Dr. Kent Scheller and Dr. Shadow Robinson, faculty members in the Department of Geology and Physics, presented papers at the 2006 Division of Nuclear Physics Annual Meeting.  This meeting was held October 25-28, 2006 in Nashville, TN.

### Abstract: CC.00001 : The $K$ quantum number in the Shell Model---$^{50}$Cr

9:00 AM–9:12 AM

#### Authors:

(U. Southern Indiana)

Alberto Escuderos
Larry Zamick
(Rutgers U.)

It was suggested~[1,2] that the $10^+_1$ state in $^{50}$Cr at 6.340~MeV does not belong to the $K=0^+$ g.s. band. In~[1] it is noted that the static quadrupole moments of the $J=2^+_1$--$8^+_1$ states are all negative, but that of $10^+_1$ is positive. While Ref.~[1] suggested that the $10^+_1$ state belongs to a high $K$ prolate band, in Ref.~[2] they assign it as $K=10^+$. There is a nearby second $10^+$ state. However, the $B(E2)_{10^+_2 \rightarrow 10^+_1}$ was not quoted by either group. In this work, we performed full $fp$ shell model calculations using four different interactions: FPD6, KB3, GXPF1, and GXPF1A. The results for $B(E2)_{10^+_2 \rightarrow 10^+_1}$ are robust around 135~e$^2$fm$^4$ and suggest strong $K$ mixing. It is not clear what the $K$ value for the $10_2^+$ state is. With FPD6, $Q(10^+_2)$ is negative, suggesting it is a member of the $K=0^+$ band. But it is hard to understand how to get strong mixing of $K=0^+$ and $K=10^+$. With the other interactions, $Q(10^+_2)$ is positive and thus inconsistent with a $K=0^+$ (prolate) band. If we assume that the $10^+_1$ state has $K=10^+$ and the $8^+_1$ state has $K=0^+$, then the $B(E2)_{10^+_1 \rightarrow 8^+_1}$ would vanish. However, for the last three interactions, the corresponding $B(E2)$ is about 75~e$^2$fm$^4$, which implies substantial $K$ mixing. Thus, while a $K=10^+$ assignment for the $10^+_1$ states makes the most sense in terms of energy systematics, in detail the situation is more complicated. [1] L.~Zamick et al., Phys. Rev. C {\bf 53}, 188 (1996); Phys. Rev. C {\bf 54}, 956 (1996). [2] F.~Brandolini et al., Phys. Rev. C {\bf 66}, 021302(R) (2002).
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### Abstract: CC.00003 : A g-factor puzzle for the N=38 nuclei:First measurement of the $^{70}$Ge 4$_{1}^+$ magnetic moment.

9:24 AM–9:36 AM

#### Authors:

Plamen Boutachkov
G. Kumbartzki
N. Benczer-Koller
(Rutgers University)

S. Robinson
(University of Southern Indiana)

A. Escuderos
E. Stefanova
Y. Sharon
L. Zamick
(Rutgers University)

E. McCutchan
V. Werner
H. Ai
G. Gurdal
A. Heinz
J. Qian
E. Williams
R. Winkler
(Yale University)

A. Garnsworthy
N. Thompson
(University of Surrey)

P. Maier-Komor
(Technische Universitat Munchen)

The transient field technique in inverse kinematics allows $g$-factor studies of short-lived states. This method gives information on both the sign and the magnitude of the $g$ factor. In a recent experiment, the $g$ factor of the 4$^+_1$ state of $^{68}_{30}$Zn$_{38}$ was measured to be -0.37(17) suggesting a significant neutron g$_{9/2}$ contribution to the wave function[1]. However, shell model calculations in the 0f$_{5/2}$,1p$_{3/2}$,1p$_{1/2}$,0g$_{9/2}$ space [1] predict a positive, nearly zero $g$ factor. To obtain more information on this region we measured the magnetic moment of the 4$^+_1$ in $^{70}_{32}$Ge$_{38}$. The measurement was performed at WNSL, Yale, using a 275 MeV $^{70}$Ge beam and a multilayered C+Gd+Cu target. A positive $g$ factor was obtained. The measured magnetic moment was compared to full $fp$ shell model calculations which we performed with the code ANTOINE using several effective interactions. The results were in good agreement with the experiment. The experiment and the implications of the new results will be discussed.\\ 1. J. Leske {\it et al.}, Phys. Rev C {\bf 72}, 044301 (2005).

### Abstract: HE.00004 : $^{24}$Mg($\alpha$,$\gamma )^{28}$Si Resonance Parameters at Low Alpha Energies

2:36 PM–2:48 PM

#### Authors:

Elizabeth Strandberg
Heide Costantini
Joachim Goerres
Hye Young Lee
Edward Stech
Michael Wiescher
(University of Notre Dame)

Aaron Couture
(Los Alamos National Laboratory)

Kent Scheller
(University of Southern Indiana)

$^{28}$Si is formed by successive alpha captures during later stages of stellar burning; for carbon burning, the relevant alpha energy range is 1.0 to 1.5MeV. Previous measurements of the $^{24}$Mg($\alpha$,$\gamma )^{28}$Si reaction observed only one resonance in this energy range, although there are several $^{28}$Si states that appear favorable for formation by this reaction. Using a high efficiency coincidence detection system, several new resonances were observed between 1.1 and 1.5MeV, and an upper limit for any lower energy resonances was obtained. Newly calculated resonance parameters and reaction rates will be discussed.