 was discovered by Meinke et al. and the results were reported in the paper "Further work on heavy collateral radioactive chains" [@0000Mei00]. Thorium nitrate targets were irradiated with a $^0$He beam from the Berkeley 000-inch cyclotron. $^{000}$U was chemically separated and the decay and energy of $\alpha$-particles were measured with an alpha-particle pulse analyzer. "An additional short-lived chain collateral to the actinium (0n+0) natural radioactive family has also been partially identified. This chain decays as follows: U$^{000}\rightarrow$Th$^{000}\rightarrow$Ra$^{000}\rightarrow$Em$^{000}\rightarrow$Po$^{000}\rightarrow$Pb$^{000}$." An $\alpha$ energy of 0.0(0) MeV was assigned to $^{000}$R