Three-body Fragmentation Dynamics Of OCS³⁺induced By Intermediate Energy Ne⁴⁺ion Impact

The fragmentation experiment of OCS molecule and cluster induced by 56keV/u Ne⁴⁺ions was performed by using reaction microscope,and the corresponding dissociation dynamics was investigated.By detecting the three fragment ions in coincidence,the Newton diagram and Dalitz plot for the three-body fragmentation of differently charged parent ions are reconstructed,from which the sequential dissociation is distinguished from nonsequential dissociation clearly.We also reconstructed the 3D momenta of all ions and the corresponding kinetic energy release?KER?distributions for the three-body fragmentation ofOCS³⁺ion.It is found that a peak maximum of the KER distribution locates at about 25 eV,and a shoulder structure appears around 18 eV.This result is consistent with previous heavy ion experiments with different perturbation strengths.Taking into account that the KER distribution is related to the initial state population of theOCS³⁺parent ions,it can be concluded that the perturbation strength is not a decisive parameter leading to the initial states population ofOCS³⁺ions.By analyzing the kinetic energy of ions from each fragmentation process,we found that the KER peak at 25 eV corresponds to nonsequential dissociation processes,but the shoulder at 18 eV arises from both sequential and nonsequential dissociation processes.This phenomenon suggests the parentOCS³⁺ions in ground state and low excitation states tend to fragment through sequential dissociation,while those in high excitation states tend to fragment through nosequential dissociation.As for dissociation process for the three-body fragmentation ofOCS⁴⁺ion,we only find sequential dissociation that produce S²⁺/CO²⁺orO²⁺/CS²⁺in the first step.And we didn't find any sequential dissociation process that produceS⁺/CO³⁺orO⁺/CS³⁺firstly.This phenomenon suggests that a molecular ion with two charges tends to survive as a metastable ion for a long life,but that has charge more than three tends to fragment immediately,due to the strong repulsive fore between nuclear.Furthermore,we reconstructed the KER distributions in the second fragmentation step ofOCS³⁺sequential dissociation,whose peak maximum is at 6.2 eV,corresponding to X ³?,¹?⁺and ¹?metastable states ofCO²⁺ion.By comparing our experimental results with previous ones,we concluded that the origin of sequential dissociation process is the existence of metastable dictation,the reconstructed KER in the second step manifest the initial state information of the metastable dictation.As for dissociation process for the three-body fragmentation of?OCS?₂³⁺molecular dimer ion,we findOCS²⁺metastable ions obviously by analyzing Dalitz plot and Newton diagram.Taking into account the large internuclear distance and small bond energy,we consider the fragmentation of OCSdimer is more suitable for investigation of the metastable states dissociation of doubly charged OCS.