
^{18}C (1995TI07)(See the Isobar Diagram for ^{18}C) GENERAL: See 18.1 [General Table] (in PDF or PS) and 18.2 [Table of Energy Levels ] (in PDF or PS). Mass of ^{18}C: The atomic mass excess of ^{18}C adopted by (1993AU05) is 24.920 ± 0.030 MeV, based on the Qvalue of the ^{48}Ca(^{18}O, ^{18}C)^{48}Ti reaction. ^{18}C is then bound by 4.188 MeV with respect to breakup into ^{17}C + n. See also (1982FI10, 1987AJ02, 1992WA22).
The halflife of ^{18}C has been measured to be 66^{+25}_{18} ms (1988MU08), 78^{+20}_{15} ms (1989LE16), 94 ± 27 ms (1991RE02), (95 ± 10) ms (1991PR03). Branching to states in ^{18}N has been measured by (1991PR03) and is presented here in 18.6 (in PDF or PS). These authors also measured the total branching probability to gamma emitting states plus the ground state of ^{18}N to be P_{γ} = (81 ± 5)%. The βdelayed neutron emission probability is P_{n} = 1  P_{γ} = (19 ± 5)%. Other values reported for P_{n} are (25 ± 4.5)% (1988MU08), (50 ± 10)% (1989LE16), (43.3 ± 6.5)% (1991RE02). The ^{18}C(β^{}) decay is also discussed in the analysis of GamowTeller rates presented in (1993CH06). Experimental GamowTeller matrix elements are compared with results of shellmodel calculations.
The angular distribution of the π^{+} to the ground state of ^{18}C has been measured at E_{π} = 164 MeV by (1984GI10) [see also for excitation function at θ = 5° for E_{π} ≈ 140 to 240 MeV]. There is also some indication of the population of an excited state at E_{x} = 1.55 MeV (1984GI10). See also (1983AJ01).
At E(^{18}O) = 112 MeV the ground state and an excited state at 1.62 ± 0.024 MeV are observed by MeV (1982FI10). See also (1983AJ01).
