We herein report on the density-and temperature-dependent decay of the 93m Nb nuclear excited atom and present a simple interpretation of the underlying physics. This anomaly indicates nuclear resonant absorption and delocalisation of the long-lived Mössbauer state in the crystal. A non-linear magnetoelectric response, on low-frequency drive current, appeared in the bulk metal of a high-purity niobium crystal and then disappeared along with the disappearance of delocalised nuclear excitation. Several non-linear resonant peaks, of the order of several hundred Hertz, increased in magnitude with the applied magnetic field, and the central frequencies of these peaks decreased with temperature.

A search for excited electrons produced in pp collisions at √ s = 13 TeV via a contact interaction qq → ee * is presented. The search uses 36.1 fb −1 of data collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider. Decays of the excited electron into an electron and a pair of quarks (eqq) are targeted in final states with two electrons and two hadronic jets, and decays via a gauge interaction into a neutrino and a W boson (νW) are probed in final states with an electron, missing transverse momentum, and a large-radius jet consistent with a hadronically decaying W boson. No significant excess is observed over the expected backgrounds. Upper limits are calculated for the pp → ee * → eeqq and pp → ee * → eνW production cross sections as a function of the excited electron mass m e * at 95% confidence level. The limits are translated into lower bounds on the compositeness scale parameter of the model as a function of m e *. For m e * < 0.5 TeV, the lower bound for is 11 TeV. In the special case of m e * = , the values of m e * < 4.8 TeV are excluded. The presented limits on are more stringent than those obtained in previous searches.