A Study of the Bound States of ¹⁵O and A Study of T = 3/2 States in ¹³C, ¹⁷O, and ²¹Ne

Citation

Hensley, David Cecil (1969) A Study of the Bound States of ¹⁵O and A Study of T = 3/2 States in ¹³C, ¹⁷O, and ²¹Ne. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/BG95-MF12. https://resolver.caltech.edu/CaltechTHESIS:08232017-144937824

Abstract

The bound states ¹⁵O were studied in the ¹⁶O(³He, α)¹⁵O reaction, and the binding energy of the 6th excited state ¹⁵O with respect to ¹⁴N + p was measured with special care, for astrophysical reasons. In addition, T = 3/2 states in ¹³C, ¹⁷O, and ²¹Ne were studied in the (³He, p) reaction ¹¹B, ¹⁵N, and ¹⁹F and in the (³He, α) reaction on ¹⁴C, ¹⁸O, and ²²Ne. In all cases, the reaction products were analyzed with a 61-cm radius, double-focusing magnetic spectrometer and detected by a 16-counter array in the focal plane of the spectrometer. The results for the four nuclei studied are summarized below.

(1) ¹⁵O: the spins and parities of all of the bound states of ¹⁵O were either determined for the first time or confirmed. The 6th excited state has J^π = 7/2⁺ and lies 21.2 ± 0.6 keV below the ¹⁴N + p threshold; the 5th excited state has J^π = 5/2⁺. A correction of -4.6 ± 0.6 keV to the previously accepted mass excess of ¹⁵O was determined; the new mass excess of ¹⁵O is 2855.3 ± 0.6 keV. On the basis of this work, it is shown that the 6th excited state ¹⁵O has a negligible effect on the stellar rate of the ¹⁴N(p, γ) ¹⁵O reaction.

(2) ¹³C: four T = 3/2 states were identified in ¹³C at the following excitation energies (spin and parity are included, where determined): 15105 ± 3 keV (3/2^-); 18655 ± 10 keV; 18692 ± 15 keV; and 19122 ± 5 keV (≤ 7/2^-). The 15.10-MeV state has a width, Γ ≤ 6 keV.

(3) ¹⁷O: seven T = 3/2 states were identified in ¹⁷O at the following excitation energies: 11076 ± 4 keV (1/2^-); 12467 ± 4 keV (3/2^-); 12947 ± 5 keV (1/2⁺); 12994 ± 5 keV (5/2^-); 13636 ± 4 keV (3/2⁺ or 5/2⁺); 14210 ± 10 keV; 14243 ± 10 keV.

(4) ²¹Ne: five T = 3/2 states were identified in ²¹Ne at the following excitation energies: 8856 ± 6 ke V (3/2⁺ or 5/2⁺); 9136 ± 6 keV (1/2⁺); 9962 ± 6 keV (1/2^- or 3/2^-); 10602 ± 10 keV; and 10901 ± 10 keV.

Analog-state correspondences were made on the basis of relative intensities, excitation energies, and spin-parity assignments; four completed T = 3/2 quartets were established. The completed T = 3/2 quartets were then used to test the quadratic mass equation for isobaric multiplets. Within the experimental uncertainties, the lowest mass-13 and mass-17 quartets are fitted by the quadratic mass equation, but the two lowest mass-21 quartets deviate significantly.

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