| This dissertation mainly presents the experimental studies on the photodissociation spectrum (the depletion spectrum of parent CS2+ ions and the enhanced spectrum of CS+ and S+) and photodissociation dynamics of the small molecular ions including sulfur(CS2+). The main results are summarized as followings.Study on the [1+1] photodissociation spectra of CS2+ via Hâ†B2∑u+â†X2Î g,3/2 transitionPure parent ions, CS2+ (X2Î g,3/2(000)), were prepared by [3+1] REMPI of CS2 molecules at 483.2nm. The photodissociation spectra (depletion spectrum of parent CS2+ ions and the enhanced spectrum of CS+ and S+ )via B2∑u+ (Ï…1Ï…20;Ï…1= 0～2,Ï…2=0,2)â†X2Î g,3/2 (000) transitions were obtained by scanning the first dissociation laserλ1 at the range of 270285nm. The measured branching ratios CS+/S+ of 2～4 indicates that in the [1+1] photodissociation process the dissociation channel of S+(4S) +CS( X1∑+ ) is not a favorable channel in comparison with that of CS+(X2∑+)+S(3P). The released kinetic energy of fragment ions in the [1+1] photodissociation process of CS2+ is limited and the products may be in the excitedstates. The [1+1] photodissociation process of CS2+ via the Hâ†B2∑u+â†X2Î g,3/2 transition can be expressed as followingCS2+(B2∑u+)(?)CS2+ (higher state within 8.7～9.2eV)CS2+ (higher state within 8.7～9.2eV)→CS+S+ CS2+ (higher state within 8.7～9.2eV)→CS++S Study on the [1+1'] photodissociation spectra of CS2+ via C2∑g+â†B2∑uâ†X2Î g,3/2 transitionThe [1+1'] photodissociation spectra (depletion spectrum of CS2+ ions and the enhanced spectrum of CS+ and S+) via C2∑g+(Ï…1Ï…20)â†B2∑u+ (000,100)â†X2Î g,3/2(000) transitions were obtained by fixing the first dissociation laserλ1 at281.9 or 277.2 nm and scanning the second dissociation laserλ2 at the wavelength range of 606?765nm. The transition bands(Ï…1= 0?4,Ï…2= 0,2,4) were assigned in thespectrum and the ten vibrational bands for the C2∑g+(Ï…1Ï…20)â†B2∑u+(100) transitionswere observed for the first time. The spectroscopic constants of v1= 666.2±2.5 cm-1, v2= 363.2±1.9 cm-1, X11= -5.5±0.1 cm-1, X22= 1.6±0.1 cm-1, X12= -8.6±0.2 cm-1, and k122= 44.9±2.5 cm-1 (Fermi resonance constant) for C2∑g+ state are deduced by usingleast-squares fitting according to the [1+1'] photodissociation spectra. There were only two energetically allowed channels (S+(4S)+CS(X1∑+) and CS+(X2∑+)+S(3P)) for the predissociation of C2∑g+ state, an isotropic fragment distribution for differentpolarizations of dissociation laser has been observed. The released kinetic in S+ is lager than that in CS+. The branching ratios CS+/S+ value was about 1 in the [1+1'] process. Based on the [1+1] and [1+1'] photodissociation spectra the wavelength and level dependence of the product branching ratios CS+/S+ has been found and thedissociation dynamics of CS2+ ions viaC2∑g+ electronic states can be expresses asfollows. Study on the competition between the [1+1] and [1+1'] photodissociation channelsThe branching ratio CS+/S+ for [1+1'] process of CS2+ is differ obviously from [1+1] process within the different energy range. A model is provided to deal with thecompetition between the [1+1] dissociation channel via Hâ†B2∑u+ (000,100)â†X2Î g,3/2 transition and the [1+1'] dissociation channel via the C2∑g+ (000,100)â†B2∑u+ (000,100)â†X2Î g,3/2 transition for CS2+ ions. The first dissociation laserλ1 wasfixed at 281.9nm and 277.2nm, and the second dissociation laserλ2 at 722.4nm and 720.6nm in the experiment. From the dependence of the product branching ratios R(S+/CS+) on the intensities ratio R1(I2/I1) of two dissociation lasers, the excitation cross sections ratio of Rσ(σC/σH)= 0.55±0.07 for the competition between C2∑g+ (000)â†B2∑u+(000) and Hâ†B2∑u+(000) transitions, and 0.43±0.04 for that betweenC2∑g+(100)â†B2∑u+(100) and Hâ†B2∑u+(100) transitions have been obtained by fitting the experiment data R-R1 with this theoretical model.
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