Theoretical and experimental studies on hydrogen migration in dissociative ionization of the methanol monocation to molecular ions H3+ and H2O+12. Issue 29 (29th May 2019)

• Record Type: Journal Article
• Authors: Wu, Hua; Xue, Yuanxin; Wen, Junqing; Wang, Hui; Fan, Qingfei; Chen, Guoxiang; Zhu, Jin; Qu, Fanghui; Guo, Jiale
• Is Part Of: RSC advances. Volume 9:Issue 29(2019)
• Page Start: 16683
• Page End: 16689
• Publication Date: 2019-05-29
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c9ra02003a
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Hydrogen migration processes of methanol monocation CH3 OH + to H3 +, COH +, H2 O + and CH2 + were studied theoretically and experimentally. Abstract : The dissociative ionization processes of the methanol monocation CH3 OH + to H3 + + CHO and H2 O + + CH2 are studied by ab initio method, and hydrogen migration processes are confirmed in these two dissociation processes. Due to the positive charge assignment in dissociation processes, the fragmentation pathways of CH3 OH + to H3 + CHO + and CH3 OH + to H2 O + CH2 + are also calculated. The calculation results show that a neutral H2 moiety in the methanol monocation CH3 OH + is the origin of the formation of H3 +, and the ejection of fragment ions H3 + and H2 O + is more difficult than CHO + and CH2 + respectively. Experimentally, by using a dc-slice imaging technique under an 800 nm femtosecond laser field, the velocity distributions of fragment ions H3 +, CHO +, CH2 +, and H2 O + are calculated from their corresponding sliced images. The presence of low-velocity components of these four fragment ions confirms that the formation of these ions is not from the Coulomb explosion of the methanol dication. Hence, the four hydrogen migration pathways from the methanol monocation CH3 OH + to H3 + + CHO, CHO + + H3, H2 O + + CH2, and CH2 + + H2 O are securely confirmed. It can be observed in the time-of-flight mass spectrum of ionization and dissociation of methanol that the ion yields of fragment ions H3 + and H2 O + are lower than CHO + and CH2 + respectively, which is consistent with the theoretical results according to which dissociation from the methanol monocation to H3 + and H2 O + is more difficult than CHO + and CH2 + respectively.