Study of the C14(p, n)N14 and C14(α, n)O17 Reactions

Abstract

Targets of 38.7% carbon 14, deposited from a glow discharge in acetylene, were used for the determination of the following threshold energies: ${\mathrm{C}}^{14}(p, n){\mathrm{N}}^{14}$, 671.5±0.5 kev; ${\mathrm{C}}^{14}(p, n){\mathrm{N}}^{{14}^{*}}$, 3149.6±1.1 kev; ${\mathrm{C}}^{14}(\alpha , n){\mathrm{O}}^{17}$, 2340±3 kev. Corresponding reaction energies are -626.4±0.5, -2938.3±1.0, and -1820±2 kev. The latter two thresholds were detected by the counter-ratio technique. The ${\mathrm{C}}^{14}(p, n){\mathrm{N}}^{14}$ excitation curve was extended to 3.4 Mev, covering a resonance at 2908±4 kev with a natural width of 71±5 kev. Resonance energies agree with previous experimental results but the widths are larger, perhaps due to target thickness errors. Absolute cross sections are compared with those of ${\mathrm{N}}^{14}(n, p){\mathrm{C}}^{14}$. Compound nucleus spins and partial widths are calculated. ${\mathrm{C}}^{14}(\alpha , n){\mathrm{O}}^{17}$ resonances with energies and natural widths of 2553±4, 1.6±1; 2642±3, 10±1; (2798±11, 22±10)?; 3335±15, 100±20; and 3508±4, 54±3 kev were observed. The 0° differential cross section at 2642 kev is 31 mb/sterad ±60%. An angular distribution taken at this resonance leads to a total cross section of 300 mb and a compound-nucleus spin of either $1^{-}$ or $3^{-}$. A method is presented for evaluating resonance width, height, and area to find target thickness and natural width.