Ion fragmentation from noninterconverting electronic states

Abstract

The photoionization and fragmentation of CH3ONO+ were studied using threshold photoelectron-coincident photoion mass spectrometry, photoelectron spectroscopy, and triple sector mass spectrometry.(AIP)

Dissociation of Singly and Multiply Charged Nitromethane Cations: Femtosecond Laser Mass Spectrometry and Theoretical Modeling

“…The results of our mass spectral measurements and calculations both explain the findings of previous mass spectrometry studies on NM radical cation − and identify new dissociation pathways from higher cation charge states of NM. The contribution of both singly and multiply charged cations to shock detonation in energetic materials , makes the decomposition pathways, identified in this work, of potential importance to the energetic performance of NM.…”

“…The dissociation reactions of isolated NM radical cation have been studied for decades with mass spectrometry. − Since the 1980s, the NM radical cation has been known to exist in three isomeric forms shown in Scheme , − with both the methylnitrite and aci -nitromethane structures accessible from the ionized parent nitromethane structure . Both the methylnitrite and aci -nitromethane cation states are lower in energy than the parent NM cation state. , …”

“…The nitromethane structure undergoes direct C–N bond cleavage to form NO 2 + or CH 3 + , and N–O cleavage from this structure produces CH 3 NO + . The methylnitrite structure undergoes N–O bond cleavage to form NO + − or CH 3 O + (observed as CH 2 OH + ). , The aci -nitromethane structure undergoes H loss to form CH 2 NO 2 + and OH loss to form CH 2 NO + . , While extensive measurements on prepared methylnitrite, − aci -nitromethane, − and isotopically labeled species , have enabled these detailed pathway assignments, little quantum chemical modeling of NM cation decomposition has been performed. , Hence, many questions regarding the dissociation pathways of NM cation remain unanswered. New quantum chemical calculations are needed to enhance our understanding of the many possible dissociation pathways in NM radical cation, including those involving rearrangement to methylnitrite or aci -nitromethane structures.…”

Kinetics and mechanism of the collision-activated dissociation of the acetone cation

“…Qian et al [34,41] recently reviewed the available information about the unimolecular dissociation and CAD of the acetone, methyl nitrite, and nitromethane cations. They indicated that several of these studies had concluded that the dissociation of the nitromethane [42,43] and methyl nitrite [43,44] cations (to NO+, MeO+, and Me+) and acetone cation (to MeCO+ [17,23,25,27,[30][31][32][33][34] and Me+ (29]) cannot be described by QET. J Am Sue Mass Spectrum 1992,3,427-444…”

“…Molecular beam studies of the CAD of the nitromethane cation [41] (which also has electronically isolated states [40]) have indicated that its low energy CAD also involves electronic transitions (rather than vibrational excitation) [41]. Other examples of non-QET behavior have been reported previously [42][43][44].…”