Femtosecond photoelectron imaging of NO at 410 nm

The simultaneous measurement of the photoelectron kinetic energy and angular distributions of NO were performed as a function of 410 nm laser intensities by femtosecond photoelectron imaging. The photoelectron kinetic energies are nearly independent of the laser intensities. The insensitivity of the photoelectron kinetic energy to the laser peak intensity suggests that peaks in the photoelectron spectra result from Freemen resonance, characteristic of the occurrence of real population on the intermediate states. The relative amplitudes of photoelectron peaks indicate that lower laser intensities emphasize the resonant population while higher laser intensities favor nonresonant population. The A2 Σ+(υ = 2) state can be weakly coupled to the BΠ2(υ=4) state, results in a small part of population on BΠ2(υ=4) state transferred from A2 Σ+(υ = 2) state. The strong field effect leads to more anisotropy of ATI than that of non-ATI. The modulation of populations in electronic states can be achieved by adjusting laser peak intensities. The results can provide some important basis for realizing quantum manipulation of molecules experimentally.