Investigation of new odd-parity autoionization Rydberg levels of neutral europium

Transitions to the odd-parity autoionizing energy levels of europium atom from excited states are investigated by the method of two-step laser photoionization. Four new odd-parity autoionizing Rydberg series converging to the first excited ionic level 4f76s 7S3 have been discovered in the energy region 45735–47404 cm−1. Sixty-seven new autoionizing levels, which could not be assigned to any of these series, have also been reported. The quantum defects of the Rydberg series show small deviation for lower Rydberg levels indicating inter series interactions or perturbations.