Visualizing vibrationally resolved attosecond time delay in resonance-enhanced multiphoton ionization of NO molecules

We demonstrate a combined experimental and theoretical study to measure attosecond-resolved resonance-enhanced multiphoton ionization (REMPI) of NO molecules using the phase-locked strong 400-nm and weak 800-nm laser pulses. By performing the time-dependent wave-packet simulation, our results show that a vibrational-dependent REMPI occurs through two intermediate electronic states A (2)Sigma(+) and B (2)Pi, from which a molecular wave packet at different internuclear distances results in an ionization time delay up to 630 as. We find that the nonadiabatic coupling between electronic states A (2)Sigma(+)(v = 2) and B (2)Pi (v ' = 4) plays a crucial role in the angular-dependent phase variations of emitted electrons. This work extends the application of the REMPI technique to visualize the effect of vibrational motions of intermediate resonance states on the strong-field-induced ionization in attosecond timescales.