Licentiate Thesis defense: Isomers of ions in space and planetary atmospheres

Ion chemistry has become increasingly important in the evolution of the chemical
inventory of extraterrestrial environments. Isomers of ions have also come to play
an important role as, in many instances, the cold environments in the interstellar
medium and high layers of planet and satellite atmospheres do not supply enough
energy to overcome isomerization barriers and the isomers eectively act as separate
In this licentiate thesis, several studies of the [CH3N]+ isomers are presented.
Reactivity studies of the two isomers, the methanimine radical cation (H2CNH+)
and aminomethylene (HCNH2
+) with hydrocarbons C2H4, C2H2 and CH4, and
IRPD spectroscopy of both species have been performed. Complimentary ab initio
calculations aid in the determination of formation pathways of observed product
channels and in the assignment of the vibrational bands seen in the IRPD spectrum.
The results show that reaction pathways of the two isomers generally involve
adduct formation followed by hydrogen ejection where the product or pathway is
dependent on the ingoing reactant isomer. The IRPD spectrum allows identi-
cation of the dierent isomers via vibrational transitions. Isomer generation by
electron ionization favours methanimine cation production with an abundance of
70% while with VUV photoionization it is possible to selectively produce isomers.
It is concluded that isomerism must be considered when investigating the chemical
environment of interstellar objects.