Pump-probe studies of autoionizing states of noble gases combining laser and synchrotron radiation—The nf′ Rydberg states of neon

A mode-locked tunable Ti:Sapphire oscillator has been synchronized with the time structure of a storage ring and used to study the photoionization of noble gases. In multi-bunch operation of the ring the setup permits the observation of the dynamics from a few nanoseconds down to the tens of picoseconds range. The characteristics of the setup are demonstrated by following the two-color ionization of helium (via the 1s3p 1Po state) and argon (via the 3p5 (2P3/2) 3d state). In the CW mode we have also examined the two-color ionization of neon via the 2p5 (2P1/2) 3d′ state. In neon the nf′ Rydberg series was followed up to n∼50, and the quantum defect was determined.