Photoelectron spectroscopy of ammonia via a fast predissociative state

Abstract

We report a study on resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) involving the fast predissociative à state of ammonia, using nano- and femtosecond lasers. The multiphoton scheme involves (1+1), (2+2), (2+2)+1 and (2+2)+2 photon processes. We have found a progression of stretching vibrations ν₁ in the PE spectrum when pumping NH₃ Ã v₂=0, 1 and 3 as intermediate states. The stretching vibration intensity distributions in the photoelectron spectrum are calculated by using the Chebychev method of the wavepacket propagation. The femtosecond spectrum shows a similar feature to the nanosecond spectrum. However, high laser power also causes band broadening and shifting effect as well as above threshold multiphoton ionization.