(See Energy Level Diagrams for 18F)
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).
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).
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, 1972OG1A, 1972PU1B, 1973DI1B, 1973VA12, 1973WI15, 1974DI16, 1974HA61, 1974KA22, 1974OL06, 1974RA11, 1975DI03, 1975NO10, 1975VO09, 1976BE1K, 1976LE1F, 1977AR06).
μ1.12 = +2.85 nm (1976FU06).
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/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.).
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for a listing of the earlier work and (1977LE1N: 5 - 9.2 MeV; d0, d1+2), (1975SO1E: 9.0 - 14.0 MeV; α0, α1, α2, unpublished), (1973BA53: 19.2 - 24 MeV; d3, d4) and (1973WH03: 32.5 - 35.2 MeV; α to first nine T = 0 states in 14N and 6Li elastic).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).
See (1974KL1B, 1976DA07, 1977KL1E) and 22Na in (1978EN06) for reaction (a). A sharp γ-line is reported in reaction (b) at Eγ = 3728 ± 2 keV as a cascade via 18F*(1.12): it is suggested that it comes from the de-excitation of the Jπ(Kπ) 5-(0-) state (1977KO2K; abstract). Two γ-lines are reported with Eγ = 937.21 ± 0.12 and 184.12 ± 0.07 keV [(0.94 → 0), (1.12 → 0.94)]: Ex = 937.24 ± 0.12 and 1121.36 ± 0.15 keV (E.K. Warburton, private communication).
A number of resonances have been observed for Eα < 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 Jπ of 18F states with Ex < 6.9 MeV. Studying the strengths of the γ-transitions (see Table 2 in the Introduction) has led Rolf and his collaborators to suggest Kπ 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 total cross-section ratios σ(n1)/σ(p1) have been measured for Eα = 7 to 12 MeV: major maxima are observed at Eα = 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 Eα = 10 - 13 MeV to 100 ± 24 keV for Eα = 15 - 19 MeV. See also (1977LI19).
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 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) 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 Ex 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 Ex increases (1976CH24). See also (1970TO03).
The total cross section for formation of 6Li and 10B (reactions (d) and (e)) has been studied for Eα = 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).
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 (1972GA1E).
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). See also (1972BA1P, 1977MA2G).
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).
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: Ed = 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 (σn1/σp1): 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 Ed ≈ 10 - 13 MeV to 70 ± 17 keV at Ed ≈ 13 - 16 MeV (1972GR10). See also (1970DA14). Polarization measurements have been carried out for Ed = 3 to 15 MeV: see Table 18.16 (in PDF or PS) in (1972AJ02) and (1972AN1G, 1972AN21: Ed = 3 to 4 MeV; n0, n1) and (1975WA1L, 1976LI1R: 4.3 to 15 MeV; n0, n1). See also (1974LO1B) and 17F in (1977AJ02).
Excitation functions and polarization studies have been reported for several proton groups for Ed = 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 Ed = 4.0 to 6.0 MeV (1970DA14). See also (1973CA30). The ratio σn1/σp1 has been studied for Ed = 7 to 17 MeV by (1974AU1B). See also (1971GR2B, 1974DA13), (1973ME18, 1975CR05, 1975GR12, 1976BO48, 1976SA04; theor.) and 17O in (1977AJ02).
The yield of elastically scattered deuterons and elastic polarization measurements have been reported for Ed = 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: Ed = 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).
The ground-state polarization has been studied at Ed = 15 MeV by (1974LU06). Vector analyzing powers have been studied at Ed-bar = 29 MeV for the transitions to the first two states of 15N and 15O (1977MA2R).
The yields of various groups of α-particles have been measured for Ed ≤ 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).
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). [For mixed isospin states observed in 14N(α, α1) see Table 18.14 (in PDF or PS).]
For polarization measurements see (1977ST06: Ed-bar = 6.84 MeV, θlab = 29° and 34°, α3, iT11 = 0.856 ± 0.006 and 0.842 ± 0.015), (1976PE08: Ed-bar = 11, 12, 13, 14 MeV: many α groups) and (1976LU1A: 16 MeV; α0, α2). See also (1971GR2B, 1974JO1F, 1976GO1B, 1976RI1C), (1972AJ02, 1974LO1B), (1973TU1A; applied) and (1973FR04; theor.).
Measurements of lifetimes are displayed in Table 18.12 (in PDF or PS) (1966AL04, 1973WA19, 1974CO01). (1966AL04) report that ΔEx(1.13 → 0.94) = 194 ± 1 keV: Ex of 18F*(1.13) is then 1131.0 ± 1 keV [based on Ex = 937.0 ± 0.2 keV]: see, however, Table 18.17 (in PDF or PS). Angular distributions are reported at Et = 1.1 to 1.7 MeV by (1976MA54: n0). See also (1974NO15) and 19F.
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 (Jπ; 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 τm 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 (1d25/2)5+ state (1967PO09, 1967SC09). Parity mixing is being studied by observing the γ-decay of 18F*(1.04, 1.08) [Jπ = 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.).
At Eα = 40 to 52 MeV, deuteron spectra are dominated by the groups to 18F*(1.13), Jπ = 5+ [1d25/2 configuration]. Many other states have also been observed: see Table 18.19 (in PDF or PS) in (1972AJ02) (1968MA33; note energy resolution problems).
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 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 (1975MI1A), (1977GO01; theor.) and (1972AJ02).
A study of direct capture cross sections at Ep = 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 (Qm) [18F*(5.603, 5.604, 5.668, 5.785) with Jπ = 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 Ep = 0.3 to 1.9 MeV: spectroscopic factors are derived for 18F states below Ex = 6.2 MeV. The agreement with stripping data is good (1973RO34).
Twelve resonances have been observed in this reaction for Ep < 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 Ex = 1119.0 ± 0.6 keV for the Jπ = 5+ state (based on Ex = 937.1 ± 0.4 keV), while (1973SE03) report 1121.0 ± 0.3 keV based on Ex = 936.9 ± 0.2 keV, and (1975RO05) have determined Ex = 2100.68 ± 0.14 and 3133.87 ± 0.15 keV: see Table 18.19 (in PDF or PS). See also (1970ZA1D).
Several resonances have been observed in the total yield of neutrons measured from threshold to Ep = 5 MeV: see Table 18.18 (in PDF or PS) (1973BA31). At higher energies the yields of n0 (Ep = 7 - 13.5 MeV) and n1 (7 - 12.5 MeV) exhibit some gross structures (1969AN06).
The elastic scattering has been studied for Ep = 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).
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) (1957AH20, 1962BR08, 1973SE02). For astrophysical questions see 17O(p, γ)18F (1974RO1N, 1975RO20) and (1971BA1A, 1973CL1E, 1974DE1M, 1977CL1F).
For a report of angular distributions see (1972AJ02): the work quoted was not published.
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 , 1.12 , 2.53 [0 + 2], 3.06 [0 + 2], 3.84 [0 + 2], 4.12 [0 + 2], 4.66  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). At E(3He) = 25 MeV 18F*(5.606, 5.674) [Jπ = 1-] have been studied to estimate their proton widths which are of astrophysical significance (1974BR1C; abstract). See also (1972EN03, 1976SC1H; theor.).
Angular distributions have been measured for Ep = 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.
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, 3.73, 3.79, 3.84, 4.11, 4.23, 4.36, 4.40, 4.65, 4.75). The angular distributions are consistent with the Jπ 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 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(6Li) = 34 MeV angular distributions have been obtained for the transitions to 18F*(0, 0.94) [Jπ = 1+, 3+]: there appears to be a sizable contribution due to two-step processes (1974WH07, 1974WH1E, 1975WH01). See also (1974DU15).
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).
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.
Angular distributions of the d0 group have been measured at Ed = 16 to 155.6 MeV; ln = 0: see (1972AJ02). Angular distributions to excited states reported in (1972AJ02) have not been published. See also (1973OR09; theor.). For reaction (b) see (1968DE21).
Angular distributions of triton groups have been reported at Ed = 8.9 (t0, t1, t3) and 14.8 MeV (t0): see (1972AJ02). The angular distribution to 18F*(1.04) [Jπ = 0+, T = 1] (1972BU1E; unpublished abstract; Ed = 28 MeV) is compared with that for the transition to the 18Og.s. in the mirror reaction (1973CO17). For a polarization study at Ed = 12.3 MeV see (1976NE1C) and 21Ne in (1978EN06).
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 Ex < 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 Jπ = 1- for both 18F*(5.60, 5.67): Γα/Γ ≈ 1 (1971LI27). See also (1976GA27) and 22Na in (1978EN06).
At Ep = 45 MeV, 3He groups are observed to 18F*(0, 1.04, 1.70, 3.06, 6.27 ± 0.03) (1969HA38).
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 region 5 to 9 MeV (1973HR03): see also 22Na in (1978EN06). Angular distributions have also been measured at Ed = 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 < Ed < 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 (1976GU1E; applied work) and (1974NO15; theor.).