LOW-ENERGY, HIGH-RESOLUTION ION-SCATTERING MASS-SPECTROMETRY OF STRAINED MOLECULES AND THEIR ISOMERS

A new method for differentiation of strained molecules and their isome rs is reported. In essence it is a combination of soft chemical ioniza tion, with very low energy collision-induced dissociation. The instrum ent is a guided-ion beam tandem mass spectrometer, specially optimized for high energy resolution scattering. This has been coupled to a var iable temperature microflow tube that allows study of the pyrolysis ch emistry of neutral sample molecules. To illustrate the method, data is presented for the quadricyclane/norbsmadiene/toluene isomer system. T he MC ions derived from the three isomers are easily distinguished in our experiment, while cations derived from quadricyclane and norbomadi ene were found to be indistinguishable by other methods. Good isomer s ensitivity is only observed at collision energies below 3 eV, and some discussion is given on experimental considerations important for high resolution/low energy scattering. (C) 1997 Elsevier Science B.V.