A Quadrupole Ion Trap with Cylindrical Geometry Operated in the Mass-Selective Instability Mode

Wells, Justin; Badman, Ethan R.; Cooks, R. Graham

doi:10.1021/ac971198h

Cited by 143 publications

(139 citation statements)

References 33 publications

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“…Fluorescence detection of ions stored in a linear quadrupole [26] would reduce the laser scattering from trap electrodes yet provide fluorescence collection from a larger laser-cloud interaction volume. Cylindrical ion traps [27,28] offer the possibility to detect through a ring electrode formed from highly transparent (ϳ80%) Ni screen. This design would also provide fluorescence collection from a significantly greater solid angle as shown in reference [29] and increase the trap dimensions to reduce laser background scattering.…”

Section: Discussionmentioning

confidence: 99%

Pulsed fluorescence measurements of trapped molecular ions with zero background detection

Khoury¹,

Rodriguez‐Cruz²,

Parks³

2002

J Am Soc Mass Spectrom

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Sensitive methods have been developed to measure laser-induced fluorescence from trapped ions by reducing the detection of background scattering to zero levels during the laser excitation pulse. The laser beam diameter has been reduced to ϳ150 m to eliminate scattering on trap apertures and the resulting laser-ion interaction is limited to a volume of ϳ10 Ϫ5 cm 3 which is ϳ0.03-0.15 of the total ion cloud volume depending on experimental conditions. The detection optics collected fluorescence only from within the solid angle defined by laser-ion interaction volume. Rhodamine 640 and Alexa Fluor 350 ions, commonly used as fluorescence resonance energy transfer (FRET) fluorophores, were generated in the gas phase by using electrospray ionization and injected into a radiofrequency Paul trap where they were stored and exposed to Nd:YAG laser pulses at 532 and 355 nm for times up to 10 m. Fluorescence emitted by these ions was investigated for several trap q z values and ion cloud temperatures. Analysis of photon statistics indicated an average of ϳ10 photons were incident on the PMT detector per 15 ns pulse for ϳ10 3 trapped ions in the interaction volume. Fluorescence measurements displayed a dependence on trapped ion number which were consistent with calculations of the space charge limited ion density. To investigate the quantitative capability of these fluorescence techniques, the laser-induced fragmentation of trapped Alexa I on traps provide a controlled environment in which fluorescence measurements can be performed on an ensemble of ions over timescales sufficient to consider small ion numbers and slow reaction rates. Laserinduced fluorescence measurements of trapped ions have been used in spectroscopic studies of atomic structure [1][2][3][4], the vibrational spectra of small molecules [5][6][7][8], as well as to characterize the dynamic cooling [9] and crystallization of atomic ions [10 -12].This paper introduces techniques that eliminate the detection of laser background scattering on trap apertures and internal surfaces allowing measurements to achieve both high sensitivity and large dynamic range. In previous pulsed laser measurements of molecular fluorescence collected from trapped species (discussed in references [5][6][7][8]), the radiative lifetimes were sufficiently long to allow collection of fluorescence radiation after the laser pulse. This greatly simplified methods to reduce the detection of background resulting from scattered laser radiation. However, experiments described in this paper apply the Nd:YAG pulsed laser to excite strongly emitting molecules having fluorescence lifetimes shorter than the laser pulse. This required the reduction of background laser scattering during laser excitation, a more demanding constraint.Techniques described in this paper will help to extend fluorescence measurements as an in situ probe of trapped ion properties including chemical identity, the growth and decay of specific ion populations, ion spectroscopy. Fluorescence emission from trapped ions also presen...

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Section: Discussionmentioning

confidence: 99%

Pulsed fluorescence measurements of trapped molecular ions with zero background detection

Khoury¹,

Rodriguez‐Cruz²,

Parks³

2002

J Am Soc Mass Spectrom

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“…In practical LITs, higher-order fields are inevitable for many reasons, such as the truncation of the electrodes, the use of simplified electrodes, and the existence of the ion ejection slots [30,[33][34][35][39][40][41][42]. Moreover, it is well known that ITs with some positive even-order fields might improve performance [33,[39][40][41][42][43][44][45].…”

Section: The Effects Of Higher-order Fieldsmentioning

confidence: 99%

“…Moreover, it is well known that ITs with some positive even-order fields might improve performance [33,[39][40][41][42][43][44][45]. For example, the addition of octopole [40][41][42][43][44][45] or dodecapole fields [30,33,39] can compensate for the detrimental field caused by the slot and, therefore, the mass resolution and mass accuracy are enhanced.…”

Section: The Effects Of Higher-order Fieldsmentioning

confidence: 99%

Theoretical Study of Dual-Direction Dipolar Excitation of Ions in Linear Ion Traps

Dang

Wang

et al. 2016

J. Am. Soc. Mass Spectrom.

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Abstract. The ion enhanced activation and collision-induced dissociation (CID) by simultaneous dipolar excitation of ions in the two radial directions of linear ion trap (LIT) have been recently developed and tested by experiment. In this work, its detailed properties were further studied by theoretical simulation. The effects of some experimental parameters such as the buffer gas pressure, the dipolar excitation signal phases, power amplitudes, and frequencies on the ion trajectory and energy were carefully investigated. The results show that the ion activation energy can be significantly increased by dual-direction excitation using two identical dipolar excitation signals because of the addition of an excitation dimension and the fact that the ion motion radius related to ion kinetic energy can be greater than the field radius. The effects of higher-order field components, such as dodecapole field on the performance of this method are also revealed. They mainly cause ion motion frequency shift as ion motion amplitude increases. Because of the frequency shift, there are different optimized excitation frequencies in different LITs. At the optimized frequency, ion average energy is improved significantly with relatively few ions lost. The results show that this method can be used in different kinds of LITs such as LIT with 4-fold symmetric stretch, linear quadrupole ion trap, and standard hyperbolic LIT, which can significantly increase the ion activation energy and CID efficiency, compared with the conventional method.

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“…Also, axial focusing DC fields have been created in the quadrupole LIT by mounting extra electrodes or decreasing the axial length [23,24]. The cylindrical ion trap has a longitudinal symmetry but its 3D electric field suffers the same trapping inefficiencies as any other Paul trap [25].For repeated ion injections, the segmented LIT and ring electrode traps [26,27] was proposed, which can compartmentalize the first ion bunch in one or more segments and finally ion injection can be repeated. However, their constructions are complicated and expensive due to their inherent multiple sections, segments mounting, rf, and DC voltage supply.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Computer simulation of the gap-tripole ion trap with linear injection, 3D ion accumulation, and versatile packet ejection

Salazar

Masujima

2008

J. Am. Soc. Mass Spectrom.

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The behavior of a completely new ion trap is shown with SIMION 7.0 simulations. The simulated trap, which was a mix of a linear and a 3D trap, was made by axially setting two ion guides with a gap between them. Each guide consisted of three rods with three symmetrically delayed radio frequency (rf) voltages (tripole). The "injected" ions were linearly contained by pulsed potentials on the entrance and exit plates. Then the three-dimensional (3D) rf field in the gap, which was created by the tripole special rod arrangement, could trap the ions when the translational energy was dampened by collisions with low-pressure nitrogen. Because the injected ions were trapped in the small gap, the trapping cycle could be repeated many times before ion ejection, so a high concentrated ion cloud could be obtained. This trapping and accumulation methodology is not possible in most conventional multipole linear traps with even number of poles. Compared with quadrupole linear trap at the same rf amplitude, tripole lost more ions due to strong charge repulsion in the ion cloud. However, tripole could catch up the ions at higher voltage. Radial and axial mass-independent ejection of the ions localized in the tripole gap was very simple, compared with conventional linear ion traps that need extra and complicated electrodes for effective axial ejection. F or analytical sciences, high sensitivity is one of the key points for success. In many types of mass spectrometers, the signal-to-noise ratio increases considerably by analyte accumulation, and the linear ion trap (LIT) concept has been widely used for ion accumulation in hybrid instruments [1][2][3][4][5][6][7]. The LIT has been suitable for the construction of miniature mass analyzers, gas-phase reactions, atomic spectroscopy, precursor fragmentation, and beam physics experiments [8][9][10][11][12][13][14][15][16]. In the case of quadrupole LIT, it can perform ion trapping and mass analysis, all in a single package [17]. The LIT is considered to have higher trapping efficiency and capacity than conventional 3D quadrupole ion trap (3D QIT or Paul Trap). The trapping efficiency for LIT is very high (~100%) compared with the 5% range for QIT when high-speed ions are externally injected [2,18,19]. Compared with the 3D QIT, space-charge repulsion is minimized in LIT because the charges can be dispersed in its big central volume.We have proposed a new ion optics, called "tripole" which consists of three parallel rods, carrying three rf voltages with symmetrically delayed phase shifts [20]. The rotating electric field of the tripole showed stable ion guiding for wide ranges of AC amplitude, better Address reprint requests to Dr. T. Masujima, Analytical Molecular Medicine and Devices Laboratory, Faulty of Frontier Medical Sciences, Graduate School of Hiroshima University, 1-2-3 Kasumi, Minarni-ku, Hiroshima 734-8551, Japan. E-mail: tsutomufehiroshima-u.ac.jp collisional focusing than hexapole and octapole, and similar focusing as quadrupole (rod pole). Also, the ion optic showed interest...

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A Quadrupole Ion Trap with Cylindrical Geometry Operated in the Mass-Selective Instability Mode

Cited by 143 publications

References 33 publications

Pulsed fluorescence measurements of trapped molecular ions with zero background detection

Pulsed fluorescence measurements of trapped molecular ions with zero background detection

Theoretical Study of Dual-Direction Dipolar Excitation of Ions in Linear Ion Traps

Computer simulation of the gap-tripole ion trap with linear injection, 3D ion accumulation, and versatile packet ejection

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