Ultrafast Coulomb explosion of the NH3 dimer, trimer, and tetramer in strong laser fields

This study investigates the ultrafast fragmentation of ammonia clusters, (NH₃)ₙ ($n=2$, 3, and 4), by using ion-ion multibody coincidence measurements after interaction with a strong femtosecond laser. Specifically, the Coulomb explosion and proton transfer channels in the dimer, as well as the Coulomb explosion of tri- and tetramers, are assigned. The kinetic energy release distributions and Newton plots of each channel are extracted and analyzed. To gain further insights into the dissociation process, an ab initio molecular dynamics simulation was performed to uncover the dissociation mechanism. In addition, the stretching of clusters during the Coulomb explosion was identified using classical trajectory calculation combined with the genetic algorithm. This combined experimental and theoretical study holds significant importance in improving the understanding of the ultrafast Coulomb explosion process in molecular clusters.