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AssigneeThe Ohio State University Research Foundation
InventorsAlan G. Marshall, Tom L. Ricca, Tao-Chin L. Wang
Estimating the term…
An ion cyclotron resonance cell has applied thereto an excitation which has a time domain waveform which is the inverse Fourier transform of a frequency domain excitation spectrum which has been chosen by the user to yield selective excitation and/or suppression of ranges of ion mass-to-charge ratios. To minimize the dynamic range of the time domain signal resulting from the inverse Fourier transform, the phases of the various discrete frequency components in the frequency domain spectrum which are used in calculating the inverse Fourier transform are not constant but rather are varied as a function of the frequency of the components. The phase of each component is assigned such that the frequency components in the time domain signal are not all in phase at any point in time, thereby avoiding large magnitude spikes in the time domain waveform. The phases of the various frequency components may follow a non-linear function of the frequencies of the components, such as a quadratic function. By varying phase in this manner, the time domain signal which is applied to the excitation plates of the ion cyclotron resonance cell has a frequency domain power spectrum which is substantially flat over the specified band or bands of frequencies of interest. The time domain waveform may be shifted and/or weighted before being applied to the excitation plates. Tailored excitation may also be applied in this manner to the end plates of an ion trap cell to cause tailored ejection of specific bands or ranges of ions with retention of remaining ions within the cell.
Ion mass spectrometry apparatus comprising:
A method of providing ion excitation to an ion cell, comprising the steps of:
In an ion cyclotron resonance mass spectrometer of the type having an ion cyclotron resonance cell including excitation plates and detection plates, a magnet producing a substantially constant unidirectional magnetic field through the ion cyclotron resonance cell such that the electric field from potentials applied to the excitation plates is transverse to the applied magnetic field, means connected to the detector plates of the cell for detecting resonance motion of ions in the cell and providing a signal indicative thereof, and excitation amplifier means connected to the excitation plates for applying electrical potentials to the plates to form an electric field between the plates in accordance with an input signal to the excitation amplifier means, the improvement comprising:
In an ion trap cell of the type having a ring electrode and end plate electrodes, an ionizing source, and a means for detecting ions ejected from the cell to produce a signal indicative thereof, the improvement comprising:
A method of ejecting selected mass-to-charge ratio ions from an ion trap cell of the type having a ring electrode and end plates, comprising the steps of:
A method of obtaining mass spectra from an ion cyclotron resonance mass spectrometer having enhanced dynamic range, comprising the steps of:
Dependencies are inferred from the claim text.