Wang Feng, Zhang Limin, Wang Zhong, Hou Yi, Ren Wenqing, Zhuang Xiujuan, Yu Shuqin. Dynamics Study on the Multi-Photon Dissociation of CS2+ to CS+[J]. Chinese Journal of Chemical Physics , 2004, 17(3): 309-316. doi: 10.1088/1674-0068/17/3/309-316
Citation: Wang Feng, Zhang Limin, Wang Zhong, Hou Yi, Ren Wenqing, Zhuang Xiujuan, Yu Shuqin. Dynamics Study on the Multi-Photon Dissociation of CS2+ to CS+[J]. Chinese Journal of Chemical Physics , 2004, 17(3): 309-316. doi: 10.1088/1674-0068/17/3/309-316

Dynamics Study on the Multi-Photon Dissociation of CS2+ to CS+

doi: 10.1088/1674-0068/17/3/309-316
Funds:  Project supported by the National Natural Science Foundation of China (20373067)and the National Climbing Project NKBRSF research Program(G1999075304).
  • Received Date: 2004-02-18
  • The dynamics on the multi-photon dissociation of CS2+ molecular ions to produce CS + ions has been investigated by measuring the CS + photofragment excitation(PHOFEX)spectrum in the wavelength range of 385~435 nm,where the CS2+ molecular ions were prepared purely by[3+1]multiphoton ionization of the neutral CS2molecules at 483.2 nm. With the ~60 ns delay,which is much more than the laser pulse width(~5 ns),between ionization laser and dissociation laser,the threshold wavelength of dissociation laser to produce CS+ fragment ion from CS2+ molecular ions was obviously observed in the PHOFEX spectrum. The adiabatic appearance potential of the CS+ was determined to be(5.852 ± 0.005)eV above the X 2Σg,3/2(0,0,0)level of CS2+. The product branching ratios,(CS+/S+),as measured from the PHOFEX spectra,increase from 0 to slightly larger than 1 in the wavenumber range of 47200~50400 cm-1 . The[1+1]dissociation mechanism to get to CS++S from CS2+ was discussed and preliminarily attributed to(i)CS2+(X 2Πg)→ CS2+(A2Πu)through one-photon excitation,(ii)CS2+(A2Πu)→ CS2+(X*)via internal conversion process due to the vibronic coupling between the A and X states,(iii)CS2+(X*)→ CS2+(B 2Σ+u)through the second photon excitation,and(iv)CS2+(B 2Σ+u)→CS +(X 2Σ+)+S(3P),because of the potential curve crossing with the repulsive 4Σ- state and/or the 2Σ- state correlated with the second dissociation limit. However,when the dissociation laser overlaps the ionization laser in time scale in the laser-molecule interaction zone,the appearance threshold is not available in the PHOFEX spectrum. This fact shows that there are other mixed three-photon paths of[1+1+1'],[1+1'+1'],and[1+1'+1]to produce CS+ fragment ion from CS2+ molecular ions besides the above[1+1]dissociation mechanism,that is,CS2+(X 2Πg)→ CS2+(A 2Πu)through one-photon excitation[1]of dissociation laser,CS2+(A 2Πu)→CS2+(X*)via internal conversion process due to the vibronic coupling between the A and X states,CS2+(X*)→ CS2+(B 2Σ +u)through the second photon excitation by dissociation laser[1]or ionization laser[1'],and third photon excitation by ionization laser[1']or dissociation laser[1]to reach the adiabatic appearance potential to produce CS+ with the dissociation laser wavelengths longer than 423. 89 nm,at which the[1+1]dissociation mechanism to get to CS+ is unavailable.
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    沈阳化工大学材料科学与工程学院 沈阳 110142

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Dynamics Study on the Multi-Photon Dissociation of CS2+ to CS+

doi: 10.1088/1674-0068/17/3/309-316
Funds:  Project supported by the National Natural Science Foundation of China (20373067)and the National Climbing Project NKBRSF research Program(G1999075304).

Abstract: The dynamics on the multi-photon dissociation of CS2+ molecular ions to produce CS + ions has been investigated by measuring the CS + photofragment excitation(PHOFEX)spectrum in the wavelength range of 385~435 nm,where the CS2+ molecular ions were prepared purely by[3+1]multiphoton ionization of the neutral CS2molecules at 483.2 nm. With the ~60 ns delay,which is much more than the laser pulse width(~5 ns),between ionization laser and dissociation laser,the threshold wavelength of dissociation laser to produce CS+ fragment ion from CS2+ molecular ions was obviously observed in the PHOFEX spectrum. The adiabatic appearance potential of the CS+ was determined to be(5.852 ± 0.005)eV above the X 2Σg,3/2(0,0,0)level of CS2+. The product branching ratios,(CS+/S+),as measured from the PHOFEX spectra,increase from 0 to slightly larger than 1 in the wavenumber range of 47200~50400 cm-1 . The[1+1]dissociation mechanism to get to CS++S from CS2+ was discussed and preliminarily attributed to(i)CS2+(X 2Πg)→ CS2+(A2Πu)through one-photon excitation,(ii)CS2+(A2Πu)→ CS2+(X*)via internal conversion process due to the vibronic coupling between the A and X states,(iii)CS2+(X*)→ CS2+(B 2Σ+u)through the second photon excitation,and(iv)CS2+(B 2Σ+u)→CS +(X 2Σ+)+S(3P),because of the potential curve crossing with the repulsive 4Σ- state and/or the 2Σ- state correlated with the second dissociation limit. However,when the dissociation laser overlaps the ionization laser in time scale in the laser-molecule interaction zone,the appearance threshold is not available in the PHOFEX spectrum. This fact shows that there are other mixed three-photon paths of[1+1+1'],[1+1'+1'],and[1+1'+1]to produce CS+ fragment ion from CS2+ molecular ions besides the above[1+1]dissociation mechanism,that is,CS2+(X 2Πg)→ CS2+(A 2Πu)through one-photon excitation[1]of dissociation laser,CS2+(A 2Πu)→CS2+(X*)via internal conversion process due to the vibronic coupling between the A and X states,CS2+(X*)→ CS2+(B 2Σ +u)through the second photon excitation by dissociation laser[1]or ionization laser[1'],and third photon excitation by ionization laser[1']or dissociation laser[1]to reach the adiabatic appearance potential to produce CS+ with the dissociation laser wavelengths longer than 423. 89 nm,at which the[1+1]dissociation mechanism to get to CS+ is unavailable.

Wang Feng, Zhang Limin, Wang Zhong, Hou Yi, Ren Wenqing, Zhuang Xiujuan, Yu Shuqin. Dynamics Study on the Multi-Photon Dissociation of CS2+ to CS+[J]. Chinese Journal of Chemical Physics , 2004, 17(3): 309-316. doi: 10.1088/1674-0068/17/3/309-316
Citation: Wang Feng, Zhang Limin, Wang Zhong, Hou Yi, Ren Wenqing, Zhuang Xiujuan, Yu Shuqin. Dynamics Study on the Multi-Photon Dissociation of CS2+ to CS+[J]. Chinese Journal of Chemical Physics , 2004, 17(3): 309-316. doi: 10.1088/1674-0068/17/3/309-316

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