First identification of excited states in $^{114,115}$Rh

Excited states in the very neutron-rich nuclei $^{114, 115}$Rh have been identified for the first time from a study of the prompt $\gamma$-rays emitted in the spontaneous fission of $^ {252}$Cf with the Gammasphere detector array. Eight levels with twelve transitions in the $\Delta I=1$ yrast band and five levels with eight transition in a side band in $^{114}$Rh are found. The level scheme is proposed to be built on $7^-$ excited state. The signature inversion of the yrast bands in $^ {106, 112, 114}$Rh are observed and the inversion point of $^ {114}$Rh is determined to be 10.6$\hbar$, which is smaller than 12.5$\hbar$ of $^{112}$Rh and 13.7$\hbar$ of $^{106}$Rh. Possible explanations will be presented. The level scheme of $^ {115}$Rh is established by observing eight levels with thirteen transitions in the yrast band and five levels with eight transition in a side band (yrare band). The existence of the large signature splitting and a yrare band in $^{115}$Rh shows features which are typical for triaxially deformed nuclei. Calculations based on the rigid-triaxial-rotor- plusquasiparticle model are performed to predict triaxiality with $\gamma =28^{\circ}$ for $^{115}$Rh. The results will be reported.