Stark mixing in the exotic helium atom cascade process

Our purpose is to construct a realistic cascade model for exotic helium atoms beyond the phenomenological ones used so far, and to answer the problem of the s- and p-orbit absorption ratio. The difficulty in resolving this problem mainly arises from the Stark-mixing process, which induces transitions between different angular momentum states with the same principal quantum number. As a result of the Stark-mixing, the high n-state absorption rate increases. We newly derive the Stark-mixing transition rate for exotic helium atoms using the impact-parameter method, and compare it with the rate from a phenomenological model, called the sliding-transition model. (orig.)