Diffusionlike aspects of multiphoton absorption in electrically polarized highly excited hydrogen atoms

We have observed microwave transitions of overall order up to 16 in hydrogen atoms initially in n = 60 lowest-energy Stark states. Increases in n as large as 4 occur with little change in the electric quantum number n/sub e/. Thus hydrogen atoms electrically polarized along the direction of a strong linearly polarized microwave electric field respond one dimensionally to this field by maintaining their polarization. At some microwave frequencies the final-state n-distribution is smooth above threshold field values estimated for stochastic transitions.