(See Energy Level Diagrams for 19F)
Shell model: (WI57H, BR59M, GO60L, TA60L, BA61N, BH62, HO62A, HA63A, BR64Z, DR64A, HA64S, IN64, BA65CC, YU65D, BA66Z, IN66, LA66L, RI66G, AR67B, BO67K, EN67, FL67D, GU67, GU67A, HA67A, IN67, AR68C, CO68L, EI68A, EL68, GU68A, GU68C, GU68D, HA68H, HA68M, HA68P, HA68T, HI68F, MO68A, WO68A, BE69G, GU69B, KU69G, MA69N, SE69B, TA69G, EL70A, GI70D, MC70J, OL70, AR71L, AR71O, GU71L, LE71O, WI71B, LE72).
† 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) are reported in pion-induced reactions.
Astrophysical questions: (BA70A).
Other theoretical topics: (IN64, KA64D, AM65, FA65A, GO65E, OK65A, RO65E, WO65B, YO65B, DA66D, DO66E, GI66A, SU66F, FL67D, GU67, NE67B, OS67, DW68, GA68E, GU68A, GU68B, GU68D, MO68A, PA68K, LO69C, MA69N, LE71I, LE72).
Ground state: μ = +2.628383 ± 0.000005 nm (BA64KK: see also (FU69E)). See (BE63T, CA63B, BO64S, BR64Z, DR64A, LI64H, ST64, HU65C, RI66F, CO67R, GU67A, PA67T, SH67N, EL68, HI68F, LE68G, HI69, PE69H, WU69, LE70, AR71L, GU71L, WI71B, LE72).
The yield of 18F (reaction (a)) has been determined for E(7Li) = 2.5 to 3.5 MeV (NO61). The yields of the α0, α1+2 and α3 groups (reaction (e)) have been measured for E(7Li) = 3.2 to 4.0 MeV by (HO62B), while (CA70B) report that the cross sections for reactions (b), (c), (d) and (e) vary strongly over the range E(7Li) = 4 to 14 MeV but with little, if any, cross-correlation. A coherence energy of about 0.4 MeV is reported (CA70B). See also (MO67O), 18O, 16O and 17O in (71AJ02) and 15N in (70AJ04).
At E(6Li) = 5.3, 5.6 and 6.0 MeV angular distributions have been obtained for the protons corresponding to 19F*(2.78) (RI68M).
Thirty resonances in the yield of capture γ-rays are observed below Eα = 5.1 MeV: the parameters for these are displayed in Table 19.7 (in PDF or PS) (PR57A, AI69, AI69B, AI70, DI71A, DI71E, RO71P). Branching ratios are shown in Table 19.9 (in PDF or PS) (AI69, AI69B, AI70, DI71E, RO71P), and lifetime measurements are listed in Table 19.10 (in PDF or PS) (TO68E, TO68J, RO71P). See also (TO67F).
Correlation experiments on the transitions 5.47 --> 2.78 --> 0.197 fix J = 9/2 for 19F*(2.78) and J = 7/2 and 1/2 for 19F*(5.46, 5.34) (TO68E, TO68J). See, however, reaction 23. Measurements of γ-ray angular distributions and radiative widths lead to the Jπ values listed in Table 19.7 (in PDF or PS) (AI69, AI69B, AI70, DI71E) as well as to J = 7/2 for 19F*(4.39) (AI69B). The capture yield for Eα = 4.2 to 4.7 MeV is dominated by two resonances corresponding to the first two T = 3/2 states [19F*(7.54, 7.66)] with Jπ = 5/2+ and 3/2+ analogous to 19O*(0, 0.097) (AI69B). The resonance at Eα = 4.97 MeV corresponds to a J = 11/2 state at 7.935 MeV: it appears to be the 11/2+ member of a K = 3/2+ rotational band based on the 3/2+ state at Ex = 3.91 MeV (DI71E). 19F*(6.09) has a very definite non-isotropic decay and hence J = 1/2 is ruled out: Jπ is probably 3/2-. 19F*(5.95, 6.08, 6.17) are tentatively assigned Jπ = 1/2(-), (7/2+), 7/2(-) (D. Rogers, private communication) [see, however, Table 19.8 (in PDF or PS)].
This reaction has been studied at E(7Li) = 15 and 20 MeV. The spectra have been compared with those from the 16O(7Li, t)20Ne reaction. The similarities suggest that 19F*(0.11) [Jπ = 1/2-] arise from the coupling of a p1/2 hole with 20Ne(0); that 19F(1.46, 1.35) [Jπ = 3/2- and 5/2-] and 19F*(4.00, 4.04) [Jπ = 7/2- and 9/2-] correspond respectively to the 2+ and 4+ members of the 20Ne ground state band. The Jπ = 11/2- and 13/2- states in 19F based on the 6+ state of 20Ne at 8.79 MeV are reported at 8.25 and 8.91 MeV (± 50 keV). [See, however, reaction 7.] Angular distributions for 19F*(0.11, 1.35, 1.46, 4.00 + 4.04, 5.43, 8.25, 8.91) have been measured (MI70D). See also (AR71O; theor.).
The excitation function for neutrons (reaction (a)) has been measured for Et = 0.3 to 2.2 MeV (LO61E) and 0.7 to 2.1 MeV by (JA55). See also (CH67O). Resonances in the yields of p0, p1, α0 and α1+2 (reactions (b) and (d)) 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]. Additional states from the α0 yield are reported by (GE65). See also (JO59F, KO67N). Two pronounced peaks are observed in the elastic scattering (reaction (c)) at Et = 2.6 and 3.2 MeV [19F*(13.9, 14.4)] (ET68: Et = 1.4 to 3.5 MeV). The elastic scattering has also been studied for Et = 9 to 13 MeV (GL65B).
At Eα = 26.7 and 33.1 MeV, angular distributions have been measured for the p0-->2, p3-->5 and p6 groups (YA61).
This reaction (and its mirror reaction 16O(6Li, t)19Ne: see 19Ne) have been studied at E(6Li) = 24 MeV. The states most strongly excited by both reactions correspond to members of the Kπ = 1/2+ (g.s.) rotational band, with the exception of the 7/2+ state. It is suggested that it is the second 7/2+ state (at Ex = 5.46 MeV) which is a member of the g.s. rotational band although it is more weakly populated in both reactions than predicted [see, however, Table 19.11 (in PDF or PS), footnote d]. Up to Jπ = 9/2+, cross sections are observed to increase with increasing spin. Members of a Kπ = 1/2- rotational band based primarily on a configuration of four s-d shell particles and a p-shell hole are also populated in these reactions: again cross sections increase with increasing spin. Table 19.11 (in PDF or PS) presents the data on the 16O(6Li, 3He)19F and 16O(6Li, t)19Ne reactions (BI71D). See also (GA71G).
At E(7Li) = 20 MeV, α-particles to the 19F states with Ex < 4.5 MeV have been observed (BI69). At E(7Li) = 30.3 MeV, the excitation of 19F*(7.25, 10.2, 12.1, 13.4), in addition to lower states, is reported by (GL69B). See also (RO69J; theor.).
Resonances for capture radiation observed for Ep = 0.3 to 3.0 MeV are displayed in Table 19.12 (in PDF or PS) (BU59H, NE62, HU63C, AL65I, DU69F, WO69E). 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 19.9 (in PDF or PS) (NE62, AL65I, WO69E). See also (SK69A) and (LA59A).
Recent yield measurements are reported for 2.5 to 3.0 MeV (PR67B), 2.6 to 3.0 MeV (BL60; σt), 2.6 to 3.3 MeV (BE69U: rel. total yield, high resolution), 3.0 to 7.0 MeV (DI69C; n1γ, n2γ, n3γ and n), 3.5 to 10 MeV (BA64K; σt), 3.6 to 4.0 MeV (BE68S; n1γ, n2γ, n3γ) and 6.9 to 13.5 MeV (BL65E, AN69A; σt for n0, n2 (unresolved), n5, n6, n7, n8 (unresolved); not all groups over the entire range). See also (BR59K). Observed resonances are displayed in Table 19.13 (in PDF or PS) (MA56E, BA64K, PR67B, BE68S, BE69U, DI69C).
(AN69A) find that the rather large cross section for the reaction to 18F(0) [ΔT = 1, ΔJ = 1] over the range Ep = 6.9 to 13.5 MeV and the cross section for the reaction to 18F*(3.06) [ΔT = 0, ΔJ = 2] indicate the operation of a spin-flip mechanism in the effective two-body force, and a sizable value for the quadrupole term in the multipole expansion of that force.
For a summary of threshold measurements and angular distribution studies, see 18F.
Scattering studies have been carried out at Ep = 0.60 to 1.45 MeV (YA62, YA62A; p0), 0.79 to 3.55 MeV (CA61A; p0 (and p1γ at higher energies)), 1.39 to 3.20 MeV (SE69B; p0, high resolution), 1.7 to 3.5 MeV (SO62, ST64L; p0), 2.5 to 3.0 MeV (PR67B; p1γ), 3.0 to 7.0 MeV (DI69C; p1γ), 3.2 to 5.4 MeV (BE68S, BE69N; p1γ), and 7.9 to 16.3 MeV (ST64F, ST66A; p0, p1). For a spallation study, see (EP69B).
Observed resonances are shown in Table 19.14 (in PDF or PS) (CA61A, SO62, YA62, YA62A, ST64F, ST64L, ST66A, PR67B, DI69C, SE69B). All the positive-parity states with large proton width observed experimentally up to Ep = 3.2 MeV can be associated with a doorway state. Both the experimental data and shell-model calculations indicate that the 5/2+ resonance at Ep = 2.768 MeV [19F*(10.613)] may be identified as the analog of 19O*(3.16) although isospin impurities are present in 19F*(10.613) (SE69B).
Yield measurements are reported for Ep = 0.50 to 0.75 MeV (SK71A; α0), 0.73 to 1.05 MeV (KA63D; α0), 0.79 to 3.55 MeV (CA61A; α0 (and α1+2γ at the higher energies)), 0.9 to 2.1 MeV (AM63, AM64C; α0), 1 to 3 MeV (CL60; α0), 1.1 to 2.6 MeV (KA64F; α0), 1.39 to 3.20 MeV (SE69B; α0, high resolution), 2.2 to 6 MeV (GO63E; α0), 2.5 to 3.0 MeV (PR67B; α1+2γ), 3.0 to 7.0 MeV (DI69C; α1+2γ), 3.2 to 5.5 MeV (BE69N; α1+2γ, α3γ), and 7.9 to 14 MeV (ST64F; α0). See also (BL60, AM61, EC64A, SC64). Observed resonances are displayed in Table 19.14 (in PDF or PS) (CL60, AM61, CA61A, AM63, GO63E, AM64C, KA64F, ST64F, PR67B, DI69C, SE69B). See also 15N in (70AJ04).
Thresholds for slow neutron production and for γ-rays are shown in Table 19.15 (in PDF or PS) (HA56, BU58B, BU59). Angular distributions have been measured at Ed = 3 MeV (and analyzed by DWBA) to many of the states with Ex < / = 7.4 MeV: the closely spaced states were not resolved; however, lp = 4 for the neutrons corresponding to 19F*(2.78), and therefore Jπ = 9/2+, 7/2+. In addition, neutron groups corresponding to 19F states at 5.11 [7/2-, 5/2-], 5.49 [u], 5.62, 5.94, 6.09 [u], 6.26 [u] [1/2+], 6.53 [u] [5/2+, 3/2+, 1/2+], 6.80 [u] [3/2-, 1/2-], 6.93 [u], 7.26 and 7.40 MeV (± 0.03 MeV) are reported [(u = unresolved states)] [Jπ of dominant state(s)] (GU68G). See also (BE63, MO64K, HE69). The lifetime of 19F*(1.55) is < 1 psec (NI69A); see, however, Table 19.10 (in PDF or PS).
At Ed = 5.0 and 5.2 MeV, reaction (b) appears to involve 19F states at ~ 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 19.16 (in PDF or PS) (SC70L: E(3He) = 16 MeV; (LE68M, GR70B): E(3He) = 11 MeV). See also (ER65).
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). See also (LA66L, RO66E, RO67B, WA70B; theor.).
The decay is primarily by allowed transitions to 19F*(0.197, 1.55), Jπ = 5/2+, 3/2+, with very weak branches also observed to 19F*(0.11), Jπ = 1/2- (log f1t = 10.16) and 19F*(4.39), Jπ = 7/2+ (log ft = 3.60): see Table 19.17 (in PDF or PS) (AL59F, JO59G, OL66, CO70N). 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 forbiddenness 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 19.9 (in PDF or PS) (OL66, CO70N). See also (OK61) and (MC70S; theor.).
The energy of the first excited state is 109.894 ± 0.005 keV; its width is (5.1 ± 0.7) x 10-7 eV (BO62J, SE62F). Lifetimes of 19F*(0.11, 1.46) are shown in Table 19.10 (in PDF or PS) (SE62F, BO64L). The scattering cross section is relatively small and structureless in the range Eγ = 14 to 30 MeV (LO67C). See also (BO60F, RE60, BO62).
Maxima are reported at (10.6), 12.4, 14.0, 16.1, 17.2 and 19.3 MeV in the (γ, n) cross section (KI60B). Three ground state photoneutron groups are reported, corresponding to 19F*(12.10, 12.38, 16.24) ((SH71), and N.K. Sherman, private communication). These states are thought to have Jπ = 1/2- or 3/2-; T = 1/2. See also (GE60, BA67RR) and (59AJ76). At Eγ = 20.5 MeV, the (γ, n) cross section is 3.30 ± 0.41 b (DE61A, DE62G).
The nuclear absorption cross section shows a peak at Eγ = 20.09 ± 0.05 MeV with an integrated cross section of 3.5 MeV · mb (TE64C) and a very broad giant resonance extending beyond 30 MeV and with considerable strength also below 20 MeV (BE69J). These results disagree with those of (DO66B, NI67D) which show considerable structure. See also (SA60E, DE65N, JO70C, DI71F, FR71F) and (SP58A, FU59, AN71D; theor.).
At Ee = 41.5 MeV (180°) the elastic scattering cross section has been measured by (GO63A) and the excitation of a 3/2+ state of 19F at Ex = 7.7 MeV [T = 3/2: see Table 19.9 (in PDF or PS)] is reported by (BA63F). The excitation of 19F*(0.197, 1.35, 1.55) has been observed by (HA70B): Γγ(1.35 --> 0) = (8.1 ± 1.7) x 10-10 eV (E3) and Γγ(1.55 --> 0) = (1.76 ± 0.15) x 10-4 eV (E2) (WA70C). See also (WA70O) and (PR65C, GO66M; theor.).
Reaction (b), studied at Ee = 18, 24.5 and 30 MeV, shows resonances (assuming ground state transitions) at Ex = 11.42, 11.90, 12.74, 15.70 and 18.7 MeV in 19F (DO62B).
Angular distributions have been reported at En = 2.56 MeV (DA60C; γ0.110, γ0.197), 14.1 MeV (CL70A; n0+1+2, n3+4+5) and 14.2 MeV (BO66N; n0+1+2, n3+4+5, n6 and n to 19F*(4.7, 5.4)). Gamma-ray energy measurements are reported by (SP68) and (WH69A): see Table 19.18 (in PDF or PS). Branching ratios are listed in Table 19.9 (in PDF or PS) (SP68). See also (BI59B, KO59A, AN61, RO61, VE66B, NI71A) and (DO63B; theor.).
Table 19.19 (in PDF or PS) displays energy levels of 19F derived from measurements of inelastically scattered protons and γ-rays (SQ56, VA61H, VA62C, GU68G, PO69). See also (59AJ76). Angular distributions of various proton groups have been measured at Ep = 4.26, 5.96 and 6.87 MeV (TH67J; p0, p1, p2), 6.6 MeV (VA61H, VA62C; p2 --> p6), 6.78 to 7.41 MeV (KO61I; p3+4+5, p6), 13.9 MeV (LU66A; p0, p2, p5) and 17.5 MeV (CR68; p0, p2 --> p7, p8+9, p10, p11 and p to 19F*(5.43)). (TH67J) report that the scattering below Ep = 7 MeV is adequately described as scattering from an axially symmetric quadrupole-deformed potential, and that only positive parity states are strongly excited. Branching ratios for observed transitions are shown in Table 19.9 (in PDF or PS) and lifetimes in Table 19.10 (in PDF or PS) (PO69, LA70I). (PO69) find a pronounced inhibition of the four E1 transitions involved in the decay of 19F*(1.35, 1.46, 1.55) in accord with the predictions of (HA64S). Partial widths have been determined by (PO69). (LA70I) have studied the decay of 19F*(1.46): from the angular distribution of the γ-rays, measurement of their linear polarization and from τm, |M|2(E2) = 14+26-8, |M|2(M1) = 0.10 ± 0.03 W.u. The mixing ratios in the γ-decay of 19F*(1.46) are -0.1 < δM2/E1 < 0.0 for 1.46 --> 0.20, 0.30 < δE2/M1 < 0.38 for 1.46 --> 0.11 and |δM2/E1| < 0.06 for 1.46 --> 0. These results indicate that 19F*(1.46) cannot be explained as a p1/2 proton hole coupled to the pure ground state rotational band (HA71P). See also (PR63A) for other linear polarization data and (KL65, RO66G, TH66, HI67, HI68) for other angular correlation work. See also (NE64E).
Additional parameters measured for the 5/2+ state at 0.197 MeV are : Q = 0.11 ± 0.02 b (SU64A: see also (SU58B)), Q = -(0.10 ± 0.02) b (RI68P); μ = 3.69 ± 0.04 nm (FR61C): [see also (BO64Q)]; τm=128 ± 2 nsec (KL68C), 129.9 ± 2.3 nsec (BE67J): see also Table 19.10 (in PDF or PS) for additional measurements of τm for this and for other 19F states (GA63B, VA63, BO65T, ME69I, PO69). See also (PR63A).
Angular distributions of elastically scattered deuterons have been measured at Ed = 2.0 and 2.2 MeV (BI68B), 2.6 to 4.0 MeV (ZA69C) and at 15 MeV (DI65A, DE66A, DE70A). In addition, angular distributions have been measured at Ed = 15 MeV for five groups of inelastically scattered deuterons (DE70A; d1 --> d5). Analysis by DWBA leads to B(E2)(downarrow) = 9 ± 3 W.u. for the 0.197 --> 0 transition and 10 ± 3 W.u. for the 1.56 --> 0 transition, and to B(E3)(downarrow) = 1.4 ± 0.6 W.u. for the 1.35 --> 0 transition (DE70A). See also (VE69D, VE70B; theor.).
Angular distributions of elastically scattered 3He particles are reported at E(3He) = 4.0, 6.0 and 8.0 MeV (MA66G), at 9 MeV (SI65D), at 11.0 MeV (SC70M) and at 29 MeV (CA61H, GA62G). See also (BR59C) and (HO68F; theor.). (CO67Q) also report the excitation of 19F*(0.11).
Angular distributions of elastically scattered α-particles have been measured at Eα = 19.9 to 23.3 MeV (AG68, AG70B, FE70), and at 38 MeV (AG60). The energy of the γ-ray from the 1.35 --> 0.11 transition is 1235.8 ± 0.2 keV. Using Ex = 109.893 ± 0.004 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). For a listing of the τm for this state and 19F*(1.35, 2.78) see Table 19.10 (in PDF or PS) (PA68L, RO68E, JA69N, JO69). See also (CA58G, BR59C, FR63F, FR64A, BL70F). For reaction (b) see (LA63).
B(E1)(uparrow), from the Coulomb excitation of 19F*(0.110) = 6.3 x 10-30 e2 · cm2; B(E2)(uparrow) for 19F*(0.197) = 5 x 10-51 e2 · cm4. Reported mean lifetimes for these states are displayed in Table 19.10 (in PDF or PS) (ST60, RI62A).
† This reaction should be comletely deleted. Please refer to the Errata for this evaluation found directly after the list of references in (74AJ01).
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 (DU71D; theor.).
At Et = 2.6 MeV, alpha groups are observed to states with 2.7 < Ex < 6.6 MeV: see Table 19.20 (in PDF or PS) (SI61). The lifetime, τm, of 19F*(4.65), Jπ = 13/2+ [Kπ = 1/2+ rotational band] is 2.3 ± 0.5 psec (see also Table 19.10 (in PDF or PS)): the E2 strength of the transition to 19F*(2.78) is 5.0 ± 1.1 W.u. (BH69A).
Alpha-particle groups have been observed to 19F* = 0, 113 ± 8 and 192 ± 12 keV (MI52).