Radial trap frequency

FIGURE 10.4 Images of fluorescence from ions, (a) Two ions at thermal equilibrium in the trap, (b) A laser-cooled °Ca+ ion trapped together with a sympathetically-cooled " °Ca 0+ ion at thermal equilibrium, (c) The same two °Ca ions as in (a) but with a modulation voltage applied at a frequency near the COM mode resonance frequency of 98.7 kHz. (d) The same ions as in (b) but with a modulation voltage applied at a frequency close to the COM mode resonance frequency of 89.4 kHz. In all experiments, the radial trap frequencies were 380 kHz and the exposure time of the CCD chip was 100 ms. (Reproduced from Drewsen, M. Mortensen, A. Martinussen, R. Staanum, R Sprensen, J.L., Phys. Rev. Lett. 2004, 93, 243201. With permission from the American Physical Society.)... 

Orbitrap, which was introduced into the market in 2005, is a new type of mass analyser, operating by radially trapping ions about a central spindle electrode. An outer barrel-like electrode is coaxial with the inner spindle-like electrode and mass/ charge values are measured from the frequency of harmonic ion oscillations, along... 

Tolmachev, A.V. Udseth, HR. Smith, R.D. Radial Stratification of Ions As a Function of Mass to Charge Ratio in Collisional Cooling Radio Frequency Multipoles Used As Ion Guides or Ion Traps. Rapid Commun. Mass Spectrom. 2000,74, 1907-1913. 

PENNING TRAP 2 deceleration and trapping induction of cyclotron frequency u>c increase of radial energy pulsed ejection... 

Mass selective ejection of the ions in a radial direction occurs by applying an AC voltage between the two cut rods. As for the 3D ion trap, an AC frequency corresponding to qz = 0.88 is used. Ions of successively higher masses are brought to this qz value by increasing V. An ejection efficiency of about 50 % is achieved at 5 Th s scan rate [25]. 

Makarov invented a new type of mass spectrometer by modifying the Kingdom trap with specially shaped outer and inner electrodes (see Fig. 2.28). Also, in this case a purely electrostatic held is obtained by a dc voltage applied to the inner electrode. Ions injected into the device undergo a periodic motion that can be considered the result of three different periodic motions (1) rotation around the inner electrode (2) radial oscillation and (3) axial oscillations. These three components exhibit well-defined frequencies ... 

In an ICR cell, two-dimensional spectrometry begins with application of the stored waveform inverse Fourier transform (SWIFT) excitation. This technique removes all but a single chosen ion from the trap (Marshall et al., 1985) and is performed by first determining which ions are to be ejected and their cyclotron frequency. Inverse Fourier transform then produces an excitation waveform that excites selected ions radially until they come into contact... 

FIGURE 9.10 Plots analyzing single ion trajectories from SIMION calculations of an ion stored at =0.785 in trap model 1 starting at (a through d) the center of the trap and (e through h) displaced from the center of the trap. Panels (a, e) show plots of axial (z) position as a function of time, and panels (c, g) show plots of radial (x) position as a function of time. Panels (b), (d), (f), and (h) show frequency power spectra, plotted on a log scale, of the radial (x) and axial (z) motion. The solid circles ( ) in panels (h) and (d) mark frequencies predicted by Equation 9.12. 

The ion trap used in the experiments and shown in Figure 10.2b has the following dimensions Tq = 3.50 mm, Zq = 2.70 mm, Zendcap = 20.00 mm, andR = 4.00 mm these values have been chosen in order to achieve a nearly perfect radial quadrupole RF field [19] and a near-harmonic DC-axial potential over a few millimeters. Numerical simulations show that these choices of ion-trap dimensions result in ti = 0.248. The applied RF field is coupled resonantly to the ion-trap electrodes at a radial frequency... 

The NPL (Figure 11.12) is based on the trap described by Schrama et al. [32] The outer electrodes (very fine hollow tubes of tantalum of 1 mm inner diameter and 2 mm outer diameter) are grounded, but they can receive a small DC potential. The inner electrodes, also in tantalum, are ca 0.5 mm diameter and separated from the outer electrodes by 0.56 mm. The amplitude of the RF potential is 260 Vp p at a frequency of 17.8 MHz, resulting in secular frequencies for strontium ion of 1.8 MHz (radial) and 3.0 MHz (axial). The electrodes are isolated from each other with a ceramic tube and the trap is mounted on a structure of machinable macor. Two compensation... 

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