The interconversion of the radial motional modes of an ion in a Penning trap mass spectrometer by 4n-polar external radio frequency fields (n= 1,2,3,4)
Annalen der Physik. Bd. 525. H. 8-9. Wiley 2013 S. 688 - 706
Erscheinungsjahr: 2013
ISBN/ISSN: 1521-3889
Publikationstyp: Zeitschriftenaufsatz
Sprache: Englisch
Doi/URN: 10.1002/andp.201300069
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Inhaltszusammenfassung
In Penning trap mass spectrometry ion masses are determined by measuring the free cyclotron frequency ν_c = qB/(2πm) via the resonant conversion of the magnetron into the cyclotron motional mode, induced by the interaction with an external radio-frequency field. With octupolar rf-fields of frequency ν_rf ≈ 2ν_c the mass resolution has been improved by more than an order of magnitude as compared to conventional quadrupolar fields of frequency v_rf ≈ ν_c and with the same pulse duration. T...In Penning trap mass spectrometry ion masses are determined by measuring the free cyclotron frequency ν_c = qB/(2πm) via the resonant conversion of the magnetron into the cyclotron motional mode, induced by the interaction with an external radio-frequency field. With octupolar rf-fields of frequency ν_rf ≈ 2ν_c the mass resolution has been improved by more than an order of magnitude as compared to conventional quadrupolar fields of frequency v_rf ≈ ν_c and with the same pulse duration. This result raises the question what one might expect from using 12-polar rf-fields with frequency ν_rf ≈ 3ν_c or even 16-polar rf-fields with frequency ν_rf ≈ 4ν_c. In this paper the theoretical model for the interconversion of the radial modes by quadrupolar and octupolar rf-fields is generalized to general 4n-polar fields. As in the earlier work the complex amplitudes of the cyclotron and magnetron oscillators are used as dynamical variables and the Hamiltonian equations of motion are reformulated in terms of Bloch vector components. The resulting non-linear differential equations can be solved numerically. Results are presented on excitation functions (conversion at the exact resonance frequency) and on conversion line shapes (dependence of conversion on the detuning parameter). The most important observation is the decrease of the resonance width by a factor of 2 × 10^3 as one passes from quadrupolar (n = 1) to 12-polar (n = 3) and 16-polar (n = 4) excitation.» weiterlesen» einklappen
Klassifikation
DFG Fachgebiet:
Teilchen, Kerne und Felder
DDC Sachgruppe:
Naturwissenschaften
