https://arxiv.org/pdf/1812.11447위 링크의 정보 참고하시면 좋을 것 같습니다. As mentioned in the three step model, at one half-cycle after ionization, the electron turns back towards the parent ion to recombine when the laser electric field changes sign. Hence, the harmonics are produced twice each cycle and each half cycle of the driving laser produces a short (subfemtosecond) burst of XUV radiation. Thus, the ha..