(See Energy Level Diagrams for 18O)
Shell model: (1970FL1A, 1970SA1M, 1971KU1F, 1972BB07, 1972EN03, 1972GA02, 1972LE13, 1972MC1C, 1972PR08, 1972WA09, 1973BA1Q, 1973IG02, 1973JU1A, 1973LA1D, 1973MA1K, 1973MC06, 1973SA32, 1973SM1C, 1973TR09, 1973VA05, 1973VA1D, 1974AV05, 1974DE50, 1974KU1F, 1974LO04, 1974TR07, 1974WA17, 1974WE1J, 1974WR1A, 1975BA81, 1975DR01, 1975LE1H, 1975SA04, 1976DE13, 1976PI01, 1976SZ1A, 1977GO1U, 1977IB01, 1977SA13, 1977SH11, 1977VA1E, 1977VA1F).
Electromagnetic transitions and giant resonances: (1970FL1A, 1970SI1J, 1972EN03, 1973CO1F, 1973HA1N, 1973HO29, 1974DE50, 1974LO04, 1974MC1F, 1974TR07, 1975HO20, 1976LA13, 1976SH04, 1976VO1C, 1977BR03, 1977ER01, 1977KN1F, 1977MO1V, 1977SA13).
Special states: (1972BB07, 1972EN03, 1972GA02, 1972HI17, 1972HO13, 1972LE13, 1972RA08, 1973BA1Q, 1973HO29, 1973JU1A, 1973KN1C, 1973MC06, 1973VA05, 1973VI11, 1974BA20, 1974BA71, 1974BO22, 1974CO25, 1974HO1F, 1974KI1B, 1974WE1J, 1975BA81, 1975GL03, 1975LO1G, 1976DE13, 1976EI02, 1976FE09, 1976HO14, 1976LA13, 1976PI01, 1976PI14, 1976PR07, 1976SZ1A, 1976VI1D, 1977ER01, 1977HA2D, 1977SA13, 1977SA05, 1977SH11, 1977VA1E, 1977VA1F).
Astrophysical questions: (1972CL1A, 1972CO1E, 1972UL1A, 1973AR1E, 1973AU1B, 1973AU1C, 1973EN1A, 1973TA1D, 1974BE1R, 1974SC1F, 1975AU1D, 1975CO1J, 1975EN1A, 1975LA1E, 1975TR1A, 1976BO1M, 1976FI1E, 1976KO1K, 1976ME1H, 1976WA1M, 1977CL1H, 1977CO1U, 1977HA2C, 1977NO1E, 1977TO1J).
Applied work: (1976GR1J).
Muon and pion capture and reactions: (1974EN10, 1974KA07, 1974LI1D, 1974LI1N, 1974TA18, 1975EI02, 1975LI04, 1976AL1L, 1976CO1V, 1976EN02, 1976HEZU, 1976TR1A, 1977AL1C, 1977HE1M, 1977IV1B, 1977MA02, 1977RO1U, 1977SI01).
Complex reactions involving 18O: (1972MI11, 1973KO1D, 1973WI15, 1974KO25, 1975GL03, 1975LE1J, 1975RE17, 1975TA1C, 1975TS01, 1975VO09, 1976EI02, 1976GL06, 1976HI05, 1976LA04, 1976MO10, 1976PEZY, 1976VI01, 1977AR06, 1977BA3T, 1977BE10, 1977BO2F, 1977FE04, 1977GL03, 1977LO1L, 1977PE08, 1977RE1C).
Other topics: (1970SI1J, 1971KU1F, 1971ST40, 1972BA23, 1972CA37, 1972GA02, 1972GO17, 1972HO13, 1972KU1C, 1972MC1C, 1972PR08, 1972RA08, 1972TS02, 1973BE35, 1973CO1F, 1973GO1H, 1973IG02, 1973KR16, 1973MA48, 1973PA1F, 1973SA24, 1973SA32, 1973ST25, 1973TR09, 1973VA05, 1973VI11, 1974BA20, 1974BO22, 1974CO25, 1974HO1F, 1974KI1B, 1974KI1C, 1974KU1F, 1974RE03, 1974SA05, 1974SE1B, 1974SH09, 1974SH1G, 1974UH1A, 1974WA17, 1974ZU1A, 1975BA2F, 1975BA81, 1975HE10, 1975HE1H, 1975LE1H, 1975LO1G, 1975MI02, 1975SA04, 1975SH1H, 1975ST03, 1976BA2G, 1976HO14, 1976KR1D, 1976MA04, 1976OF1A, 1976PA03, 1976PI01, 1976PR07, 1976VI1D, 1977GO1T, 1977SA05, 1977SH11, 1977SH13, 1977SO11, 1977VA1E).
Ground state of 18O: (1970SI1J, 1973HO29, 1973HO32, 1973LE07, 1973MC06, 1973SP1A, 1973VA1D, 1974DE50, 1974DE1E, 1974EN10, 1974MC1F, 1974RE03, 1974SH1G, 1975AL19, 1975BE31, 1975MI02, 1976AS07, 1976BE1G, 1976CH1T, 1976CO1V, 1976PA03, 1977AN21, 1977BR03, 1978FO05, 1977IB01).
B(E2; 0+0 → 2+1) = 0.00453 ± 0.00025 b2 · e2 (1977FL10).
Relative spectroscopic factors for 18O*†(0, 1.98, 3.56):
†(Assuming constructive interference from the coupling through the second 2+ state (1977FL10).)
Cross sections to various of the final states have been measured at E(7Li) = 5.00 MeV (1966MC05).
Gamma-ray energies of 1982.3 ± 0.8 [1.98 → 0], 1571.9 ± 2.5 [3.56 → 1.98], 1649.8 ± 2.2 [3.63 → 1.98] and 1938.6 ± 2.1 keV [3.92 → 1.98], due to the transitions shown in brackets, have been measured by (1969TH01).
Angular distributions have been studied at Ec.m. = 12.9 and 14 MeV for the transitions to 18O*(0, 1.98) (1977CH22).
Gamma-ray angular distribution and correlation measurements lead to Jπ = 4+, 1-, 1- and 5- for 18O*(7.12, 7.62, 8.04, 8.13), as well as to Jπ assignments for lower states involved in the cascade decay: see Table 18.3 (in PDF or PS) (1958GO1A, 1958PH37, 1966LE1B, 1967LE02). See also (1973CL1E, 1973MI1D, 1975KA1L; astrophys. questions).
Observed anomalies in the scattering for Eα = 2 to 8.2 MeV are shown in Table 18.5 (in PDF or PS) (1958WE29, 1970MO13). The yield of elastic scattering has been measured up to Eα = 16.5 MeV (1970MO13). See also (1973OE01) and 14C in (1976AJ04).
At E(7Li) = 20.4 MeV, triton groups are observed corresponding to a number of states of 18O with Ex < 12.6 MeV. Angular distributions were obtained for some of these, including 18O*(0, 1.98, 7.12, 11.69) with Jπ = 0+, 2+, 4+, 6+. The latter two are the most strongly populated in this reaction: they appear to be part of the ground-state rotational band (1970MO17). See also (1974DO03; theor.).
Excitation functions have been measured for α0 and α1 for Et = 0.8 - 1.7 MeV (1973AB1E; unpublished). Some broad structures may be indicated. See also (1972AJ02). For reaction (b) see (1974NI1A; theor.).
Proton groups corresponding to states of 18O are displayed in Table 18.6 (in PDF or PS). Angular distributions have been measured at many energies to Et = 10.15 MeV: see Table 18.6 (in PDF or PS) in (1972AJ02) and (1974KA1N: 2.0 and 3.0 MeV; p0 and p3; abstract). Analysis of spectroscopic factors suggest that 18O*(5.34) [0+3] is largely (s1/2)2 while 18O*(3.63) [0+2] has a dominantly collective nature as does 18O*(5.25) [2+3] (1974FO14, 1976LA13): see (1976LA13) for a general discussion of the properties of the states of 18O. See also (1977MO1W).
Lifetime measurements are reported in Table 18.4 (in PDF or PS) (1963LI07, 1973WA19, 1974CO01, 1974MC17, 1975HE25, 1977HE12, 1977LIZS). See also (1974WA1F, 1977HE1D). See also (1972AJ02) and (1972BR11, 1973FE06, 1974BA71, 1974BO22, 1975IB01; theor.).
At Eα = 65 MeV, the (α, 2He) reaction populates 18O*(3.56) [Jπ = 4+]. This reaction appears to preferentially populate (d5/2)24+ states (1976JA13).
At E(12C) = 114 MeV, the population of 18O*(3.56) is reported (1971SC1F, 1972SC21). In reaction (a) at E(10B) = 100 MeV the reaction preferentially populates this state also [first (d5/2)24+ state] (1977HA2E; prelim.).
Proton groups have been observed to 18O states with Ex < 8 MeV. Angular distributions have been obtained for Ed = 3.6 to 18 MeV and spectroscopic factors have been obtained: see Table 18.7 (in PDF or PS) (1965MO16, 1966WI07, 1975DR04, 1976LI01). See also the discussion in (1977PE08). At Ed = 18 MeV (1976LI01) find that the results are consistent with a weak-coupling model. See also (1976SC36; theor.). Proton-gamma coincidence measurements by (1967MO09) are displayed in Table 18.3 (in PDF or PS). See also (1972AJ02).
The decay is to 18O*(4.46): γ-rays with Eγ = 0.82 ± 0.02, 1.65 ± 0.02, 1.98 ± 0.02 and 2.47 ± 0.03 MeV with intensities 0.60 ± 0.03, 0.63 ± 0.04, 1.00 ± 0.04 and 0.43 ± 0.03 have been observed. These are due to the decay of 18O*(4.46) to 18O*(3.63, 1.98) and the subsequent decay of these two states (1964CH19).
Differential cross sections have been measured at 98° for the n0 and n1 groups for Ex = 10 to 17 MeV: structures are reported at Ex = 10.2, 10.4. 11.1, 11.4, 11.6, 12.2, 12.9, 14.4, 15.4 and 16.5 MeV (1975AL03: bremsstrahlung). [The first italicized structure is the strongest in the n1 yield, the last three in the n0 yield.] Preliminary work from threshold to 42 MeV also shows strong structures in the (γ, n) and (γ, 2n) cross section; the most prominent occur at 10.2, 11.3, 12.9, 13.6, 14.5 and 15.5 MeV. The main dipole giant resonance is centered at 23.3 MeV (1976BE1H, 1976FA1F, 1976KN07). The decay of the GDR to 14C, 16O, 17N and 17O states has been studied by (1976BA41). See also (1977KN1F; theor.).
Reaction (c) has been measured with monoenergetic photons from threshold to 30 MeV and shows peaks at Eγ = 17.3, 19.2, 20.8, 23.4 and 27.5 MeV. The measured integrated cross section is 29.8 MeV · mb up to 30.6 MeV (1976BE20). See also (1972DO19) and (1972AJ02).
The width of 18O*(6.20) is 0.18 ± 0.03 eV, assuming Γγ0/Γ = 0.88; Ex = 6202.7 ± 0.8 keV (1974HA15).
The 18O charge radius, rrms = 2.789 ± 0.027 fm (1973FE13, 1975SC18; analysis by a phase shift calculation assuming a harmonic oscillator shell model charge distribution). See also the earlier values by (1970SI02, 1970SI1K, 1971SC29).
At Ee = 92.5 and 105.9 MeV, and assuming B(E2) for the 1.98 MeV transition is 9.0 e2 · fm4, the results of (1971GR33) are consistent with B(E2) = (1.7) and 4.8 ± 0.5 e2 · fm4 for 18O*(3.92, 5.26), with B(E3) = 160 ± 15 e2 · fm6 for 18O*(5.10) and with Γπ(0+ → 0+) = (3.4 ± 0.4) × 10-7 and (2.4 ± 0.7) × 10-6 eV, respectively, for 18O*(3.63, 5.34). See also (1976NOZW). For earlier reports of the excitation of 18O states to Ex = 27 MeV see reaction 19 in (1972AJ02). See also (1973BI1A, 1973TH1B, 1974DE1E, 1977MI1F) and (1973HO29; theor.).
Angular distributions have been measured for Ep = 0.84 to 66.5 MeV: see Table 18.8 (in PDF or PS) in (1972AJ02) and (1974ES02: 24.5 MeV; see below), (1977CO1G: 35.2 MeV; p0) and (1972LE1G, 1972LE27, 1972LE28: 66.5 MeV; p0). The difference of the rms matter radius for 18O with that of 16O is ≈ +0.37 ± 0.07 fm (1973LE07). The first excited state, 18O*(1.98), has |g| = 0.287 ± 0.015 and τm = 2.99 ± 0.12 psec (1976AS04): see also the "18O*(1.98)" section here and Table 18.4 (in PDF or PS).
At Ep = 24.5 MeV (1974ES02) have studied the angular distributions of the proton groups to 18O*(1.98, 3.56, 3.63, 3.92, 4.46, 5.10, 5.26, 5.53, 7.12): a modified DWBA analysis leads to Jπ = 2+, 4+, 0+, 2+, 1-, 3-, 2+, 2- and 4+ for these states. A coupled-channels calculation suggests β2 = 0.37 ± 0.03, 0.56 ± 0.06 and 0.18 ± 0.04 for 18O*(1.98, 5.10, 7.12). Such calculations also support evidence for a rotational band involving 18O*(0, 1.98, 7.12). The 3- state at 5.10 MeV is strongly excited and collective in nature: B(E3) = 1120 e2 · fm6. For 18O*(1.98, 3.92, 5.26), B(E2) = 45, 8.3 and 24 e2 · fm4 (1974ES02). (1974BE63) have measured the magnetic moment of the 4+ state 18O*(3.56): |g| = 0.62 ± 0.10 suggesting a mainly (d5/2)2 configuration for this state.
At Ep = 27.8 MeV, sharp states (Γ ≤ 50 keV) are reported at Ex = 16.40 ± 0.03 and 17.02 ± 0.03 MeV: they are presumed to be T = 2 states (1974NE1D; unpublished abstract). See also (1974PI05), (1972AJ02) for the earlier work and (1976ES1B; theor.). For polarization measurements see 19F.
Angular distributions of elastically scattered deuterons have been measured at Ed = 7.0 to 15 MeV (also d1 at 15 MeV): see Table 18.8 (in PDF or PS) in (1972AJ02) and (1974SE01: Ed = 14.8 MeV). The population of states with Ex < 5.5 MeV is also reported: see (1972AJ02). See also (1973ST1B, 1974NE1D) and 20F.
The elastic scattering has been studied at Et = 6.4 and 7.2 MeV (1964PU01).
Angular distributions of many α-groups have been measured at Eα = 21.4 (1966LU05) and 40.5 MeV (1966HA19): see Table 18.8 (in PDF or PS) in (1972AJ02). The elastic scattering has also been studied at Eα = 22, 24 and 28 MeV (1972OE01, 1973OE01). The transitions to 18O*(4.46, 5.10) are L = 1 and 3, respectively, fixing Jπ = 1- and 3- for these states. B(E2) values for 18O*(1.98, 4.46) and B(E3) for 18O*(5.10) are also reported (1966HA19). Measurements of α-groups near 180° for Eα = 20.0 to 23.4 MeV confirm assignments of natural parity for 18O*(1.98, 3.56, 3.63, 3.92, 4.46, 5.10, 5.26, 5.34, 6.20, 6.40, 7.12, 7.62, 7.85, 8.21, 8.28, 8.82, 8.96, 9.03, 9.10, 9.36, 9.39, 9.68, 9.72 ± 0.03, 9.88, 10.12, 10.29, 10.38, 11.62, 11.69). The levels at Ex = 5.38, 8.48 and 8.64 MeV were not observed, and those at 5.53, 6.35 and 6.88 MeV were populated weakly indicating unnatural parity: Jπ = 3+ and 2- respectively for 18O*(5.38, 5.53) (1971OL06). See also (1977KN1E).
Alpha-gamma correlation measurements involving 18O states below Ex = 6.4 MeV [see Table 18.3 (in PDF or PS)] lead to Jπ = 1- and 3- for 18O*(6.20, 6.40). Other Jπ values agree with previous assignments. The transitions 3.92 → 1.98 and 5.26 → 1.98 are almost pure M1 (1971BE45).
Lifetime measurements for 18O*(1.98, 3.56) are displayed in Table 18.4 (in PDF or PS) (1974BE25). See also (1971BE60). 18O*(1.98) has a negative g-factor (1975FO03), |g| = 0.35 ± 0.04 (1975SP03). See also (1975GR41, 1976GO1M) and (1973SU1A, 1974CH58, 1974KU15, 1975SU1C; theor.).
Perturbed angular correlations have been measured between the 1.98 MeV γ-rays and the 18O* particles which were resolved into their 8+, 7+ and 6+ charge states: |g| < 0.36 for 18O*(1.98) (1972GO06). Elastic scattering angular distributions (reaction (a)) have been measured at E(18O) = 47.5, 55 and 57.5 MeV (1976WE05). See also 30Si in (1978EN06), (1976EY01) and (1977BA3E, 1977PE1J; theor.). For reaction (b) see (1974CH1Q). See also (1971BE60) and (1974GO1L).
Angular distributions have been measured at E(16O) = 24, 28 and 32 MeV (1972GE18; elastic) and 39.7, 44.5, 49.6 and 54.5 MeV (1972SI16), and at E(18O) = 25, 27, 29, 36 and 42 MeV (1975KA24; 18O*(0, 1.98)), 35 MeV (1977CA1Q; 18O*(0, 1.98, 4.46, 5.10)) and 42 and 52 MeV (1974VA22, 1975RE15; 18O*(0, 1.98, 3.56 + 3.63, 3.92, 4.46, 5.10, 7.12); some are partial distributions). (1974VA22) find β2R = 1.08 ± 0.15 and β3R = 0.86 ± 0.15 for 18O*(1.98, 5.10). (1975KA24) suggest that caution is indicated in analyzing data taken at energies above the Coulomb barrier when recoil effects cannot be neglected.
Angular distributions for reaction (b) have been studied at E(18O) = 42 and 52 MeV (1974VA22; 18O*(0, 1.98, 3.56 + 3.63, 4.46, 5.10, 7.12)) and at 52 MeV (1976KUZX; elastic). See also (1973GO01), (1972AJ02, 1975VO1B), (1974KU1E, 1977PL02; theor.) and 36S in (1978EN06). For reaction (a) see (1977KA2E).
At Ebs = 19, 21.5 and 25 MeV, the relative yield of γ-rays from 18O*(1.98, 3.63) has been measured (1972TH15). At Ebs = 26 MeV the decay of 18O*(1.98, 3.63, 3.92, 4.46, 6.88) has been studied by (1977TA1M). See also (1972SH07, 1976TH1E) and reaction 43 in 18F. Proton spectra have been measured for Ee = 15 to 26 MeV (1975TS03): see 19F.
Angular distributions have been measured at En = 14 to 14.4 MeV: see (1972AJ02). Gamma rays from the de-excitation of 18O*(1.98, 3.56, 3.63) are reported by (1976PR08). See also 20F and (1971MI12; theor.).
Many states of 18O have been populated in this reaction: see Table 18.8 (in PDF or PS) (1969KA1A, 1970KA31). See also (1972BU1E; abstract), (1977RO1T) and (1972EN03, 1973CO17; theor.) and reaction 46 in 18F.
Alpha-particle groups are reported to the thirteen excited states observed in the 16O(t, p) reaction [see Table 18.6 (in PDF or PS)] and to other states with Ex < 8.7 MeV [see footnote c in Table 18.9 (in PDF or PS)] (1962HI06). Table 18.9 (in PDF or PS) displays the very accurate Ex measurements of (1973OL02) obtained from γ-measurements. This study, as well as the angular correlation work of (1973BE48), leads to some J-assignments, and to the branching ratios displayed in Table 18.3 (in PDF or PS). (1975SO05) have determined Γπ/Γ for the 0+ → 0+ transitions from 18O*(3.63, 5.34) to be (3.0 ± 0.6) × 10-3 and ≤ 2.3 × 10-3. Using the adopted values of τm for these states [see Table 18.4 (in PDF or PS)] < M >π = 6.0 ± 0.7 fm2 and ≤ 4.5 fm2. 18O*(5.34) appears to be the expected nearly spherical (s1/2)2 state (1975SO05). For lifetime measurements see Table 18.4 (in PDF or PS) (1973OL02). For the earlier work see (1972AJ02).