Simultaneous Two-Ion Mass Spectroscopy

Physics Reports, 2006

Like few other parameters, the mass of an atom, and its inherent connection with the atomic and nuclear binding energy is a fundamental property, a unique fingerprint of the atomic nucleus. Each nuclide comes with its own mass value different from all others. For short-lived exotic atomic nuclei the importance of its mass ranges from the verification of nuclear models to a test of the Standard Model, in particular with regard to the weak interaction and the unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. In addition, accurate mass values are important for a variety of applications that extend beyond nuclear physics. Mass measurements on stable atoms now reach a relative uncertainty of about 10 −11. This extreme accuracy contributes, among other things, to metrology, for example the determination of fundamental constants and a new definition of the kilogram, and to tests of quantum electrodynamics and fundamental charge, parity, and time reversal symmetry. The introduction of Penning traps and storage rings into the field of mass spectrometry has made this method a prime choice for high-accuracy measurements on short-lived and stable nuclides. This is reflected in the large number of traps in operation, under construction, or planned worldwide. With the development and application of proper cooling and detection methods the trapping technique has the potential to provide the highest sensitivity and accuracy, even for very short-lived nuclides far from stability. This review describes the basics and recent progress made in ion trapping, cooling, and detection for high-accuracy mass measurements with emphasis on Penning traps. Special attention is devoted to the applications of accurate mass values in different fields of physics.

Organic Mass Spectrometry, 1994

Analytical Chemistry, 1999

Experimental data and simulations of trapped-ion motion are used to characterize the phenomenon of compounddependent mass shifts in a quadrupole ion trap mass spectrometer. The ratio of axial to radial dimensions of the ion trap and the nature and pressure of the bath gas are identified as experimental variables which influence the chemical mass shift. Systematic changes in chemical shifts occur with changes in the chemical structure of the ion, for example between members of a homologous series of alkylbenzene molecular ions. Simulations, performed using a new version of the program ITSIM, indicate that the mass shift is the result of two interacting factors: (i) delayed ion ejection from the trap during the mass analysis scan due to field imperfections associated with the end-cap electrode apertures and (ii) the compounddependent modification of this delay by collisions with the bath gas. Both elastic collisions and inelastic collisions, including those which lead to dissociation, appear to contribute to the shortening of the delay and hence to affect the magnitude of the chemical mass shifts.

Journal of the American Society for Mass Spectrometry, 1992

Advances in Mass Spectrometry, 1992

Enhanced trajectory control m the quadrupole ion trap, m the presence of hehum buffer gas, has brought about enormous ~mprovements m mass range (mass hmlts m excess of 70000Da have been achieved), mass resolution (full width at half-maximum, 1 130000 at m/z 3510), and multistage tandem mass spectrometry (MS) n where n ~< 13 The compatlbdlty of the ion trap with external ion sources, such as electrospray and atmospheric pressure discharges, has greatly extended the range of apphcatlon of the ion trap Brief descriptions of the diagrammatic representation of ion trajectory stablhty and ion trapping theory precede a review of axial modulation, mass-selective axial ~on ejection, ~on ~solat~on, colhs~onreduced dissociation, tandem mass spectrometry and dynamically programmed scans The progress made during the past 3 years in all aspects of 1on trap mass spectrometry is reviewed

International Journal of Mass Spectrometry and Ion Processes, 1995

The separate and combined influences of a phase-locked relationship between the drive (r.f.) and excitation (a.c.) frequencies, and the noise level on the drive voltage, on the ejection of ions from a quadrupole ion trap have been investigated at each of two scanning rates, 10 and 5000 u s-l. The half-width of an individual mass peak, which has been shown previously to vary directly with the mass scanning rate, is dependent also on the a.c.-r.f, phase relationship, and can be minimized. However, it is not practical to resolve an ion-intensity signal beyond that point where the peak halfwidth becomes significantly less than the uncertainty in its position. It has been observed that the position of mass peaks with half-widths of 1 or 2mu can vary by as much as 0.25% as the a.c.r.f, phase difference is varied over one complete cycle. Furthermore, the noise level present on the amplitude of the r.f. drive of the ion trap used in this study (primarily 60 and 120 Hz) can cause an uncertainty in peak positions of as much as 0.1%. With the a.c.-r.f, phase difference locked at a favorable value and the scan function triggered by the phase of the line voltage, it is possible to achieve mass-peak stability to within 5 mu for m/z 264 corresponding to a resolution of 50 000. The results of a simulation study of peak position as a function of the a.c.-r.f, phase difference at a mass-scanning rate of 5000 u s i are in good agreement with experimental results. Simulated trajectories were used also to determine the effect of the a.c.-r.f, phase relationship on the phase-at-ejection of the a.c. and r.f. potentials.

Physical Review A, 2019

The precise knowledge of the atomic masses of light atomic nuclei, e.g. the proton, deuteron, triton and helion, is of great importance for several fundamental tests in physics. However, the latest high-precision measurements of these masses carried out at different mass spectrometers indicate an inconsistency of five standard deviations. To determine the masses of the lightest ions with a relative precision of a few parts per trillion and investigate this mass problem a cryogenic multi-Penning trap setup, LIONTRAP (Light ION TRAP), was constructed. This allows an independent and more precise determination of the relevant atomic masses by measuring the cyclotron frequency of single trapped ions in comparison to that of a single carbon ion. In this paper the measurement concept and the first doubly compensated cylindrical electrode Penning trap, are presented. Moreover, the analysis of the first measurement campaigns of the proton's and oxygen's atomic mass is described in detail, resulting in mp = 1.007 276 466 598 (33) u and m 16 O = 15.994 914 619 37 (87) u. The results on these data sets have already been presented in [F. Heiße et al., Phys. Rev. Lett. 119, 033001 (2017)]. For the proton's atomic mass, the uncertainty was improved by a factor of three compared to the 2014 CODATA value. the Atomic Mass Evaluation (AME) [12, 13]. Unfortunately, especially the measurement of the interesting light ion (and particle) masses are complicated by the sizable systematic frequency shifts originating in the relatively large ratio of kinetic energies compared to the low rest mass energy. Consequently, we have developed the LIONTRAP (Light Ion TRAP) apparatus, which is optimized to minimize these systematic shifts. Recently, as a first application, we have performed a mea

International Journal of Mass Spectrometry and Ion Processes

A linear-geometry, radio-frequency, quadrupole ion trap has been developed to generate, purify, accumulate and study atomic and molecular ions in the gas phase. By employing a trap-based system, both reactant and product ions can be stored for significant time periods, which can both enhance the efficiency of gas-phase reaction processes and create an environment to observe collision products after vibrational and rotational excitations have had time to relax. Relaxation occurs via viscous cooling with a dilute buffer gas or via laser cooling. Furthermore, the setup is particularly useful for performing optical spectroscopy on the trapped ions. Atomic and molecular ovens are used to generate thermal beams of neutral species, which are then ionized by electron bombardment. The ions can be trapped, or they can be collided with neutral molecules (e.g. C60) under well defined experimental conditions. The collision energies are variable over a range from nearly 0 to 200 eV. This feature makes possible studies of complex formation, charge transfer and collision-induced fragmentation as a function of kinetic energy. A wide range of masses of up to 4000 u can be stored and manipulated with this apparatus. Two mass spectrometric techniques for the analysis of trapped ionic species are presented. In one method, parametric excitation of the secular motion is used to generate mass spectra with resolutions as high as 1 part in 800 with a simple experimental setup. The second method is capable of quickly generating mass spectra over the entire range of trapped masses, but has only moderate resolution. These spectra are generated by linearly sweeping the rf-trapping voltage to zero and detecting ions as their trap depth falls below a threshold value. In the trapping volume, which is 10 cm in length and 200 #m in diameter, 106 ions can be loaded and stored, corresponding to an ion density above 108 cm-3. Such densities facilitate spectroscopy of the stored ions. Both laser-induced fluorescence and photodissociation measurements have been carried out with a cw laser system providing near-infrared, visible, and ultraviolet beams. Absolute, total cross-sections and branching ratios of the photodissociation of MgC~0 have been measured.

Journal of the American Society for Mass Spectrometry, 2002

International Journal of Mass Spectrometry and Ion Processes, 1994

A two-electrode ion trap consisting of concentric single-sheet "core" and "ring" hyperboloids has been constructed and experimentally tested for Fourier transform ion cyclotron resonance mass spectrometry. The trap may be visualized as a modified Penning trap in which the end caps are brought together until they merge into a single "core" electrode. The trap is operated in "parametric" mode (i.e., both d.c. and r.f. voltages superimposed on the core and ring electrodes). Ion cyclotron motion is excited (or detected) by applying (or measuring) the voltage difference between the core and ring electrodes at the "parametric" resonant frequency, wr = (w+ -w_), in which w+ and w_ are the reduced cyclotron and magnetron frequencies.