Search

We present an experimental demonstration of an ingenious technique to control the alignment of the atomic internal state in the x-ray region using a periodic crystal field. The alignment directions of ${\mathrm{Ar}}^{16+}$ and ${\mathrm{Fe}}^{24+}$ ions were readily controlled by selecting the array of atomic planes using three-dimensional resonant coherent excitation, and were probed via the anisotropy of the deexcitation x-ray emission. We applied this method to a double resonance experiment, and succeeded in controlling the population of the specific magnetic substate in a $\ensuremath{\Lambda}$-type three-level configuration.

We report the Autler-Townes doublet demonstrating a novel type of coherent interaction of atoms not with photons but with a periodic crystal field when the atom is in flight through a crystal at high velocity. It was observed by the nonoptical X-VUV (vacuum-ultraviolet) double resonance of three-dimensional resonant coherent excitation with good coherence. The states strongly coupled in the VUV region were probed by the excitation in the x-ray region. The characteristic spectra are well interpreted by an analogy of the dressed atom concept often adopted for the atom-photon interaction.

We have measured deexcitation x rays emitted from the resonant coherently excited 2{sup 1}P{sub 1} state of heliumlike Fe{sup 24+} ions of 423 MeV/amu, planar channeling through a Si crystal. Large anisotropy in the angular distribution of deexcitation x-ray emission is observed: the x-ray emission in the direction parallel to the channeling plane is favored by a factor of 2 compared to the perpendicular direction. This anisotropy originates from the direction of the periodic crystal field, which populates specific m states in resonant coherent excitation and aligns the excited states.

We have observed resonant coherent excitation (RCE) of H-like ${\mathrm{Ar}}^{17+}$ ions traveling through a $1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$-thick Si crystal at an energy of $391\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$ in the nonchanneling condition. A three-dimensional periodic array of atomic planes induces RCE of the nonchanneling ions. The high energy heavy ions together with the thin crystal allow us to observe this new RCE through the measurements of the charge-state distribution of the emerging ions. The observed resonances are much narrower than those of planar-channeling ions due to the absence of the large Stark shift caused by the planar potential.

We demonstrate that transitions between Zeeman-split sublevels of Rb atoms are resonantly induced by the motion of the atoms (velocity: about 100 m/s) in a periodic magnetostatic field (period: 1 mm) when the Zeeman splitting corresponds to the frequency of the magnetic field experienced by the moving atoms. A circularly polarized laser beam polarizes Rb atoms with a velocity selected using the Doppler effect and detects their magnetic resonance in a thin cell, to which the periodic field is applied with the arrays of parallel current-carrying wires., Comment: 4 pages, 4 figures; minor corrections, Ref. [9] removed, published in PRL

Spectra of Al K α X rays induced by H and He ion bombardments in the energy range of 0.2–0.4 MeV/amu have been measured with a Bragg spectrometer and Z 1 dependence of single K- plus multiple L-shell (KL l ) ionization has been investigated. The result shows that the L-shell ionization probability of Al by light ion bombardments follows the scaling law of direct Coulomb ionization considering the binding energy correction.

Cross sections for single and double K-shell ionization of Be were obtained from K α diagram and hypersatellite X-ray yields produced by C, N, O and Ne ion bombardments with the energies from 0.3 to 1.3 MeV. The data are compared with the theoretical predictions which consider 2pσ-2pπ MO coupling. The results show a good agreement except for the collision system of Ne+Be.

The interactions between a fast incident electron and a metallic spherical particle full of a free electron gas as the conduction electrons are studied using the hydrodynamic equations of Bloch. The obtained energy spectrum of a transmitted electron is composed of the well known peak due to the bulk plasma oscillations with small corrections and the peak due to the surface plasma oscillations which are given by sum of various modes of oscillations with different energies. The energy value of the surface oscillations at maximum intensity increases with increasing particle size and tends to that in the foil case. Numerical examples are given for aluminum particle coated with aluminum oxide and for colloidal alkali metal in alkali halide. The latter example is compared with experimental observations. The possibility of the plasma radiation is also discussed. The radiated photon energy is the same as that in the Mie scattering from small particle. Energy spectrum, angular distribution and photon yield are num...

An energy loss peak at 2 eV in the energy spectrum of electrons transmitted through thin copper films is observed and the variations of the energy value and of the intensity of the peak with film thickness are studied. The cross section for the surface plasmon excitation is calculated from optical data. The observed variations of the energy value and of the intensity of the peak show quantitative and qualitative agreements, respectively, with calculated values. It is concluded that the peak is mainly due to the surface plasmon which does not emit plasma radiation.

Al Kα X-ray spectra for equi-velocity H + and H + 2 ions of ≃ 0.9 MeV/amu incident on thin aluminum oxide films with thickness 100 and 300 A were observed. The intensity ratio of the KL 1 satellite line to the KL 0 main one for H + 2 incident on the films of thickness 100 and 300 A was about 10% and 4% larger than that for incident H + , respectively.

The energy spectrum of channeling radiation from 350 MeV electrons was measured in the case of the (110) plane of silicon crystal. The result shows good agreement with the spectrum calculated by quantum theory and corrected for detector efficiency.

Using the Rutherford backscattering method, the stopping cross-sections of amorphous silicon doped with rare gases to a concentration of a few percent were measured for helium ions. The effective stopping cross-sections of the rare gases were deduced by assuming Bragg's rule and by using Ziegler's cross-section values for silicon. The results were systematically about 30 percent lower than Ziegler's values for the gaseous state, in the energy range near 1 MeV. The incident energies were 1.0–2.6 MeV for samples containing 8% argon, and 1.0–1.6 MeV for those containing 7% krypton or 4% xenon.

Hydrogen coverage on W(001) was measured by using the resonant nuclear reaction 1H(15N, αγ)12C. The detection limit of the hydrogen coverage was 1/50 of the full monolayer, i.e. 4×1013 H atoms/cm2. The coverage dependence of the sticking probability of hydrogen was estimated by considering the ion-stimulated desorption of hydrogen. The zero-point energy of the vibration of adsorbed hydrogen atoms in the direction perpedicular to the surface was obtained by the Doppler broadening of the resonance width as 64±16 meV.

The shadow cone formed by the scattering of ions from an atom was calculated using Moliere potential. Calculated radii of the shadow cone by replacing the Thomas-Fermi radius, a TF with 0.85 a TF show a good agreement with an experiment for 1 keV helium ions on a titanium atom.

The hydrogen content in a-SiC:H films prepared by the plasma decomposition of gas mixtures of silane and methane or ethylene was measured by 1H(15N, αγ)12C nuclear reaction (NR) and infrared absorption spectroscopy (IR). The contents observed by both methods can be made to agree well for most of the films by putting the average value of the inverse absorption cross section for the CH n (n=1, 2 and 3) stretching mode over all values of n as A s=1.0×1021 cm-2. In some films prepared from silane and ethylene mixtures, the hydrogen content given by NR was higher than that by IR. Hydrogen release from films with a hydrogen content of over 30 atm.% was observed during NR analysis. The mechanism of the hydrogen release is discussed by comparing the IR spectra before and after ion bombardment.