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USNDP

18F (1983AJ01)


(See Energy Level Diagrams for 18F)

GENERAL: See also (1978AJ03) and Table 18.11 [Table of Energy Levels] (in PDF or PS).

Shell model: (1977AN1P, 1977GR16, 1977SO1C, 1978CO08, 1978DA1N, 1978MA2H, 1979BU12, 1979DA15, 1980GO01, 1980KU05, 1980MA18, 1981EL1D, 1981ER03, 1981GR06, 1982KI02).

Cluster, collective and deformed models: (1977BU22, 1978BU03, 1978PI1E, 1978SA15, 1978TA1A, 1979BU12, 1979SA31, 1980RO19, 1981CH24).

Electromagnetic transitions: (1976MC1G, 1977BU22, 1977HA1Z, 1977HE1L, 1978BU03, 1978DE1K, 1978SA15, 1979SA31, 1980KO1L, 1980KU05, 1981CH24).

Special states: (1977AN1P, 1977GR16, 1977HE18, 1977SH18, 1978AN1P, 1978BU03, 1978EN1D, 1978ER1C, 1978KO1W, 1978KR1G, 1978MA2H, 1978PI1E, 1978SA15, 1978TA1A, 1979BA35, 1979BU12, 1979DA15, 1979SA31, 1979WI1Q, 1979ZA07, 1980BR21, 1980GO01, 1980HA41, 1980MA18, 1980RO19, 1980SH1K, 1981AD1E, 1981AR1D, 1981BI03, 1981EL1D, 1981ER03, 1981SO03, 1982KI02, 1982NA03).

Astrophysical questions: (1977SI1D, 1978WO1E, 1981WE1F).

Applied topics: (1977FI13, 1978FR1R, 1978WI1F, 1978WO1C, 1979BA52, 1979KA07, 1979WI1G, 1980LA1K, 1980YA08).

Complex reactions involving 18F: (1977AS03, 1977SC1G, 1977YA1B, 1978SH18, 1979BO22, 1979VI09, 1980EV1A, 1980WI1K, 1980WI1L, 1980YA08, 1981GR08).

Pion induced capture and reactions: (1977ST27, 1978SP07, 1981NI03).

Other topics: (1977AN1P, 1977GR16, 1977SH18, 1977SO1C, 1978AN1P, 1978CO08, 1978DE1K, 1978EN1D, 1978GO1U, 1978JO1C, 1978KR1G, 1978MA2H, 1978SH1B, 1979BA35, 1979BE2L, 1979CO09, 1979DE18, 1979GO1W, 1979HW01, 1979KU04, 1979WI1Q, 1980BR21, 1980DE1F, 1980GO01, 1980TA1L, 1981AR1D, 1981BI03, 1981CH24, 1981EL1D, 1981ER03, 1981SO03, 1982FI1C, 1982KI02, 1982NA03).

Ground and 1.12 MeV states of 18F: (1976MC1G, 1977HA1Z, 1978ZA1D, 1980MA18, 1981AR1D).

μ1.12 = +2.86 ± 0.03 nm (1978LEZA);

Q1.12 = 0.13 ± 0.03 b (1974MI21); see also (1978LEZA).

1. 18F(β+)18O Qm = 1.6555

The positron decay is entirely to the ground state of 18O [Jπ = 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 18Og.s. is allowed indicates Jπ = 1+ for 18Fg.s.. The ratio εK+ = 0.030 ± 0.002; see (1978AJ03). See also (1976BE1E, 1981BE2N, 1982PI1B) and (1980AF1A; theor.).

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

Cross-section measurements have been carried out in the range E(6Li) = 1.9 to 36 MeV: see (1978AJ03) and (1976PO02; 4 to 13 MeV; 6Li elastic), (1978SO01; 9 to 14 MeV and 20 MeV; α0, α1, α2), (1980FU06; 20 to 36 MeV; 6Li to 12C*(0, 4.43)) and (1978CU03; 20 to 34 MeV; d to 16O*(0, 6.13, 6.92, 7.12, 8.87, 10.36, 11.09, 16.3)).

The cross section for the isospin-forbidden α1 group [to 14N*(2.31), 0+, T = 1] is 1 to 2% of the cross section to the allowed α0 and α2 groups for E(6Li) = 3.2 to 6 MeV (1981SC13) while for 9 to 14 MeV it varies from 0.4 to 1.8% (1978SO01). At 20 MeV, the α1 yield is 0.02% of the allowed yield (1978SO01). Structures are reported at E(6Li) = 11.0 and 13.0 MeV in the α0 yield, at 11.5 and (13.0) MeV in the α1 yield and at ≈ 11.7 and 12.8 MeV in the α2 yield (1978SO01), while (1981SC13) report a resonance in the α1 yield at E(6Li) = 4.2 MeV: Ex = 15.99 ± 0.02 MeV, Γc.m. = 290 ± 30 keV, Jπ = 2+ (one-level BW fit). It is suggested that this resonance is due to 2+ states with T = 0 and T = 1 which are unresolved (1981SC13). The excitation functions for the 6Li ions to 12C*(0, 4.43) shows a single isolated structure at E(6Li) = 22.8 MeV, in the range 20 - 36 MeV, with Γ ≈ 0.8 MeV. It is unlikely to be due to an isolated state in 18F (1980FU06). At E(pol. 6Li) = 20 MeV analyzing power measurements are reported for many deuteron and α groups and for elastically scattered 6Li ions (1978MA13, 1979MA1T). Breakup processes have been studied by (1980NE05), cross sections at very high energies by (1980SK1A), fusion by (1981DE1H, 1981DE2K). See also 16O, 17O in (1982AJ01), and 14N, 15N in (1981AJ01) and 12C in (1980AJ01).

For a discussion of the earlier work see (1978AJ03). See also (1979TU1B, 1981KR1K), (1978FI1E, 1978HO1C) and (1978ME1J, 1978ME20, 1978ME14, 1979BE59, 1979SU1F, 1981ME1E, 1981ME1F, 1981OS1D; theor.).

3. 12C(7Li, n)18F Qm = 5.964

See (1972AJ02).

4. 12C(9Be, t)18F Qm = -4.4744

Angular distributions are reported at E(9Be) = 12 to 27 MeV to 18Fg.s. and to the unresolved states at 1 MeV (1979JA22, 1981JA09).

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

See (1978AJ03). The work on reaction (b) displayed there has not been published.

6. 12C(12C, 6Li)18F Qm = -14.960

See (1980KO02).

7. 13C(14N, 9Be)18F Qm = -6.232

See (1978PI1E).

8. 14N(α, γ)18F Qm = 4.4159

A number of resonances have been observed for Eα < 3 MeV: see Table 18.14 (in PDF or PS). Studies of these, principally by the Toronto and Queen's groups [see references in (1978AJ03) and (1977BE46, 1979KI12, 1980MA26)] in conjunction with work on 14N(α, α), 16O(3He, p), 17O(p, γ) and 17O(p, α) [see Tables 18.16 (in PDF or PS), 18.17 (in PDF or PS), 18.18 (in PDF or PS)] have led to the determination of branching ratios, mixing ratios and widths (Table 18.12 (in PDF or PS)), lifetimes (Table 18.13 (in PDF or PS)) and the Ex, Jπ and Kπ assignments for 18F states with Ex < 6.9 MeV. 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.

The non-resonant S-factor for this reaction, S ≈ 0.7 MeV · b (1972CO1C). See also (1978TA1U; astrophys.).

9. 14N(α, n)17F Qm = -4.7347 Eb = 4.4159

See (1978AJ03).

10. 14N(α, p)17O Qm = -1.1908 Eb = 4.4159

Observed resonances are displayed in Table 18.14 (in PDF or PS). See also (1978AJ03).

11. 14N(α, α)14N Eb = 4.4159

Observed anomalies in the elastic scattering are exhibited in Table 18.14 (in PDF or PS). Resonances in the α1 isospin-forbidden yield are displayed in Table 18.14 (in PDF or PS) of (1978AJ03). In the α1 study, carried out for Eα = 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 < Ex < 17.5 MeV. Many of these states have also been reported in the 16O(d, α1) reaction [Table 18.16 (in PDF or PS) of (1978AJ03)]. 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 Ex relatively suppresses high-J states in the 16O + d work. A study of the energy dependence of averaged intensities of the partial waves shows some indication that the lower partial waves reconserve isospin as Ex increases (1976CH24).

12. (a) 14N(α, 2α)10B Qm = -11.6132 Eb = 4.4159
(b) 14N(α, 6Li)12C Qm = -8.7989

The total cross section for formation of 10B and 6Li have been studied for Eα = 21 to 42 MeV by (1974JA11) who discuss the astrophysical importance of these processes. For spallation studies see (1979VI05, 1980RE1B, 1981GO1E). See also (1980BA2K; theor.).

13. 14N(6Li, d)18F Qm = 2.942

Angular distributions have been measured for E(6Li) = 5.3 to 6 MeV: see (1978AJ03).

14. 14N(7Li, t)18F Qm = 1.949

At E(7Li) = 15 MeV, triton groups are observed to the known T = 0 states with Ex < 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 Kπ = 1+ band also appears to be selectively populated. States at Ex = 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 (1979SA31; theor.).

15. (a) 14N(11B, 7Li)18F Qm = -4.249
(b) 14N(13C, 9Be)18F Qm = -6.2320

These reactions have been studied at E(11B) = 115 MeV and E(13C) = 105 MeV. Differential cross sections at three angles are reported for the transitions to 18F*(9.58, 10.57 ± 0.07, 11.2) in reaction (a) and to 18F*(5.30, 6.57, 9.58, 10.60 ± 0.08, 11.2) in reaction (b). In addition to these states 18F*(14.18) is strongly excited in both reactions, and transitions to 18F*(15.79 ± 0.10, 18.62 ± 0.12) are also reported (1979BR04).

16. 14N(16O, 12C)18F Qm = -2.7461

See (1977VO08).

17. 15N(3He, γ)18F Qm = 14.1603

Excitation functions have been measured for E(3He) = 2.5 to 16 MeV for the γ0 and γ1→4 yields. Resonances are observed corresponding to Ex = (19.00 ± 0.15) [γ1→4], 20.1 ± 0.2 [γ0, γ1→4], 22.7 ± 0.2 [γ0, γ1→4] and (24.1 ± 0.2) MeV [γ1→4], with Γc.m. = 0.5 ± 0.15, 1.6 ± 0.1, 1.2 ± 0.1 and 1.4 ± 0.3 MeV, respectively. The γ0 yield is dominated by 18F*(20.1) (1981WA1R) [see for (2J + 1)Γ3HeΓγ values]. It is suggested that the structures decaying by γ0 have Jπ = 2- (and possibly T = 1) (1981WA1R, and J. Lowe, private communication).

18. 15N(3He, p)17O Qm = 8.554 Eb = 14.1603

See 17O in (1982AJ01).

19. 15N(α, n)18F Qm = -6.4175

See (1978AJ03).

20. 15N(6Li, t)18F Qm = -1.634

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

21. (a) 15N(11B, 8Li)18F Qm = -13.050
(b) 15N(12C, 9Be)18F Qm = -12.1190

These reactions have been studied with E(11B) = E(12C) = 115 MeV. Reaction (a) is dominated by the transitions to 18F*(1.12) [presumably the Jπ = 5+ state, although the group is unresolved] and to 18F*(7.15, 9.45) [Jπ = (7-) and (6-)]. In reaction (b) no single state is strongly preferentially populated (1979RA10, 1981GO11). Differential cross sections for 18F*(4.40, 6.10, 7.15, 9.45) [Jπ = 4-, (5-), (7-), (6-)], fitted by FRDWBA, are discussed by (1981GO11). See also (1977FO1E).

22. 16O(d, γ)18F Qm = 7.5263

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

23. 16O(d, n)17F Qm = -1.6243 Eb = 7.5263

Excitation functions have been measured for the n0 and n1 groups from threshold to 17 MeV: see (1978AJ03). Some structure is observed: that which is attributed to states of 18F is displayed in Table 18.15 (in PDF or PS). Polarization measurements are reported for Ed = 3 to 15 MeV: see (1978AJ03) and at Ed-bar = 5 to 15 MeV (1981LI23; pol. n0+1). See also 17F in (1982AJ01), (1980HU1J, 1980HU1D) and (1981NO1B).

24. 16O(d, p)17O Qm = 1.9197 Eb = 7.5263

Excitation functions and polarization studies have been reported for several proton groups for Ed = 0.3 to 17 MeV: see (1978AJ03) and (1978RO1M; Ed-bar = 14 to 17 MeV). 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). See also 17O in (1982AJ01).

25. 16O(d, d)16O Eb = 7.5263

The yield of elastically scattered deuterons and elastic polarization measurements have been reported for Ed = 0.65 to 56 MeV: see (1978AJ03) and (1982AOZZ; Ed = 13.8 to 16.5 MeV), (1981FR1C; TAP; Ed-bar = 20 MeV), (1981CL1C; VAP; Ed-bar = 20.5 MeV; also to 16O*(6.13)), (1980MA10; VAP; Ed-bar = 52 MeV), (1980HA14; VAP; Ed-bar = 56 MeV). For total cross sections at high energies see (1979DE31). See also 16O in (1982AJ01), (1978RO1M) and (1979NI1B, 1980AY01, 1981AO01, 1982YA1A; theor.).

26. (a) 16O(d, t)15O Qm = -9.4065 Eb = 7.5263
(b) 16O(d, 3He)15N Qm = -6.6340

Vector analyzing powers have been studied at Ed-bar = 29 MeV (1978CO13: to 15N*(0, 6.32) and 15O*(0, 6.18)) and 52 MeV (1977BE70: to 15N*(0, 6.32, 9.94, 10.71)). See also (1978AJ03) and (1981MA14).

27. 16O(d, α)14N Qm = 3.1104 Eb = 7.5263

The yields of various groups of α-particles have been measured for Ed ≤ 20 MeV: see (1978AJ03) and (1979MA2Q; 0.65 to 1.1 MeV; α0), (1978RI05; 6.7 to 12.5 MeV; α3) and (1982AOZZ; 13.8 to 16.5 MeV; α0). The yield curves have been fitted in terms of a large number of states in 18F: see Tables 18.15 (in PDF or PS) here and 18.16 (in PDF or PS) in (1978AJ03).

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 < Ex < 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 Ex range. The average coherence width increases from ≈ 100 keV at Ex = 14 MeV to ≈ 500 keV at Ex = 20 MeV. The level densities appear to be consistent with predictions of the Fermi-gas model (1973JO13). See also (1981JO1D). [For mixed isospin states observed in 14N(α, α1) see Table 18.14 (in PDF or PS) in (1978AJ03)].

Polarization measurements are reported for Ed = 6.8 to 16 MeV: see (1978AJ03). The T21 analyzing power of the transition to 14N*(4.91) [0-] has been measured at Ed = 8.06 MeV (θ = 45°) to 0.5% (1981KA21). See also (1979TO1A, 1980PR1A, 1981TO1G), (1979MA2Q: applications), (1978SE01, 1979SE04; theor.) and 14N in (1981AJ01).

28. 16O(d, 6Li)12C Qm = -5.6885 Eb = 7.5263

See (1978AJ03).

29. 16O(t, n)18F Qm = 1.2690

See (1978AJ03). See also (1976HE1N) and (1980KU1H; applied).

30. 16O(3He, p)18F Qm = 2.0328

Excitation energies derived from measurements of γ-rays are displayed in Table 18.16 (in PDF or PS), together with l-assignments obtained from distorted-wave analyses, and Jπ; T and Kπ assignments from branching ratios, radiative widths, linear polarization, γ-ray angular distributions and τm measurements [see also Tables 18.12 (in PDF or PS) and 18.13 (in PDF or PS)]. Studies of this reaction, together with the work on 14N(α, γ) and 17O(p, γ), have defined the low-lying states of 18F.

The g-factor of 18F*(0.94) [Jπ = 3+] is +0.54 ± 0.06 (1981ST21), 0.58 ± 0.07 (1978GO1T). τm of 18F*(1.04) = 2.7 ± 0.7 fsec. The weighted mean "best" value [see Table 18.12 (in PDF or PS)] is 2.7 ± 0.4 fsec. This leads to |M|2 = 10.3 ± 1.5 W.u., and using the E1 strength of the 18F*(1.08 → g.s.) decay leads to a value for the circular polarization of the 1.08 → g.s. γ-ray [Pγ] [0-; T = 0 to 1+; 0] = ± (5.8 ± 0.4) keV-1< 1.04|VPNC|1.08 > (1981KE04). The experimental value for Pγ = (-0.7 ± 2.0) × 10-3 (1978BA08). (1981AD1E) reports a best value of Pγ = (-0.1 ± 1.2) × 10-3. The importance of the decays of 18F*(1.04, 1.08) [Jπ = 0+, T = 1; Jπ = 0-, T = 1, respectively] lies in testing the parity non-conserving (PNC) component of nuclear forces: see also (1980BI11), (1981HA1H) and (1980HA41; theor.). The magnetic moment of 18F*(1.13) = +2.855 ± 0.030 nm, in agreement with shell-model predictions for a (1d25/2)5+ state: see (1978AJ03). See also (1979HA1M), (1977FI13, 1980HE06; applied) and 19Ne.

31. 16O(α, d)18F Qm = -16.3204

Angular distributions of the deuteron groups to 18F*(1.12) [Jπ = 5+] have been studied at Eα = 28.0 to 33.6 MeV (1978CO10, 1979CO1P). See also 20Ne and (1972AJ02).

32. 16O(6Li, α)18F Qm = 6.053

Angular distributions for α0 are reported at E(6Li) = 5.5 to 13.3 and 26 MeV: see (1978AJ03). 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, 3.72, 3.79, 3.84). The angular distributions for the first three groups are forward peaked and show little structure at back angles. 18F*(1.04, 3.06) are not observed, as expected from isospin conservation. States at Ex = 4.12, 4.23, 4.4, 5.61, 6.11, 6.20, 6.53, 6.80 and 6.88 were populated (1976MO24). See also (1981MA26; theor.).

33. 16O(11B, 9Be)18F Qm = -8.290

Forward angle differential cross sections are reported at E(11B) = 115 MeV to 18F*(1.1) [Jπ = 3+ + 5+] and to 18F*(4.65) [Jπ = 4+] (1980PR09). See also (1979RA10).

34. (a) 16O(12C, 10B)18F Qm = -17.661
(b) 16O(13C, 11B)18F Qm = -9.4074

Forward angle differential cross sections are reported at E(13C) = 105 MeV 18F*(1.12, 4.65) (1980PR09). For reaction (a) see (1978AJ03).

35. 16O(14N, 12C)18F Qm = -2.7461

Angular distributions are reported at E(14N) = 76.2 MeV to 18Fg.s. (1977MO1A).

36. 16O(16O, 14N)18F Qm = -13.2100

See (1978AJ03).

37. 17O(p, γ)18F Qm = 5.607
Q0 = 5606.2 ± 0.6 keV (1976RO1T); see also (1978SE08).

Gamma-ray measurements lead to the very accurate Ex determinations for 18F states below 6.2 MeV: see Table 18.17 (in PDF or PS). Observed resonances are displayed in Table 18.18 (in PDF or PS); branching ratios, radiative widths and multipole mixing ratios are shown in Table 18.12 (in PDF or PS); and τm in Table 18.13 (in PDF or PS).

The direct capture cross section has been studied for Ep = 0.3 to 1.9 MeV: 18F*(5.603, 5.605, 5.668, 5.786) have Jπ = 1+, 1-, 1- and 2-. The 1- states have mixed isospin. Astrophysical considerations are discussed in (1978AJ03) and (1975ZI1A, 1977RO1H, 1978RO1D).

38. 17O(p, n)17F Qm = -3.544 Eb = 5.607

Observed resonances are displayed in Table 18.18 (in PDF or PS). See also (1978AJ03).

39. 17O(p, p)17O Eb = 5.607

The elastic scattering has been studied for Ep = 0.5 to 13 MeV [see (1978AJ03)] and 1.4 to 3.0 MeV (1977SE12, 1978SE08): observed anomalies are displayed in Table 18.18 (in PDF or PS).

40. 17O(p, d)16O Qm = -1.920 Eb = 5.607

See (1978AJ03).

41. 17O(p, α)14N Qm = 1.191 Eb = 5.607

The yield of α0 shows a number of resonances for Ep = 0.49 to 3.0 MeV: see Table 18.18 (in PDF or PS). The R-matrix fit of (1979KI13), obtained from data from Ep = 400 to 1400 keV, confirms the earlier result [see, e.g., reaction 31 in (1978AJ03)] that a significant quantity of 17O is burned up in the (p, γ) rather than in the (p, α) reaction for a wide range of stellar temperatures (1979KI13). See also (1977RO1H, 1978RO1D; astrophys.).

42. 17O(d, n)18F Qm = 3.382

See (1972AJ02).

43. 17O(3He, d)18F Qm = 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 Jπ = (2+) or 3+. Since l = 2 for 18F*(4.65), Jπ ≤ 5+, with 4+ most likely (1969PO11). See also (1979SA31; theor.).

44. 17O(12C, 11B)18F Qm = -10.350

Forward angle differential cross sections are reported for the transition to 18F*(1.12) at E(12C) = 115 MeV (1980PR09).

45. 18O(p, n)18F Qm = -2.4379

Angular distributions of a number of neutron groups are reported for Ep = 5.5 to 13.5 MeV: see (1978AJ03). The τm of 18F*(1.04) [Jπ = 0+; T = 1] is 2.7+0.6-0.4 fsec (1980KE05): see Table 18.13 (in PDF or PS). See also 19F.

46. 18O(3He, t)18F Qm = -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 Ex = 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, 3.72, 3.79, 3.84, 4.12, 4.23, 4.36, 4.40, 4.65, 4.75). The angular distributions are consistent with the Jπ assignments shown in Table 18.11 (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 Ex < 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). At E(pol. 3He) = 33 MeV the analyzing power angular distribution for t0 has been measured by (1981BA1G).

47. 18O(6Li, 6He)18F Qm = -5.165

At E(6Li) = 34 MeV angular distributions have been obtained for the transitions to 18F*(0, 0.94): there appears to be a sizeable contribution due to two-step processes: see (1978AJ03).

48. 18Ne(β+)18F Qm = 4.447

The half-life of 18Ne is 1672 ± 4 msec (see 18Ne). The decay is to 18F*(0, 1.04, 1.08, 1.70): see Table 18.19 (in PDF or PS) for the branching ratios and log ft values.

49. 19F(γ, n)18F Qm = -10.4313

Cross sections to 30 MeV for the transitions to 18F*(0.94, 1.04, 1.08, 3.06, 3.13, 4.75) are reported by (1979TH05). See also (1978AJ03), (1980YA08; applied) and 19F.

50. 19F(n, 2n)18F Qm = -10.4313

See (1978CO18, 1980CO1U). See also 20F and (1978AJ03).

51. 19F(p, d)18F Qm = -8.2067

Angular distributions of the d0 group have been measured at Ep = 16 to 155.6 MeV: ln = 0: see (1972AJ02) and (1977GU14: 17.7 MeV). At Ep = 19.3 MeV angular distributions are also reported to excited states of 18F: see Table 18.20 (in PDF or PS). The angular distributions associated with 0h - 2p states in 18F are only qualitatively accounted for by DWBA. Those corresponding to 1h - 3p negative-parity states generally cannot be accounted for by a single-step mechanism, while the distributions to states arising from 2p - 4h configurations do not show the features associated with direct interaction (1980DE05). See also (1982MA1H) and (1978AJ03).

52. 19F(d, t)18F Qm = -4.1740

Angular distributions of triton groups have been reported at Ed = 8.9 (t0, t1, t3) and 14.8 MeV (t0): see (1972AJ02). See also (1978AJ03).

53. 19F(3He, α)18F Qm = 10.1465

Many α-particle groups have been observed [see Table 18.21 (in PDF or PS) in (1978AJ03)].

54. (a) 19F(10B, 11B)18F Qm = 1.024
(b) 19F(14N, 15N)18F Qm = 0.4021
(c) 19F(19F, 20F)18F Qm = -3.830

See (1972AJ02).

55. 20Ne(p, 3He)18F Qm = -15.558

At Ep = 45 MeV, 18F*(0, 1.04, 1.70, 3.06, 6.27) are populated: see (1978AJ03).

56. 20Ne(d, α)18F Qm = 2.7954

At Ed = 11 MeV α-groups are observed to many states of 18F with Ex < 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 Ed = 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 range 5 to 9 MeV (1973HR03). Angular distributions have also been measured at Ed = 2 to 14.7 MeV: see (1978AJ03). Measurements of the tensor analyzing power for Ed-bar = 10.25 to 12.0 MeV leads to assignments of unnatural parity for 18F*(0, 0.94, 1.08 + 1.12, 1.70, 2.10, 3.36, 3.72, 4.12, 4.23, 4.36, 4.40, 5.603 + 5.605 + 5.67, 5.79, 6.10 + 6.10, 6.14 + 6.16, 6.31, 6.48) and to natural parity for 18F*(3.79, 3.84, 4.86): assignments of Jπ = 2-, 1+, 0+, 1-, 1+, 3+, 3+ are made for 18F*(4.23, 4.36, 4.75, 4.86, 5.603, 6.16, 6.48) [all T = 0 except 18F*(4.75)] (1978DA02).

57. 20Ne(α, 6Li)18F Qm = -19.578

See (1979LE1R, 1980LE21; theor.).

58. 24Mg(12C, 18F)18F Qm = -15.676

See (1978NO02).