
^{18}F (1978AJ03)(See Energy Level Diagrams for ^{18}F) 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: (1972LI1E, 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 ^{18}F: (1971BI22, 1972OG1A, 1972PU1B, 1973DI1B, 1973VA12, 1973WI15, 1974DI16, 1974HA61, 1974KA22, 1974OL06, 1974RA11, 1975DI03, 1975NO10, 1975VO09, 1976BE1K, 1976LE1F, 1977AR06). Applied topics: (1973WE1N, 1975AL1B, 1976GU1E, 1977DE1X, 1977PA1K). Ground and 1.12 MeV states of ^{18}F: (1970SI1J, 1971SH26, 1971TA1A, 1972NA05, 1972VA36, 1972YO1B, 1973MC06, 1973MI1C, 1973SU1B, 1974MC1F, 1974RE03, 1974SH1G, 1974SHYR, 1976CH1T, 1976PA03, 1977BR03).
μ_{1.12} = +2.85 nm (1976FU06).
The positron decay is entirely to the ground state of ^{18}O [J^{π} = 0^{+}, T = 1]; the halflife 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 ^{18}O_{g.s.} is allowed indicates J^{π} = 1^{+} for ^{18}F_{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.).
Cross section measurements have been carried out in the range E(^{6}Li) = 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; d_{0}, d_{1+2}), (1975SO1E: 9.0  14.0 MeV; α_{0}, α_{1}, α_{2}, unpublished), (1973BA53: 19.2  24 MeV; d_{3}, d_{4}) and (1973WH03: 32.5  35.2 MeV; α to first nine T = 0 states in ^{14}N and ^{6}Li 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(^{6}Li) = 4 MeV due to Coulomb barrier effects. At higher energies, Ericsontype 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 isospinforbidden α_{1} group [to ^{14}N*(2.31), 0^{+}, T = 1] shows an energy dependence very unlike those for the α_{0} and α_{2} 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 α_{1} group is two orders of magnitude lower than those for the α_{0} or α_{2} groups (1965CA06, 1967DZ01). At the higher energies the d_{3} and d_{4} yields are smooth functions for E(^{6}Li) = 19.2 to 24 MeV (1973BA53) as are the αyields and the yield of elastically scattered ^{6}Li for E(^{6}Li) = 32.5 to 35.2 MeV (1973WH03). The elastic scattering of vector polarized ^{6}Li ions has been studied at E(^{6}Li) = 22.8 MeV (1976WE10). See also ^{16}O and ^{17}O in (1977AJ02), ^{14}N and ^{15}O in (1976AJ04) and ^{12}C in (1975AJ02).
See (1972AJ02).
See (1974KL1B, 1976DA07, 1977KL1E) and ^{22}Na in (1978EN06) for reaction (a). A sharp γline is reported in reaction (b) at E_{γ} = 3728 ± 2 keV as a cascade via ^{18}F*(1.12): it is suggested that it comes from the deexcitation of the J^{π}(K^{π}) 5^{}(0^{}) state (1977KO2K; abstract). Two γlines 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).
See (1972AJ02).
See (1975KL1A).
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 ^{17}O(p, γ) and ^{16}O(^{3}He, 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 ^{18}F states with E_{x} < 6.9 MeV. Studying the strengths of the γtransitions (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 ^{18}F: 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 lowlying states of ^{18}F. For the earlier work see (1972AJ02). See also (1972VL1B). The nonresonant Sfactor for this reaction, S ≈ 0.7 MeV · b (1972CO1C). See also (1971BA1A, 1972CO1E, 1973AR1E, 1973CL1E, 1975FO19, 1975SC1Y; astrophys. questions).
The total crosssection ratios σ(n_{1})/σ(p_{1}) 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).
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.
Observed anomalies in the elastic scattering are exhibited in Table 18.13 (in PDF or PS). Resonances in the α_{1} isospinforbidden yield are displayed in Table 18.14 (in PDF or PS) (1974CH1T, 1976CH24). In the α_{1} study, carried out for E_{α} = 7.6  16.9 MeV, a partial wave analysis involving a method of removing ambiguities and parametrizing Smatrix elements gives the level parameters of 151 isospin mixed, natural parity states in ^{18}F with 10.4 < E_{x} < 17.5 MeV. Many of these states have also been reported in the ^{16}O(d, α_{1}) work of (1973JO13). The agreement is best for lowlying 2^{+} or 4^{+} states, and is quite good for 3^{} and 5^{} states, while for highJ states the greater centrifugal barrier for ^{16}O + d at the same E_{x} relatively suppresses highJ states in the ^{16}O + 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 ^{6}Li and ^{10}B (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 ^{14}N in (1976AJ04).
Angular distributions have been measured for E(^{6}Li) = 5.3 to 6.0 MeV (1968RI13: d_{0}, d_{1→4}). See also (1972GA1E).
At E(^{7}Li) = 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 αtransfer mechanism. The transitions to ^{18}F*(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 ^{16}O(^{3}He, p)^{18}F and ^{17}O(^{3}He, d)^{18}F) are predominantly of a 4p  2h nature and are excited by the transfer of four nucleons into the (2s, 1d) shell (1968MI09). At E(^{7}Li) = 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 ^{18}F*(1.70, 2.10, 2.52, 3.36, 4.40, 5.30, 6.57, 9.58, 11.22, 14.18).] See also (1972GA1E).
See ^{17}O in (1971AJ02) and (1973AB1D).
At E(^{6}Li) = 30 MeV preferential excitation of odd parity states of ^{18}F below E_{x} = 5 MeV is reported. Angular distributions of the tritons to ^{18}F*(0, 0.94, 2.10, 4.40) [J^{π} = 1^{+}, 3^{+}, 2^{}, 4^{}] are all strongly forward peaked (1972LI24). See also (1972BA1P, 1977MA2G).
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).
Excitation functions have been measured for the n_{0} and n_{1} 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 ^{17}F), (1972GR10: threshold to 15.8 MeV; yield of ^{17}F) 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 ^{18}F 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; n_{0}, n_{1}) and (1975WA1L, 1976LI1R: 4.3 to 15 MeV; n_{0}, n_{1}). See also (1974LO1B) and ^{17}F in (1977AJ02).
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; p_{1}), (1972CO15, 1973DA17: 9.3 and 13.3 MeV; p_{0}, p_{1}, p_{3}, p_{4}, p_{5}, p_{8}) and (1973JO10: 12.3 MeV; p_{1}). 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 p_{0}, 63 keV for p_{1} and 62 keV for p_{3} 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 ^{17}O in (1977AJ02).
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 ^{16}O in (1977AJ02).
The groundstate polarization has been studied at E_{d} = 15 MeV by (1974LU06). Vector analyzing powers have been studied at E_{dbar} = 29 MeV for the transitions to the first two states of ^{15}N and ^{15}O (1977MA2R).
The yields of various groups of αparticles 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; α_{0}), (1974CH1U, 1975CH1N, abstracts: 6.0  7.0 MeV; α_{3}) and (1973JO13: 2  14 MeV; α_{0}, α_{1}). The yield curves have been fitted in terms of a large number of states in ^{18}F: see Tables 18.15 (in PDF or PS) and 18.16 (in PDF or PS). A detailed study by (1973JO13) of the isospinforbidden α_{1} yield, analyzed by Smatrix theory, identifies a large number of isospin mixed states in ^{18}F, 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 Fermigas model (1973JO13). [For mixed isospin states observed in ^{14}N(α, α_{1}) see Table 18.14 (in PDF or PS).] For polarization measurements see (1977ST06: E_{dbar} = 6.84 MeV, θ_{lab} = 29° and 34°, α_{3}, iT_{11} = 0.856 ± 0.006 and 0.842 ± 0.015), (1976PE08: E_{dbar} = 11, 12, 13, 14 MeV: many α groups) and (1976LU1A: 16 MeV; α_{0}, α_{2}). See also (1971GR2B, 1974JO1F, 1976GO1B, 1976RI1C), (1972AJ02, 1974LO1B), (1973TU1A; applied) and (1973FR04; theor.).
The groundstate polarization has been studied at E_{dbar} = 16 MeV (1976JA1G). See also (1976JA1H).
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 ^{18}F*(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: n_{0}). See also (1974NO15) and ^{19}F.
Excitation energies derived from measurements of γrays (1973RO03) are displayed in Table 18.17 (in PDF or PS), together with lassignments 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 γray 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 ^{14}N(α, γ) and ^{17}O(p, γ), the work on the ^{16}O(^{3}He, p)^{18}F reaction completes the definitive study of the lowlying states of ^{18}F by Rolf and his coworkers. See (1972AJ02) for the earlier work. The magnetic moment of ^{18}F*(1.13) = +2.855 ± 0.030 nm, in agreement with shellmodel predictions for a (1d^{2}_{5/2})_{5+} state (1967PO09, 1967SC09). Parity mixing is being studied by observing the γdecay of ^{18}F*(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.).
At E_{α} = 40 to 52 MeV, deuteron spectra are dominated by the groups to ^{18}F*(1.13), J^{π} = 5^{+} [1d^{2}_{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).
Angular distributions for the α_{0} group have been measured at E(^{6}Li) = 5.5 to 13.3 MeV (1968GR22) and at 26 MeV (1969DA19). At E(^{6}Li) = 34 MeV angular distributions are reported to ^{18}F*(0, 0.94, 1.1 [unres.]) and forward angle data has been obtained for ^{18}F*(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 zerorange twoparticle 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 αparticle in ^{16}O with the incident ^{6}Li ion. ^{18}F*(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).
At E(^{12}C) = 114 MeV, the population of the 5^{+} state ^{18}F*(1.12) is reported (1972SC21). See also (1971SC1F).
See (1972AJ02).
See (1974RO04).
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 ^{18}F near 5.607 MeV (Q_{m}) [^{18}F*(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 ^{17}O(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 ^{18}F 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 ^{18}F; 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 ^{14}N(α, γ) and ^{16}O(^{3}He, 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 ^{18}F. 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).
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 n_{0} (E_{p} = 7  13.5 MeV) and n_{1} (7  12.5 MeV) exhibit some gross structures (1969AN06).
The elastic scattering has been studied for E_{p} = 0.5 to 1.33 MeV (1973SE02), 8.5 to 10.5 MeV (1975CR04; also p_{1} and p_{2}) and 11.0 to 13.0 MeV (1967AL06): observed anomalies are displayed in Table 18.18 (in PDF or PS).
See (1975CR05).
The yield of α_{0} 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 ^{17}O(p, γ)^{18}F (1974RO1N, 1975RO20) and (1971BA1A, 1973CL1E, 1974DE1M, 1977CL1F).
For a report of angular distributions see (1972AJ02): the work quoted was not published.
At E(^{3}He) = 15 MeV, DWBA analysis of angular distributions of deuteron groups corresponding to the ground state of ^{18}F [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 ^{18}F*(4.11) may be assigned J^{π} = (2^{+}) or 3^{+}. Since l = 2 for ^{18}F*(4.65), J^{π} ≤ 5^{+}, with 4^{+} most likely (1969PO11). At E(^{3}He) = 25 MeV ^{18}F*(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, 1976SC1H; theor.).
Not reported.
Angular distributions have been measured for E_{p} = 5.53 to 6.12 MeV (1973FR10: n_{0} → n_{4}) and 6.9 to 13.5 MeV (1969AN06: n_{0} → n_{8}; not all resolved). See also (1971DR09), (1972AJ02), (1973CL1E; astrophys. questions), (1976KA13; theor.) and ^{19}F.
At E(^{3}He) = 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 ^{18}F*(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 ^{18}F*(1.04) (1970DU08). At E(^{3}He) = 17.3 MeV, angular distributions to ^{18}F states with E_{x} < 4 MeV have been analyzed using DWBA and a twobody interaction between the incident and target nucleons. An exact coupledchannel calculation was also made for the transition to ^{18}F*(1.04) (1968HA30).
At E(^{6}Li) = 34 MeV angular distributions have been obtained for the transitions to ^{18}F*(0, 0.94) [J^{π} = 1^{+}, 3^{+}]: there appears to be a sizable contribution due to twostep processes (1974WH07, 1974WH1E, 1975WH01). See also (1974DU15).
The halflife of ^{18}Ne is 1672 ± 4 msec (see ^{18}Ne). The decay is to ^{18}F*(0, 1.04, 1.70): see Table 18.20 (in PDF or PS) for the branching ratios and log ft values.
Photoneutron spectra have been studied by (1976SH12) and the yield of 0.94 and 1.04 MeV γrays by (1972TH15), and the γrays from ^{18}F*(0.94, 1.04, 1.08, 2.10, 2.52, 3.06, 3.13, 3.72) by (1977TA1M): see ^{19}F. See also (1976TH1E).
The lifetime of the 5^{+} state ^{18}F*(1.12) has been measured by (1972AD01): see Table 18.12 (in PDF or PS). Several γrays, including an intense line at 0.94 MeV, are reported by (1976PR08). See also ^{20}F.
Angular distributions of the d_{0} 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).
Angular distributions of triton groups have been reported at E_{d} = 8.9 (t_{0}, t_{1}, t_{3}) and 14.8 MeV (t_{0}): see (1972AJ02). The angular distribution to ^{18}F*(1.04) [J^{π} = 0^{+}, T = 1] (1972BU1E; unpublished abstract; E_{d} = 28 MeV) is compared with that for the transition to the ^{18}O_{g.s.} in the mirror reaction (1973CO17). For a polarization study at E_{d} = 12.3 MeV see (1976NE1C) and ^{21}Ne in (1978EN06).
At E(^{3}He) = 5.9 MeV, 41 αparticle groups have been observed, corresponding to the ground state of ^{18}F and to excited states with E_{x} < 7.5 MeV (1959HI67): see Table 18.21 (in PDF or PS). Angular distributions of the αparticles corresponding to ^{18}F*(3.06, 3.13) are reported by (1966MA43; E(^{3}He) = 4.0, 6.0 and 8.0 MeV): l = 2 and 1, respectively. Alpha  α_{0} angular correlations measured in the range E(^{3}He) = 5.0 to 6.0 MeV establish J^{π} = 1^{} for both ^{18}F*(5.60, 5.67): Γ_{α}/Γ ≈ 1 (1971LI27). See also (1976GA27) and ^{22}Na in (1978EN06).
See (1971BA68) and (1972AJ02).
See (1972AJ02).
Not reported.
At E_{p} = 45 MeV, ^{3}He groups are observed to ^{18}F*(0, 1.04, 1.70, 3.06, 6.27 ± 0.03) (1969HA38).
At E_{d} = 11 MeV αgroups are observed to many states of ^{18}F with E_{x} < 7 MeV. Weak or absent (each ≤ 0.3% of the total yield at 30°) are the groups corresponding to ^{18}F*(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 αgroups to ^{18}F*(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 isospinforbidden transition to ^{18}F*(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 ^{22}Na 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; α_{0}, α_{1}, α_{3}, α_{5} → α_{7}). Measurements of the tensor analyzing power near 180° for 10.5 < E_{d} < 12.0 MeV lead to natural π for ^{18}F*(4.85) and to unnatural π for ^{18}F*(4.23, 5.60, 5.79) (1977DA1F). ^{18}F*(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.).
Not reported.
