B. A. Mamyrin

Mass spectrometric analysis of clusters formed in laser ablation of a sample

Experimental data are used as a basis for discussion of the principal methods of cluster formation in the laser ablation of targets: condensation during expansion of the cloud of evaporated material, clustering at the surface accompanying redeposition of material back on the target, and emission of entire nanoblocks from the target. Methods of distinguishing between these processes are discussed.

Experimental determination of the difference of the beta-decay constants for atomic and molecular tritium

The results of an experiment measuring the difference Δλ=λa−λ m of the beta-decay constants of atomic and molecular tritium are reported. The difference Δλ is determined by comparing the rates of growth of the relative content of radiogenic helium-3 in samples containing atomic and molecular tritium. The result Δλ=(4.6±0.8)×10−12s−1 corresponds to a relative change of the decay constant by ∼0.26%.

Determination of the ratio of the axial-vector to the vector coupling constant for weak interaction in triton beta decay

Data on the chemical shifts of the half-lives of atomic and molecular tritium are used to determine the ratio of the axial-vector to the vector coupling constant for weak interaction in triton beta decay. The result is (GA/GV)t=−1.2646±0.0035.

Production of atomic hydrogen in an rf gas discharge and mass spectrometer diagnostics of the process

84 investigated in the present study as part of the preparation for a series of experiments on the influence of variations in the electron environment on the lifetime of the b-active tritium nucleus. In the first experiment of the series it is proposed to investigate the chemical shift of the half-life for an atomicmolecular tritium pair. Since the energy of dissociation of molecular tritium is close to that of molecular protium, and since atomic tritium, because of its higher mass and lower mobility, recombines more slowly than atomic protium, the procedure used to obtain atomic tritium can be worked out in experiments with protium ~called hydrogen from now on!. Atomic hydrogen is produced by thermal dissociation in a tungsten furnace, by low-frequency and radio-frequency gas discharges, or by means of a plasma arc. In the present study we have used the rf gas discharge method to obtain atomic hydrogen. The high efficiency of this method helps to minimize the heating of the discharge cell and can be implemented without the intrusion of electrodes in the discharge volume, thereby ensuring high purity of the atomic hydrogen product. The problems associated with the stabilization and detection of atomic hydrogen stem from its high chemical activity, by virtue of which atoms rapidly recombine at the walls of the discharge volume and in mutual collisions. For this reason, most diagnostic techniques applied to atomic hydrogen are based on measurements of secondary effects attributable to the presence of atomic hydrogen. For example, a chemical target of molybdenum oxide has been used as the atomic hydrogen detector in some studies. When hydrogen atoms are incident on such a target, the oxide undergoes reduction, and the target changes color. However, the small range of measurement of the flux density (10–10 atoms/s •cm) and low accuracy (630% error! limit the possibilities of this method. Bass and Broida have measured the optical spectra of hydrogen atoms in the condensed and gaseous phases, but did not establish any relationship between the concentration of hydrogen atoms and the line intensities of the optical spectra. One approach that looks promising is the determination of hydrogen atoms by electron spin resonance ~ESR!. This method utilizes the presence of an unpaired electron due to the paramagnetism of the hydrogen atom, a property that can be exploited for detection by ESR. Only papers in which ESR has been used to measure atomic hydrogen in the condensed phase are known in the literature. Here we report mass spectrometer measurements of atomic hydrogen produced in an rf gas discharge. The experimental apparatus ~Fig. 1! consists of an rf oscillator 1 ~1 MHz, 300 W!, a discharge tube 2, an MI 1201 mass spec-

Precision electromagnet for a mass spectrometer

A precision electromagnet generating a magnetic field with an induction ranging from 0.05 to 0.50 T is designed, manufactured, and studied. It is intended for a magnetic resonance mass spectrometer with a rated resolution of about 106. The magnetic field inhomogeneity on a circular orbit with a diameter of 400 mm along which the ion beam moves is no more than ±1 × 10−5 of induction B0 at the center of the magnetic gap. At any point of the orbit, the magnetic field is kept constant with an accuracy of higher than 10−6 for several minutes, which is sufficient to record mass spectra.

Atomic effects in tritium beta decay and their role in determining the ratio G A /G V and the lifetime of the free neutron

The helium-isotope mass-spectroscopy method for measuring the triton decay constant for various cases of the electron environment was used to determine the tritium half-life without allowance for decay to beta-electron bound states and to calculate the respective reduced half-life, which proved to be (fT1/2)t = 1129.6 ± 30.0 s. The equations relating fT1/2 to GA/GV made it possible to obtain the value of (GA/GV)t = −1.2646 ± 0.0035 and to estimate the neutron lifetime at τn = 890.3 ± 3.9(stat.) ± 1.4(syst.) s.

Mass spectrometer for measuring the mass distributions of cluster ions in the range 105–107 amu

The mass analysis of heavy cluster ions in the range m/q=105–107 amu is investigated. A dynamic mass spectrometer is described for measurements of the mass distributions of charged particles generated in pulsed sources of polyatomic clusters in the given range. The main parameters and characteristics of the instrument are given. The distribution of cluster ions with respect to the ratio m/q is determined for a specific source of gold cluster ions formed in the inelastic sputtering of gold island films with fission fragments of 252Cf nuclei.

Half-lives of atomic tritium and free triton determined from the chemical shift of the beta decay time constant

Data on the chemical shift of the beta decay time constant were used to determine the experimentally justified half-lives of atomic tritium (t1/2)a=12.264±0.018 year and free triton (t1/2)t=12.238±0.020 year.

Constraints on the Decay Period of a Free Neutron from the Characteristics of Tritium Beta Decay

The reduced decay period of the triton, (ft1/2)T=(1129.6±3)s, and the free-neutron decay period, (t1/2)n=(616.7±;2.7±1.3) s, are determined from the experimental and theoretical values of the chemical shifts of atomic and molecular tritium.