To test the Pauli exclusion principle for the helium atom, Gordon Drake carried out very precise calculations for hypothetical states of the He atom that violate it, which are called paronic states. Later, K. Deilamian et al. used an atomic beam spectrometer to search for the paronic state 1s2s S 0 calculated by Drake. The search was unsuccessful and showed that the statistical weight of this paronic state has an upper limit of 5 × 10. (The exclusion principle implies a weight of zero.)