Quenching of high Rydberg states of sodium in strong 1.06 μm laser fields

An experiment is described in which the absorption spectrum of the Rydberg series of sodium (principal quantum number, n>or=4) is studied in a strong non-resonant laser field. The field is generated from a PTM laser oscillator/amplifier system operating at 1.06 mu m, producing 250 MW in a 10 ns pulse. After splitting, most of the beam is focused into a sodium heat pipe oven where field strengths up to 8*10 7 V m -1 are generated. The other fraction of the beam is used to form a plasma from a solid lead target which is used as a continuum source for absorption spectroscopic measurements. Quenching of high-lying state (n>11) has been studied, the lowest quenched state being found to be dependent on laser intensity I l in the form I l varies as n -(3.9+or-0.8) . Such quenching is significantly different from that observed in a DC field. Additionally, line broadening, profile asymmetry and intensity dependent shifts are observed.