A new Floquet-based method for calculation of multiphoton transition probabilities of non-hydrogenic atoms in strong microwave fields

A new Floquet-based method is introduced which can be used widely in calcul ations on atoms and molecules in strong microwave or laser fields. Accurate calculations using this new method take several orders of magnitude less C PU time than with the standard Floquet approach and are less expensive in t erms of computer memory than with the single Brillouin zone method. Illustr ative results have been obtained for an experimentally examined threshold m icrowave spectrum of potassium; novel structure in this has been found and understood theoretically.