(See Energy Level Diagrams for 19F)
† Gamma rays with Eγ = 109.8 ± 0.1 and 197.0 ± 0.1 keV (PO69B), 109.8 ± 0.2 and 197.98 ± 0.19 keV (BL70G) and 198.10 ± 0.10 keV (EC72) have been reported in pion-induced reactions.
= +2.628866 (8) nm (V. Shirley, private communication);
μ0.198 = +3.60 nm (FU76H);
The mass of 19F derived from the work of (SM75B) is 18.99840317 (6) a.m.u. Using the conversion factor 931.5016 (26) MeV/a.m.u., the mass excess of 19F would then be -1.4875 MeV. (WA77) adopts -1.48738 ± 0.00013, as we do also.
For reaction (a) see (LO77B). The yield of 18F [reaction (b)] has been determined for E(7Li) = 2.5 to 3.5 MeV (NO61). The yields of α-particles have been measured by (HO62B; 3.2 to 4.0 MeV; α0, α1+2, α3), by (CA70E; 4.4 to 14 MeV; α0), by (CR72B, FO74J (prelim. results); 12 to 25 MeV; α0), by (TS73A; 28 to 35 MeV; α to 15N*(5.27, 5.30, 6.32, 8.57, 9.16, 9.83, 10.70, 12.56)). (CA70E) report that the cross section for reactions (c), (d), (e), (f) vary strongly over the range E(7Li) = 4 to 14 MeV but with little, if any, cross correlation. Strong fluctuations continue to E(7Li) = 25 MeV (FO74J) and there is some evidence of structures at higher energies (TS73A). For total reaction cross sections at several energies in the range E(7Li) = 4.5 to 13.0 MeV see (PO72A). See also 18O here, 16O and 17O in (77AJ02) and 15N in (76AJ04).
Excitation functions for α0 have been measured for E(6Li) = 7.7 to 16.8 MeV: structures are observed but they are not correlated (CO74F).
Angular distributions have been reported at E(6Li) = 5.3 to 6.0 MeV for the proton group to 19F*(2.78) (RI68M).
Resonances in the yield of γ-rays are observed below Eα = 8.2 MeV: the parameters for these are displayed in Table 19.8 (in PDF or PS) (AI70, RO72G, RO72Y, WO72C, RO73O, UN74, RO76F, SY76, DI77A, FI77C, SY77). Branching ratios are shown in Table 19.7 (in PDF or PS) and lifetime measurements in Table 19.10 (in PDF or PS). The Jπ values shown in Table 19.8 (in PDF or PS) are based on correlation and angular distribution measurements and on branching ratio determinations. The Ex of states involved in cascade decays are 4377 ± 1 and 4548 ± 2 keV (RO76F), 3999.6 ± 1.2 and 4031.9 ± 0.4 keV (RO73O). The Kπ = 1/2- band involves 19F*(0.110 [1/2-], 1.46 [3/2-], 1.35 [5/2-], 4.00 [7/2-], 4.03 [9/2-], 7.16 [11/2-]) (RO73O) and possibly 19F*(8.29) [(13/2-)] (UN74) [Jπ in brackets]. The situation concerning the other bands is not as clear: see (72AJ02) for a discussion of the evidence for other assignments of Jπ and Kπ. It is suggested that 19F*(10.41) is likely to be the second 13/2+ (2s, 1d)3 state in 19F (SY76). See also (RO71R) and (SC75I; astrophys. considerations).
The elastic scattering has been studied for Eα = 1.75 to 5.50 MeV (SM59C, SM61A, MO72F) and for 5.2 to 12.0 MeV (WE73M; abstract): see Table 19.9 (in PDF or PS) for the observed resonances. For reaction (b) see (JE74).
At E(13C) = 105 MeV, 19F*(4.04, 8.27, 8.97, 12.26, 12.67) are strongly populated. 19F*(2.80, 4.64) are also observed. It is suggested that 19F*(8.97, 12.26, 12.67) have Jπ = 11/2-, 17/2- and 15/2-, respectively, with 19F*(12.26) belonging to the lowest Kπ = 1/2- band (PI76H). See, however, Table 19.6 (in PDF or PS).
Resonances in the yield of γ0+1+2 (reaction (a)) are reported at Et = 1.5 and 2.4 MeV with Γ = 0.10 and 0.12 MeV (SC73F; abstract). The excitation function for reaction (b) has been measured for Et = 0.3 to 2.1 MeV (see (72AJ02)), 1.1 to 1.7 MeV (MA76BB; n0) and at Et = 1.6 to 3.7 MeV (RE77A): there is evidence for a maximum at Et = 2.5 MeV. At Et = 3.7 MeV the cross section is ~ 0.4 b (RE77A).
Resonances in the yields of p0, p1, α0 and α1+2 are reported by (KO67L) corresponding to states with Ex = 12.42, 12.67, (12.75), 12.83, 12.91, 12.97, (13.06) and (13.14) MeV (± ~ 25 keV) [not all resonances observed in every channel]. See also (KA74B). An analysis by the Humblet-Rosenfeld theory of the elastic yield (reaction (d)) in the range Et = 1.4 to 3.7 MeV suggests a large number of resonances: their parameters are displayed in Table 19.11 (in PDF or PS) (WE73L). See also (72AJ02), (LE76L; theor.), (BA73GG, RE77A; applied), 18O and 18F here, and 15N in (76AJ04).
Angular distributions have been measured at Eα = 20.1 MeV (PO75D; p0 --> p5), 26.7 and 33.1 MeV (YA61; p0 --> 2, p3 --> 5) and at 40 MeV (VA76K): see Table 19.12 (in PDF or PS). At Eα = 40 MeV 19F*(9.872) is strongly excited: it is suggested that it is a 11/2- state and that the 11/2- cluster strength is split between it and 19F*(8.957) (KO77B; abstract). See also (FO74J) and (AR75J, GE75J; theor.).
This reaction (and its mirror reaction 16O(6Li, t)19Ne: see reaction 4 in 19Ne) have been studied at E(6Li) = 24 MeV. Members of the Kπ = 1/2+ and 1/2- rotational bands have been identified: see Table 19.13 (in PDF or PS) (GA72A, BI72G). See also (FO73J, MA77G).
Many states of 19F have been populated in this reaction: see Table 19.14 (in PDF or PS) (TS74). See also (GL69B, WE73L, BA72P). It is suggested that 19F*(8.89, 9.81), which are strongly populated at E(7Li) = 35 MeV, are the third 11/2+ and the second 13/2+ states (TS74). See also (GO75Y).
This reaction, as well as the analog reaction [16O(10B, 7Li)19Ne] have been studied at E(10B) = 100 MeV: an attempt is made to match analog states [see reaction 5 in 19Ne] but problems of energy resolution are evident (HA76C).
The angular distribution for the transition to 8Beg.s. + 19Fg.s. has been measured at E(16O) = 60 MeV (SC72C).
This reaction has been studied at E(3He) = 18 MeV (BI74D; abstract).
At Eα = 47.5 MeV many states of 19F have been populated: angular distributions to the two 7/2+ states 19F*(4.38, 5.47) and to the two states 11/2+ states 19F*(6.50, 7.94) are reported.
It is concluded that 19F*(4.38) is mostly (d5/2)3 J = 7/2 and that the higher state is more deformed. In the case of the 11/2+ states both appear to be deformed to the same extent suggesting that there is no single 11/2+ member of the ground-state rotational band (FO75G).
Resonances for capture radiation observed for Ep = 0.3 to 3.0 MeV are displayed in Table 19.15 (in PDF or PS). At the Ep = 0.85 MeV resonance [19F*(8.80)], the intensity of the transition 8.80 --> 3.91 and the anisotropy of the 8.80 --> 3.91 --> 0 γ-rays limit J of 19F*(3.91) to 3/2 or 5/2. J = 5/2 is ruled out by the angular distribution of the γ-rays. At the Ep = 1.17 MeV resonance [19F*(9.10)], the angular distribution of the γ-rays to the 5/2+ state at 0.197 MeV indicate Jπ = 7/2+ [9/2+ not completely excluded] for 19F*(9.10). J = 5/2 or 9/2 is suggested for 19F*(2.78). The γ-decay of the resonances at Ep = 1.77 and 1.93 MeV is very complex (AL65I). For branching ratios and Γγ see Table 19.7 (in PDF or PS) (NE62, AL65I, WO71E, WO72C). See also (CL73C; astrophys. considerations).
Yield measurements have been reported from Ep = 2.5 to 13.5 MeV: the measurements by (BE69U; n; 2.6 --> 3.3 MeV), (BA73K; σt; 2.6 --> 3.9 MeV), (DI69C; n1, γ, n2γ, n3γ) and n; 3.0 --> 7.0 MeV), (BA64K; σt; 3.5 --> 10 MeV) and (FR73H; n0 --> n4; 4.6 --> 6.6 MeV) lead to the resonances shown in Table 19.16 (in PDF or PS). See also 18F.
Scattering studies have been carried out for Ep = 0.6 to 16.3 MeV [see (72AJ02)] and at Ep = 3.4 to 6.2 MeV (OR73; p0, R-matrix analysis) and with polarized protons for Ep = 3.8 to 6.1 MeV (AL75F; p0, p1) and at 6.0 to 16.6 MeV (MU76A; p0; prelim.). Observed resonances are displayed in Table 19.17 (in PDF or PS). Pronounced resonance structure continues to Ep = 12 MeV (MU76A). Polarization measurements are also reported at Ep = 24.5 MeV (ES74). See also (PL74B, LO74F, PL76C, KU77G, PL77A) and (BA75A, ES76; theor.).
Polarized protons at Ep = 24.4 MeV have been used to study both reactions (a) and (b) (PI73D): see 16O and 17O in (77AJ02). Total cross sections for several deuteron and triton groups are reported at Ep = 20.0, 24.4, 29.8, 37.5 and 43.6 MeV by (PI74B). See also (DA76K, PL76C).
Yield measurements have been studied for Ep = 0.50 to 14 MeV: see (72AJ02). See also (WO72C). Observed resonances are displayed in Table 19.17 (in PDF or PS). The (astrophysical) hydrogen burning of 18O proceeds predominantly (>/= 99 %) through the reaction 18O(p, α)15N (RO74I). See also (FO75B, CL77C). Total cross section measurements are reported by (PI74B; 20.6, 26.1, 34.2, 42.2 MeV; α0, α1+2, α3). See also (LO74F), (TU73; applied) and (NI74; theor).
Angular distributions of neutron groups corresponding to 19F states with Ex < 8.2 MeV have been measured at Ed = 3 and 4 MeV: see Table 19.18 (in PDF or PS) (GU68G, TA72G). Gamma-ray measurements are reported in Tables 19.18 (in PDF or PS) (Ex), 19.7 (in PDF or PS) (branching ratios) and 19.10 (in PDF or PS) (τm) (LE72K, LE75M). For slow neutron threshold measurements see Table 19.15 (in PDF or PS) in (72AJ02). At Ed ~ 5.1 MeV, reaction (b) appears to involve 19F states at Ex ~ 8 to 10 MeV (BO70B).
Angular distributions of the deuterons corresponding to many states of 19F have been analyzed by DWBA: the results are shown in Table 19.18 (in PDF or PS) (SC70L; E(3He) = 16 MeV). See also (GR70B). The spectroscopic factors obtained by DWBA for 19F*(7.54, 8.80), the T = 3/2, Jπ = 5/2+ and 1/2+ analogs of 19O*(0, 1.47) are in good agreement with those obtained for the 19O states in the 18O(d, p)19O reaction (FO71L). See also (SC70L) and (EN72B, VI73; theor).
The decay is primarily by allowed transitions to 19F*(0.197, 1.55), Jπ = 5/2+ and 3/2+, respectively. Very weak branches are also observed to 19F*(0.11, 4.39), Jπ = 1/2- and 7/2+, respectively: see Table 19.19 (in PDF or PS). The half-life is 26.91 ± 0.08 sec: see reaction 1 in 19O. The character of the allowed decay to the 5/2+ and 3/2+ states, and the forbiddeness of the decay to the ground state of 19F are consistent with Jπ = 5/2+ for the ground state of 19O, and then with (7/2+) for 19F*(4.39): see (OL66). Gamma-ray branching ratios are displayed in Table 19.7 (in PDF or PS) (OL66, CO70N). See also (CO70T). A preliminary study of the allowed decay to 19F*(0.197) has been carried out to measure the F/GT mixing ratio (PE76).
The energy of the first excited state is 109.894 ± 0.005 keV: its width is (5.1 ± 0.7) x 10-7 eV (SE62F, BO62J). 19F*(1.46, 3.91, 7.66) are also excited: for τm of the first of these states see Table 19.10 (in PDF or PS) (BO64L); Ex = 3906 ± 6 and 7663 ± 4 keV for the latter (SH72D) [see also for Γγ]. The scattering cross section is relatively small and structureless for Eγ = 14 to 30 MeV (LO67C).
The (γ, n0) and (γ, n1) cross section, derived from bremsstrahlung show peaks at Eγ = 12.10 ± 0.04 [0.20 ± 0.05], 12.38 ± 0.04 [0.17 ± 0.05], 13.82 ± 0.05 [0.25 ± 0.10] and 16.24 ± 0.05 [0.30 ± 0.15] MeV [Γ in brackets]. It is suggested that the two lower states have Jπ = 1/2- and the two upper states have Jπ = 3/2-. The integrated cross section in the interval Eγ = 11.9 --> 17.9 is 14.4 ± 2.2 MeV · mb (SH76G). The cross section for (γ, Tn) has been measured for Eγ = 10.5 to 28 MeV: it shows a clear resonance at Eγ ~ 12 MeV and unresolved structures at higher energies. The integrated cross section to 29 MeV is 108 ± 7 MeV · mb (VE74D). See also (BE76W). Additional structures have been reported in earlier work [see (72AJ02)] and by (BA71SS, VA72K, CA73J). See also (TH72M, NO75G, WO75A), (BU74I, AB75D, BR75H, DA77E) and 18F.
The integrated (γ, 2n) cross section to 60 MeV is given as 9.1 ± 0.9 MeV · mb by (AN76) who also report a number of structures. The cross section for reactions (a) and (b) for Eγ = 22 to 28 MeV shows no structure (VE74D). See also (VA72K, CA73J, MA76K) and (BE76W).
The integrated cross sections for the p0 and p1 processes at 90° for Eγ = 13.3 --> 25.4 and 15.2 --> 26.0 MeV are, respectively, 1.80 ± 0.27 and 0.50 ± 0.45 MeV · mb/sr. The (γ, p0) cross section at 90° shows broad structures at Eγ = 15.0, 17.0 and 23 MeV (TS75). Peaks have also been reported corresponding to 19F*(10.4, 11.4, 11.9, (12.8), 13.6, 15.4, 16.5, (18.1)) (FO60E). See also (TH72M, TH76) and 18O.
This reaction has been studied for the transition to 16Og.s. for Eγ = 18 to 23 MeV. Two peaks are observed at Eγ = 18.8 and 20.1 MeV: the angular distribution of t0 indicates Jπ = 1/2- or 3/2-, T = 1/2. The triton GDR contributes ~ 1 % of the total GDR (SK74A).
The rms radius of 19F = 2.885 ± 0.015 fm (HA73H). Elastic and inelastic form factors have been measured for a number of 19F states: see (HA73H, OY75). Table 19.20 (in PDF or PS) shows the extracted radiative ground-state transition strengths (OY75, HA73H, WI75). The deformation parameters for the ground state Kπ = 1/2+ rotational band are β2 = 0.43 ± 0.02, β4 = 0.12 ± 0.02 (OY75).
Angular distributions of neutron groups have been reported for En = 2.6 and 14.1 and 14.2 MeV: see (72AJ02). Ex for the first six excited states of 19F, derived from γ-ray measurements, are 109.8 ± 0.2, 197.2 ± 0.2, 1345.4 ± 0.3, 1456.9 ± 1.1, 1554.0 ± 0.3 and 2775.1 ± 3.5 keV (SP68) [see (72AJ02) for other, unpublished, measurements]. Eγ = 110.1 ± 0.2 and 197.2 ± 0.3 keV (OP72), 1236.9 ± 0.6 and 1358.6 ± 0.7 keV (PR76B). Gamma decay of states with Ex < 5.4 MeV is reported by (NI72B). See also (LE73L, RO74D) and 20F.
Table 19.21 (in PDF or PS) displays energy levels of 19F derived from this reaction (GU68G, PO69, BH78A). Angular distributions of various proton groups have been measured from Ep = 4.3 to 17.5 MeV: see (72AJ02) and at 30 MeV (DE74Q, DE73L; see Table 19.21 (in PDF or PS)). The ground state rotational band is characterized by β2 = 0.44 ± 0.04, β4 = 0.14 ± 0.04 (DE73L, DE74Q). See Tables 19.7 (in PDF or PS) and 19.10 (in PDF or PS) for branching ratio and τm measurements. See also (SO72B, HE73H). For reaction (b) see (HI72G). See also (LE73L), (RU73; applied work), (PE73A, DE77G; theor.) and (72AJ02).
Angular distributions of elastically scattered deuterons have been measured for Ed = 2.0 to 15 MeV: see (72AJ02). In addition, angular distributions have been measured at Ed = 15 MeV for d1 --> d5 (DE70A) and B(Eλ) have been derived. See also (BE71HH). For polarization measurements see (BO72E, AN77E) and (EN78). See also (SE72; theor.).
Elastic angular distributions have been measured at Et = 2 and 7.2 MeV: see (72AJ02).
Elastic angular distributions have been measured for E(3He) = 4.0 to 29 MeV [see (72AJ02)] and at 16 MeV (VE74C; also to 19F*(0.20)). The triton reduced width for 19F, derived from a study of reaction (b) at E(3He) = 30.0 and 40.7 MeV, is 0.021 (OH72A). See also (YO72).
Angular distributions of elastically scattered α-particles have been measured at Eα = 19.9 to 23.3 MeV and at 38 MeV [see (72AJ02)]. Many inelastic groups have also been studied: see Table 19.22 (in PDF or PS) (KR73C). The ground state Kπ = 1/2+ rotational band is characterized by β2 = 0.35 and β4 = 0.12 (KR73C).
The energy of the γ-ray from 1.35 --> 0.11 transition is 1235.8 ± 0.2 keV. Using Ex = 109.894 ± 0.005 keV for the energy of the first excited state, Ex for 19F* is then 1345.7 ± 0.2 keV (WA67F). At Eα = 12.7 MeV, a state at 4.648 MeV is populated which is then observed to γ-decay to the 9/2+ state at 2.78 MeV. The angular distribution of the cascade γ-rays and the lifetime of 19F*(4.65), set Jπ = 13/2+ for 19F*(4.65) (JA69N). See also (BE71AA, BA72W). For reactions (b) and (c) at Eα = 60.2 MeV, see (CH72G).
Elastic angular distributions have been studied at E(16O) = 21.4 and 25.8 MeV (MO75N) and at E(19F) = 27, 30, 33 and 36 MeV (reaction (a)) [also to 19F*(1.46) at the two higher energies] and at 27, 30 and 33 MeV (reaction (b)) (GA73J). See also (VO73L, VO75D) and (OH76, SC77E; theor.).
At Ed = 52 MeV, 3He groups are observed, and angular distributions are reported, corresponding to states at Ex = 0.15 ± 0.04, 1.51 ± 0.03, 2.83 ± 0.04 (l = 4), 3.99 ± 0.07, 4.56 ± 0.02 (l = 1), 5.44 ± 0.05, 5.69 ± 0.07 (l = 1), 6.10 ± 0.03, 6.78 ± 0.02 (l = 1) and 10.42 ± 0.15 MeV (KA70G). See also (IN71C) and (EN72B, EL73B, SA73W; theor.).
Observed α-groups are displayed in Table 19.23 (in PDF or PS) where spectroscopic factors are compared with those of analog states in n19Ne (SI61, GA74C). For τm of 19F*(4.65) see Table 19.10 (in PDF or PS) (BH69A).
At Ep = 45 MeV, 3He groups are observed to some T = 1/2 states in 19F and to the 3/2+, T = 3/2 analog of 19O*(0.095): Ex = 7.660 ± 0.035 MeV (HA69H). At Ep = 40 MeV comparison of the ground-state angular distributions in this reaction and in the mirror (p, t) reaction [see reaction 15 in 19Ne] shows a suppression of the S = 1, T = 0 component of the (p, 3He) cross section: this is observed to occur for all TZ = 1/2 nuclei with A < 40 (NA76N).
The population of the first three states of 19F has been observed (MI52).