Microwave multiphoton n-decreasing transitions in electrically polarised, highly excited hydrogen atoms

Microwave n-decreasing multiphoton transitions have been observed, for the first time, in n=60 and n=63 hydrogen atoms initially formed static-field polarised in their lowest energy Stark states with electric quantum number n e =1-n. Resonant n changing down one or two units can dominate the overall microwave transition probability. Regions of microwave frequency exist where n changing down two to four units significantly reduces the microwave ionisation probability.