(See Energy Level Diagrams for 19F)
GENERAL: See 3 [Electromagnetic Transitions in A = 18-19] (in PDF or PS), 19.8 [General Table] (in PDF or PS), 19.9 [Table of Energy Levels] (in PDF or PS) and 19.10 [Radiative decays in 19Ne] (in PDF or PS).
μg.s. = +2.628866 (8) nm (1978LEZA)
μ0.197 = +3.607 (8) nm (1978LEZA)
Q0.197 = -0.12 ± 0.02 b (1978LEZA)
Mass distribution from the sequential decay of the compound nuclei formed from 10B + 9Be and 10B + 10B at Elab/A = 11 MeV were measured by (1993SZ02). It was determined that the hot composite systems as light as 19F and 20Ne can behave like liquid droplets with no remnant shell effects.
Vector analyzing power measurements for the elastic scattering have been reported at E(7Li) = 21.1 MeV (1984MO06). Fusion cross sections have been measured by (1982DE30). For other channels in the interaction of 12C + 7Li see (1978AJ03, 1983AJ01, 1987AJ02) for earlier work. More recently, neutron yield spectra for 40 MeV 7Li on 12C were measured by (1987SC11). The 12C(7Li, 7Be)12B reaction was studied at projectile energies of 14, 21, and 26 MeV/A by (1990NA24). Measurements and analysis of elastic breakup of 54 MeV 7Li on 12C are discussed in (1992GA03). See also the coupled-channels investigation of the effects of projectile breakup and target excitations in the scattering of polarized 7Li by 12C at Elab = 21 MeV by (1988SA10). An evaluation of hypernuclear production cross-section by projectile fragmentation in 7Li + 12C at 3.0 GeV/A is presented in (1989BA92).
Uncorrelated structures have been observed in the excitation functions for reactions (a) and (b). Angular distributions have been measured for reaction (d) at E(6Li) = 28 MeV (1988SM01). See also 18O in the present review and see 13C and 15N in (1991AJ01). Fusion cross sections have also been measured.
Cross sections were measured for E(10B) = 17.16 - 31.32 MeV at θlab = 14.3° - 41.6° (1988MA07). Several excited states in 19F were studied. A fluctuation and resonance analysis was carried out.
Resonances in the yield of γ-rays are observed below Eα = 8.1 MeV (Ex = 10.4 MeV): the parameters for these are displayed in 19.13 (in PDF or PS). Branching ratios are shown in 19.10 (in PDF or PS) and τm measurements in 19.11 (in PDF or PS). The Jπ values shown in 19.13 (in PDF or PS) are based on correlation and angular distribution measurements and on branching ratio determinations. In work reported since the previous review (1987AJ02), measurements were made by (1987MA31) for the resonance at Ex = 4.550 or 4.556 MeV. Widths of nine states between Ex = 8.288 and 10.411 MeV were measured by (1988HE03). These new results are included in 19.13 (in PDF or PS). See also the study by (1989GA06) of the T = 3/2 levels at Ex = 7.538, 7.660, 9.927 MeV.
The discussion in (1987AJ02) notes that the 19F levels involved in cascade decay are at Ex = 3999.6 ± 1.2, 4031.9 ± 0.4, 4377 ± 1 and 4548 ± 2 keV. 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-]) and possibly 19F*(8.29)[13/2-] [Jπ in brackets]. See, however, reaction 11. See (1972AJ02) for a discussion of the evidence for other assignments of Jπ and Kπ. 19F*(10.41) is likely to be the second 13/2+ (2s, 1d)3 state in 19F. For references see (1983AJ01). See also the comment (1985DI16) and reply (1985MO20) on negative-parity alpha cluster states in 19F.
In work reported since the previous review (1987AJ02), nine states in 19F between Ex = 8.288 and 10.411 MeV were studied by (1988HE03). Alpha widths were measured. T = 3/2 levels at Ex = 7.538, 7.660 and 9.927 MeV were studied by (1989GA06). These results are included in 19.14 (in PDF or PS).
In related work, optical potentials for 15N + α were extracted for Eα = 0 - 150 MeV (1993AB02) and alpha particle strength functions were obtained from resonance parameters by (1988LE05). See also the tables of thermonuclear reaction rates (1985CA41, 1988CA26). Cross sections for α scattering on light nuclei for ion beam analysis are presented in (1991LE33).
At E(6Li) = 22 MeV angular distributions are reported to 19F*(0.11, 1.35[u], 1.46, 4.0[u], 8.29[u]). Comparisons are made with the results from the 16O(6Li, d)20Ne reaction, in an attempt to determine whether 19F*(8.95) is the 11/2- member of the Kπ = 1/2- band, of which 19F*(8.29) is the 13/2- member (1984MO08, 1985DI16, 1985MO20). Configuration mixing appears to be involved in the 11/2- states [19F*(7.17, 8.95, 9.87)] and in the 7/2- states [19F*(4.00, 5.42)] to which they decay (1987FO03).
Groups are reported at E(13C) = 105 MeV leading to states which are generally unresolved; Jπ assignments are suggested: see (1983AJ01).
For reaction (a) see (1978AJ03). The excitation function for reaction (b) has been measured for Et = 0.3 to 3.7 MeV: there is evidence for a maximum at Et = 2.5 MeV. For resonances in the yields of p0, p1, α0, α1+2 see (1978AJ03). The elastic yield [reaction (d)] shows a large number of resonances; their parameters are displayed in 19.15 (in PDF or PS). See also (1987AJ02).
More recently, double differential neutron yields for reaction (b) at Ex = 20 MeV were reported in (1993DR03, 1993DR04). An analysis of reaction (d) by a quasi-resonating-group method is described in (1987ZH13). A study of the isospin dependence of the A = 3 isospin potential using reaction (d) for Ex = 33 MeV is discussed in (1987EN06). See also (1986AI04).
Angular distributions have been measured at Eα = 20.1 to 40 MeV: see (1978AJ03, 1983AJ01, 1987AJ02). States observed in this reaction are displayed in 19.12 (in PDF or PS) of (1978AJ03). See also the shell-model study of nuclear form factors in (1987LE15). An application of a perturbed angular correlation measurement to the study of high temperature superconducting oxides is described in (1990KOZG).
This reaction (and its mirror reaction 16O(6Li, t)19Ne [see 19Ne, reaction 5]) have been studied at E(6Li) = 24 and 46 MeV: see (1978AJ03, 1983AJ01). Members of the Kπ = 1/2+ and 1/2- rotational bands have been identified: see 19.16 (in PDF or PS). Other groups, mainly to unresolved states, have also been observed. A recent measurement to determine the structure of 19F between Ex = 5.5 - 7.5 MeV was reported in (1992ROZZ).
Many states have been populated in this reaction: see 19.14 (in PDF or PS) in (1978AJ03) and (1984MO28; E(7Li) = 20 MeV). Angular distributions in the latter work have been analyzed via Hauser-Feshbach compound nucleus calculations and FRDWBA. The Kπ = 1/2+ and 1/2- states [see 19.16 (in PDF or PS)] are discussed in (1984MO28).
More recently a discussion of the theory of cluster-stripping reactions was presented in (1990OS03). Differential cross sections were calculated with the exact finite-range distorted wave Born approximation (1991OS04).
For early polarization measurements see (1983AJ01). More recently differential cross sections and analyzing powers were measured for Ed = 89 MeV (1990SA27). See 16O, reaction 67 in (1993TI07). For other channels see (1978AJ03).
At Eα = 47.5 MeV angular distributions have been studied for deuterons leading to the 1/2+, 5/2+, 3/2+, 9/2+, 13/2+ and 7/2+ members of the K = 1/2+ band [19F*(0, 0.197, 1.55, 2.78, 4.65, 5.47)], to two 11/2+ states 19F*(6.49, 7.94) [both of which are strongly populated] and to the 7/2+ state at 4.38 MeV. The reaction populates strongly only those positive-parity states that are predominantly (sd)3: see (1983AJ01).
This reaction was studied for Ep = 80 to 2200 keV by (1980WI17). A large number of resonances have been investigated and Eres, total and partial widths, branching and mixing ratios and ωγ values are reported. Transition strength arguments as well as analyses of γ-ray angular distribution data lead to Jπ assignments: see 19.10 (in PDF or PS), 19.17 (in PDF or PS), and 19.18 (in PDF or PS) for a display of the results. More recently measurements were made for Ep < 0.22 MeV by (1990VO06), and the results are included in 19.18 (in PDF or PS).
Absolute cross sections measured for direct capture lead to C2S values for a number of states of 19F. Reduced widths and Jπ determinations led (1980WI17) to postulate 19F*(3.91, 4.55, 4.38, 6.59, 6.50, 10.43) as the Jπ = 3/2+, 5/2+, 7/2+, 9/2+, 11/2+, 13/2+ states of the Kπ = 3/2+ rotational band; 19F*(7.70 or 7.26, 6.09, 9.82, 6.93, 9.87) as the Jπ = 1/2-, 3/2-, 5/2-, 7/2- and 11/2- members of the excited Kπ = 1/2- rotational band; and 19F*(4.56, 4.68, 5.42, 6.10, 7.17) as the Jπ = 3/2-, 5/2-, 7/2-, 9/2- and 11/2- members of the Kπ = 3/2- rotational band. Evidence suggesting the presence of isospin mixing in the 5/2+, first T = 3/2 state in 19F at 7.54 MeV has been pointed out (1980WI17). See also 19.9 (in PDF or PS).
Stellar reaction rates have also been calculated: the data cover T9 = 0.01 - 5.0. The consequences for the final termination of the CNO tri-cycle are discussed by (1980WI17). See also (1987AJ02). See also the more recent tables of thermonuclear reaction rates in (1983HA1B, 1985CA41, 1988CA26).
Yield measurements are reported from Ep = 2.5 to 13.5 MeV [see (1978AJ03) for the references]. The observed resonances are displayed in 19.19 (in PDF or PS). Measurements of spin observables for this reaction with polarized protons at Ep = 135 MeV were reported by (1989WAZZ). Total cross sections for production of 18F for Ep < 30 MeV were measured by (1990WA10). A cryogenic 18O target technique is discussed in (1993FI08). See also (1986AI04).
Scattering studies have been carried out for Ep = 0.6 to 16.3 MeV and for Ep = 6.1 to 16.6 MeV: see (1978AJ03, 1983AJ01, 1987AJ02). Pronounced resonant structure is evident up to 14 MeV. Observed resonances are shown in 19.20 (in PDF or PS). For polarization measurements see (1982GL08; Ep = 800 MeV). See also (1987AJ02) and (1989PLZV).
For polarization measurements at Ep = 90 MeV see (1986VO10) and see (1978AJ03). See also the tables of astrophysical reaction rates (1983HA1B, 1985CA41) and a study of the effect of electron screening on low energy fusion cross sections (1987AS05).
Yield measurements have been studied for Ep = 72 keV to 14 MeV: see (1972AJ02, 1983AJ01, 1987AJ02): observed resonances are displayed in 19.20 (in PDF or PS). Use of the resonance at Ep = 150 keV for 18O depth profiling is discussed in (1991BA54).
Angular distributions of neutron groups corresponding to 19F states with Ex < 8.2 MeV have been measured at Ed = 3 and 4 MeV: see 19.18 (in PDF or PS) in (1978AJ03) and 19.21 (in PDF or PS) here. See also the Ed = 25 MeV measurements of (1992TEZY).
Angular distributions of the deuterons corresponding to many states of 19F have been analyzed by DWBA: the results are shown in 19.21 (in PDF or PS). Spectroscopic factors for population of Jπ = 1/2+, 5/2+, 3/2+ levels at Ex = 0, 0.199, 1.554 MeV by (3He, d) at E(3He = 25 MeV have been deduced by (1994VE04). The spectroscopic factors obtained 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: see (1978AJ03). A search for a state at Ex = 7.90 MeV [just below the 18O + p threshold, and of astrophysical interest] has been unsuccessful: θ2p < 5 × 10-5 (1986CH29). See also (1987AJ02).
Cross sections were measured at Eα = 65 MeV and analyzed with DWBA (1992YA08). Spin-parity and isospin assignments were proposed. Spectroscopic factors were obtained and compared with shell-model calculations. See 19.22 (in PDF or PS).
The decay is primarily by allowed transitions to 19F*(0.197, 1.55), Jπ = 5/2+, 3/2+. Very weak branches are also observed to 19F*(0.11, 1.35, 3.91, 4.39), Jπ = 1/2-, 5/2-, 3/2+, 7/2+: see 19.23 (in PDF or PS). The half-life is 26.96 ± 0.07 s: 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 with (7/2+) for 19F*(4.39). Gamma-ray branching ratios are displayed in 19.24 (in PDF or PS). See also (1983AJ01, 1985BR29).
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: see (1978AJ03). More recently, photoneutron angular distributions were measured by (1989KU10) for Eγ = 15 - 25 MeV. E1 absorption strengths were deduced. An atlas of photoneutron cross sections is presented in (1988DI02). See also (1972AJ02, 1987AJ02). A model for describing relative (γ, n) and (γ, p) yields is discussed in (1986IS09).
(1984KE04) have measured absolute differential cross sections for the p0 and p1 channels at 7 angles for Eγ = 13.4 to 25.8 MeV. Angle integrated cross sections for (γ, p0) show pronounced structures at Eγ = 15.45, 16.70, 17.35, and 18.55 MeV as well as a broad bump at ≈ 20.5 MeV. Additional minor structures may exist at Eγ = 13.65, 14.35, 15.85, 17.90, 19.5, 21.3, 22.2, and 23.5 MeV. In the (γ, p1) reaction broad bumps appear at ≈ (17.0) and 21.5 MeV. The E2 cross section [from (γ, p0) angular distribution coefficients] is estimated to be ≈ 0.37 of the E2 EWSR (1984KE04). The (γ, ptot) cross section to 26 MeV has been derived by (1985KE03). See also (1978AJ03). A model for describing relative (γ, p) and (γ, n) yields is discussed in (1986IS09).
In reaction (b) the (γ, t0) reaction has been studied for Eγ = 18 to 23 MeV: two peaks are observed at Eγ = 18.8 and 20.1 MeV. It is suggested that Jπ = 1/2- or 3/2-, T = 1/2. The (γ, t0) process contributes ≈ 1% to the total GDR strength: see (1978AJ03).
The energy of the first excited state is 109.894 ± 0.005 keV; its width is (5.1 ± 0.7) × 10-7 eV. 19F*(1.46, 3.91, 7.66) are also excited. The scattering cross section is relatively small and structureless for Eγ = 14 to 30 MeV: see (1978AJ03).
The time spectrum of gamma rays following muonic capture reactions on the 19F muonic atom was measured by (1993GO09). The hyperfine transition rates of muonic 19F atoms were determined from these measurements. The hyperfine dependence of muon capture is related to the weak axial and pseudoscalar coupling in the nuclear medium.
With Ee = 78 to 340 MeV, most states of 19F below Ex = 7.7 MeV have been observed with an energy resolution of 25 - 50 keV. Longitudinal and transverse form factors have been derived and compared with shell-model calculations. The spectrum of positive-parity longitudinal excitations is dominated at higher momentum transfer by the 1/2+, 3/2+, 5/2+, 7/2+ and 9/2+ members of the ground state Kπ = 1/2+ band. The C2 strength is concentrated at Ex < 1.5 MeV with a small secondary concentration for 5.5 < Ex < 6.5 MeV. The C4 strength is spread from 3 to 6 MeV, predominantly in 19F*(2.78) [Jπ = 9/2+]. The spectra of longitudinal excitations of negative parity states are dominated by 19F*(1.35) [Jπ = 5/2-] and 19F*(5.5) [5/2- + 7/2-]. In the transverse mode 19F*(0.11, 6.79) [Jπ = 1/2-, 3/2-, respectively] are prominent. Agreement with theory is good for 5/2- and 7/2- but poorer for 1/2- and 3/2- states. The parity of 19F*(5.34) is uncertain while that of 19F*(6.55) is probably positive. States are reported at 7.587 and 7.753 MeV with Jπ = (5/2-) and (7/2-), respectively (1985BR15). The form factors for 19F*(0, 0.11, 2.78) have also been studied by (1986DO10) for q = 0.4 - 2.8 fm-1. Cross section measurements for 19F states with Ex ≤ 4.4 MeV performed with Ee = 500 MeV and momentum transfer q = 1.4 - 2.6 fm-1 were reported by (1987DO10). Form factors were compared with shell model calculations. For electromagnetic transition rates see 19.25 (in PDF or PS). For the earlier work see (1978AJ03, 1983AJ01, 1987AJ02). See also (1988BR1D).
Capture gamma rays were measured from broad neutron resonances in 19F (1991IG1A). Strong primary M1 transitions to low-lying 20F states were observed.
Angular distributions of neutron groups from elastic and inelastic scattering have been reported at En = 2.6, 14.1 and 14.2 MeV: see (1972AJ02). Neutron activation cross sections for reactions (b, c, d, f) were measured for En = 13.4 - 14.9 MeV by (1992KA1G). Reaction (e) is included in a review of (n, d) reactions for En = 14 - 15 MeV by (1993AT04). Nuclear model codes are used to calculate neutron induced reactions on 19F for En = 2 - 20 MeV by (1992ZH15). See also (1989HO1H).
19.21 (in PDF or PS) in (1978AJ03) displays energy levels of 19F derived from inelastic proton scattering. Angular distributions of various proton groups have been measured from Ep = 4.3 to 35.2 MeV [see (1978AJ03, 1983AJ01)] and at Ep = 2.76 and 2.97 MeV (1986OU01). The ground-state rotational band is characterized by β2 = 0.44 ± 0.04, β4 = 0.14 ± 0.04. The gyromagnetic ratio of 19F*(0.197) is g = 1.442 ± 0.003 (1969BL18), 1.438 ± 0.005 (1984AS03). The mixing ratio for the 1.46 → 0.11 transition (3/2- → 1/2-; K = 1/2- band) δ(E2/M1) = 0.248 ± 0.020. The E2 strength is 18.7 ± 1.9 W.u. The 1.46 → 0 transition is pure E1 (δ = 0.01 ± 0.03). For references see (1983AJ01). See also 20Ne in (1987AJ02). A study of Coulomb excitation by protons and antiprotons is discussed in (1993PI10). A discussion of the need for (p, p) cross-section data in thin-film analyses by Rutherford backscattering is presented in (1993BO40).
Experimental and theoretical studies of nucleon and cluster knockout by Ep = 30 - 150 MeV protons are reviewed in (1987VD1A). See also (1988BA83). The reactions 19F(p, p'γ) and 19F(p, αγ) were used in a study of proton-induced gamma ray emission spectroscopy to determine flourine concentration in materials by (1992ZS01).
This reaction is discussed in detail under 20Ne in (1987AJ02); resonances are displayed in 20.23 (in PDF or PS), 20.24 (in PDF or PS), and 20.25 (in PDF or PS) in (1987AJ02). A recent measurement of the excitation function for Ep = 0.3 - 3.0 MeV is reported in (1993DA23). The absolute yield, angular distribution, and resonance width of photons from the 340.5 keV resonance was measured by (1991CR06). Tests of a new standard for flourine determination utilizing this reaction are described in (1992ZS01). See also the related work of (1994TA1B). An accelerator calibration procedure utilizing 19F(p, αγ) is discussed in (1993LA1E). See also (1994BB10). A DWBA analysis for energies below the Coulomb barrier is presented in (1991HE16).
Elastic angular distributions have been studied for Et = 2 and 7.2 MeV: see (1972AJ02). More recently, differential cross sections were measured at Et = 33 MeV and analyzed with a phenomenological optical model (1987EN06).
See reaction 12 of 19O.
Elastic angular distributions have been measured for E(3He) = 4.0 to 29 MeV [see (1972AJ02, 1978AJ03)] and at 25 MeV (1982VE13). < r2 > 1/2matter = 2.72 ± 0.12 fm (1982VE13). A strong-absorption model analysis for E(3He) = 25 and 41 MeV is presented in (1987RA36).
Elastic angular distributions have been studied at Eα = 19.9 to 23.3 MeV and at 38 MeV: see (1972AJ02) and more recently at 50 MeV (1991FR02). Many inelastic groups have also been studied: see 19.22 (in PDF or PS) in (1978AJ03). Differential cross sections for 19F levels at Ex = 0.20, 1.55, and 2.78 MeV were measured at Eα = 50 MeV by (1991FR02) and analyzed in a coupled-channels approach. See also (1988LE05) in which the alpha-particle strength function distribution for targets with 12 ≤ A ≤ 40 is discussed.
The energy of the γ-ray from the 1.35 → 0.11 transition is 1235.8 ± 0.2 keV; Ex is then 1345.7 ± 0.2 keV. |g| = 0.269 ± 0.043 (1983BI03). See also 19.10 (in PDF or PS). For τm see 19.11 (in PDF or PS). 19F*(4.65) decays to the 9/2+ state 19F*(2.78): the angular distribution of the cascade γ-rays and τm for 19F*(4.65) indicate Jπ = 13/2+. See also (1983AJ01, 1987AJ02).
Angular distributions (reaction (a)) have been studied at E(12C) = 40.6 MeV [see (1983AJ01)] and at 30.0 to 60.1 MeV [as well as at E(19F) = 63.8 MeV] (1984TA08, 1986TAZO; to 19F*(0, 0.197, 1.55, 2.78)) and at E(19F) = 46.5 to 57.1 MeV (1984MA32; to 19F*(0, 0.197)) [see (1984MA32, 1986VO12) for yield measurements] and at E(12C) = 30, 40, 50, 60 MeV (1988TA12) to 19F*(0.197, 1.554, 2.780 MeV). Measurements of evaporation residues at E(19F) = 32 - 72 MeV were reported in (1990AN14). See also (1990XE01).
Angular correlations involving the α-decay to 15Ng.s. of twenty 19F states have been measured at E(19F) = 78.5, 82 and 144 MeV and analyzed with DWBA and strong absorption model calculations. Two new states with Jπ = 5/2- or 7/2- are reported at 7.740 and 8.277 MeV [estimated ± 0.04 MeV]. It is suggested that 19F*(7.26, 9.287) are 3/2+ and (7/2, 9/2)+, respectively (1985SM04, 1987AJ02). See also (1983AJ01), and see the more recent application of molecular orbital theory to heavy ion scattering in (1988DI08).
Elastic angular distributions have been studied at E(16O) = 21.4 and 25.8 MeV and at E(19F) = 27, 30, 33, and 36 MeV (reaction (a)) [also to 19F*(1.46) at the two higher energies], and E(16O) = 60 and 80 MeV (1986FUZV; also to 19F*(0.20, 1.55, 2.78)). See also the measurements of evaporation residue at E(19F) = 32 - 72 MeV reported in (1989AN1D, 1990AN14). For reaction (b) at E(18O) = 27, 30, 33 MeV, see (1978AJ03) and at E(18O) = 10 - 16 MeV, see (1990XE01). See also (1987AJ02).
For fusion cross sections see (1985RO01). See also (1987AJ02). Measurements of evaporation residue for Elab(19F) = 32 - 72 MeV are reported in (1989AN1D, 1990AN14). A parametrization of measured fusion-evaporation residue excitation functions is described in (1988DO07). See also the comment (1989FR05) on this work and the reply (1989DO03). See also (1990SC18).
See reaction 1 of 19Ne.