A Study of the Li⁷(He³,n)B⁹ Reaction by Time-of-Flight Techniques

Author: Dietrich, Frank Sigel, III

Year: 1964

Degree: Dissertation (Ph.D.)

Advisors: Barnes, Charles A.; Kavanagh, Ralph William; Lauritsen, Thomas

Committee Member: Unknown, Unknown

Option: Physics

DOI: 10.7907/Q5EC-9W47

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.

The Li^7(He^3,n)B^9 reaction has been investigated at incident energies from 5.2 to 12.5 Mev, using a pulsed-beam time-of-flight spectrometer in conjunction with the ONR-CIT tandem accelerator. The spectrometer includes a pre-acceleration beam-bunching system, which increases the average target current by a factor of approximately 10 for protons and deuterons, and 4 for He^3 and alpha beams. Previously unreported B^9 levels were found at the energies listed below, together with their widths:

[...]

At 12.5-Mev bombarding energy, neutron groups corresponding to known B^9 states at 17.19 and 17.63 Mev were observed. No other B^9 states were resolved below 17.9-Mev excitation. The neutron groups were superimposed on an intense background continuum, attributable to processes leading to the final configuration 2[alpha] + p + n. An angular distribution at 8.7-Mev incident energy of neutrons leading to the 14.67-Mev state is roughly isotropic in the center-of-mass system, and the total cross section is 8 mb. A T=3/2 assignment for the 14.67-Mev state is suggested by its narrow width, and by recent studies of the Li^7(t,p)Li^9 and Li^7(He^3,p)Be^9 reactions. A comparison of the Li^7(He^3,p)Be^9 and Li^7(He^3,n)Be^9 reactions shows that the cross sections for formation of the 14.67-Mev B^9 state and the analogous Be^9 state are approximately equal, if barrier-penetration effects in the outgoing channels are removed.

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