BLACK CANYONS FOR IONS STORED IN AN ION-TRAP MASS-SPECTROMETER

Effects from higher order non-linear resonances, 'black canyons', have been observed for ions stored within the quadrupole ion-trap mass spectrometer. At specific q(z) values, higher-order field effects were observed to cause decreased intensity of chemical ionization (CI) reagent ions, due to inefficient storage, as well as collision-induced dissociation. Effects have been observed, whether or not the CI reagent ions are mass-selected, and exhibit increased severity with longer storage times. Previous reports have shown 'black holes' due to inefficient storage of product ions in tandem (MS/MS) spectra, but have reported no such effects in normal mass spectra. Without employing resonant excitation, higher-order field effects were investigated and found to occur continuously along iso-beta(z) lines for beta(z)= 113, 1/2, and 2/3. Described in this paper are the direct effects from higher-order fields on ions stored at specific q(z) values, and indirect effects caused by those ions. Also described in this paper is new evidence for 'black canyons' occurring at beta(z) = 1/3 at negative a(z) values.