Ac Stark shifts induced by a YAG laser in the nP and nF Rydberg series in xenon

Nonresonant ac Stark shifts of Rydberg states in Xe have been investigated by probing an atomic transition with a weak UV light in the presence of an intense YAG-laser pulse. Rydberg atoms produced through two-photon excitation, 5p → np (n = 15–48) and 5p → nf (n = 12–49), are subsequently ionized. IR-laser-induced shifts of the resonant ionization profiles are then measured. The measured shift, 3.9 ± 0.3 cm−1 at 1010 W cm−2, is more than a factor of 2 smaller than that expected from the basis of ponderomotive term, 8.5 cm−1 at 1010 W cm−2. In addition, the shift varies linearly as a function of the IR-laser intensity and does not depend on the principal quantum number of the np and nf series investigated here.