在二维的空间里的离子迁移谱简化模型，离子从封闭空间的中间飞过，封闭空间充满的空气分子，发生多次碰撞后到达时间-After the two-dimensional space of the ion mobility spectrometry simplified model, ions　the middle of the enclosed space flying, air molecules enclosed space is filled, the occurrence of multiple collisions arrival time