The Photodissociation Dynamics Of CS₂ Molecule

This thesis is mainly in relation to photodissociation of Carbon Disulfide(CS2)molecule using time-sliced velocity map ion imaging technique combined with Dalian Coherent Light Source(DCLS).These results are beneficial to further understanding of both the evolution of complicated electronically excited potential energy surfaces of CS2 and their topological structures.About forty years ago,the emission spectrum of CS and S2 species were observed from several comets by satellite,but the question "where are these species from?" still remained unclear.In this study,some direct experimental evidences for C+S2 channel from CS2 photodissociation by two-photon UV and one-photon VUV excitations were provided via the velocity map ion imaging technique.The carbon atom product images were acquired at a broad excitation wavelength range,which evidentially proved S2 was a daughter of CS2 molecule in the interstellar medium.Besides,the S+CS product channel was found to be relatively large,hence CS2 molecules,which exist in the upper atmosphere,should participate in the evolution of atmospheric composition and in the cycling of atmosphere by absorbing ultraviolet or vacuum ultraviolet solar irradiation followed by photodissociation,such as the formation of acid rain.Carbon disulfide(CS2)is a linear triatomic molecule with 16 valence electrons,its structure and photodissociation behavior are similar to that of the previously studied CO2 and OCS.It is a prototype molecular system to study the evolution of wave-packets on complex potentials.Here we studied the CS2 photodissociation process via both two-photon UV and one photon VUV excitations,leading to vibrationally excited CS and S2 product images.Both the anisotropy parameter ? values and vibrational state distributions of CS and S2 products were obtained by data simulations.After analysis of the ? values,we pointed out that the two 1B2 electronic states of CS2 should play a major role in the isomerization and photodissociation processes occurring at high energies.And plausible mechanisms of the photodissociation of CS2 had been proposed with the help of theoretical calculation.However,high electronic state product channels,such as C(1D2)+S2 and C+S2(a1?g/b1?g+)channels,are still ambiguous and await for an appropriate explanation theoretically.With the help of laser dispersion design,it is possible to study the complex system like CS2.And the DCLS can provide 50-150 nm tunable VUV-FEL light source,which means quick switch of photolysis wavelength within a wide range is available,therefore,the overall efficiency of the experiment has been greatly improved.Compared to(2+1)REMPI detection,the VUV light source produced by four wave mixing technique had increased the efficiency of carbon atom detection.Lastly,we refer to time-sliced velocity map ion imaging again,which is one of the most important techniques during the state-to-state dynamics study of CS2 molecule.