I. SPECTROMETER MEASUREMENT OF THE RATES OF GAMMA-RADIATION AND INTERNAL PAIR FORMATION FROM SOME REACTIONS IN LIGHT NUCLEI
ABSTRACT - PARTS I - III
In part III the measurements with beta-ray spectrometer of thegamma-rays and internally-formed positrons from the reactions C13(dp)C14and C13(dn)N14 are described; the energy levels of N14 and C14 arediscussed. A measurement of the internally-formed positron spectra from the Be9 + d reactions is described, and an attempt is made to determine themultipolarity of the 2.87- and 3.38-Mev transitions from the ratio of therates of pair emission to gamma radiation; the results are in agreementwith electric-dipole assignments to the transitions. Also described isthe measurement of the internal conversion electrons associated with the 0.871-Mev radiation from the O16(dp)O17 reaction; the result is shown to be consistent with an electric quadripole assignment to this transition.
In Part II methods are developed for analyzing the date of Part III.These include the measurement of absolute gamma-ray intensities by Comptonconversion of the radiation in "thick" foils and photoelectric conversionin "thin" foils. Methods for analyzing internal-pair spectra and internalconversion spectra are given and several problems discussed. Measurementsof the internal conversion coefficients of the 0.713-Mev transition of B10and the 1.332-Mev transition of Ni60 are described.
Part I is concerned with the penetration of the secondary electronsthrough the converters in which they are produced. The effective stopping power of aluminum and beryllium are calculated for use in theCompton "thick" - converter method of measuring gamma-ray intensitiesdeveloped in Part II. Also included is a discussion of the scattering ofelectrons in the converters.
II. ENERGY LEVELS OF THE MIRROR NUCLEI, N13 AND C13
ABSTRACT PART IV
The low energy levels (< 6 Mev) of the mirror nuclei, N13 andC13, are studied on the assumption that rr and pp nuclear forces areequal. By means of dispersion theory it is shown that the first excitedstates of these nuclei are 2S1/2 and that the large displacementis due to their large reduced width and the difference in theextra-nuclear wave functions for the odd particle; the magnitude ofthe reduced widths suggests that a one-body type of interaction is involvedbetween the odd particle and the C12 core. In particular,a square-well type of model gives a satisfactory account of the levelshift, reduced widths, and the low-energy (< 1 Mev) scattering of neutrons by carbon. The C12 + n s-wave interaction is also studied bymeans of the effective range theory. Some evidence is given that thesecond excited state of N13 is a doublet, one component of which appearsat 3.68-Mev and the other at 3.90-Mev in C13, and the 3.68-Mev componentis most likely 2P3/2 and the 3.90 2d. The reduced widthof the ground states of N13 and C13, as calculated from the knowledgeof the s-wave C12(p γ) and C12(n γ) cross sections, is about 1/10of the value expected for a familiar one-body type of interactions, butit is nearly equal to the reduced width of the 3.52-Mev level of N13.This reduced width is used to calculate the ground-state level shift dueto the difference in the extra-nuclear wave functions. The shift of the second pair of excited states, if they are 2P3/2, can be about 1/3accounted for as due to the difference of the extra-nuclear wave functions for theodd particle and about 1/3 as due to the difference in the electromagneticspin-orbit interactions of the odd particle.
