## Doctoral Dissertations

Winter 1992

Dissertation

Physics

#### Degree Name

Doctor of Philosophy

John R Calarco

#### Abstract

We have excited the giant resonance region in $\sp{12}$C via inelastic electron scattering and have measured the first complete angular correlations for charged particle (p and $\alpha$) emission for this reaction for six values of momentum transfer ranging from 0.24fm$\sp{-1}$ to 0.93fm$\sp{-1}$.

By analyzing the $\alpha$ emission decay channels via the Legendre and resonance formalisms, we unambiguously determined the multipole contributions to the total cross section for $\alpha$ decay to the ground state of $\sp8$Be ($\alpha\sb0$ decay) and have set limits on these contributions for $\alpha$ decay to the first excited state of $\sp8$Be ($\alpha\sb1$ decay). We have found that, in both cases, E2 radiation is the strongest contribution as theoretically expected but that E0 and E3 contributions cannot be ignored. This emphasizes the importance of measuring complete correlations.

By constructing total multipole form factors, the first to be measured for an isoscalar resonance in the $\sp{12}$C nucleus tagged on $\alpha$ decay, and fitting these form factors within the distorted wave Born approximation and with a transition charge density specified by the Tassie model, we were able to deduce multipole transition strengths. These strengths were then expressed as fractions of the appropriate sum rule since this approach provides us with a reliable way to compare the mean value of transition strengths for various transition operators.

In particular, the (e,e$\sp\prime\alpha$) E2 isoscalar sum rule strengths were compared to those deduced from (p,p$\sp\prime\alpha$) and ($\alpha,\alpha\sp\prime\alpha$) experiments for both $\alpha\sb0$ and $\alpha\sb1$ decay and for several energy regimes. The result is that the proton scattering strengths agree with those from our analysis while those from $\alpha$ scattering are too low. For these two experiments, however, the cross section was assumed to be entirely E2 in nature and complete angular correlations were not measured, implying insensitivity to interfering multipoles.

COinS