Identification of new negative-parity levels in ${}^{152,154}\mathrm{Nd}$

From an experiment with Gammasphere and a ${}^{252}\mathrm{Cf}$ spontaneous fission source, a new negative-parity band in ${}^{154}\mathrm{Nd}$ and new negative-parity levels in ${}^{152}\mathrm{Nd}$ were identified and the yrast bands were extended to ${18}^{+}$ in ${}^{154}\mathrm{Nd}$ and ${20}^{+}$ in ${}^{152}\mathrm{Nd}$ in a triple gamma coincidence study. These new negative-parity bands are consistent with octupole vibrational mode. There is a constant difference as a function of spin between the $J_1$ values for the negative-parity band in ${}^{152}\mathrm{Nd}$ and $J_1$ for the similar negative-parity band in ${}^{154}\mathrm{Nd},$ however, their $J_2$ values are essentially identical. These bands indicate a new kind of identical band.