A specialized isotope mass spectrometer for determining the isotopic ratio of lithium by ERIAD (electrospray with atomization in an ion source) is described. The device uses a Mattuha-Herzog-type mass analyzer with double focusing to use ion beams with a large spread in energy and simultaneous registration of signals of both lithium isotopes (6Li and 7Li), and a two-channel receiver based on a doublet of microchannel plates. The gas-dynamic interface is built according to the Kontorowitz-Gray scheme; from the gas-dynamic point of view, it is "long", that is, the distance between the nozzle and the skimmer is 4 times the size of the "Mach barrel" at the operating pressure (200 Pa). The device is desktop, its weight does not exceed 20 kg. The measurement time is 1000 s, sample replacement time is 100 s, measurement accuracy is ~ 0.1%. Keywords: mass spectrometry, electrospray, ion source, isotopes of lithium.

We developed a specialized mass-spectrometer for measuring the lithium isotopic ratio using electrospray ionization with controlled in-source fragmentation and atomization (in-source atomization, ERIAD). We used a Mattauch–Herzog double-focusing mass analyzer suspended under accelerating voltage; this makes its coupling with the gas-dynamic interface much easier. The mass analyzer is optimized up to the second degree; it can operate with ion beams with a broad energy spread, typical for ERIAD. Both isotopes, 6 Li and 7 Li, are detected simultaneously by a two-channel microchannel plate detector. The gas-dynamic interface is of the Kontorovitz–Gray type; it is gas-dynamically “long”: the nozzle-skimmer distance is four times longer than the Mach barrel at the operation pressure (200 Pa). The instrument is a desktop; it weighs approximately 20 kg. It is suitable for rapid analysis: one run takes 1000 s, and sample replacement takes only 100 s. The measurement precision in a series of 11 LiCl conventional measurements was 0.3%.

Описан специализированный изотопный масс-спектрометр для определения изотопного отношения лития методом ЭРИАД (электрораспыление с атомизацией в источнике ионов). В приборе используются масс-анализатор типа Маттауха-Герцога с двойной фокусировкой для использования пучков ионов с большим разбросом по энергии и одновременной регистрации сигналов обоих изотопов лития (6Li и 7Li) и двухканальный приемник на основе дублета микроканальных пластин. Газодинамический интерфейс построен по схеме Конторовица-Грея (с газодинамической точки зрения он "длинный", т. е. расстояние между соплом и скиммером в 4 раза превышает размер "бочки Маха" при рабочем давлении 200 Pa). Прибор настольный, его вес не превышает 20 kg. Время измерения 1000 s, время замены пробы 100 s, точность измерения содержания изотопа 7Li~ 0.1%. Ключевые слова: масс-спектрометрия, электрораспыление, источник ионов, изотопы лития.

The significance of the problem of determining the concentration of beryllium in solutions is substantiated. A method of ERIAD mass-spectrometry (atmospheric pressure electrospray with in-source atomization) is compared with a number of other common procedures used for solving the aforementioned problem and a number of advantages of ERIAD mass-spectrometry are highlighted. The possibility of measuring the beryllium concentration in various chemical forms (sulfate, nitric acid and chloride salts) using ERIAD mass-spectrometry is studied. The layout and the principle of operation of a small-size mass spectrometer MI-20 Low Mass (MS-Bio, Russia), which is intended for the determination of beryllium in solutions, are described. A method is proposed for the preparation of a beryllium salt solution using a lithium salt as an internal standard. The resolution of the instrument made it possible to separate lithium isotopes (6Li and 7Li). It is shown that beryllium can be detected from the salts of chloride and nitric acids with close relative sensitivity coefficients. The obtained detection limit for beryllium chloride in those measurements was ~1–2 × 10–8 M. At the same time, the analytical signal of beryllium cannot be detected during electrospray of the solution of beryllium sulfate under any experimental conditions. It has been suggested that this effect may be attributed to the features of dissolution of beryllium sulfate, in particular, to hydrolysis and formation of complex compounds with sulfate, including complex polymer and colloidal forms.

A specialized single channel inlet system has been developed for urea breath tests and scientific studies using Isotope Ratio Mass Spectrometer Helicomass. The system consists of sampling needle, manifold with its purification system, the possibility to introduce sample and standard, high vacuum Mamyrin leak valve to inlet the sample to electron ionization ion source, and the purification procedure including series of sequential pumpings out and blowdowns with compressed nitrogen. The system inlets sample up to 4•10–6 Torr in the mass-spectrometer analytical chamber. The measuring precision was 0.1% for 21 measurements, which meets the test requirements. The measuring time was 15 min per sample including the standard measurement, system purification, the sample measurement, and the second purification. The combination of system and Helicomass mass-spectrometer fits requirements for procedure used to identify infections by Helicobacter pylori.

The significance of the problem of determining the concentration of beryllium in solutions is substantiated. A method of APESI mass-spectrometry (atmospheric pressure electrospray ionization with in-source atomization) is compared with a number of other common procedures used for solving the aforementioned problem and a number of advantages of APESI mass spectrometry are highlighted. The possibility of measuring the beryllium concentration in various chemical forms using APESI mass-spectrometry is studied. We used sulfate, nitric acid and chloride salts of beryllium. The measurements were carried out on a specialized small-sized mass spectrometer MI-20 «LowMass» developed at MS-Bio Company, Russia. A schematic diagram of the device designed to determine the concentration of beryllium in solutions is presented and described. A technique of solution preparation and measurement procedure are proposed. Presented ass spectra obtained on the samples containing beryllium and lithium isotopes were used as an internal standard. It is shown that beryllium can be detected from the salts of chloride and nitric acids with close relative sensitivity coefficients. The obtained detection limit for beryllium chloride in those measurements was ~1 – 2 × 10–8 M. At the same time, the analytical signal of beryllium cannot be detected during electrospray of the solution of beryllium sulfate under any experimental conditions. It has been suggested that this effect may be attributed to the features of dissolution of beryllium sulfate, in particular, to hydrolysis and formation of complex compounds with sulfate, including complex polymer and colloidal forms.

Carbon C + ions formed in a mass-spectrometric electrospray source with controlled in-source fragmentation and atomization interface have been observed for the first time. The measurements were performed in a special MI-20 LowMass mass spectrometer (MS-Bio LLC) using aqueous methanol solutions of lithium and beryllium salts. The peak of C + ions was substantially broadened as compared to the peaks of metal ions. A model is proposed that explains the formation of C + ions due to charge exchange immediately at the high-vacuum boundary near the skimmer output.

Steady-state field evaporation of tungsten at high temperatures (T ~ 2000 K) has been studied using a magnetic mass spectrometer equipped with the field ion source. Only low-charged ions (W+2 and W+) have been observed in the course of evaporation. The distribution of the ion currents by tungsten isotopes correspondents to standart isotopic ratio for natural tungsten. Some deviations from standart isotopic ratio were observed owing to fluctuations and unstable nature of evaporation process. O.L. Golubev, N.M. Blashenkov

AbstractCarbon C^+ ions formed in a mass-spectrometric electrospray source with controlled in-source fragmentation and atomization interface have been observed for the first time. The measurements were performed in a special MI-20 LowMass mass spectrometer (MS-Bio LLC) using aqueous methanol solutions of lithium and beryllium salts. The peak of C^+ ions was substantially broadened as compared to the peaks of metal ions. A model is proposed that explains the formation of C^+ ions due to charge exchange immediately at the high-vacuum boundary near the skimmer output.

Field evaporation of tungsten at T ~ 2000 K was studied using a sector magnetic mass spectrometer with a field ion source and a field emission microscope. Only low-charge ions W +2 and W + of all W isotopes were observed in the process of evaporation. The mass distribution of ion currents of isotopes agreed roughly with the standard isotopic ratio for natural tungsten, although certain deviations from it, which were attributed to fluctuations and the erratic nature of evaporation process, were also detected.

A model of a gas-dynamic interface with a high-vacuum ion-pulling system has been developed. The main part of the ion source is the ERIAD electrospray with in-source atomization (ion extraction from solution elements at atmospheric pressure), owing to which it is possible to measure concentrations of elements that are capable of being cations in a solution. The interface is constructed according to the Kontrovitsa–Gray type with a slight misalignment of the inlet and outlet. From the gas-dynamic point of view, the interface is “long,” since its length is several times longer than the resulting “Mach barrel.” Tests have shown that the interface circuit allows application of a voltage as high as 800 V between the nozzle and the skimmer, thus providing atomization of elements of not only the first, but also the second group of elements of the periodic system. The developed interface model can be used as a prototype for upgrading dual-focusing mass spectrometers for future elemental measurements.

This article describes the development of the experimental setup for researching the plant leaves absorption spectrum and its biological testing. The spectrometric method based on measurement of tissue optical properties by means of double-integrating-sphere system. During the study of light absorption by lettuce leaf it was noted that the total absorption of living and freshly cut leaf is identical, but changes over time after the cut. The "absorption map" of the lettuce leaf surface was compiled.

Passivation of a silicon–ytterbium nanofilm interface with СО and О2 molecules chemisorbed on the opposite side of films is studied. The transfilm inhibition of silicides is found to be caused by the Coulomb interactions between the localized electrons forming the donor–acceptor bonding of molecules with films and the conductivity electrons of ytterbium (6s-band). This interaction increases the energy of the chemisorbed molecules–ytterbium films system. At a given amount of chemisorbed molecules this increase is higher for the thinner rather than thicker films. This correlation with the film thickness favors the lack of chemical interaction between silicon and ytterbium, when СО and О2 molecules are chemisorbed on the nanofilm surface.

Обнаружена и исследована пассивация границы раздела кремний-пленки иттербия нанометровой толщины молекулами СО и О2, хемосорбированными на противоположной стороне пленок. Установлен механизм транспленочного торможения силицидообразования. Он обусловлен кулоновским взаимодействием между локализованными электронами, формирующими донорно-акцепторную связь молекул с пленками, и электронами проводимости (6s-зона) иттербия. Это взаимодействие повышает энергию систем слой хемосорбированных молекул-пленки иттербия. При заданном количестве хемосорбированных молекул это повышение будет больше в случае более тонких пленок. Такая связь с толщиной пленок и обусловливает в конечном счете отсутствие химического взаимодействия между кремнием и иттербием в случае, когда на поверхности нанопленок последнего хемосорбированы молекулы СО и О2. Работа (за исключением части, посвященной работе выхода, рис. 5) выполнена при поддержке Программы фундаментальных исследований Президиума РАН N 1 "Наноструктуры: физика, химия, биология, основы технологий" (проект N 1.1.8.6). DOI: 10.21883/FTT.2017.08.44766.31

A magnetic mass spectrometer with a field ion source has been used to study the steady-state field evaporation of molybdenum at a temperature of 1000–2000 K. Ions of all seven molybdenum isotopes have been observed in the process of evaporation; only low-charge ions Mo+2 and Mo+ have been detected. The critical ionization distances and ionization regions for single- and double-charge Mo ions have been identified based on the measured ion energies and the experimentally determined intensity of the evaporation field. It has been demonstrated that ions are produced in the process of field evaporation of surface atoms at certain distances from the emitter surface in a very narrow spatial region.

Изотопное отношение испаряемых ионов, критические расстояния ионизации и зоны ионизации в

Steady-state field evaporation of molybdenum at high emitter temperatures (T ∼ 2000 K) has been studied using a magnetic mass spectrometer equipped with a field ion source. Only low-charge ions (Mo+2 and Mo+) have been observed in the course of evaporation. The measured ion energies and evaporating field strengths (F ev) were used to determine the critical ionization distances (x cr) and ionization zones (Δ) for singly and doubly charged ions. The obtained x cr and Δ values show that the formation of ions takes place at a certain distance from the emitter surface.