Parametric resonances and a high-pressure RF-only-mode event in Fourier transform mass spectrometry.

摘要

The dissertation describes two roles that the electric-trapping field can play in the detection of ions by Fourier transform mass spectrometry (FTMS). In the first study (Chapter 2) the proper ideal for the shape of the electric-trapping well is considered. Numerical calculations show that non-quadrupolar trapping potentials result in the parametric coupling of the axial and radial motions of the ions. This coupling causes the ion cloud to expand radially. The detection performance of high mass-to-charge ions in a 7-tesla magnetic field were modeled by the benzene molecular ion under scaling conditions and showed a loss of detection performance over the same m/q ranges that were predicted to satisfy the resonance condition in the cubic cell. Additional calculations show that parametric resonances become broader and the rate of radial expansion greater as the trapping potential becomes more anharmonic. The study concludes that the quadrupolar potential is the proper ideal for FTMS.;The second study (Chapter 3) details the operation of the FT-mass spectrometer under the high pressure conditions of a new event in the FTMS sequence called an RF-only-mode event. During the event an rf-potential is superimposed onto the normally static trapping potential so that the FTMS operates as a QUISTOR. The utility of the event is demonstrated with the ;The experimental chapters are proceeded by a review of FTMS fundamentals and recent advances that are extending the m/q range of FTMS.