UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The direct capture reactions t([alpha, gamma]) Li7 and O16 (p, [gamma])F17. Riley, Peter Julian

Abstract

The differential cross section for the capture of tritium by alpha particles to form Li⁷ has been measured using a tritium-zirconium target and 1.64 mev. alpha particles. The differential cross section for the gamma-ray transition to the ground state of Li⁷ was found to be 2.54± .46 x 10¯³¹ cm.² per steradian at 90° to the incident alpha beam direction. At the same energy, the ratio of the differential cross section at 90° for transitions to the first excited state to that for transitions to the ground state of Li⁷ was found to be approximately 0.40. The T(α,ɣ )Li⁷ 90° differential cross section has been measured relative to the differential cross section at 1.64 mev. using alpha particles of energies 0.515, 0.72, 0.98, 1.23, and 1.94 mev. From the smooth change of the reaction cross section with energy it can be concluded that the reaction proceeds by direct radiative capture. At all energies, the ratio of the differential cross section at 90° for transitions to the first excited state to that for transition to the ground state was approximately 0.4. Preliminary angular distribution measurements at 0° and at 90° to the incident alpha beam direction indicate that the angular distribution is not isotropic. The ratio of the yield at 0° to the yield at 90° was found to be 1.40 ± 0.37 at an alpha particle energy of 1.64 mev. Differential cross section measurements for direct radiative capture of protons by 0¹⁶ have been made relative to the cross section at 800 kev., using a solid tungsten-dioxide target and protons of energies 0.618, 09823, 1.13, 1.536, and 2.04 mev. Absolute 90° differential cross section values were based on the measurement of the 90° differential cross section for transitions to the first excited state in F¹⁷ at 800 kev. of 10.4 ± 1.3 x 10¯³² cm.² per steradian made by Robertson. The differential cross section for the gamma ray transitions to the first excited state of F¹⁷, at 90° to the incident proton beam direction, was found to vary smoothly from 0.41 x 10¯³¹ cm.² per steradian at 0.618 mev. to 11.9 x 10¯³¹ cm.² per steradian at 2.04 mev. At all energies the ratio of the differential cross section at 90° for transitions to the ground state to that for transitions to the first excited state was approximately 0.20.

Item Media

Item Citations and Data

Rights

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

Usage Statistics