Tino Gäumann

Fast and slow decompositions of ionized prop-1-en-1-ols. A unified view of [C3H6O]+· isomers with the CCCO frame

Abstract Ionized (E)- and (Z)-prop-1-en-1-ols, [CH3CHCHOH]+·, were generated by electronimpact ionization of the unstable enols and by dissociative ionization of 3-methylnorborn-5-en-2-ols. The loss of hydrogen from molecular ions decomposing in the ion source takes place from C-1, C-2 and C-3 positions in a nearly random manner, as determined by deuterium labelling. This is due to reversible isomerization of [CH3CHCHOH]+· to [CH2CHCH2OH]+· and [d CH 2 CH 2 C dHOH]+· prior to decomposition. The appearance energy for the hydrogen loss was determined as AE([C3H5O]+) = 10.63 ± 0.06 eV, which sets the energy of the transition state at 854 kJ mol−1. Low-energy [CH3CHCHOH]+· decomposes mainly to CH3CH2CO+, while at higher internal energies the formation of CH2CHCHOH+ is preferred. [C2H5]+ and [CHO]+ ions arise mainly as secondary fragments with Ae([C2H5]+) = 12.50 ± 0.10 eV andAE([CHO]+) = 12.95 ± 0.15 eV.

The decomposition of 1-heptene ions in the time range from ps to μs: An FIK study

The time-dependent fragmentation of 1-heptene ions after field ionization has been studied, using extensive D- and 13C-labelling. Nearly all fragment ions are formed by different mechanisms; if simple CC bond cleavage, eventually coupled with an H-transfer, prevails at short times, complicated rearrangement reactions precede fragmentation on a longer time-scale. Similarities with fragmentation after electron impact are discussed.

An ICR study of the reactions of CH5+ and C2H5+ with n-hexane labelled with 13C

Abstract The reactions occurring in the chemical ionization (CI) of n-hexane with methane as reagent gas have been studied in an ion cyclotron resonance mass spectrometer. Extensive use of 13 C-labelled reactants was made. The results obtained substantiate the different modes of reaction of the two major reactant ions in methane, viz. CH 5 + acts as a proton donor to form an hexonium ion intermediate and C 2 H 5 + acts as an hydride acceptor to form an hexyl ion. The decomposition of the latter ion is discussed in terms of rearrangement steps involving the formation of substituted protonated cyclopropane intermediates. An approximate value of 4 · 0 8 s −1 is suggested for the migration frequency of hydrogen atoms in the rearrangement process. Analytical application of CI(CH 4 ) is also considered.

Doubly charged ions in the field ionization mass spectrum of 1-heptene

Abstract Surface processes in the field ionization of 1-heptene give rise to the doubly charged ions (MR) 2+ and (MMR) 2+ (M and R represent the 1-heptene molecule and an olefinic fragment, respectively). The use of 13 C- and D-labelling allows investigation of these phenomena in detail. The mechanisms proposed for dimerization and subsequent fragmentation are supported by the data of seventeen labelled compounds.

Metastable decomposition of C7H14 alkene ions

Abstract Unimolecular decomposition of molecular ions from 1-heptene and 5-methyl-1-hexene has been studied in the metastable time domain using the MIKE technique. With the aid of extensive 13C labelling, it was possible to specify which C atoms are involved in the different fragmentation reactions leading to the most abundant daughter ions.

Multiple Pulses and Dimensions in FTICR

This chapter introduces two-dimensional FTICR. Since two-dimensional spectroscopy depends on many details that are not directly connected to it but are nevertheless important for the success of a two-dimensional experiment, a few points are discussed at the beginning for those who wish to work in this field. A more detailed review of new achievements in FTICR has been presented elsewhere.(1)

Pyrolysis effects on the reactions of alkoxide anions

Abstract The distribution of products in negative chemical-ionization spectra of alcohols are shown to remain unaffected (

Application of radiation chemistry for conservation of archaeological waterlogged wood and osteological objects

Abstract The application of radiation chemistry to the conservation of archaeological objects is described. Methyl methacrylate is introduced into the voids of the objects to be conserved either by an exchange process or—if allowed by the mechanical strength of the object—by vacuum impregnation. It is neither necessary nor desirable to fill the object completely with the monomer that is subsequently polymerized with 60 Co γ-rays.