The trident process in laser pulses

We study the trident process in laser pulses. We provide exact numerical results for all contributions, including the difficult exchange term. We show that all terms are in general important for a short pulse. For a long pulse we identify a term that gives the dominant contribution even if the intensity is only moderately high, $a_0gtrsim1$, which is an experimentally important regime where the standard locally-constant-field (LCF) approximation cannot be used. We show that the spectrum has a richer structure at $a_0sim1$, compared to the LCF regime $a_0gg1$. We study the convergence to LCF as $a_0$ increases and how this convergence depends on the momentum of the initial electron. We also identify the terms that dominate at high energy.