An isometric state of Sn¹¹⁵ excited by the In¹¹⁵ (p, n) reaction

Abstract

Using a pulsed-beam technique, a short-lived isomeric state of $\text{Sn}{}^{115}\text{(T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 159±1μ}\text{sec}\text{)}$ was excited and its decay properties investigated. Three gamma-rays of 107, 120 and 500 keV energy of the same half-life were found, denoting that the isomeric state decays by a double cascade. The last two gamma-rays were coincident. The K-shell and total internal conversion coefficients were determined for the 107 and 120 keV transitions by measuring the yields of both singles and gamma-gamma coincidence spectra. The following values were obtained: α_K(120) = 0.69±0.07; α_T(120) = 0.78±0.08; α_K(107) = 3.8±0.8; α_T(107) = 5.4±0.7, which are consistent with an M2 transition of 107 keV and an E2 transition of 120 keV energy. A scheme for the first excited states of Sn¹¹⁵ is proposed and a comparison with the pairing plus quadrupole force calculation of Kisslinger and Sorensen is made.