Cross sections for the reactions Mn(n, p), Fe(n, p), and Ni(n, p) have been measured at an incident energy of 198 MeV, with protons observed over a range of energies corresponding to excitations of up to about 35 MeV in the residual nuclei Cr, Mn, and Co, respectively. Measurements were carried out at center-of-mass angles between 1. 6' and 19. 9'. A multipole analysis of the results yielded the distribution of Gamow-Teller (GT) and spin-dipole strength for each target. The total GT strength below an excitation energy of 8.5 MeV was 1.? units for Mn, 2.9 units for Fe, and 3.8 units for Ni. Shell model calculations of the GT strength distribution, carried out in a restricted vector space, show fair to good agreement with the data up to an excitation energy of 8.5 MeV, but overestimate the total strength by a factor of between 3 and 4.

Results from a complete set of polarization-transfer observables for quasifree (prf) scattering at 495 MeV are reported. Measurements were carried out on CD2, carbon, and calcium targets at a laboratory scattering angle of 18° using the new neutron time-of-flight facility at LAMPF. The ratio of spinlongitudinal to spin-transverse responses at a momentum transfer of approximately 1.72 fm _1 is extracted from the data and compared to distorted-wave calculations incorporating a random-phase approximation description of the nuclear response. No enhancement is observed in the experimental ratio.PACS numbers: 25.40.Lw, 24.70.+SThe investigation of collective spin-isospin excitations in nuclei has been a rich field for observation of new phenomena [1]. At low excitation energies (co < 20 MeV) and small momentum transfers (q ^ 0) the spin-isospin particle-hole interaction is strongly repulsive, leading to collective excitations such as the giant Gamow-Teller resonance. The quenching of measured Gamow-Teller strengths relative to a model-independent sum rule has led to extensive theoretical studies of possible mechanisms, ranging from conventional configuration mixing to underlying subnucleonic degrees of freedom.At higher excitations (co^ 30-160 MeV) and momentum transfers (q~\-2 fm -1 ), the spin-longitudinal interaction, taken to be driven by one-pion exchange, is expected to become mildly attractive, while the spin-transverse interaction mediated by rho exchange continues to remain repulsive due to the larger mass of the rho compared to the pion. Although signatures of shell structure, such as discrete states and giant resonances, disappear in this sector, the nucleus should continue to respond collectively through the action of the residual particle-hole interaction. The very dissimilar momentum dependence of the spin-longitudinal and -transverse interactions should give rise to different phenomena in the corresponding nuclear spin-isospin responses. For example, relative to a noninteracting Fermi gas, the spin-transverse response (RT) is predicted to be quenched and pushed to higher energy loss, while the spin-longitudinal response (R L ) is predicted to be enhanced and shifted to lower energy loss due to an enhanced pion field within the nucleus [2]. The very (non)existence of such collectivity is directly connected to the form and magnitude of the spinisospin-dependent parts of the residual interaction, and hence to the basic underlying degrees of freedom in the nuclear system.Quasifree scattering can provide detailed information on the nuclear response. At intermediate energies (incident particle energies of several hundred MeV) and moderate momentum transfers (q > 0.5 fm _1 ), quasifree scattering is a dominant part of the nuclear excitation spectrum. A broad structure is seen with a peak near co=q 2 /2m (m being the nucleon mass) and a width determined by the Fermi momentum. At momentum transfers above about 1 fm" 1 , this region of excitation is well separated from the low-lying discrete states and resonance r...

At 200, 300, and 400 MeV bombarding energies, we measured cross section angular distributions for the Li(p, n) Be(g.s. +0.43 MeV) reaction and 0' cross sections for the ' C(p, n)' N(g. s.) reaction.Systematics of these reactions are presented.The center-of-mass cross section for the Li(p, n) Be(g.s. +0.43 MeV) reaction, when plotted as a function of momentum transfer, is nearly independent of energy. The laboratory cross section for this reaction at 0' in the energy range from 60 to 400 MeV is also independent of energy, having a constant value, to within experimental errors, of 35.5 mb/sr with an estimated uncertainty of +1.5 mb/sr.

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PART l AL COPYRIGHT L IZENSE I hereby g r a n t t o Simon F r a s e r U n l v e r s l t y the r i g h t t o lend my t h e s i s , p r o j e c t o r extended essay ( t h e t i t l e o f which i s shown below) t o u s e r s o f t h e Simon F r a s e r University L l b r a r y , and t o make p a r t i a l o r s i n g l e c o p i e s o n l y f o r such users o r I n response t o a r e q u e s t from t h e l i b r a r y o f any o t h e r u n l v e r s l t y , o r o t h e r e d u c a t i o n a l I n s t i t u t i o n , on i t s own b e h a l f o r f o r one o f I t s users. I f u r t h e r egree t h a t p e r m i s s i o n f o r m u l t i p l e copying o f this work f o r s c h o l a r l y purpcses may be g r a n t e d by me o r t h e Dean o f Graduate Studies. I t i s u n d e r s t m d t h a t c o p y i n g o r publication o f t h i s work f o r f i n a n c l~l gain s h a l l not be a l l o w e d w i t h o u t my w r i t t e n permission. Abstract Tests of isospin symmetry in (n,p), (p,p') and (p,n) reactions at 280 MeV for populating the T = 1 isospin triads in A=6 and A=12 nuclei have been performed at TRIUMF. DWIA calculations for the A=12 triad where the known f t asymmetry is included in the analysis show good agreement with experimental (n,p) and (p,pl) data. Similar calculations for the A=6 triad where no asymmetry was assumed show that twice the (p,pt) cross sections taken in the region q = 0.2-0.35 fm-' are slightly ((5.1 f 2.4)%) lower compared with the (p,n) and (n,p) cross sections at q = 0.1 fm-'. This asymmetry may be negligible when the data are extrapolated to q = 0. At q = 0.67 fm-' the the (n,p) cross section is = 45% larger than the (p,pt) cross section. DedicationIn memory of my parents. AcknowledgementI would like to thank Prof. Hausser for taking me on as a graduate student and for financial support during this time, and for sharing with me his wealth of knowledge and experience in all stages of the experiment and ana1ysis;and in particular for his assistance in the theoretical aspects of this work. As well, many people have assisted and advised me in many ways throughout the course of my work at TRIUMF: