Atomic-beam Method Research Articles

NMR-ON study of 197PtNi

Nuclear magnetic resonance measurement has been performed for 197Pt oriented at 7 mK in a Ni host. The magnetic hyperfine splitting frequency at external magnetic fields of 0.2, 0.4 and 0.6 T were determined to be 229.4(1), 228.2(2) and 226.9(3) MHz, respectively. By using published values of the magnetic resonance frequency of 197PtNi and magnetic moments determined by atomic beam methods, the hyperfine anomaly between the two isotopes is deduced to be 191Δ197 = +13(5)%. Which is extremely large compared to the theoretical value of +0.2%. Based on the same reasoning, the hyperfine anomaly with 195Pt, an isotope with the same spin and parity, is found to be 195Δ197 = +15(5)%. We conclude therefore that the published magnetic moment of 197Pt is more likely in error. If we assume the hyperfine anomaly195Δ197 = 0, a magnetic moment μ (191Pt) = 0.45(1) μN is obtained.

Radiative lifetime measurements of odd-parity highly-excited levels of Sn I by time-resolved laser spectroscopy

Natural radiative lifetimes of five higher-lying odd-parity levels 5p7s 3Po1, 5p5d 3Po1, 5p6d 3Fo1, 3Do1 and 3Fo3 in neutral tin are measured by the time-resolved laser-induced fluorescence (TR-LIF) technique and the atomic beam method. All these lifetimes are not longer than 100 ns and they are found to be shorter than the lifetimes of even-parity levels in the same energy region. The results reported in this paper provide important transition parameters for highly-excited atomic Sn, which may be useful for theoretically calculating excited heavy atoms.

Isotope Effects on H and D Coadsorptions on Si Surfaces

We studied isotope effects on D and H coadsorptions on the Si(100) and Si(111) surfaces, employing an atomic beam method combined with a desorption measurement technique. We evaluated D:H ratios to be approximately 6:4 for both the Si(100) and Si(111) surfaces exposed to the atomic H/D beam mixed with equal amounts of H and D atoms. This observed isotope effect was interpreted in terms of mass-dependent abstraction of surface adatoms by incident atoms. The observed D:H ratios could be well reproduced by the simulation based on the previously reported isotope effect on D(H) abstraction by H atoms.

Direct measurement of the fine-structure interval of27Alin its ground2Pstate

The $J=\frac{3}{2}\ensuremath{\leftarrow}\frac{1}{2}$ fine-structure transition in atomic ${}^{27}\mathrm{Al}$ in its ground ${}^{2}P$ state has been detected in the laboratory by far-infrared laser magnetic resonance. The fine-structure interval has been measured accurately as 3359.6228(17) GHz or 112.064 95(6) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. The spectra show the hyperfine structure associated with a nuclear spin of $\frac{5}{2}$ for ${}^{27}\mathrm{Al}.$ The splittings are well reproduced by the hyperfine parameters determined earlier by atomic beam methods. The analysis of the laser magnetic-resonance spectra casts doubt on the published value for the Zeeman parameter ${g}_{3/2}$ also from the atomic beam measurements. Although the value determined in this paper is intrinsically much less accurate, it is in better agreement with the value obtained by a completely independent theoretical calculation.

Photochemically induced oxidation and silver deposition on amorphous germanium sulfide films studied using atomic force microscopy and ion beam methods

Amorphous thin films of composition GeS 1.7 deposited using a thermal evaporation technique were studied using a combination of atomic force microscopy (AFM), Rutherford backscattering (RBS) and nuclear reaction analysis (NRA). The effects of photo-induced oxidation and metal deposition on these films were also studied by these techniques. This combination of experimental methods allows us to identify the chemical nature of surface structures, and correlate changes in morphology to those of sample stoichiometry for various chemical and photochemical reactions. We find that the GeS 1.7 films grow in a layer-like structure when deposited at rates of less than 0.02 nm/s on a Si(111) substrate held at 298 K. The films are quite inert to further reaction in the dark, however exposure to oxygen in the presence of ultraviolet radiation results in formation of an oxide which begins to nucleate at defect sites and then grows in a fractal pattern across the surface. Correlation of surface coverage from the AFM images and absolute oxygen density from NRA demonstrates that the reacted overlayer formed is an oxide consisting of approximately 20 at.% of oxygen. Deposition of Ag on these films results in formation of a reacted overlayer, as determined by AFM and RBS, followed by growth of Ag islands.

A novel technique for the polarized atomic-beam targets production

A novel technique for the polarized atomic-beam target production is suggested. Using this technique shows promise of obtaining the polarized internal beam targets from a wide region of elements with densities of 10 11 – 10 12 atoms/cm 3. It combines the developed new approach to the supersonic internal gas-jet target design with a classical atomic beam method of hyperfine state selection in inhomogeneous magnetic fields. The main operation principles and advantages of the suggested technique are described. The importance of the experimental study at storage rings of spin-dependent scattering of polarized electrons and protons on polarized nuclei is noticed.

Beta asymmetry of the first forbidden 1/2+→1/2−transition inNe19and its relationship to the parity nonconserving nucleon-nucleon interaction

We report a measurement of the \ensuremath{\beta} asymmetry of the first-forbidden transition from the 1/${2}^{+}$ ground state of $^{19}\mathrm{Ne}$ to the 1/${2}^{\mathrm{\ensuremath{-}}}$ level at 110 keV in $^{19}\mathrm{F}$. Using atomic beam methods to prepare a 100% polarized source of $^{19}\mathrm{Ne}$, we identify the 1/${2}^{+}$\ensuremath{\rightarrow}1/${2}^{\mathrm{\ensuremath{-}}}$ decays by the detection of the subsequent 110 keV gamma emitted in coincidence with a beta. The average \ensuremath{\beta} asymmetry of the first-forbidden transition is measured to be 〈A〉=17\ifmmode\pm\else\textpm\fi{}12 %. We simultaneously make an improved measurement of the branching ratio of the same transition and find \ensuremath{\Gamma}=(1.13\ifmmode\pm\else\textpm\fi{}0.09)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ in good agreement with previous results. Our measurement is used to obtain an improved calibration of the isovector parity-mixing matrix element between the 1/${2}^{+}$ ground state of $^{19}\mathrm{F}$ and the 1/${2}^{\mathrm{\ensuremath{-}}}$ level at 110 keV.

Optical Methods for Plasma Edge Diagnostics in Magnetic Confinement Experiments

AbstractThe radial extension of the plasma edge being determined by the ionisation length of the atomic hydrogen, the rtanges of the main plasma parameters to be covered are: 1010 cm-3 < ne <. 1013cm-3 5 eV < Te- < 100 eV, density of neutral particles below 1010 cm-3. Physical quantities to be measured are the electron density ne and temperature Te, the density and temperature (velocity distribution) of hydrogen and of the main impurities (oxygen, carbon, metals). Relying mainly on emission spectroscopy, laser induced fluorescence and atomic beam methods, most of these quantities can be determined with the desired space and time resolution. Experimental arrangements will be described and typical results will be presented.

Atomic beam, optogalvanic and stored ion spectroscopy for radioactive isotopes

Systematic studies of the optical isotope shift and the hyperfine splitting of long chains of stable and radioactive isotopes were performed. The method applied was laser induced resonance absorption; the experimental techniques were the atomic beam method with fluorescence detection and the optogalvanic method. The theory of hyperfine splitting and isotope shift of atoms is reviewed in short with emphasis on the aspects interesting for nuclear physics and on the evaluation problem. The experimental methods are described and their key parameters sensitivity and resolution are discussed. Preliminary results on stored thorium ions are given. Sample results for the nuclear quantity δ derived from atomic beam experiments with tin and strontium are presented.

ChemInform Abstract: GAS‐SURFACE INTERACTIONS AND DYNAMICS; THERMAL ENERGY ATOMIC AND MOLECULAR BEAM STUDIES

Abstract Recent advances in the use of thermal energy atomic and molecular beam methods to explore the dynamics of physical and chemical processes occuring at surfaces are reviewed. Both experimental and theoretical aspects are surveyed. Topics include diffraction of light atoms and molecules, inelastic scattering and phonon processes, rotational and vibrational energy exchage, trapping, sticking and desorption, and chemical reactions. The aim is to show how recent experiments and theoretical studies have contributed to the understanding of surface structures, kinetics and dynamics.

The use of atomic beam and optical methods in the study of fundamental symmetries

We review the status of experimental tests of time reversal invariance in nuclear beta decay and discuss narrow resonance NMR techniques which are suitable for precise measurements of nuclear magnetic moments and searches for nuclear electric dipole moments.

Gas—surface interactions and dynamics; Thermal energy atomic and molecular beam studies

Recent advances in the use of thermal energy atomic and molecular beam methods to explore the dynamics of physical and chemical processes occuring at surfaces are reviewed. Both experimental and theoretical aspects are surveyed. Topics include diffraction of light atoms and molecules, inelastic scattering and phonon processes, rotational and vibrational energy exchage, trapping, sticking and desorption, and chemical reactions. The aim is to show how recent experiments and theoretical studies have contributed to the understanding of surface structures, kinetics and dynamics.

Limit onIm(CSCA*)from a Test ofTInvariance inNe19Beta Decay

An investigation of the time-reversal-odd angular correlation $\stackrel{^}{\ensuremath{\sigma}}\ifmmode\cdot\else\textperiodcentered\fi{}(\stackrel{^}{J}\ifmmode\times\else\texttimes\fi{}\frac{\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}}{E})$ in $^{19}\mathrm{Ne}$ $\ensuremath{\beta}$ decay is reported. In this correlation, $\stackrel{^}{\ensuremath{\sigma}}$, $\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}$, and $E$ are the $\ensuremath{\beta}$ spin, momentum, and energy, respectively, and $\stackrel{^}{J}$ is the initial $^{19}\mathrm{Ne}$ spin. The sample was polarized by an atomic beam method and the $\ensuremath{\beta}$ polarization was measured with four Mott-scattering polarimeters. The magnitude $R$ of the angular correlation is found to be -0.079 \ifmmode\pm\else\textpm\fi{} 0.053, consistent with timereversal invariance. This result also implies $\mathrm{Im}({C}_{S}{{C}_{A}}^{*})=0.19\ifmmode\pm\else\textpm\fi{}0.13$.

Non-optical observation of laser-induced zero-field level-crossing effects in an atomic beam

Level-crossing effects have been detected non-optically with the use of a Rabi-type atomic-beam method. The sodium beam was excited by intense linearly polarised radiation from a CW narrow-band dye laser. Several superimposed resonances were observed in the atomic-beam signal when scanning the magnetic field around zero. The two narrower resonances are interpreted as high-order non-linear effects. They arise from the coupling of laser-induced Zeeman coherences in the ground state (including a hexa-decapole moment) with the populations of the Zeeman sublevels.

The source for a vector polarized lithium-6 beam at the Heidelberg en-tandem

The source for negative polarized lithium ions at the Heidelberg EN-tandem is described. The polarized beam is produced following the atomic beam method. A nearly 100% efficient surface ionizer is used. Accelerated beams of 6Li 3+-ions are up to 150 nA on the target. The vector polarization can be estimated to be 0.57≤| P|≤0.65. The production and acceleration of vector and tensor polarized beams of 6Li, 7Li and 23Na are discussed.

Absolutegf-values for nine resonance lines of neutral scandium

Absolutegf-values for nine resonance lines of Sc I have been experimen­tally measured by the atomic-beam method. Difficulties in evaporation of scandium were overcome by using a tantalum boat. Thesegf-values can be used to put more extensive measurements of relativegf-values on an absolute scale. Comparisons are made with other determinations of absolutegf-values for Sc I.

Absolute f-values for resonance lines of neutral titanium

view Abstract Citations (20) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Absolute f-values for resonance lines of neutral titanium. Bell, G. D. ; Kalman, L. B. ; Tubbs, E. F. Abstract Absolute f-values for 13 resonance lines of neutral titanium are reported which were measured experimentally by the atomic-beam method. The atomic beam was produced entirely by effusion from within a TiC boat in order to overcome the difficulties in evaporating titanium, and microbalance weighings of instantaneous titanium-deposit rates were compared with quantitative chemical analyses of total deposits to determine gettering effects. Boltzmann factors were applied to the beam-concentration measurements to calculate the f-values. The present results are compared with previous experimental results, and conversion factors are supplied for placing previously obtained relative f-values on an absolute scale. The effect of an improved absolute scale for neutral-titanium gf-values on the solar photospheric titanium abundance is considered. Publication: The Astrophysical Journal Pub Date: September 1975 DOI: 10.1086/153818 Bibcode: 1975ApJ...200..520B Keywords: Abundance; Line Spectra; Optical Resonance; Solar Spectra; Titanium; Absorption Spectra; Atomic Beams; Neutral Particles; Photosphere; Solar Atmosphere; Titanium Carbides; Transition Probabilities; Atomic and Molecular Physics full text sources ADS |

The hyperfine structure Stark effect - III. The 2 P ½ level of aluminium

The quadratic Stark effect in the hyperfine structure of the 2 P ½ ground level of aluminium has been investigated by the method of atomic beams. A frequency shift caused by the application of an electric field has been interpreted in terms of an effective Stark operator, and the associated tensor polarizability α ten ( J = ½, F = 3) has a measured value of (8.13±0.72) × 10 –4 a 3 0 . The case of J = ½ is a special one in that the theoretical value of α ten ( J = ½, F = 3) vanishes in the absence of hyperfine structure effects. The inclusion of the hyperfine structure operator in a calculation of the tensor polarizability has led to a small theoretical value in agreement with experiment.

Diagonal and Off-Diagonal Hyperfine Structure in the Ground Multiplets of Boron and Aluminum by the Atomic Beam Method; Magnetic Dipole Radial Parameters

The magnetic resonance spectra of the ground 2P multiplets of 11B and 27Al have been remeasured by the method of atomic beams and the coupling constants A3/2, B3/2, and gJ(2P3/2) and gJ(2P1/2) for 11B, and A1/2 for 27Al, have been redetermined to higher precision. Measurements have also been made, by the triple resonance method, of two ΔMJ = 0, ΔMI = ± 1 transitions in both 11B and27 Al and from these the off-diagonal magnetic dipole coupling constants A3/2,1/2 have been determined.These measurements have enabled us to evaluate the magnetic dipole radial parameters [Formula: see text], [Formula: see text], and [Formula: see text] for both boron and aluminum. The departures of [Formula: see text] and the ratio [Formula: see text] from their restricted Hartree–Fock values are plotted as functions of the occupation number N for all elements with (2p)N and (3p)N ground configuration for which data are available. The trends are briefly discussed.

Nuclear excitation in muonic 209Bi

The hyperfine spectra of muonic L and K X-rays of 209Bi have been reanalyzed by taking into account the resonance processes and the observed isomer shifts in addition to the M1 and the E2 interaction. The M1 and E2 hyperfine structure constants of the 1s, 2p and 3d muonic states and the nuclear static moments of the excited states 15 2 + and 9 2 + are determined from the best fits to the experimental spectra. The hfs constants and the M1 moments are in good agreement with theoretical predictions from the core excitation model. The quadrupole moment of the ground state remains to be 20% higher than that determined by the atomic beam method. A plausible interpretation is that this discrepancy might be due to the deformation of the lead core.