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Dynamics Study on the Multi-Photon Dissociation of CS2+ to CS+
Wang Feng ,Zhang Limin,Wang Zhong,Hou Yi,Ren Wenqing,Zhuang Xiujuan,Yu Shuqin*
Author NameAffiliationE-mail
Wang Feng Laboratory of Bond Selective ChemistryDepartment of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026  
Zhang Limin Laboratory of Bond Selective ChemistryDepartment of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026  
Wang Zhong Laboratory of Bond Selective ChemistryDepartment of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026  
Hou Yi Laboratory of Bond Selective ChemistryDepartment of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026  
Ren Wenqing Laboratory of Bond Selective ChemistryDepartment of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026  
Zhuang Xiujuan Laboratory of Bond Selective ChemistryDepartment of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026  
Yu Shuqin* Laboratory of Bond Selective ChemistryDepartment of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026 sqyu@ustc.edu.cn 
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.
Key words:  CS2+,Photodissociation,Photofragment excitation
FundProject:
CS2+多光子光解产生CS+的动力学研究
王峰,张立敏,王仲,侯毅,任文清,庄秀娟,俞书勤*
摘要:
在射流气束条件下,利用第一束483.2 nm的电离激光使中性CS2分子通过(3+1)共振增强多光子电离(REMPI)制备出纯净的CS2+分子离子;用第二束解离激光在385~435 nm扫描,由获得的光解离碎片激发(PHOFEX)谱研究了光解CS2+产生CS+的两种动力学途径. 当第一束电离激光和第二束解离激光在时间上有约60 ns 的延迟(远大于激光脉宽约5 ns)时,光解CS2+母体离子产生CS+碎片离子有明显的阈值效应,由PHOFEX谱确定了CS+的绝热出现势(5.852±0.005)eV(从CS2+
关键词:  CS2+  光解离  光碎片激发
DOI:10.1088/1674-0068/17/3/309-316
分类号: