R-MATRIX FLOQUET THEORY OF MULTIPHOTON PROCESSES .9. 3-PHOTON LASER-INDUCED DEGENERATE STATES IN ARGON

A bound state and an autoionizing state of a complex atom, resonantly coupled by a multiphoton process in a strong laser field, can become d egenerate at a certain laser frequency and intensity. These states are referred to as laser-induced degenerate states or LIDS. The ab initio , fully nonperturbative R-matrix Floquet method has been used to study the behaviour of LIDS coupled by three photons in argon. A simple sin gle-photon model has been successfully applied to interpret the calcul ation and to predict a further degeneracy at a higher frequency and in tensity.