High-order harmonic generation enhanced by laser-induced electron recollision

We theoretically investigate correlated electron dynamics in high-order harmonic generation, using all-electron ab initio simulations for three-dimensional real alkali-metal atoms. The resulting harmonic spectra exhibit a plateau extended beyond the usual cutoff and a prominent resonance peak above the plateau. These remarkable features arise from the cation response dramatically enhanced by laser-induced electron recollision, which is a key process of attosecond science. This demonstrates that high-order harmonic spectroscopy provides possibilities to explore dynamical electron correlation in strong laser pulses.