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Photodissociation branching ratios of 12C16O from 108000 cm-1 to 113200 cm-1 by the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging method: observation of the channels for producing O(1D)
Hong Gao
Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
Abstract:
The photoabsorption and photodissociation of carbon monoxide (CO) in the vacuum ultraviolet (VUV) region is one of the most important photochemical processes in the interstellar medium, thus has attracted numerous experimental and theoretical studies. Here, we employed the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging (TS-VMI) method to measure the relative branching ratios [C(3P0) + O(1D)]/{ [C(3P0) + O(3P)] + [C(3P0) + O(1D)]} and [C(3P2) + O(1D)]/{ [C(3P2) + O(3P)] + [C(3P2) + O(1D)]} in the VUV photoexcitation energy range 108000-113200 cm-1. Here, one tunable VUV laser beam is used to excite CO to specific rovibronic states, and a second independently tunable VUV laser beam is used to state-selectively ionize C(3P0) and C(3P2) for detection. State-selective photoionization through the 1VUV+1UV/Visible resonance-enhanced multiphoton ionization (REMPI) scheme has greatly enhanced the detection sensitivity, which makes many new weak absorption bands observable in the current study. The branching ratio measurement shows that the spin-forbidden channels C(3P0) + O(1D) and C(3P2) + O(1D) only open at several discrete narrow energy windows. This might be caused by certain accidental resonance-enhanced spin-orbit interactions between the directly excited Rydberg states and valence states of triplet type which finally dissociate into the spin-forbidden channels.
Key words:  Carbon monoxide, photodissociation, vacuum ultraviolet, branching ratio
FundProject:
Photodissociation branching ratios of 12C16O from 108000 cm-1 to 113200 cm-1 by the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging method: observation of the channels for producing O(1D)
Hong
Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
摘要:
The photoabsorption and photodissociation of carbon monoxide (CO) in the vacuum ultraviolet (VUV) region is one of the most important photochemical processes in the interstellar medium, thus has attracted numerous experimental and theoretical studies. Here, we employed the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging (TS-VMI) method to measure the relative branching ratios [C(3P0) + O(1D)]/{ [C(3P0) + O(3P)] + [C(3P0) + O(1D)]} and [C(3P2) + O(1D)]/{ [C(3P2) + O(3P)] + [C(3P2) + O(1D)]} in the VUV photoexcitation energy range 108000-113200 cm-1. Here, one tunable VUV laser beam is used to excite CO to specific rovibronic states, and a second independently tunable VUV laser beam is used to state-selectively ionize C(3P0) and C(3P2) for detection. State-selective photoionization through the 1VUV+1UV/Visible resonance-enhanced multiphoton ionization (REMPI) scheme has greatly enhanced the detection sensitivity, which makes many new weak absorption bands observable in the current study. The branching ratio measurement shows that the spin-forbidden channels C(3P0) + O(1D) and C(3P2) + O(1D) only open at several discrete narrow energy windows. This might be caused by certain accidental resonance-enhanced spin-orbit interactions between the directly excited Rydberg states and valence states of triplet type which finally dissociate into the spin-forbidden channels.
关键词:  Carbon monoxide, photodissociation, vacuum ultraviolet, branching ratio
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