
^{20}F (1959AJ76)(See Energy Level Diagram for ^{20}F) GENERAL: See also Table 20.1 [Table of Energy Levels] (in PDF or PS). Theory: See (1957RA1C).
See ^{20}Ne.
Not observed.
See ^{19}F.
The proton yield has been measured from E_{d} = 0.79 to 0.88 MeV (1956AH1A). See also (1959ZI16) and ^{19}O.
The cross section has been measured for E_{d} = 0.5 to 3.0 MeV. Resonances are observed at E_{d} = 1.40, 1.75, 2.15, and 2.90 MeV, with widths of 500, 400, 300, and 600 keV, respectively, corresponding to ^{20}F*(13.60, 13.92, 14.28, and 14.95 MeV) (1957BO04). See also ^{16}N.
See (1956SH1A).
Not reported.
Not reported.
The thermal capture cross section is 9.4 ± 2 mb (1947SE33). The γspectrum has been measured by (1957CA28) who find transitions with E_{γ} (corrected for recoil) of 6.600 ± 0.011, 6.019 ± 0.011, 5.54 ± 0.02, 5.28 ± 0.02, and 5.10 ± 0.02 MeV, with intensities of 30, 16, 24, 27, and 14 photons per 100 captures, respectively. The 6.60 MeV line is the ground state transition; the other transitions are not uniquely determined. Upper limits for transitions to ^{20}F*(0.65, 0.83, and 0.99 MeV) are 1, 3, and 7 photons per capture, respectively. The γrays of energy 5.54 and 5.28 MeV may result from transitions to ^{20}F*(1.06 and 1.31) (1957CA28). Two resonances for ^{20}F production are observed at E_{n} = 280 and 590 keV, with widths ≈ 20 keV and peak cross sections of 1.2 and 1.3 mb, respectively; ωΓ_{γ} ≈ 15 eV (1950HE92). A number of additional resonances appear in the range E_{n} = 25 to 2000 keV: see (1958HU18). See also (1951KI35).
The coherent scattering cross section is 3.8 ± 0.3 b; the total cross section (epithermal, bound) is 4.0 ± 0.1 b (1958HU18). The cross section is approximately constant at ≈ 3.7 b from 0.02 eV to 20 keV (1958HU18). Resonances in the total cross section are listed in Table 20.2 [Resonances in ^{19}F(n, n)^{19}F] (in PDF or PS). The J^{π} assignments indicated for the first three levels (pwave) are based on elastic scattering distributions and total cross sections (1958BL54). Total cross sections have been measured to E_{n} = 5 MeV by (1958WI36), from E_{n} = 3 to 14 MeV by (1954NE03), from E_{n} = 3.8 to 8.1 MeV by (1957BO13), from E_{n} = 4.4 to 5.6 MeV by (1956BE98) and from E_{n} = 7 to 14 MeV by (1958BR16). The cross section shows structure at least as high as E_{n} ≈ 7.5 MeV: see (1956BE98, 1957BO13, 1958WI36). For the presentation of the data as a whole, see (1958HU18). Angular distributions have been measured and phase shifts determined at five energies in the range E_{n} = 0.66 to 2.92 MeV by (1958WI36). See also (1955PA1B, 1957LA14) and (1956NE1C; theor.).
Observed resonances in the yield of 0.1 and 0.2 MeV γradiation (see ^{19}F) for E_{n} < 1 MeV are exhibited in Table 20.3 [Resonances in ^{19}F(n, n'γ)^{19}F] (in PDF or PS). A satisfactory fit to the excitation function for E_{n} < 300 keV is obtained on the assumption for pwave resonances at E_{n} = 100 and 260 keV. The excitation functions for 0.1, 0.2, 1.24, and 1.37 MeV γrays have been measured to E_{n} = 2.2 MeV (1955FR1B). The cross section for excitation of ^{19}F*(2.79) has been studied from E_{n} = 3 to 3.6 MeV. The very slow rise for the first 300 keV above threshold suggests a large spin difference between the 2.79 MeV level and the ground state (1957FR57). See also (1955AJ61, 1956VA29).
The cross section at E_{n} = 14.1 MeV is 62 mb (1958AS63); at E_{n} = 14.5 MeV it is 60 mb (1953PA1C). See also (1952AJ38, 1958RA1H).
The excitation function has been measured from E_{n} = 4.7 to 8.0 MeV; it shows a single broad maximum at 7.5 MeV. For E_{n} < 8 MeV, the (n, α) cross section is at least twice as large as the (n, p) cross section (1955MB01). At E_{n} = 14.5 MeV, σ(n, α)/σ(n, p) = 1.2 ± 0.4 (1958KO03); σ(n, p) = 135 mb (1953PA1C). See (1958HU18).
Observed resonances are listed in Table 20.4 [Resonances in ^{19}F(n, α)^{16}N] (in PDF or PS) (1955BO98, 1955MB01 : see graph in (1958HU18 )). See also (1937WI1A , 1955BO1C , 1955GR18 , 1958KO03).
Energy levels of ^{20}F derived from the proton groups are listed in Table 20.5 [Proton groups from ^{19}F(d, p)^{20}F] (in PDF or PS) (1952WA1A, 1956EL1A, 1957KH16). The J^{π} assignments given in the table result from analysis of angular distributions by stripping theory. The angular distribution of the ground state protons has been studied at a number of energies (1953BR1C, 1956TA1D, 1956VA17, 1957ON1A, 1957SE1D). The pattern varies strongly with energy, suggesting compound nucleus interaction rather than stripping: it is concluded that an earlier assignment of J = 1^{+} (1953BR1C) is not supported (1957SE1D). See also (1956OK1A, 1956TO1C; theor.). At E_{d} = 1.05 MeV, γ rays are observed with E_{γ} = 0.64 and 1.06 MeV (1954TH1B). It is of interest to note that among the levels of ^{20}F there occur seven groups with equal spacings of 165n keV, where n is an integer for each group (1952WA1A, 1956EL1A). Above E_{x} = 5 MeV, only odd parity levels appear; below this value, even parities predominate. The levels appear in groups of the same parity, separated by ≈ 0.6 MeV (1956EL1A).
Not observed.
Not observed.
Not observed.
Not observed.
Not observed.
Not observed.
Not observed.
Alpha particle groups have been observed at E_{d} = 7.8 MeV corresponding to the ground state and to a level at 0.57 ± 0.13 MeV (1951MI1A).
See (1950JE1A).
