theor.).

The cross section for reactions (b), (c) and (e) rise monotonically and rapidly with energy up to E(⁶Li) = 4 MeV due to Coulomb barrier effects. At higher energies, Ericson-type fluctuations are observed (1967DZ01, 1970JO09). Neither the direct reaction nor the statistical compound nucleus model alone is adequate to describe the data (1970JO09). The cross section for the isospin-forbidden α₁ group [to ¹⁴N*(2.31), 0⁺, T = 1] shows an energy dependence very unlike those for the α₀ and α₂ groups, characterized by a maximum at ≈ 4 MeV, a minimum at ≈ 5 MeV, and a further rise to 6 MeV. Typically the cross section for the α₁ group is two orders of magnitude lower than those for the α₀ or α₂ groups (1965CA06, 1967DZ01). At the higher energies the d₃ and d₄ yields are smooth functions for E(⁶Li) = 19.2 to 24 MeV (1973BA53) as are the α-yields and the yield of elastically scattered ⁶Li for E(⁶Li) = 32.5 to 35.2 MeV (1973WH03). The elastic scattering of vector polarized ⁶Li ions has been studied at E(⁶Li) = 22.8 MeV (1976WE10). See also ¹⁶O and ¹⁷O in (1977AJ02), ¹⁴N and ¹⁵O in (1976AJ04) and ¹²C in (1975AJ02).

3. ¹²C(⁷Li, n)¹⁸F Q_m = 5.964

See (1972AJ02).

4. (a) ¹²C(¹⁰B, α)¹⁸F Q_m = 8.754
(b) ¹²C(¹¹B, αn)¹⁸F Q_m = -2.701

See (1974KL1B, 1976DA07, 1977KL1E) and ²²Na in (1978EN06) for reaction (a). A sharp γ-line is reported in reaction (b) at E_γ = 3728 ± 2 keV as a cascade via ¹⁸F*(1.12): it is suggested that it comes from the de-excitation of the J^π(K^π) 5^-(0^-) state (1977KOZZ; abstract). Two γ-lines are reported with E_γ = 937.21 ± 0.12 and 184.12 ± 0.07 keV [(0.94 → 0), (1.12 → 0.94)]: E_x = 937.24 ± 0.12 and 1121.36 ± 0.15 keV (E.K. Warburton, private communication).

5. ¹²C(¹²C, ⁶Li)¹⁸F Q_m = -14.960

See (1972AJ02).

6. ¹³C(¹⁴N, ⁹Be)¹⁸F Q_m = -6.232

See (1975KL1A).

7. ¹⁴N(α, γ)¹⁸F Q_m = 4.4159

A number of resonances have been observed for E_α < 3 MeV: see Table 18.13 (in PDF or PS). Recent studies of these by (1972CO1C), and by the Toronto group (1972RO24, 1973RO03, 1973RO05, 1973RO06, 1973RO07, 1977BE46), the latter in conjunction with work on the ¹⁷O(p, γ) and ¹⁶O(³He, pγ) reactions (Tables 18.17 (in PDF or PS) and 18.18 (in PDF or PS)) have led to the determination of the branching ratios, mixing ratios and widths (Table 18.11 (in PDF or PS)), lifetimes (Table 18.12 (in PDF or PS)) and excitation energies and J^π of ¹⁸F states with E_x < 6.9 MeV. Studying the strengths of the γ-transitions (see Table 2 in the Introduction) has led Rolf and his collaborators to suggest K^π assignments for the first 0⁺, 0^-, 1⁺ and 1^- bands in ¹⁸F: see Tables 18.10 (in PDF or PS) and 18.17 (in PDF or PS) for a listing of these. The reader is referred to the series of papers by the Toronto group for the most complete and definitive arguments on the parameters of the low-lying states of ¹⁸F. For the earlier work see (1972AJ02). See also (1972VL1B).

The non-resonant S-factor for this reaction, S ≈ 0.7 MeV · b (1972CO1C). See also (1971BA1A, 1972CO1E, 1973AR1E, 1973CL1E, 1975FO19, 1975SC1Y; astrophys. questions).

8. ¹⁴N(α, n)¹⁷F Q_m = -4.7347 E_b = 4.4159

The total cross-section ratios σ(n₁)/σ(p₁) have been measured for E_α = 7 to 12 MeV: major maxima are observed at E_α = 8.12, 9.5, 10.07 and 11.52 MeV (1969SC21) [see Table 18.13 (in PDF or PS) in (1972AJ02) and compare with Tables 18.14 (in PDF or PS), 18.15 (in PDF or PS) and 18.16 (in PDF or PS) here]. (1972GR10) find that the mean level width increases from 40 ± 9 keV for E_α = 10 - 13 MeV to 100 ± 24 keV for E_α = 15 - 19 MeV. See also (1977LI19).

9. ¹⁴N(α, p)¹⁷O Q_m = -1.1908 E_b = 4.4159

Observed resonances are displayed in Table 18.13 (in PDF or PS). Excitation functions of several proton groups have been measured for E_α = 10 to 25 MeV (1970ZE01); they show gross structures.

10. (a) ¹⁴N(α, α)¹⁴N E_b = 4.4159
(b) ¹⁴N(α, αp)¹³C Q_m = -7.5506
(c) ¹⁴N(α, d)¹⁶O Q_m = -3.1104
(d) ¹⁴N(α, ⁶Li)¹²C Q_m = -8.7989
(e) ¹⁴N(α, 2α)¹⁰B Q_m = -11.6132

Observed anomalies in the elastic scattering are exhibited in Table 18.13 (in PDF or PS). Resonances in the α₁ isospin-forbidden yield are displayed in Table 18.14 (in PDF or PS) (1974CH1T, 1976CH24). In the α₁ study, carried out for E_α = 7.6 - 16.9 MeV, a partial wave analysis involving a method of removing ambiguities and parametrizing S-matrix elements gives the level parameters of 151 isospin mixed, natural parity states in ¹⁸F with 10.4 < E_x < 17.5 MeV. Many of these states have also been reported in the ¹⁶O(d, α₁) work of (1973JO13). The agreement is best for low-lying 2⁺ or 4⁺ states, and is quite good for 3^- and 5^- states, while for high-J states the greater centrifugal barrier for ¹⁶O + d at the same E_x relatively suppresses high-J states in the ¹⁶O + d work: see Table 18.16 (in PDF or PS). A study of the energy dependence of averaged intensities of the partial waves shows some indication that the lower partial waves reconserve isospin as E_x increases (1976CH24). See also (1970TO03).

The total cross section for formation of ⁶Li and ¹⁰B (reactions (d) and (e)) has been studied for E_α = 21 to 42 MeV by (1974JA11) who discuss the astrophysical importance of these processes. For the earlier work on reactions (a), (b) and (c), see (1972AJ02). See also (1973BO1J, 1974JE1A, 1976LE1K), (1974FA1A; theor.) and ¹⁴N in (1976AJ04).

11. ¹⁴N(⁶Li, d)¹⁸F Q_m = 2.942

Angular distributions have been measured for E(⁶Li) = 5.3 to 6.0 MeV (1968RI13: d₀, d_1→4). See also (1972GA1E).

12. ¹⁴N(⁷Li, t)¹⁸F Q_m = 1.949

At E(⁷Li) = 15 MeV, triton groups are observed to the known T = 0 states with E_x < 7.4 MeV: the T = 1 states are not excited although such transitions are not forbidden in principle, suggesting a direct α-transfer mechanism. The transitions to ¹⁸F*(1.70, 2.53, 3.36, 4.23, 5.30, 6.57) account for more than one half of the summed cross section at 15°. It is proposed that these states (which are only weakly excited in ¹⁶O(³He, p)¹⁸F and ¹⁷O(³He, d)¹⁸F) are predominantly of a 4p - 2h nature and are excited by the transfer of four nucleons into the (2s, 1d) shell (1968MI09). At E(⁷Li) = 36 MeV the K^π = 1⁺ band also appears to be selectively populated. States at E_x = 9.58 ± 0.02, 11.22 ± 0.03 and 14.18 ± 0.04 MeV are strongly populated. It is suggested that the first two are the 6⁺ and 7⁺ members of that band (1977CO09). [Angular distributions are reported for ¹⁸F*(1.70, 2.10, 2.52, 3.36, 4.40, 5.30, 6.57, 9.58, 11.22, 14.18).] See also (1972GA1E).

13. ¹⁵N(³He, p)¹⁷O Q_m = 8.554 E_b = 14.1603

See ¹⁷O in (1971AJ02) and (1973AB1D).

14. ¹⁵N(α, n)¹⁸F Q_m = -6.4175

See (1966AD07, 1973CL1E).

15. ¹⁵N(⁶Li, t)¹⁸F Q_m = -1.634

At E(⁶Li) = 30 MeV preferential excitation of odd parity states of ¹⁸F below E_x = 5 MeV is reported. Angular distributions of the tritons to ¹⁸F*(0, 0.94, 2.10, 4.40) [J^π = 1⁺, 3⁺, 2^-, 4^-] are all strongly forward peaked (1972LI24). See also (1972BA1P, 1977MA2G).

16. ¹⁶O(d, γ)¹⁸F Q_m = 7.5263

The capture cross section rises from 0.1 μb at E_d = 0.4 MeV to 25 μb at 3.5 MeV: Γ_γ over this range is ≈ 2 eV. The results can be interpreted satisfactorily in terms of compound nucleus formation (1965OW01).

17. ¹⁶O(d, n)¹⁷F Q_m = -1.6243 E_b = 7.5263

Excitation functions have been measured for the n₀ and n₁ groups from threshold to 17 MeV: see Table 18.16 (in PDF or PS) in (1972AJ02) for a listing of the earlier work and (1972AN1G, 1972AN21: E_d = 3 to 4 MeV), (1969WO09: 3.2 MeV; yield of ¹⁷F), (1972GR10: threshold to 15.8 MeV; yield of ¹⁷F) and (1974AU1B: 7 to 17 MeV; ratio of (σ_n₁/σ_p₁): it decreases slowly with increasing energy). Some structure is observed: that which is attributed to states in ¹⁸F is displayed in Table 18.15 (in PDF or PS) (1955MA85, 1961DI06, 1968MA1C). The mean level widths range from 53 ± 11 keV at E_d ≈ 10 - 13 MeV to 70 ± 17 keV at E_d ≈ 13 - 16 MeV (1972GR10). See also (1970DA14). Polarization measurements have been carried out for E_d = 3 to 15 MeV: see Table 18.16 (in PDF or PS) in (1972AJ02) and (1972AN1G, 1972AN21: E_d = 3 to 4 MeV; n₀, n₁) and (1975WA1L, 1976LI1R: 4.3 to 15 MeV; n₀, n₁). See also (1974LO1B) and ¹⁷F in (1977AJ02).

18. ¹⁶O(d, p)¹⁷O Q_m = 1.9197 E_b = 7.5263

Excitation functions and polarization studies have been reported for several proton groups for E_d = 0.3 to 13.3 MeV: see Table 18.16 (in PDF or PS) in (1972AJ02) for the earlier work. Recent polarization work is by (1972SL10: 1.9 to 3.0 MeV; p₁), (1972CO15, 1973DA17: 9.3 and 13.3 MeV; p₀, p₁, p₃, p₄, p₅, p₈) and (1973JO10: 12.3 MeV; p₁). Some of the maxima in the yield measurements are interpreted in terms of resonances: these are shown in Table 18.15 (in PDF or PS) (1955ST1A, 1956RO1A, 1964AM1A, 1968MA53). The coherence energy determined from the yields is 75 keV for p₀, 63 keV for p₁ and 62 keV for p₃ in the ranges E_d = 4.0 to 6.0 MeV (1970DA14). See also (1973CA30). The ratio σ_n₁/σ_p₁ has been studied for E_d = 7 to 17 MeV by (1974AU1B). See also (1971GR2B, 1974DA13), (1973ME18, 1975CR05, 1975GR12, 1976BO48, 1976SA04; theor.) and ¹⁷O in (1977AJ02).

19. ¹⁶O(d, d)¹⁶O E_b = 7.5263

The yield of elastically scattered deuterons and elastic polarization measurements have been reported for E_d = 0.65 to 15 MeV: see Table 18.16 (in PDF or PS) in (1972AJ02) for the earlier work, the recent yield measurements by (1973CA30: E_d = 1.0 to 2.0 MeV) and the polarization work of (1972SL10: 1.9 to 3.0 MeV), (1972CO15: 9.3 and 13.3 MeV), (1973BR15: 11.6 MeV) and (1974BU06: 15 MeV). See also (1973CO40, 1974BO50, 1975BO41, 1975BO1P, 1975CR05, 1976LE1U, 1977FL13, 1977FR12; theor.) and ¹⁶O in (1977AJ02).

20. (a) ¹⁶O(d, t)¹⁵O Q_m = -9.4065 E_b = 7.5263
(b) ¹⁶O(d, ³He)¹⁵N Q_m = -6.6340

The ground-state polarization has been studied at E_d = 15 MeV by (1974LU06). Vector analyzing powers have been studied at E_d-bar = 29 MeV for the transitions to the first two states of ¹⁵N and ¹⁵O (1977MA2R).

21. ¹⁶O(d, α)¹⁴N Q_m = 3.1104 E_b = 7.5263

The yields of various groups of α-particles have been measured for E_d ≤ 20 MeV: see Table 18.16 (in PDF or PS) in (1972AJ02) for the earlier work and (1973CA30: 1.0 - 2.0 MeV; α₀), (1974CH1U, 1975CH1N, abstracts: 6.0 - 7.0 MeV; α₃) and (1973JO13: 2 - 14 MeV; α₀, α₁).

The yield curves have been fitted in terms of a large number of states in ¹⁸F: see Tables 18.15 (in PDF or PS) and 18.16 (in PDF or PS).

A detailed study by (1973JO13) of the isospin-forbidden α₁ yield, analyzed by S-matrix theory, identifies a large number of isospin mixed states in ¹⁸F, possibly as many as 138 with 9.2 < E_x < 19.4 MeV. The reaction mechanism appears to be almost entirely compound nuclear. The isospin impurity, averaged over 1 MeV intervals, is 3 - 10% for the above E_x range. The average coherence width increases from ≈ 100 keV at E_x = 14 MeV to ≈ 500 keV at E_x = 20 MeV. The level densities appear to be consistent with predictions of the Fermi-gas model (1973JO13). [For mixed isospin states observed in ¹⁴N(α, α₁) see Table 18.14 (in PDF or PS).]

For polarization measurements see (1977ST06: E_d-bar = 6.84 MeV, θ_lab = 29° and 34°, α₃, iT₁₁ = 0.856 ± 0.006 and 0.842 ± 0.015), (1976PE08: E_d-bar = 11, 12, 13, 14 MeV: many α groups) and (1976LU1A: 16 MeV; α₀, α₂). See also (1971GR2B, 1974JO1F, 1976GO1B, 1976RI1C), (1972AJ02, 1974LO1B), (1973TU07; applied) and (1973FR04; theor.).

22. ¹⁶O(d, ⁶Li)¹²C Q_m = -5.6885 E_b = 7.5263

The ground-state polarization has been studied at E_d-bar = 16 MeV (1976JA1G). See also (1976JA1H).

23. ¹⁶O(t, n)¹⁸F Q_m = 1.2690

Measurements of lifetimes are displayed in Table 18.12 (in PDF or PS) (1966AL04, 1973WA19, 1974CO01). (1966AL04) report that ΔE_x(1.13 → 0.94) = 194 ± 1 keV: E_x of ¹⁸F*(1.13) is then 1131.0 ± 1 keV [based on E_x = 937.0 ± 0.2 keV]: see, however, Table 18.17 (in PDF or PS). Angular distributions are reported at E_t = 1.1 to 1.7 MeV by (1976MA54: n₀). See also (1974NO15) and ¹⁹F.

24. ¹⁶O(³He, p)¹⁸F Q_m = 2.0328

Excitation energies derived from measurements of γ-rays (1973RO03) are displayed in Table 18.17 (in PDF or PS), together with l-assignments obtained from distorted wave analyses (see (1972AJ02, 1976SE12)) and (J^π; T) assignments from branching ratios and radiative widths coupled with angular correlations, linear polarization and γ-ray angular distribution studies [see Table 18.11 (in PDF or PS) and (1972RO04, 1973RO03, 1973RO05, 1973RO06)] and τ_m measurements [see Table 18.12 (in PDF or PS) (1966OL03, 1967WA06, 1973RO05, 1974BR04)]. Together with studies of ¹⁴N(α, γ) and ¹⁷O(p, γ), the work on the ¹⁶O(³He, p)¹⁸F reaction completes the definitive study of the low-lying states of ¹⁸F by Rolf and his co-workers. See (1972AJ02) for the earlier work.

The magnetic moment of ¹⁸F*(1.13) = +2.855 ± 0.030 nm, in agreement with shell-model predictions for a (1d²_5/2)_5⁺ state (1967PO09, 1967SC09). Parity mixing is being studied by observing the γ-decay of ¹⁸F*(1.04, 1.08) [J^π = 0⁺ and 0^-; T = 1 and 0, respectively] with two transmission Compton polarimeters whose magnetizations are opposite and reversed once per second (1976AD1B, 1977BA3R; prelim. discussion). See also (1973DO1D) and (1977GO01; theor.).

25. ¹⁶O(α, d)¹⁸F Q_m = -16.3204

At E_α = 40 to 52 MeV, deuteron spectra are dominated by the groups to ¹⁸F*(1.13), J^π = 5⁺ [1d²_5/2 configuration]. Many other states have also been observed: see Table 18.19 (in PDF or PS) in (1972AJ02) (1968MA33; note energy resolution problems).

26. ¹⁶O(⁶Li, α)¹⁸F Q_m = 6.053

Angular distributions for the α₀ group have been measured at E(⁶Li) = 5.5 to 13.3 MeV (1968GR22) and at 26 MeV (1969DA19). At E(⁶Li) = 34 MeV angular distributions are reported to ¹⁸F*(0, 0.94, 1.1 [unres.]) and forward angle data has been obtained for ¹⁸F*(2.10, 3.73, 3.79, 3.84). The angular distributions for the first three groups are forward peaked and show little structure at back angles. An attempt has been made to fit the data to zero-range two-particle transfer DWBA calculations with partial success. At back angles there is no agreement suggesting the necessity of including in the mechanism the exchange of an α-particle in ¹⁶O with the incident ⁶Li ion. ¹⁸F*(1.04, 3.06) were not observed, as expected from isospin conservation. States at E_x = 4.12, 4.23, 4.4, 5.61, 6.11, 6.20, 6.53, 6.80 and 6.88 were populated (1976MO24). See also (1975MI1A), (1977GO01; theor.) and (1972AJ02).

27. ¹⁶O(¹¹B, ⁹Be)¹⁸F Q_m = -8.290

See (1968OK06, 1975PO10).

28. ¹⁶O(¹²C, ¹⁰B)¹⁸F Q_m = -17.661

At E(¹²C) = 114 MeV, the population of the 5⁺ state ¹⁸F*(1.12) is reported (1972SC21). See also (1971SC1F).

29. ¹⁶O(¹⁴N, ¹²C)¹⁸F Q_m = -2.7461

See (1972AJ02).

30. ¹⁶O(¹⁶O, ¹⁴N)¹⁸F Q_m = -13.2100

See (1974RO04).

31. ¹⁷O(p, γ)¹⁸F Q_m = 5.607
Q₀ = 5606.2 ± 0.6 keV (1975RO05); see also (1973SE03).

A study of direct capture cross sections at E_p = 1.36 to 1.65 MeV concludes that the upper limits on the reduced proton widths for the three states of ¹⁸F near 5.607 MeV (Q_m) [¹⁸F*(5.603, 5.604, 5.668, 5.785) with J^π = 1⁺, 1^-, 1^- and 2^-: the 1^- states having mixed isospin] are a factor of 60 smaller than previously assumed. The stellar reaction rate for ¹⁷O(p, α) is thus correspondingly reduced and becomes of the same order as for the (p, γ) process (1974RO1N, 1975RO20). The direct capture yield has also been studied by (1973RO34) from E_p = 0.3 to 1.9 MeV: spectroscopic factors are derived for ¹⁸F states below E_x = 6.2 MeV. The agreement with stripping data is good (1973RO34).

Twelve resonances have been observed in this reaction for E_p < 1.4 MeV: Table 18.18 (in PDF or PS) displays the parameters of the corresponding states in ¹⁸F; Table 18.11 (in PDF or PS) lists the branching ratios, radiative widths and multipole mixing ratios; Table 18.12 (in PDF or PS) the lifetimes of the observed states and Table 2 in the Introduction displays the transition strengths. The study of this reaction and of ¹⁴N(α, γ) and ¹⁶O(³He, pγ) (for band assignments see Table 18.17 (in PDF or PS)) has led to a quite complete understanding of the low lying states of ¹⁸F. This work has been discussed in a series of papers by the Toronto group (1973RO03, 1973RO04, 1973RO05, 1973RO06, 1973RO07, 1977BE46). (1972BE37) have determined E_x = 1119.0 ± 0.6 keV for the J^π = 5⁺ state (based on E_x = 937.1 ± 0.4 keV), while (1973SE03) report 1121.0 ± 0.3 keV based on E_x = 936.9 ± 0.2 keV, and (1975RO05) have determined E_x = 2100.68 ± 0.14 and 3133.87 ± 0.15 keV: see Table 18.19 (in PDF or PS). See also (1970ZA1D).

32. ¹⁷O(p, n)¹⁷F Q_m = -3.544 E_b = 5.607

Several resonances have been observed in the total yield of neutrons measured from threshold to E_p = 5 MeV: see Table 18.18 (in PDF or PS) (1973BA31). At higher energies the yields of n₀ (E_p = 7 - 13.5 MeV) and n₁ (7 - 12.5 MeV) exhibit some gross structures (1969AN06).

33. ¹⁷O(p, p)¹⁷O E_b = 5.607

The elastic scattering has been studied for E_p = 0.5 to 1.33 MeV (1973SE02), 8.5 to 10.5 MeV (1975CR04; also p₁ and p₂) and 11.0 to 13.0 MeV (1967AL06): observed anomalies are displayed in Table 18.18 (in PDF or PS).

34. ¹⁷O(p, d)¹⁶O Q_m = -1.920 E_b = 5.607

See (1975CR05).

35. ¹⁷O(p, α)¹⁴N Q_m = 1.191 E_b = 5.607

The yield of α₀ shows a number of resonances for E_p = 0.49 to 3.0 MeV: see Table 18.18 (in PDF or PS) (1957AH20, 1962BR08, 1973SE02). For astrophysical questions see ¹⁷O(p, γ)¹⁸F (1974RO1N, 1975RO20) and (1971BA1A, 1973CL1E, 1974DE1M, 1977CL1F).

36. ¹⁷O(d, n)¹⁸F Q_m = 3.382

For a report of angular distributions see (1972AJ02): the work quoted was not published.

37. ¹⁷O(³He, d)¹⁸F Q_m = 0.113

At E(³He) = 15 MeV, DWBA analysis of angular distributions of deuteron groups corresponding to the ground state of ¹⁸F [l = 2] and to the excited states at 0.94 [l = 0 + 2], 1.04 [2], 1.12 [2], 2.53 [0 + 2], 3.06 [0 + 2], 3.84 [0 + 2], 4.12 [0 + 2], 4.66 [2] and 4.96 [l = 0 + 2] have been obtained by (1969PO11) who also report spectroscopic information. Thus all these states have even parity and ¹⁸F*(4.11) may be assigned J^π = (2⁺) or 3⁺. Since l = 2 for ¹⁸F*(4.65), J^π ≤ 5⁺, with 4⁺ most likely (1969PO11). At E(³He) = 25 MeV ¹⁸F*(5.606, 5.674) [J^π = 1^-] have been studied to estimate their proton widths which are of astrophysical significance (1974BR1C; abstract). See also (1972EN03, 1976SC36; theor.).

38. ¹⁷O(α, t)¹⁸F Q_m = -14.207

Not reported.

39. ¹⁸O(p, n)¹⁸F Q_m = -2.4379

Angular distributions have been measured for E_p = 5.53 to 6.12 MeV (1973FR10: n₀ → n₄) and 6.9 to 13.5 MeV (1969AN06: n₀ → n₈; not all resolved). See also (1971DR09), (1972AJ02), (1973CL1E; astrophys. questions), (1976KA13; theor.) and ¹⁹F.

40. ¹⁸O(³He, t)¹⁸F Q_m = -1.6742

At E(³He) = 16 MeV, the triton spectrum is dominated by strong groups to the ground and 0.94 MeV excited states and to the 0⁺ and 2⁺, T = 1 states at E_x = 1.04 and 3.06 MeV. Angular distributions have been measured and analyzed by DWBA for the tritons corresponding to these states and to ¹⁸F*(1.08, 1.12, 1.70, 2.10, 3.13, 3.36, 3.73, 3.79, 3.84, 4.11, 4.23, 4.36, 4.40, 4.65, 4.75). The angular distributions are consistent with the J^π assignments shown in Table 18.10 (in PDF or PS), except for the distribution to ¹⁸F*(1.04) (1970DU08). At E(³He) = 17.3 MeV, angular distributions to ¹⁸F states with E_x < 4 MeV have been analyzed using DWBA and a two-body interaction between the incident and target nucleons. An exact coupled-channel calculation was also made for the transition to ¹⁸F*(1.04) (1968HA30).

41. ¹⁸O(⁶Li, ⁶He)¹⁸F Q_m = -5.165

At E(⁶Li) = 34 MeV angular distributions have been obtained for the transitions to ¹⁸F*(0, 0.94) [J^π = 1⁺, 3⁺]: there appears to be a sizable contribution due to two-step processes (1974WH07, 1974WH1E, 1975WH01). See also (1974DU15).

42. ¹⁸Ne(β⁺)¹⁸F Q_m = 4.447

The half-life of ¹⁸Ne is 1672 ± 4 msec (see ¹⁸Ne). The decay is to ¹⁸F*(0, 1.04, 1.70): see Table 18.20 (in PDF or PS) for the branching ratios and log ft values.

43. ¹⁹F(γ, n)¹⁸F Q_m = -10.4313

Photoneutron spectra have been studied by (1976SH12) and the yield of 0.94 and 1.04 MeV γ-rays by (1972TH15), and the γ-rays from ¹⁸F*(0.94, 1.04, 1.08, 2.10, 2.52, 3.06, 3.13, 3.72) by (1977TA1M): see ¹⁹F. See also (1976TH1E).

44. ¹⁹F(n, 2n)¹⁸F Q_m = -10.4313

The lifetime of the 5⁺ state ¹⁸F*(1.12) has been measured by (1972AD01): see Table 18.12 (in PDF or PS). Several γ-rays, including an intense line at 0.94 MeV, are reported by (1976PR08). See also ²⁰F.

45. (a) ¹⁹F(p, d)¹⁸F Q_m = -8.2067
(b) ¹⁹F(p, pn)¹⁸F Q_m = -10.4313

Angular distributions of the d₀ group have been measured at E_d = 16 to 155.6 MeV; l_n = 0: see (1972AJ02). Angular distributions to excited states reported in (1972AJ02) have not been published. See also (1973OR09; theor.). For reaction (b) see (1968DE21).

46. ¹⁹F(d, t)¹⁸F Q_m = -4.1740

Angular distributions of triton groups have been reported at E_d = 8.9 (t₀, t₁, t₃) and 14.8 MeV (t₀): see (1972AJ02). The angular distribution to ¹⁸F*(1.04) [J^π = 0⁺, T = 1] (1972BU1E; unpublished abstract; E_d = 28 MeV) is compared with that for the transition to the ¹⁸O_g.s. in the mirror reaction (1973CO17). For a polarization study at E_d = 12.3 MeV see (1976NE1C) and ²¹Ne in (1978EN06).

47. ¹⁹F(³He, α)¹⁸F Q_m = 10.1465

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 (1959HI67): see Table 18.21 (in PDF or PS). Angular distributions of the α-particles corresponding to ¹⁸F*(3.06, 3.13) are reported by (1966MA43; E(³He) = 4.0, 6.0 and 8.0 MeV): l = 2 and 1, respectively. Alpha - α₀ angular correlations measured in the range E(³He) = 5.0 to 6.0 MeV establish J^π = 1^- for both ¹⁸F*(5.60, 5.67): Γ_α/Γ ≈ 1 (1971LI27). See also (1976GA27) and ²²Na in (1978EN06).

48. ¹⁹F(¹⁰B, ¹¹B)¹⁸F Q_m = 1.024

See (1971BA68) and (1972AJ02).

49. (a) ¹⁹F(¹⁴N, ¹⁵N)¹⁸F Q_m = 0.4021
(b) ¹⁹F(¹⁹F, ²⁰F)¹⁸F Q_m = -3.830

See (1972AJ02).

50. ²⁰Ne(n, t)¹⁸F Q_m = -14.794

Not reported.

51. ²⁰Ne(p, ³He)¹⁸F Q_m = -15.558

At E_p = 45 MeV, ³He groups are observed to ¹⁸F*(0, 1.04, 1.70, 3.06, 6.27 ± 0.03) (1969HA38).

52. ²⁰Ne(d, α)¹⁸F Q_m = 2.7954
Q₀ = 2.790 ± 0.010 (1975BO59)

At E_d = 11 MeV α-groups are observed to many states of ¹⁸F with E_x < 7 MeV. Weak or absent (each ≤ 0.3% of the total yield at 30°) are the groups corresponding to ¹⁸F*(1.04, 3.06, 4.66, 4.74, 4.96): T = 1 for these states (1969PO11). Angular distributions at E_d = 6.66, 7.29, 7.93 and 12.95 MeV have been obtained for the α-groups to ¹⁸F*(2.10 [not 12.95 MeV], 2.52, 3.06 [2⁺; 1], 3.13, 3.36, 4.12). The ratio of the total cross section for the isospin-forbidden transition to ¹⁸F*(3.06) to the total cross section of four T = 0 states ranges from 6% to 40%. The average is 21% suggesting isospin mixing in the compound nucleus: the yield curves show strong structures particularly in the region 5 to 9 MeV (1973HR03): see also ²²Na in (1978EN06). Angular distributions have also been measured at E_d = 2 to 14.7 MeV: see (1972AJ02) for the earlier work and (1971MO40: 2.0, 3.0, 3.2 MeV; α₀, α₁, α₃, α₅ → α₇). Measurements of the tensor analyzing power near 180° for 10.5 < E_d < 12.0 MeV lead to natural π for ¹⁸F*(4.85) and to unnatural π for ¹⁸F*(4.23, 5.60, 5.79) (1977DA1F). ¹⁸F*(6.16) is seen with moderate intensity suggesting that the previous T = 1 assignment is doubtful (H.T. Richards, private communication). See also (1976GU20; applied work) and (1974NO15; theor.).

53. ²¹Ne(p, α)¹⁸F Q_m = -1.742

Not reported.