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

Author: Hensley, David Cecil

Year: 1969

Degree: Dissertation (Ph.D.)

Advisor: Barnes, Charles A.

Committee Member: Unknown, Unknown

Option: Physics

DOI: 10.7907/BG95-MF12

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 Jπ = 7/2+ and lies 21.2 ± 0.6 keV below the 14N + p threshold; the 5th excited state has Jπ = 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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