The Dissociation Process Of Several Sulfur-containing Molecules

The submarine-detection by laser equipped in the aerocraft and the lasersubmarine-communication play important role in current military wars;but therange of detection and communication is limited, because the electromagneticwave of most wavelengths is damped by the strong absorption of seawater.There are two types of electromagnetic wave utilized in the communicationsystems, one is super-long wavelength electromagnetic wave, but it's notsuitable for military use for the small amount of information transferred andlong transferring time;the other is blue-green light which wavelength iscentred at 480 ± 30nm, it has high penetrability and damps weakly, and itswavelength is in the 'atmosphere window', therefore good detection andcommunication systems can be established using blue-green light. Severaltypes of laser have been manufactured working in blue-green wavelengthrange, but bulk, high working temperature and maintaining difficulty makethem not suitable to apply in the war fields. To solve the problems above,small type pulse-discharge laser should be urgently developed.The molecule is a kind of material with high irradiancy efficiency,and the transition spectra are in the blue-green ranges. Theefforts of developing S laser have been making since 1976. TheS23 -3 -B Σ u →XΣg2 S2molecule does not exist in gas phase in normal temperature;the sulfur vapor isproduced by the pyrogenation of solid sulfur;thus several kinds of clusterexist in sulfur vapor. Pulsed discharge makestransition and gives blue-green light emission. Therefore, theelectron-collision processes, especially the electron impact excitation oftransition, are required to study in order to obtain the mostproper incident energy;simultaneously, other cluster should bedissociate into to produced more working material. Consequently, weshould study the excited state structure and dissociation pathway of, and electron-collision processes. The long-livedfluorescence emission is observed in the experiments ofat 193nm laser;thus an idea of using in lasergives birth naturally. Hence, the theoretical investigation ondissociation is present, which includes the radical and thesulfur-containing molecule photodissociation dynamics at laser ofdifferent wavelength. It is the theoretical foundation of electron-excitation, dissociation processes.Sn (n=2,...8) S23 -3 -X Σg→ BΣuuΣg3uS (1 Π )3 -2 B Σ u, v′ ≥18)S23 -3 -S 2 ( X Σ g→BΣ )Sn (n=3,...8)S2Sn (n=3,...8) Sn (n=3,...8)3 -3 -S 2 ( B Σ u→X)CH 3S 2 CH 3CH 3S 2 CH 3S2CH 3S 2 CH3S2 CHHSCH3CH 3S 2 CH3The potential energy curves of molecule in ground and excited statesare calculated using ab initio methods and the electronic dynamic correlationenergy is corrected by using multi-reference method. Theabsorption spectra are calculated. The spin-orbit couplinginduced predissociation of is also studied, and indicates that thespin-orbit coupling interaction between and state leadsto the completely predissociation of S ( , which is a differentpoint of view from others' and agree with experiments' results well. Thepotential cuts of dissociation into and S atom are calculated, thecalculations of transition moment between different electronic states areperformed, and show that the nonadiabatic pathways are important in theS23 -3 -S 2 ( X Σ g→BΣ )3 -S2 ( BΣ u)52 u3 +S2 (2 Σ u)S3 S2dissociation of , which are main pathway in actual processes;thedissociation pathways ,which are necessary for the study of electron-molecule collision processes, are determined.S3S3The dissociation potential energy curves of radical alongbond and bond are calculated by using multi-reference method, and theninvestigated the photodissociation dynamics at 193nm.The unique dissociationproduction, that is , observed in experiments at 193nm is interpretedusing present calculation. The dissociation potential energy curves ofradical along S-bond and bond are obtained by usingmulti-reference method and atomic nature orbital basis set including Rydbergbasis functions of S atom and C atom, and the photodissociation dynamics at193nm,248nm and 266nm laser was studied via the dissociation curves.S2 CH33S-SS-CS2 +CHHSCH3H S-CThe electron-collision processes are investigated usingR-matrix theory. The integral cross sections of excited from ground statesto electronic states , , ,Sn (n=2,3)S21a Δgb 1 Σg+c 1 Σ-uA′3 Δu and A3 Σ u+ are calculated, theresults show that there are two resonance peaks at 3.88eV and 6.38 eVcorresponding to and 2 symmetry. The electron impact excitationcross section of transition show that it gives a sharp risefrom 6.42eV, and forms a platform with large value of integral cross section.The largest value of cross section below ionization threshold is above 0.3 . Itis no doubt that the cross section with such shape provide a stably foundationto the application of pulsed discharge laser, for a wide range of incidentenergies could give large value of cross section fortransition. Then, the cross sections of molecule excitation form groundstate into electronic sates leading to dissociation into and S are calculatedwith the same method, thus the molecule could dissociate via thenonadiabatic and adiabatic pathways.2Π gΠu3 -3 -S 2 ( X Σ g→ BΣ u)u2a0S23 -3 -S 2 ( X Σ g→BΣ )S3S2S3...