Development of a dedicated isotope mass spectrometer for the noninvasive diagnostics of humans infected with Helicobacter Pylori

A dedicated isotope mass spectrometer for the noninvasive diagnostics of humans infected with Helicobacter Pylori using the isotope respiratory test is developed. A low-aberration mass analyzer is calculated, an input system that makes it possible to eliminate the memory effects is developed, and a small-size ion detector is constructed. The mass spectrometer is created, and the tests are performed. The measurement accuracy of the ¹³C/¹²C and ¹⁶O/¹⁸O isotope ratios are 1.7 and 2.2‰, respectively. Preliminary medical tests show that the spectrometer can be employed for the desired diagnostics.     

Dissociative ionization of triethylamine molecules on a tungsten surface in an electric field

The surface ionization of triethylamine molecules (M) in accelerating fields of strength F from 2·10⁴ to 4·10⁶ V/cm has been studied under stationary conditions with the aid of mass spectrometry. The predominant formation of (M-H)⁺ fragment ions has been discovered. The logarithm of the relative intensity of the ion currents at T = const varies linearly with the value of F. The temperature dependence of the ion currents I(T) at F = const, which are in good agreement with the experimental dependences and make it possible to determine the kinetic parameters of the reaction, have been obtained with the aid of the theory of monomolecular dissociation of molecules in the gaseous phase and the theory of surface ionization.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 62–67, January–February, 1988.We thank N. D. Potekhina and é. Ya. Zandberg for some useful discussions.     

Isotopic ratio of evaporated ions,critical ionization distances,and ionization regions in the process of the field evaporation of molybdenum at high temperatures

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.     

Optical radiation and ionization of hydrogen atoms in heterogeneous exothermal reactions proceeding in an electric field

Optical radiation related to the Balmer series (H_α, H_β, H_γ) of hydrogen atoms is discovered when studying the isothermal reaction of trimeric acetone peroxide decomposition on the surface of oxidized tungsten in a static electric field with a strength of up to 4 × 10⁶ V/cm at T = 300 K. The distance from the surface over which desorbing excited hydrogen atoms radiate is determined from the Stark splitting of the lines. Electronically excited atoms remaining on the surface ionize according to the surface ionization mechanism.     

Composition of the ion current during field evaporation of some binary and ternary compounds at different temperatures

Experiments on the field evaporation of emitters made of Mo-Re, Ir-Ce, and W-Re binary alloys and Hf-Mo-Re ternary compound are described. It is shown that, depending on emitter preprocessing conditions (high-temperature heating in a high electric field), either atomic ions of almost all components of the alloy with different charge types are emitted simultaneously or ions of only one component of the compound are obtained. Field emitters made of alloys or multicomponent compounds may form a basis for sources of ions differing in mass and composition with the emitter composition remaining the same. Moreover, alloys and multicomponent compounds are promising for sources of ions of such materials of which field emitters are difficult, if at all possible, to prepare.     

Field surface ionization of nanosized molecular complexes

The changes in the parameters of the temperature dependences of field surface ionization ion currents upon an increase in the electric field strength at the emitter surface is estimated for systems in which the ions under investigation are the end product of dissociation of multimolecular complexes with a large number of degrees of freedom. Expressions for the maxima on the temperature dependence of ion currents of field surface ionization are derived. The sizes of molecular nanocomplexes formed on the emitter surface are estimated and their thermodynamic stability is analyzed.     

Singly charged tungsten and tantalum ions observed during high-temperature field evaporation

High-temperature field evaporation of tungsten and tantalum emitters in the temperature range from room temperature to 2500 K is studied using a static magnetic mass spectrometer equipped with a field source of ions. At room temperature, triply charged W³⁺ and Ta³⁺ ions alone are observed in the mass spectra. However, as the emitter temperature grows, the charge of the ions decreases. At T ≈ 1000 K, doubly charged W²⁺ and Ta²⁺ ions dominate in the spectra, and singly charged W⁺ and Ta⁺ ions appear in the temperature range 1900 < T < 2500 K. The evaporation rate of the singly charged ions is one to two orders of magnitude lower than the evaporation rate of the doubly charged particles. The energy parameters of field evaporation for differently charged tungsten ions are found.     

Relaxation Processes in Polymer Surface Layers

A recently built and patented device Nanoluminograph is used for the investigation of the relaxation processes in the surface layers of HDPE films, produced at various conditions. The work of the device is based on the phenomenon of radiothermoluminescence. The use of high-frequency low-power, low-temperature plasma as an ionizing source, and a reduction of the consumed energy down to several orders of magnitude (as compared to that used in similar devices) provides excitation of a surface layer as thin as 100–200 nm. The high sensitivity of the device enables one to reduce the excitation time to 1–2 seconds for obtaining a sufficient intensity of glow curves even from ultrathin layers 20–30 nm thick. All of that minimizes the modifying plasma action on the samples under investigation and provides well reproducible and reliable data. It is found that the intensity, number and positions of peaks on the glow curves are strongly influenced by the preparation conditions of polymer films. The complicated profile of glow curve peaks allows one to assume the overlapping of multiple relaxation processes. Decomposing and fitting peak profiles with the help of a PEAKFIT computer program result in revealing at least 4 relaxation transitions in the temperature region from 109 to 213 K. The temperatures and activation energies of relaxation transitions in surface layers appeared to be lower than those inferred from the DSC data for the bulk polymer. The activation energies of trap depletion upon heating are calculated. The nature of traps is discussed in terms of molecular conformations, morphology and structural defects, as well as the attribution of the observed relaxation transitions to defreezing mobility of different kinetic units.     

Changes in Ion-Current Composition in the Process of Field Evaporation of Tungsten at High Temperatures

Technical Physics - 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...     

Transfilm passivation of a silicon–ytterbium nanofilms interface with chemisorbed CO and O2 molecules

Physics of the Solid State - Passivation of a silicon–ytterbium nanofilm interface with СО and О2 molecules chemisorbed on the opposite side of films is studied. The...