Inhomogeneous RF Fields: A Versatile Tool for the Study of Processes with Slow Ions

Gerlich, D.

doi:10.1002/9780470141397.ch1

Cited by 551 publications

(417 citation statements)

References 126 publications

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“…The resulting ions were transferred through a series of radio frequency (RF) ion guides into a linear octupole ion trap. Ions were confined within the trap by RF fields applied to the trap rods 30 and DC voltages on entrance and exit electrodes. The trap was in thermal contact with a closed-cycle refrigerator and was cooled down to 35 K. (Lower temperatures using a more powerful refrigerator are now available to us.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Slow photoelectron velocity-map imaging spectroscopy of cold negative ions

Hock

Kim

Weichman

et al. 2012

The Journal of Chemical Physics

120

139

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We report high-resolution anion photoelectron spectra of thiozonide (S 3 − ) acquired by slow electron velocity-map imaging (SEVI). The ions were cryogenically cooled within an ion trap before photodetachment. We measure an electron affinity of 2.3630(9) eV, resolving discrepancies in previously reported photoelectron spectra that resulted from the presence of vibrational hot bands. The SEVI spectrum shows well-resolved, extended vibrational progressions in the symmetric stretch and bending modes of S 3 , yielding accurate frequencies for both. ■ INTRODUCTIONWith the possible exception of carbon, sulfur has more complex allotropy than any other element. 1 In addition to the numerous cyclic and polymeric forms in the solid and liquid phases, sulfur vapor is composed of the species S n (2 ≤ n ≤ 8), with trace amounts of S 9 and S 10 . 2 Aside from the diatomic S 2 , S 3 has received the most attention of these species. Its relatively small size makes it accessible to experiment and theory, and additional interest comes about because S 3 is isovalent with ozone. It has been studied by rare gas matrix IR and UV−vis spectroscopy, 3,4 resonance Raman in the gas phase, 5,6 microwave spectroscopy, 7,8 photoionization, 9 and gas-phase absorption. 10 Ab initio calculations on S 3 have focused on the question of whether the cyclic D 3h or the bent C 2v structure is the lowestenergy isomer, 11−14 finding overall agreement with experiment that the C 2v form is the stable form. High-level calculations on the structure, vibrations, and excited states of S 3 have recently been reported by Francisco et al. 15,16 In contrast to neutral S 3 , work on the S 3 − anion has largely been limited to spectroscopy in condensed phases, where it has been studied by electron paramagnetic resonance (EPR), Raman, and absorption spectroscopy. 17−19 As it is the chromophore in ultramarine pigment, 20 many of these investigations were focused on determining the properties of S 3 − in a perturbative mineral matrix or in solution. In addition, electronic absorption spectra have been measured in a cryogenic rare gas matrix. 21 Recently, the anion has been identified as the dominant form of sulfur in certain highpressure and temperature conditions approximating crustal and subduction-zone geologic fluids. 22 The new findings suggest that S 3 − may play an important role in the transport of sulfur and chalcophile metals in the earth.The neutral ← anion transition has been studied by anion photoelectron spectroscopy (PES) with resolution sufficient to resolve a progression of the ν 1 symmetric stretch. 23−25 However, the two previous studies disagreed over which peak in this progression was the vibrational origin. By assuming the anions were at the ground vibrational state, Nimlos et al. 23 obtained an electron affinity (EA) of 2.106(23) eV. Hunsicker et al. 24 found a different onset for the band, suggesting the possibility that the two experiments produced anions with different vibrational temperatures and that some of the low binding en...

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Slow photoelectron velocity-map imaging spectroscopy of cold negative ions

Hock

Kim

Weichman

et al. 2012

The Journal of Chemical Physics

120

139

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“…The octopole passes through a static gas cell containing Xe at low pressure (0.05−0.20 mTorr) to ensure that multiple ion-neutral collisions are improbable. The octopole ion guide also acts as an efficient radial trap for ions such that scattered reactant and products ions are not lost as they drift toward the end of the octopole [57][58][59]. The product and unreacted beam ions are focused into a quadrupole mass filter for mass analysis and subsequently detected with a secondary electron scintillation (Daly) detector and standard pulse counting techniques.…”

Section: General Proceduresmentioning

confidence: 99%

Sodium Cation Affinities of Commonly Used MALDI Matrices Determined by Guided Ion Beam Tandem Mass Spectrometry

Chinthaka¹,

Rodgers²

2012

J. Am. Soc. Mass Spectrom.

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The sodium cation affinities of six commonly used MALDI matrices are determined here using guided ion beam tandem mass spectrometry techniques. The collision-induced dissociation behavior of six sodium cationized MALDI matrices, Na + (MALDI), with Xe is studied as a function of kinetic energy. The MALDI matrices examined here include: nicotinic acid, quinoline, 3-aminoquinoline, 4-nitroaniline, picolinic acid, and 3-hydroxypicolinic acid. In all cases, the primary dissociation pathway corresponds to endothermic loss of the intact MALDI matrix. The cross section thresholds are interpreted to yield zero and 298 K Na + −MALDI bond dissociation energies (BDEs), or sodium cation affinities, after accounting for the effects of multiple ionneutral collisions, the kinetic and internal energy distributions of the reactants, and dissociation lifetimes. Density functional theory calculations at the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G* and MP2(full)/6-311+G(2d,2p)//B3LYP/6-31G* levels of theory are used to characterized the structures and energetics for these systems. The calculated BDEs exhibit very good agreement with the measured values for most systems. The experimental and theoretical Na + −MALDI BDEs determined here are compared with those previously measured by cation transfer equilibrium methods.

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“…where V 0 is the zero to peak AC voltage amplitude, r 0 is the field radius, and N is the number of pairs of parallel rods [17]. A mathematical model for the tripole radial electric potential and pseudopotential was developed because calculating the pseudopotential from SIMION data is an impractical and very time-consuming method that only SIMION users can reproduce.…”

Section: Conventional and Novel Ac Ion Opticmentioning

confidence: 99%

Computer simulations of a new three rods ion optic (TRIPOLE) with high focusing and mass filtering capabilities

Salazar

Masujima

2007

J. Am. Soc. Mass Spectrom.

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A novel three rod (tripole) ion optic to which three AC voltages with symmetrically delayed phase shifts were applied to each electrode. We studied its ion guiding, focusing, and mass filtering capabilities by SIMION ver. 7.0 computer simulations. An electric field mathematical model was developed to calculate the pseudopotential of the tripole radial AC force. The tripole showed stable ion guiding for wide ranges of AC amplitude; better collisional focusing than hexapole and octapole and similar focusing as quadrupole (rod pole). Also, the ion optic clearly showed interesting mass filtering potential when the phase shift was asymmetrically delayed. The symmetric shape of the pseudopotential field explained the tripole ion guiding and focusing capabilities. For mass filtering, the pseudopotential was asymmetric and its effect was balanced with DC voltage to separate the ions, depending in their masses. The resolution was much lower than quadrupole but useful when rough filtering was required. (J Am Soc Mass Spectrom 2007, 18, 413-421)

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Inhomogeneous RF Fields: A Versatile Tool for the Study of Processes with Slow Ions

Cited by 551 publications

References 126 publications

Slow photoelectron velocity-map imaging spectroscopy of cold negative ions

Slow photoelectron velocity-map imaging spectroscopy of cold negative ions

Sodium Cation Affinities of Commonly Used MALDI Matrices Determined by Guided Ion Beam Tandem Mass Spectrometry

Computer simulations of a new three rods ion optic (TRIPOLE) with high focusing and mass filtering capabilities

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