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  • 1
    Electronic Resource
    Electronic Resource
    Filar ion cyclotron resonance ion trap: Spatially multiplexed dipolar and quadrupolar excitation for simultaneous ion axialization and detection (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 63-66 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel Fourier transform ion cyclotron resonance ion trap consists of two conventional solid "end cap'' electrodes and four "filar'' electrodes, each composed of two interdigitated "combs.'' The filar trap provides for ion dipolar excitation and ejection, dipolar detection, quadrupolar axialization, and various combinations in a single trap without additional voltage divider circuitry and signal switching between operating modes, because two different functions can be conducted simultaneously by use of two spatially multiplexed electrodes. The filar electrodes produce simulated dipolar and quadrupolar potential fields which are nearly indistinguishable (near the trap center) from those produced by solid electrodes. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146312
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  • 2
    Electronic Resource
    Electronic Resource
    A mass- and velocity-broadband ion deflector for off-axis ion injection into a cyclotron resonance ion trap (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 423-427 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Off-axis ion injection into an FT-ICR ion trap is desirable for capturing ions from a continuously generated beam (e.g., electrospray). A conventional E×B (Wien) filter focuses ions of a single velocity (independent of mass). Here we show that by segmenting opposed flat electrodes into small sections, the electric field may be tailored to produce well-focused ion trajectories over a wide range of ion velocity and mass-to-charge ratio, m/z. In the limit of infinitely extended deflector electrodes, small m/z, and/or high B, ion trajectories vary as powers or roots of distance. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146607
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  • 3
    Electronic Resource
    Electronic Resource
    Bloch equations applied to ion cyclotron resonance spectroscopy: Broadband interconversion between magnetron and cyclotron motion for ion axialization (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 4486-4493 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Conversion of magnetron motion to cyclotron motion combined with collisional cooling of the cyclotron motion provides an efficient way to reduce the kinetic energy of trapped heavy ions and to reduce their magnetron radii in an ion cyclotron resonance (ICR) ion trap. The coupling of magnetron and cyclotron motion can be realized by azimuthal quadrupolar excitation. Theoretical understanding of the coupling process has until now been based on resonant single-frequency quadrupolar excitation at the combination frequency ωc=ω++ω−, in which ωc is the ion cyclotron orbital frequency in the absence of electrostatic field; and ω+ and ω− are the reduced cyclotron and magnetron frequencies in the presence of an electrostatic trapping potential. In this work, we prove that the magnetron/cyclotron coupling is closely related to a two energy level system whose behavior is described by the well-known Bloch equations. By means of a special transformation, the equations of motion for the coupling may be expressed in Bloch-type equations in spherical coordinates. We show that magnetron-to-cyclotron conversion by single-frequency quadrupolar excitation in ICR is analogous to a 180° pulse in nuclear magnetic resonance (NMR). We go on to show that simultaneous magnetron-to-cyclotron conversion of ions over a finite mass-to-charge ratio range may be produced by quadrupolar frequency-sweep excitation, by analogy to adiabatic rapid passage in magnetic resonance. Axialization by broadband magnetron-to-cyclotron conversion followed by cyclotron cooling is successfully demonstrated experimentally for a crude oil distillate sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465008
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  • 4
    Electronic Resource
    Electronic Resource
    Generation of optimal excitation pulses for two energy level systems using an inverse Fourier transform method (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 7959-7964 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The response of a two energy level system to low amplitude excitation is investigated. The flip angle of magnetization or polarization is found to be linearly related to the magnitude spectrum of the excitation pulse under the approximation of low amplitude excitation. This property can be used for synthesis of optimal excitation pulses. A comprehensive algorithm for generating optimal excitation pulses is proposed based on the response theory and the stored wave form inverse Fourier transform (SWIFT) algorithm developed previously. An example of the synthesis of a notch excitation pulse is given to demonstrate the flexibility of this newly developed method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462879
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  • 5
    Electronic Resource
    Electronic Resource
    General phase modulation method for stored waveform inverse Fourier transform excitation for Fourier transform ion cyclotron resonance mass spectrometry (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 775-777 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A general phase modulation algorithm has been developed for the stored waveform inverse Fourier transform (SWIFT) excitation method used in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR or FTMS). The algorithm, based on the time shifting theorem and the uncertainty principle, shows that the quadratic phase modulation is the theoretically optimal method for square magnitude spectral profiles. For more complicated magnitude spectral profiles, the corresponding phase functions can be generated through the algorithm by using a nonlinear grid on the frequency domain. The degree of dynamic range reduction can be estimated from a simple equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457129
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  • 6
    Electronic Resource
    Electronic Resource
    Optimal phase modulation in stored wave form inverse Fourier transform excitation for Fourier transform mass spectrometry. I. Basic algorithm (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5841-5846 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new signal processing method has been proposed for generating optimal stored wave form inverse Fourier transform (SWIFT) excitation signals used in Fourier transform mass spectrometry (FTMS or FT-ICR). The excitation wave forms with desired flat excitation power can be obtained by using the data processing steps which include: (1) smoothing of the specified magnitude spectrum, (2) generation of the optimal phase function, and (3) inverse Fourier transformation. In contrast to previously used procedures, no time domain wave form apodization is necessary. The optimal phase functions can be expressed as an integration of the specified power spectral profiles. This allows one not only to calculate optimal phase functions in discrete data format, but also to obtain an analytical expression (in simple magnitude spectral cases) that is for theoretical studies. A comparison is made of the frequency sweeping or "chirp'' excitation and stored wave form inverse Fourier transform (SWIFT) excitation. This shows that chirp excitation and SWIFT excitation with a square magnitude spectrum and a quadratic phase are counterparts of the Fourier transformation. Therefore, the results of theoretical work on chirp excitation can be used for the analysis of the time domain excitation wave forms in the SWIFT technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458405
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  • 7
    Electronic Resource
    Electronic Resource
    A theory for two-dimensional Fourier-transform ion cyclotron resonance mass spectrometry (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5291-5295 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical model, based on the Lorentz equations for ion motion and the mass action law, is developed for two-dimensional Fourier-transform mass spectrometry known as 2D FT–ICR or 2D FTMS. The theory illustrates that the modulation of 2D FT–ICR ion signals in the additional time dimension comes from the modulation of the primary ion speed by the 2D excitation pulses. The modulation of the primary ion speed is found not to be sinusoidal and the modulation of the ion signals in 2D FT–ICR spectra is found to be complicated even in the simplest chemical system. The complex modulation creates higher harmonic components in the spectra. Based on the model, a data processing algorithm is proposed. The results show that the Fourier transformation should be performed stepwise in order to obtain complete information, and that the phase portion of the frequency domain generated by the second Fourier transformation should not be discarded since it contains useful information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457575
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  • 8
    Electronic Resource
    Electronic Resource
    Optimal phase modulation in stored waveform inverse Fourier transform excitation for Fourier transform mass spectrometry. II. Magnitude spectrum smoothing (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8442-8445 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A smoothing method for generating optimal SWIFT (stored waveform inverse Fourier transform) excitation waveforms used in Fourier transform mass spectrometry (FT-ICR or FTMS) was previously proposed to substitute time-domain waveform apodization procedures. This work gives a detailed analysis of the simple smoothing procedure. The effect of the smoothing procedure on magnitude spectral edges can be easily expressed in analytical format so that the frequency resolution of excitation can be easily analyzed. The relation between the time domain apodization and the smoothing of magnitude spectra in the frequency domain is established. This provides a convenient method to estimate the time duration required for accommodation of excitation power leakage from the power distribution limits. A method for generating nonconstant frequency resolution excitation waveforms is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459281
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  • 9
    Electronic Resource
    Electronic Resource
    Personal computer based Fourier transform ion cyclotron resonance mass spectrometer (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2573-2576 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An IBM PC AT compatible computer is used to host the interface of a Fourier transform ion cyclotron resonance mass spectrometer or FTMS. A common fast memory bank for both ion-excitation waveform and data acquisition is reserved in the computer's system memory space. All the digital electronics circuitry is assembled on an IBM PC AT extension board. Neither an external frequency synthesizer nor a waveform digitizer is needed. Ion-excitation waveforms can be generated in either frequency-sweeping or inverse-Fourier transform modes. Both excitation and data acquisition can be carried out at eight megawords per second.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139900
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  • 10
    Electronic Resource
    Electronic Resource
    A simple electron-beam control circuit for FT-ICR electron impact dissociation experiments (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2798-2800 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple electron-beam control circuit has been designed and constructed for electron-impact dissociation experiments on Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR or FTMS). Two types of electron beams from a common filament are controlled by three TTL signals. The electron beam current is adjusted by varying the grid potential while the filament current is kept constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140662
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