The influence of molecular pre-orientation on the resonance-enhanced multi-photon ionization dynamics

- The pre-orientation and ionization dynamics of LiH molecules are studied together.
- The molecular orientation has some influences on the photoionization dynamics.
- The photoelectron angular distribution is associated with the molecular orientation.
- The photoelectron angular distribution varies with the laser parameters.

We investigate theoretically the influence of molecular pre-orientation on the resonance-enhanced multi-photon ionization (REMPI) dynamics, taking the LiH molecule for example. The LiH molecule is first pre-oriented by a single-cycle pulse (SCP) in terahertz (THz) region, and then excited by the femtosecond pump pulse, and finally ionized by the femtosecond probe pulse. We focus on the impact of the pre-orientation on the ionization probability, energy- and angle-resolved photoelectron spectra and photoelectron angular distribution (PAD). It is found that the ionization probability and peak intensity of energy-resolved photoelectron spectra are significantly affected by molecular orientation. The angle-resolved photoelectron spectra are related to the molecular orientation. The PAD can be changed by varying the delay time between the THz SCP and pump pulse. We also investigate the effect of temperature on excitation and ionization dynamics.

In Case 0, (a) the time-dependent populations in the excited state Pexc(t) (black solid line) and ionization continuum state Pion(t) (red dotted line), (b) the energy-resolved photoelectron spectra PI(En), (c) the angle-resolved photoelectron spectra PI(En,α), and (d) the photoelectron angular distribution Ω(β). 145