Search for nuclear excitation by electronic transition in $^{235}$U

We have searched for the nuclear excitation by electronic transition (NEET) of the isomeric level at 76 eV in $^{235}$U in a plasma induced by a YAG laser with an energy of 1 Joule and a full width at half maximum time distribution of 5 ns, operating at an intensity of 10$^{13}$ W cm$^{–2}$. We present a thorough description of the experimental conditions and analysis of our data. In this experimental situation we do not detect any excitation of the isomeric level, a result that is at variance with a previously reported one. An upper limit of 6×10$^{–6}$ per atom and per second averaged over the laser-pulse width has been set on the nuclear excitation rate. This value is compared with results obtained in previous experimental and theoretical works