Improving the quality of the ion beam exiting a quadrupole ion guide

The effect of fringing fields on the divergence of the ion beam exiting an RF quadrupole ion guide was studied using a computer simulation. It was shown that reducing the strength of the RF field towards the ion guide exit reduces ion beam divergence. Further improvement was demonstrated when creating a DC gradient towards the exit. The results of the numerical simulation were verified experimentally using a time-of-flight (TOF) mass analyzer with orthogonal acceleration. Decreasing the ion beam divergence resulted in considerably improved mass resolution of the instrument.     

Evidence of isomerization during ion isolation in the quadrupole ion trap

Evidence of ion isomerization during isolation in an ion trap mass spectrometer is presented. An ion-molecule reaction that is specific for the tolyl cation was used to monitor the relative abundance of this species. In particular, it has been observed that ion isolation in the ion trap can impart sufficient energy to the tolyl cation to cause it to isomerize to a form (presumably either the benzyl or the tropylium ion) that is not reactive with the neutral reagent. These results are important to consider in ion trap applications involving ion species having activation barriers for isomerization lower than the activation barriers for dissociation.     

Determination of the non-constant component of the ion mobility using the spectrometer of ion mobility increment

A new method for determination of the non-constant component, alpha(E), of an ion mobility, k(E), is suggested. The method uses the relationship U(C) (US) that can be experimentally obtained with a spectrometer of ion mobility increment with planar drift chamber. (UC is a compensating voltage, U(S) is separating voltage amplitude.) A general equation for alpha(E) has been derived. We have explored the possibility of determination of alpha(E) from the experimental data for different types of US(t). In two specific cases, analytical solutions have been obtained.     

离子交换纤维的交换动力学研究

本文研究了VS-1型强酸性阳离子交换纤维的交换动力学.在有限浴条件下,用放射性示踪法,研究了温度,搅拌速度,溶液浓度及pH 值对该离子交换纤维的异相同位素交换反应的影响.并推导出离子交换纤维的交换动力学方程,计算出不同条件下的粒内扩散系数D及液膜中的传输系数D/δ.从机理上明确了交换纤维的交换反应速率远比球形树脂快的原因     

Organic ion imaging beyond the limit of static secondary ion mass spectrometry

Secondary ion mass spectra and images were obtained from spikes of choline chloride, acetylcholine chloride, and methylphenylpyridinium iodide deposited onto specimens of porcine brain tissue. Samples were subsequently subjected to a dose of 10-keV Cs⁺ sufficient to suppress secondary ion emission characteristic of the targeted analytes. Following ablation of the samples by massive glycerol clusters generated by electrohydrodynamic emission, secondary ion mass spectra and images could be obtained that reflected the identity and location of the spiked analytes. The absolute intensity of secondary ion emission that followed ablation was found to be between 30 and 100% of the intensity obtained prior to exposure to the high dose of Cs’. Not all chemical noise is removed by ablation, however, so that the signal-to-noise ratios after ablation correspond to between 10 and 85% of their values observed under conditions of low primary ion dose.     

The structure of the ion: An ion kinetic energy spectrometry study

The kinetic energy release (T) values for the loss of CO from ions from five compounds have been obtained and are consistent with at least two different structures for the ion. This result is supported by the T value obtained for the decomposition of the molecular ions.     

Study of the correlated motion of ion mixtures in an rf ion trap

We observed variations of the signal position versus the filament temperature, and thus the relative amounts of Ba⁺ and BaO⁺ ions stored simultaneously in an rf trap. The tendency of variations is explained by a generalized model of two coupled ion clouds, in which the coupling condition and the frequencies of correlated motions depend on the ion masses, the force constants of the applied trapping field and the Coulomb interaction between the ions as well as the relative ion numbers of the two ion clouds.     

An ion trap-ion mobility-time of flight mass spectrometer with three ion sources for ion/ion reactions

This instrument combines the capabilities of ion/ion reactions with ion mobility (IM) and time-of-flight (TOF) measurements for conformation studies and top-down analysis of large biomolecules. Ubiquitin ions from either of two electrospray ionization (ESI) sources are stored in a three dimensional (3D) ion trap (IT) and reacted with negative ions from atmospheric sampling glow discharge ionization (ASGDI). The proton transfer reaction products are then separated by IM and analyzed via a TOF mass analyzer. In this way, ubiquitin +7 ions are converted to lower charge states down to +1; the ions in lower charge states tend to be in compact conformations with cross sections down to ～880 Ų. The duration and magnitude of the ion ejection pulse on the IT exit and the entrance voltage on the IM drift tube can affect the measured distribution of conformers for ubiquitin +7 and +6. Alternatively, protein ions are fragmented by collision-induced dissociation (CID) in the IT, followed by ion/ion reactions to reduce the charge states of the CID product ions, thus simplifying assignment of charge states and fragments using the mobility-resolved tandem mass spectrum. Instrument characteristics and the use of a new ion trap controller and software modifications to control the entire instrument are described.     

Transmission mode ion/ion reactions in the radiofrequency‐only ion guide of hybrid tandem mass spectrometers

Transmission mode ion/ion reactions have been performed within the first quadrupole, the Q0 radiofrequency (RF)‐only quadrupole, of two types of hybrid tandem mass spectrometers (viz., triple quadrupole/linear ion trap and QqTOF instruments). These transmission mode reactions involved the storage of either the reagent species and the transmission of the analyte species through the Q0 quadrupole for charge inversion reactions or the storage of the analyte ions and transmission of the reagent ions as in charge reduction experiments. A key advantage to the use of transmission mode ion/ion reactions is that they do not require any instrument hardware modifications to provide interactions of oppositely charged ions and can be implemented in any instrument that contains a quadrupole or linear ion trap. The focus of this work was to investigate the potential of using the RF‐only quadrupole ion guide positioned prior to the first mass‐resolving element in a tandem mass spectrometer for ion/ion reactions. Two types of exemplary experiments have been demonstrated. One involved a charge inversion reaction and the other involved a charge reduction reaction in conjunction with ion parking. Ion/ion reactions proved to be readily implemented in Q0 thereby adding significantly greater experimental flexibility in the use of ion/ion reaction experiments with hybrid tandem mass spectrometers. Copyright © 2009 John Wiley & Sons, Ltd.     

Rydberg states of the strontium ion

We report on the spectroscopy of highly excited strontium ions after resonant multistep laser excitation. The states observed belonged to then s (26≦n≦79),n d (25≦n≦83),n f (28≦n≦86) andn g (30≦n≦81) series of Sr⁺. A least squares fit has been applied to determine the quantum defects and their linear energy dependence in each series, together with the ionisation limit of Sr⁺. The analysis of our data lead to a revised value for this ionisation limit of 88 965.18±0.02 cm^?1, with respect to the ground state of the Sr⁺ ion. Analysis of the non core-penetratingn g states yielded experimental values for the dipole and quadrupole polarizability of Sr⁺⁺, which are in satisfactory agreement with previous calculations.     

Electric properties of the chloride ion

The dipole (), quadrupole (C), and dipole-quadrupole (B) polarizabilities and the dipole hyperpolarizability () of the chloride ion have been calculated by using the many-body perturbation theory approach and a series of large polarized GTO/CGTO basis sets. The complete fourth-order treatment of the electron correlation effects with a basis set comprising the s, p, d, f, and g functions gives: =38.01 a.u., C=211.5 a.u., B=–5.14×10³ a.u., and =128. 5×10³ a.u. as compared to the corresponding SCF values (=31.49 a.u., C=158.9 a.u., B=–2.92×10³ a.u., =57.7×10³ a.u.). The quenching of polarizabilities of the Cl^– ion in solutions and ionic crystals is discussed.     

Automerization of the 9,9,10-triethylphenanthrenonium ion

Conclusions Employing the NMR method it was shown that the 9,9,10-triethylphenanthrenonium ion undergoes rapid automerization as the result of intramolecular transitions of the ethyl group between the C₉ and C₁₀ atoms. The kinetics of the automerization was studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 441–444, February, 1971.