Precise Lifetime Measurement of $2^+_1$ State in $^{120}$Te by Recoil Distance Doppler Shift Method

The lifetime of the first 2$^+$ state of $^{120}$Te has been measured using a combination of inverse-kinematics Coulomb excitation well below the Coulomb barrier and the recoil distance Doppler shift (RDDS) method. This technique yields lifetimes with uncertainties of approximately 2\%, due mostly to a large Doppler shift and nearly background-free gamma-ray spectra. The 2$^+_2$ and 4$^+_1$ excited states were also observed, providing a measure of the transition strengths to these states relative to the 2$^+_1$ state. Results are compared to calculations with and without $2p-2h$ proton intruder configurations across the $Z=50$ shell gap. This work is supported by the U.S. DOE under contract No. DE-FG02-91ER-40609.