Charged superstring attached two different D-branes

In this paper we generalized the charged open string attached both ends to the same branes to the case where charged open superstring is stretched between two different D-branes. These branes involve constant background two-dimensions magnetic field. We focus our attention to type II superstring and consider the interaction between branes. We obtain relation between string charge and the separation of two D-branes. Further more we find the modified normal ordering constant and mode expansions of superstring