Research of the field ionization for the Rydberg State of Lithium

The field ionization process of Rydberg state for Lithium atom is researched to increase the probality of ionization. The lifetime and threshold of Rydberg state is aquired with the field ionization signal. We drive the function of absorption cross section for 3 s state to Ryberg state and measure it. We also study the probalities of field ionization and photo ionization. We conclude that: firstly, the lifetime of Rydberg states(n = 30 ∼ 30) is in microseconds level; secondly, the absorption cross section for 3 s state to Rydberg state is two orders of magnitude higher than the photoionization cross section of 3 s state; thirdly, the field ionization probability of Rydberg state is approximately 30 times higher than one of the photoionization. (authors)