强激光场中真空极化效应

摘要

The probability of the electron-positron pair creation in vacuum by a time-dependent solution-like electric field is calculated. It has been found that, in order to have prominent pair production, the electric field intensity should be higher than the Schwinger threshold and the pulse duration should be longer than a threshold. The former condition guarantees that the electron in the negative energy state could gain enough energy to transit into a positive-energy state in Compton time. The latter condition is related to momentum requirement for the transition.%通过求解狄拉克方程,对强激光场下真空极化问题进行了研究.理论计算结果表明:在仅随时间变化的电场下,要激发狄拉克海中负能级的电子,需要两个阈值条件,即激光场的电场强度大于等于1016 V/cm和激光场的持续时间大于等于10-21 s.前者主要保证负能态电子有足够的能量跃迁到正能态,后者主要是保证电子在跃迁过程中动量亏损得以补偿.