It is found that in the absence of dissipation and average photon number of the reservoir the linear entropies of the atom and the field varies with time periodically , going to zero at the disentanglement times , and the period is the same as that of bell function and the linear entropy of the total system is zero at any time . if the cavity dissipation and the average photon number of the reservoir is taken into account , the linear entropies of the atom and the field present local maxima and minima and the difference between them diminishes with time , tending to asymptotic values 结果表明，在忽略腔损耗和热库的平均光子数时，原子和场的线性熵有周期性的变化，在没有纠缠的时刻，值为0 ，此时的周期与bell函数相同，而系统的线性熵在任何时刻都为0 ；如果考虑到腔场的损耗和热库的平均光子数，原子和场的线性熵有局部的最大值和最小值，它们之间的差距随时间逐渐减小，趋向一个渐进值。
