${}^{108}\mathrm{Sn}$ studied with intermediate-energy Coulomb excitation

The unstable neutron-deficient ${}^{108}\mathrm{Sn}$ isotope has been studied in inverse kinematics by intermediate-energy Coulomb excitation using the RISING/FRS experimental setup at GSI. This is the highest Z nucleus studied so far with this method. Its reduced transition probability B (E2;0${}_{g.s.}^{+}\to 2_1^{+})$ has been measured for the first time. The extracted B($E2$) value of $0.230(57)e^2{b}^2$ has been determined relative to the known value in the stable ${}^{112}\mathrm{Sn}$ isotope. The result is discussed in the framework of recent large-scale shell model calculations performed with realistic effective interactions. The roles of particle-hole excitations of the ${}^{100}\mathrm{Sn}$ core and of the $Z=50$ shell gap for the E2 polarization are investigated.

Figure 1

De-excitation γ-ray lines following $0_{g.s.}^{+}\to 2_1^{+}$ Coulomb excitation of the ${}^{112,108}\mathrm{Sn}$ projectiles, respectively.

Figure 2

Calculated evolution of the proton ESPE with the neutron number N along the chain of Sn isotopes.

Figure 3

Comparison of measured $B(E2\uparrow$) values with LSSM predictions by taking into account ph core excitations. The $t=0$ curve corresponds to calculations only for the valence neutrons as active particles. The $t=2$ curve shows the major contribution as given by proton core excitations. The $t=4$ curves are shown for the whole tin chain in a truncated proton model space and untruncated in the gds major shell.