Magnetic Sector Mass Spectrometer Research Articles

LA-Q-ICP-MS apatite U/Pb geochronology using common Pb in plagioclase: Examples from layered mafic intrusions

Apatite geochronology is a versatile method for providing medium temperature history constraints of magmatic and metamorphic rocks. The LA-ICP-MS technique is widely applied to U/Pb geochronology using various minerals. Apatite U/Pb geochronology, in contrast to e.g., zircon, is compromised by variable amounts of common Pb incorporated into the crystal during growth. Magmatic apatite often shows a sufficient spread in data to obtain a precise and accurate lower intercept age. If this is not the case, the initial Pb isotopic composition needs to be estimated to obtain accurate and precise age information from apatite. Two approaches are common, one being the estimation of common Pb from a Pb evolution model and the other being the measurement of a coexisting mineral phase that tends to incorporate Pb but not U, e.g., feldspar. Most recent studies applying LA-ICP-MS to the analysis of Pb isotopes in feldspar utilize either multicollector or magnetic sector mass spectrometers. In this study we first evaluate the application of quadrupole mass spectrometry for apatite U/Pb geochronology combined with Pb isotopic measurements in feldspar and compare the results with modeled initial Pb isotopic compositions. The resulting age information is accurate and precise despite using plagioclase rather than K-feldspar, as is normally used, to define initial Pb isotope compositions. We apply this method to apatite-bearing gabbroic rocks from layered intrusions (Bushveld, Bjerkreim-Sokndal, Hasvik, and Skaergaard) ranging in age from ca. 2 Ga to ca. 55 Ma and generate metamorphic/cooling ages generally consistent with the known geologic history of these intrusions.

High-temperature mass spectrometric study of the vaporization processes and thermodynamic properties of samples in the Bi2 O3 -P2 O5 -SiO2 system.

The Bi2 O3 -P2 O5 -SiO2 system possesses a number of valuable properties that may be of use for various practical applications, both for obtaining new materials, e.g. optical fibers, and for replacing systems based on toxic lead silicate. Information on vaporization processes and thermodynamic properties obtained in the present study will be useful for the development of synthetic methods and approaches for modeling the thermodynamic properties of materials based on this system. High-temperature Knudsen effusion mass spectrometry was used to study the vaporization processes and to determine the thermodynamic properties of the components in the Bi2 O3 -P2 O5 -SiO2 system. Measurements were performed with a MS-1301 magnetic sector mass spectrometer. Vaporization was carried out using an iridium-plated molybdenum twin effusion cell containing the sample under study and pure bismuth(III) oxide as a reference substance. Electron ionization at an energy of 30 eV was employed in the study. At a temperature of 950 K, Bi and O2 were found to be the main vapor species over the samples studied. The Bi2 O3 activity as a function of composition in the Bi2 O3 -P2 O5 -SiO2 system was derived from the obtained Bi partial pressures. The excess Gibbs energy of the system studied was calculated at 950 K and 1273 K. The possibility of using the Kohler method for the calculation of thermodynamic properties in the Bi2 O3 -P2 O5 -SiO2 system was illustrated. The excess Gibbs energy of the Bi2 O3 -P2 O5 -SiO2 system obtained in the present study using the Knudsen mass spectrometric method at 950 K and 1273 K demonstrated significant negative deviations from ideal behavior. The excess Gibbs energy values calculated by the Kohler method were shown to be in good agreement with those obtained from experimental data. Copyright © 2016 John Wiley & Sons, Ltd.

Continuous Monitoring of the Vadose Zone Gas Phase by Mass Spectrometry

Core Ideas Continuous monitoring of vadose gases was performed with a process mass spectrometer. Large spatial and temporal variability was observed for reactive and inert gases. Gas dynamics were controlled by water fluxes, O2 depletion, and diffusion. Long‐term continuous measurements of gas concentrations in the vadose zone are required to identify gas transport processes. A magnetic sector mass spectrometer, originally developed for industrial process monitoring, was deployed in the field, and its performance was assessed for continuous monitoring of vadose zone gases. This instrument allows unattended concentration measurements of a large number of gas species without any purification. With a detection limit on the order of 10 nL L−1, it allows determination of trace gases such as Kr and Xe isotopes at their natural atmospheric abundances. Good precision and accuracy were obtained for major, minor, and trace gases with a daily calibration. Continuous monitoring of vadose zone gases for 6 mo in two boreholes at various depths at the Roselend Natural Laboratory (French Alps) showed strong spatial and temporal variability of gas concentrations, not only O2 and CO2 but also inert gases. Such time series allow determination of transport processes and interactions between water and gas fluxes in the vadose zone.

Analysis of old master paintings by direct temperature-resolved time-of-flight mass spectrometry: Some recent developments

Direct temperature-resolved mass spectrometry (DTMS) is an analytical technique in which small (μg) amounts of sample are applied to a filament and introduced into the ion source of a mass spectrometer. It is a fast fingerprinting method particularly suitable for the characterization of oils, resins, waxes, and other compound classes in tiny complex samples from paintings. DTMS results reported thus far have been obtained using instruments with nominal mass resolution. Higher mass resolutions can be achieved by magnetic sector mass spectrometers only at the expense of a severe loss of sensitivity. Modern time-of-flight mass spectrometers, however, do provide both high resolution and high sensitivity simultaneously. The availability of accurate mass information adds another dimension to DTMS. The difference between the nominal and accurate mass, the mass defect, may be graphically presented in so-called ‘Kendrick plots’. These can be used as fingerprints, enabling a quick overview of the main features in high-resolution mass spectra of complex mixtures. This paper combines DTMS with Kendrick mass defect analysis applied to a series of reference compounds commonly found in paintings. Finally, we also present the results of analysis of samples taken from the 17th-century painting of Saul and David by Rembrandt van Rijn (Mauritshuis, The Hague) that has been recently subjected to extensive conservation treatment.

Corrigendum:N-Imidazolylation of Sulfoximines fromN-Cyano Sulfoximines, 1-Alkynes, andN-Sulfonyl Azides

For the Update by Sanghyuck Kim, Ji Eun Kim, Jinsub Lee, and Phil Ho Lee, in Issue 16–17, 2015, pp 3707–3717 (DOI: 10.1002/adsc.201500636), the following correction needs to be made in the right column of page 3712: “High resolution mass spectra (HR-MS) were obtained by fast atom bombardment (FAB) using a double focusing magnetic sector mass spectrometer and electron impact (EI) ionization technique (magnetic sector – electric sector double focusing mass analyzer).” should be replaced with “High resolution mass spectra (HRMS) were obtained by fast atom bombardment (FAB) using a double focusing magnetic sector mass spectrometer and electron impact (EI) ionization technique (magnetic sector – electric sector double focusing mass analyzer) from the KBSI (Korea Basic Science Institute).”

Improved Faraday collector for magnetic sector mass spectrometers

Faraday collectors are used in isotopic ratio mass spectrometers for measurement of ion beam intensities. Ions striking the collector surface result in secondary electron emission that constitutes an error current. Typical collectors use electrical suppressors for minimizing current due to secondary electrons. However, due to mechanical errors in the placement of electrical suppressors, collection efficiency may vary for different collectors. In present study, different techniques for reducing secondary electron contribution have been investigated. These are: (a) use of magnetic field (instead of electric field) for secondary electron suppression, (b) graphite coating to reduce secondary electron emission and (c) inclination of collector to 45° with respect to ion beam. Studies have resulted in a mechanically simpler design and improved performance that has been demonstrated by measurement of 87Sr/86Sr isotopic ratio.

Order of Magnitude Signal Gain in Magnetic Sector Mass Spectrometry Via Aperture Coding.

Miniaturizing instruments for spectroscopic applications requires the designer to confront a tradeoff between instrument resolution and instrument throughput [and associated signal-to-background-ratio (SBR)]. This work demonstrates a solution to this tradeoff in sector mass spectrometry by the first application of one-dimensional (1D) spatially coded apertures, similar to those previously demonstrated in optics. This was accomplished by replacing the input slit of a simple 90° magnetic sector mass spectrometer with a specifically designed coded aperture, deriving the corresponding forward mathematical model and spectral reconstruction algorithm, and then utilizing the resulting system to measure and reconstruct the mass spectra of argon, acetone, and ethanol. We expect the application of coded apertures to sector instrument designs will lead to miniature mass spectrometers that maintain the high performance of larger instruments, enabling field detection of trace chemicals and point-of-use mass spectrometry.

On the formation of SFn– (n = 1–6) anions via a novel route and their properties

Sulfur hexafluoride (SF6 ) being a potential greenhouse gas, coupled with its numerous applications, makes the study of the formation and fragmentation of SF6 -based species important. The formation of SF6 -based anionic species has been studied using the gas feed-sputtering route and the mechanisms at play during the sputter-ejection of guest molecule-derived particles have also been probed. Studies of the formation of SFn (-) (n = 1-6) anions were conducted from various surfaces (metal and compound) that were subjected to Cs(+) ion sputtering in the presence of SF6 gas employing the gas feed-cesium sputter technique. The anions generated were mass analyzed using a double-focusing magnetic sector mass spectrometer. Quantum mechanical computations were performed to study the ground state structure and stability of neutral and negatively charged SFn (n = 1-6) systems applying density functional theory (DFT) and ab initio methods (MP2 and CC). This technique readily generated (32) SFn (-) (n = 1-6) anions for all sizes of 'n' with practicable yields. Mass spectrometric measurements of the yield of sputter-ejected (32) SFn (-) (n = 1-6) anions reveal an oscillatory pattern as a function of 'n', with odd values of 'n' being relatively more abundant. The relative yield of (34) SFn (-) (n = 1-6) anions with respect to size was also measured albeit with low signal intensity. Also observed were F(-) , S(-) , F2 (-) , (33) SF5 (-) and (33) SF6 (-) anionic species. The relevant electron affinity and bond dissociation energy (BDE) values were also computed. Gas-phase SFn (-) (n = 1-6) anions can be effectively generated by using the gas spray-cesium sputter technique. Both experimental measurements and calculations indicate the existence of odd-even oscillations in the stability and electronic structure of the SFn (n = 1-6) systems. The highest yield recorded was for the sputter-ejected SF5 (-) species and this may be attributed to its 'superhalogen' anionic character coupled with the relatively favorable F(0) fragmentation pathway of sputtered SF6 (-) . A signature pertaining to intact SF6 (-) anion ejection is also observed.

Quantification of PAHs and oxy-PAHs on airborne particulate matter in Chiang Mai, Thailand, using gas chromatography high resolution mass spectrometry

An analytical method using gas chromatography high resolution mass spectrometry was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) and 12 oxygenated PAHs (of which 4 diketones, 3 ketones, 4 aldehydes and one anhydride) on atmospheric particulate matter with an aerodynamic diameter less than 10μm (PM10). The magnetic sector mass spectrometer was run in multiple ion detection mode (MID) with a mass resolution above 10 000 (10% valley definition) and allows for a selective accurate mass detection of the characteristic ions of the target analytes. Instrumental detection limits between 0.04pg and 1.34pg were obtained for the PAHs, whereas for the oxy-PAHs they ranged between 0.08pg and 2.13pg. Pressurized liquid extraction using dichloromethane was evaluated and excellent recoveries ranging between 87% and 98% for the PAHs and between 74% and 110% for 10 oxy-PAHs were obtained, when the optimum extraction temperature of 150°C was applied. The developed method was finally used to determine PAHs and oxy-PAHs concentration levels from particulate matter samples collected in the wet season at 4 different locations in Chiang Mai, Thailand (n=72). This study brings forward the first concentration levels of oxy-PAHs in Thailand. The median of the sum of the PAHs and oxy-PAHs concentrations was 3.4ng/m3 and 1.1ng/m3 respectively, which shows the importance of the group of the oxy-PAHs as PM10 constituents. High molecular weight PAHs contributed the most to the ∑PAHs. For example, benzo[ghi]perylene was responsible for 30–44% of the ∑PAHs. The highest contribution to ∑oxy-PAHs came from 1,8-napthalic anhydride (26–78%), followed by anthracene-9,10-dione (4–27%) and 7H-benzo[de]anthracene-7-one (6–26%). Indications of the degradation of PAHs and/or formation of oxy-PAHs were observed.

Electronically excited negative ion resonant states in chloroethylenes

The negative ion mass spectra of the resonant electron capture by molecules of 1,1-dichloroethylene, 1,2-dichloroethylene-cis, 1,2-dichloroethylene-trans, trichloroethylene and tetrachloroethylene have been recorded in the 0–12eV range of the captured electron energy using static magnetic sector mass spectrometer modified for operation in the resonant electron capture regime. As a result, several novel low-intensive dissociation channels were revealed in the compounds under study. Additionally, the negative ion resonant states were recorded at approximately 3–12eV, mostly for the first time. These resonant states were assigned to the electronically excited resonances of the inter-shell type by comparing their energies with those of the parent neutral molecules triplet and singlet electronically excited states known from the energy-loss spectra obtained by previous studies.

Two-dimensional aperture coding for magnetic sector mass spectrometry.

In mass spectrometer design, there has been a historic belief that there exists a fundamental trade-off between instrument size, throughput, and resolution. When miniaturizing a traditional system, performance loss in either resolution or throughput would be expected. However, in optical spectroscopy, both one-dimensional (1D) and two-dimensional (2D) aperture coding have been used for many years to break a similar trade-off. To provide a viable path to miniaturization for harsh environment field applications, we are investigating similar concepts in sector mass spectrometry. Recently, we demonstrated the viability of 1D aperture coding and here we provide a first investigation of 2D coding. In coded optical spectroscopy, 2D coding is preferred because of increased measurement diversity for improved conditioning and robustness of the result. To investigate its viability in mass spectrometry, analytes of argon, acetone, and ethanol were detected using a custom 90-degree magnetic sector mass spectrometer incorporating 2D coded apertures. We developed a mathematical forward model and reconstruction algorithm to successfully reconstruct the mass spectra from the 2D spatially coded ion positions. This 2D coding enabled a 3.5× throughput increase with minimal decrease in resolution. Several challenges were overcome in the mass spectrometer design to enable this coding, including the need for large uniform ion flux, a wide gap magnetic sector that maintains field uniformity, and a high resolution 2D detection system for ion imaging. Furthermore, micro-fabricated 2D coded apertures incorporating support structures were developed to provide a viable design that allowed ion transmission through the open elements of the code.

Detection and identification of trace amounts of organochlorine substances by gas chromatography-high-resolution mass spectrometry

A search and identification of organochlorine compounds in soils with abnormally high level of octachlorodibenzo-p-dioxin from the northern province of Vietnam were carried out by gas chromatography-high-resolution mass spectrometry using a magnetic sector mass spectrometer in the scan and multi-ion detection modes at resolution 8000–10000. An algorithm for determining the exact mass, molecular formula, and molecular structure of organochlorine substances at ultratrace concentrations was proposed. Twenty-eight organohalogen compounds were found, 22 of which were derivatives of polychlorinated dibenzo-p-dioxins and polychlorinated diphenyl ethers with from one to three methoxy groups; the concentration range for these compounds is 0.0001–0.5% relative to the level of octachlorodibenzo-p-dioxin (OCDD). The existence of such substances was assumed, as they may be metabolites of polychlorinated dibenzo-p-dioxins (PCDD) or other chlorinated aromatic compounds, but most of these compounds have never been described in the literature. Some of the compounds could be considered as possible biotransformation products of OCDD; the others of different origin and may be byproducts of the formation of OCDD in nature.

Mass spectrometry studies of lycodine-type Lycopodium alkaloids: sauroxine and N-demethylsauroxine.

Sauroxine and N-demethylsauroxine are lycodine-type Lycopodium alkaloids. In recent years, Lycopodium alkaloids have gained significant interest due to their unique skeletal characteristics as well as due to their acetylcholinesterase activity. It is known that drugs that inhibit acetylcholinesterase can be used to treat the early stages of Alzheimer's disease. Sauroxine and N-demethylsauroxine were isolated from the aerial parts of Huperzia saururus (Lam.) Trevis. Electron ionization mass spectrometry (EI-MS) (low resolution) and collision-induced dissociation tandem mass spectrometry (CID-MS/MS) fragmentation was conducted using an ion trap, GCQ Plus mass spectrometer with MS/MS. Electron ionization high-resolution mass spectrometry (EI-HRMS) was performed in a magnetic sector mass spectrometer (Micromass VG). Using GC/EI-CID-MS/MS we obtained different fragmentation routes that connect all the ionic populations. In addition, the use of EI-HRMS allowed us to measure the exact masses of all the fragment ions, and, with all this information gathered, we tried to establish a fragmentation scheme concordant with the ascendant and descendant species. The mass spectrometry studies presented in this work complete our mass studies of Lycopodium alkaloids. The mass spectrometry work presented has been very useful to confirm the structures as well as to support the biogenetic relationships between the lycodine-type Lycopodium alkaloids: sauroxine and N-demethylsauroxine.

Mass Spectrometry in Russia

The present review covers the main research in the area of mass spectrometry from the 1990s which was about the same time as the Russian Federation emerged from the collapse of the Soviet Union (USSR). It consists of two main parts-application of mass spectrometry to chemistry and related fields and creation and development of mass spectrometric technique. Both traditional and comparatively new mass spectrometric methods were used to solve various problems in organic chemistry (reactivity of gas-phase ions, structure elucidation and problems of identification, quantitative and trace analysis, differentiation of stereoisomers, derivatization approaches etc.), biochemistry (proteomics and peptidomics, lipidomics), medical chemistry (mainly the search of biomarkers, pharmacology, doping control), environmental, petrochemistry, polymer chemistry, inorganic and physical chemistry, determination of natural isotope ratio etc. Although a lot of talented mass spectrometrists left Russia and moved abroad after the collapse of the Soviet Union, the vitality of the mass spectral community proved to be rather high, which allowed the continuation of new developments in the field of mass spectrometric instrumentation. They are devoted to improvements in traditional magnetic sector mass spectrometers and the development of new ion source types, to analysis and modification of quadrupole, time-of-flight (ToF) and ion cyclotron resonance (ICR) analyzers. The most important achievements are due to the creation of multi-reflecting ToF mass analyzers. Special attention was paid to the construction of compact mass spectrometers, particularly for space exploration, of combined instruments, such as ion mobility spectrometer/mass spectrometer and accelerating mass spectrometers. The comparatively young Russian Mass Spectrometry Society is working hard to consolidate the mass spectrometrists from Russia and foreign countries, to train young professionals on new appliances and regularly holds conferences on mass spectrometry. For ten years, a special journal Mass-spektrometria has published papers on all disciplines of mass spectrometry.

Invited Review Article: Recent developments in isotope-ratio mass spectrometry for geochemistry and cosmochemistry

Mass spectrometry is fundamental to measurements of isotope ratios for applications in isotope geochemistry, geochronology, and cosmochemistry. Magnetic-sector mass spectrometers are most common because these provide the best precision in isotope ratio measurements. Where the highest precision is desired, chemical separation followed by mass spectrometric analysis is carried out with gas (noble gas and stable isotope mass spectrometry), liquid (inductively coupled plasma mass spectrometry), or solid (thermal ionization mass spectrometry) samples. Developments in in situ analysis, including ion microprobes and laser ablation inductively coupled plasma mass spectrometry, have opened up issues concerning homogeneity according to domain size, and allow ever smaller amounts of material to be analyzed. While mass spectrometry is built solidly on developments in the 20th century, there are new technologies that will push the limits in terms of precision, accuracy, and sample efficiency. Developments of new instruments based on time-of-flight mass spectrometers could open up the ultimate levels of sensitivity per sample atom.

Theoretical and experimental study of the non-stoichiometric LinI (n = 3 and 5) clusters

The neutrals of the LinI (n=2–6) clusters were detected using Knudsen-cell which was placed into ionization chamber of the magnetic sector mass spectrometer. The first theoretical and experimental data on the Li3I and Li5I clusters were presented in this Letter. The ionization energies of the neutral of Li3I and Li5I clusters, obtained by the electron impact ionization mass spectrometry, were (5.14±0.25) and (4.62±0.25)eV, respectively. We report the geometry, ionization energies and thermodynamical stability of these clusters, calculated at the restricted coupled cluster RHF-RCCSD/cc-pVTZ(Li), cc-pVTZ-PP(I) level of theory.

A theoretical study of SnF2+, SnCl2+, and SnO2+ and their experimental search

We present a detailed theoretical study of the stability of the gas-phase diatomic dications SnF(2+), SnCl(2+), and SnO(2+) using ab initio computer calculations. The ground states of SnF(2+), SnCl(2+), and SnO(2+) are thermodynamically stable, respectively, with dissociation energies of 0.45, 0.30, and 0.42 eV. Whereas SnF(2+) dissociates into Sn(2+) + F, the long range behaviour of the potential energy curves of SnCl(2+) and SnO(2+) is repulsive and wide barrier heights due to avoided crossing act as a kind of effective dissociation energy. Their equilibrium internuclear distances are 4.855, 5.201, and 4.852 a(0), respectively. The double ionisation energies (T(e)) to form SnF(2+), SnCl(2+), and SnO(2+) from their respective neutral parents are 25.87, 23.71, and 25.97 eV. We combine our theoretical work with the experimental results of a search for these doubly positively charged diatomic molecules in the gas phase. SnO(2+) and SnF(2+) have been observed for prolonged oxygen ((16)O(-)) ion beam sputtering of a tin metal foil and of tin (II) fluoride (SnF(2)) powder, respectively, for ion flight times of about 10(-5) s through a magnetic-sector mass spectrometer. In addition, SnCl(2+) has been detected for (16)O(-) ion surface bombardment of stannous (tin (II)) chloride (SnCl(2)) powder. To our knowledge, SnF(2+) is a novel gas-phase molecule, whereas SnCl(2+) had been detected previously by electron-impact ionization mass spectrometry, and SnO(2+) had been observed before by spark source mass spectrometry as well as by atom probe mass spectrometry. We are not aware of any previous theoretical studies of these molecular systems.

Production and ionization energies of KnF (n = 2–6) clusters by thermal ionization mass spectrometry

The very small clusters of the type K(n)F are of particular importance since their first ionization energies (IEs) are lower than those of the alkali metal atoms. Theoretical calculation has demonstrated that this kind of cluster represents a potential 'building block' for cluster-assembly materials with unique structural, electronic, optical, magnetic, and thermodynamic properties. To date, however, there have been no experimental results on the IEs of K(n)F (n >2) clusters. K(n)F (n = 2-6) clusters were produced by the evaporation of a solid potassium fluoride salt using a modified thermal ionization source of modified design, and mass selected by a magnetic sector mass spectrometer where their IEs were determined. Clusters K(n)F (n = 3-6) were detected for the first time. The order of the ion intensities was K(2)F(+)> > K(4)F(+)> > K(3)F(+)K(6)F(+)> K(5)F(+). The determined IEs were 3.99 ± 0.20 eV for K(2)F, 4.16 ± 0.20 eV for K(3)F, 4.27 ± 0.20 eV for K(4)F, 4.22 ± 0.20 eV for K(5)F, and 4.31 ± 0.20 eV for K(6)F. The IEs of K(n)F increase slightly with the increase in potassium atom number from 2 to 6. We also observed that the presence of a fluorine atom leads to increasing ionization energy of bare metal potassium clusters. The modified thermal ionization source provides an efficient way of obtaining the fluorine-doped potassium clusters. These results also present experimental proof that K(n)F (n = 2-6) clusters belong to the group of 'superalkali' species.

Characterization of LED materials using dynamic SIMS

Improving the manufacturing yield in light emitting diode highly competitive market requires process control strategy similar to what has been applied to integrated circuit (IC) manufacturing for years. Dynamic secondary ion mass spectrometry (SIMS) is a key analytical technique, as it provides depth profiles with excellent detection sensitivity for dopants and impurities, while keeping high analysis throughput. Dynamic SIMS data obtained using the CAMECA IMS 7f will be presented. Based on a double focusing magnetic sector mass spectrometer, this instrument achieves benchmark performance in terms of sensitivity, depth resolution and mass resolution. Depth profiling and detection limits for dopants as well as for light elements will be shown. A method for evaluating the light elements content on high purity samples will also be detailed. Copyright © 2012 John Wiley & Sons, Ltd.

Formation of positive cluster ions LinBr (n = 2–7) and ionization energies studied by thermal ionization mass spectrometry

Clusters of the type Li(n)X (X = halides) can be considered as potential building blocks of cluster-assembly materials. In this work, Li(n)Br (n = 2-7) clusters were obtained by a thermal ionization source of modified design and selected by a magnetic sector mass spectrometer. Positive ions of the Li(n)Br (n = 4-7) cluster were detected for the first time. The order of ion intensities was Li(2)Br(+) > Li(4)Br(+) > Li(5)Br(+) > Li(6)Br(+) > Li(3)Br(+). The ionization energies (IEs) were measured and found to be 3.95 ± 0.20 eV for Li(2)Br, 3.92 ± 0.20 eV for Li(3)Br, 3.93 ± 0.20 eV for Li(4)Br, 4.08 ± 0.20 eV for Li(5)Br, 4.14 ± 0.20 eV for Li(6)Br and 4.19 ± 0.20 eV for Li(7)Br. All of these clusters have a much lower ionization potential than that of the lithium atom, so they belong to the superalkali class. The IEs of Li(n)Br (n = 2-4) are slightly lower than those in the corresponding small Li(n) or Li(n)H clusters, whereas the IEs of Li(n)Br are very similar to those of Li(n) or Li(n)H for n = 5 and 6. The thermal ionization source of modified design is an important means for simultaneously obtaining and measuring the IEs of Li(n)Br (n = 2-7) clusters (because their ions are hermodynamically stable with respect to the loss of lithium atoms in the gas phase) and increasingly contributes toward the development of clusters for practical applications.