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Synopsis After our observation of “quasi-equilibrium” in charge-state evolution for 2.0 MeV/u sulfur ions after carbon foil penetration, we have extended the initial ions to 1.0 and 2.0 MeV/u carbon ions. A significant quasi-equilibrium was observed for 1.0 MeV/u C+C collisions, where the equilibrium mean charge-state was 4.9, while for 2.0 MeV/u C+C collisions, where the equilibrium mean charge-states was 5.6, was a weak quasi-equilibrium.

We measured resonant coherent excitation of a 2s electron of 83.3 MeV/u Fe 23+ ions planar-channeling in the ( 2 ¯ 2 0 ) plane of the silicon crystal. A silicon surface barrier detector (SSD) was used as a crystal target in order to obtain information on the ion trajectory in the channel since the energy deposit ( Δ E ) to the SSD gives information on the ion trajectories where the resonant transitions occur. For the low Δ E , i.e., near the channel center, optically allowed 2s–3p transitions were much stronger compared with other transitions. Increasing Δ E , i.e., increasing the amplitude of ion trajectory, the optically forbidden 2s–3s transition rapidly became strong. On the other hand, the optically forbidden 2s–3d transitions did not become strong as rapidly as 2s–3s transition. Furthermore, it was found that the transition energies to the n = 3 states changed with Δ E . The shifts of the transition energies were consistent with the estimation for the energy levels of the Stark-mixed n = 3 states depending on the distance from the channel center.

Both equilibrium and non-equilibrium charge-state distributions were studied experimentally for 2.0 MeV/u carbon ions after passing through carbon foils. Measured charge-state distribution established the equilibrium at a target thickness of 10 μg/cm2 and this remained unchanged until a maximum target thickness of 98 μg/cm2. The equilibrium charge-state distribution, the equilibrium mean charge-state, and the width and skewness of the equilibrium distribution were compared with predictions using existing semi-empirical formulae as well as simulation results, including the ETACHA code. It was found that charge-state distributions, mean charge states, and distribution widths for C2+, C3+, and C4+ incident ions merged into quasi-equilibrium values at a target thickness of 5.7 μg/cm2 in the pre-equilibrium region and evolved simultaneously to the ‘real equilibrium’ values for all of the initial charge states, including C5+ and C6+ ions, as previously demonstrated for sulfur projectile ions at the same velocity (Imai et al., 2009). Two kinds of simulation, ETACHA and solution of rate equations taking only single electron transfers into account, were used, and both of them reproduced the measured charge evolution qualitatively. The quasi-equilibrium behavior could be reproduced with the ETACHA code, but not with solution of elementary rate equations.

Charge state distribution and its evolution for 2.0 MeV/u sulfur ions after passing through 0.9, 1.1, 1.5, 2.0, 3.0, 4.7, 6.9 and 10 μg/cm 2 carbon foils have been extensively studied following our previous paper [M. Imai, M. Sataka, K. Kawatsura, K. Takahiro, K. Komaki, H. Shibata, H. Sugai, K. Nishio, Nucl. Instr. and Meth. B 230 (2005) 63] to derive data for all the initial charge states between 6+ and 14+. Measured charge state distributions, their mean charge states and distribution widths do not flat off to establish equilibrium within the measured target thickness, and an overshooting feature of the distribution width for S 6+ projectile is observed around 1 μg/cm 2 in the target thickness. Two kinds of calculations, one based on rate equations accounting only for single charge transfer and the other applying ETACHA code, show good agreements with the experimental evolutions of mean charge and distribution width.

Time and two-dimensional position distributions of F+ ions emitted from a well-defined F/Si(1 0 0)-2 × 1 target were measured for impact of slow highly charged ions of 3.9 keV Ar5+. The time and position distributions were transformed into energy and angular distributions, which revealed that the peak emission energy was 2.0 ± 0.6 eV and the emission angle measured from the surface normal was 18 ± 4° in the (0 1 1) or ( 01 1 ¯ ) plane.

Charge state distributions of 2.0 MeV/u sulfur ions of various initial charge states (6, 10, 11, 13+) after passing through 0.9, 1.5, 2.0, 3.0, 4.7, 6.9 and 10 μg/cm2 carbon foils have been studied. It is observed that the processes involving the L-shell electrons are equilibrated within the target thickness of ∼5 μg/cm2 and the charge equilibration over this thickness is ruled by the K-shell processes. Measured charge state distributions do not flat off to establish equilibrium within the measured thicknesses, but the mean charge states almost saturate to 12.4 for all initial charge states examined. Calculation with ETACHA code, developed by Rozet et al. [Nucl. Instr. and Meth. B 107 (1996) 67], is employed, although the present impact energy is lower than the assumed region for the code.

Secondary ion emission phenomena from a water and fluorine adsorbed Si(1 0 0) surface irradiated with electrons and highly charged ions (HCIs) were studied. In the case of HCI impact (400 eV/ q Ar q + 4⩽ q ⩽8), H + and F + ions were detected in addition to Si(H) + and SiOH + ions resulted from a kinetic energy transfer. The yields of H + and F + , which were also observed in the case of electron impact, increased with q like q γ ( γ ∼3). This is the first paper reporting a strong charge state dependence of heavy adsorbate yields when slow HCIs bombard a well-defined surface covered with adsorbate.

A potential sputtering mechanism of hydrogen has been studied for impacts of slow highly charged Xe q + ions ( q =4–12) on well-defined H-terminated and water-saturated Si(1 0 0) surfaces. It was found that the sputtering yields of protons were proportional to q γ ( γ ∼5) for both the Si(1 0 0)2×1-H and Si(1 0 0)1×1-H surfaces, although the absolute yield for the Si(1 0 0)1×1-H surface was 10 times larger than that for the Si(1 0 0)2×1-H surface, i.e. the sputtering efficiency per one H–Si bond for the Si(1 0 0)1×1-H surface is five times larger that for the Si(1 0 0)2×1-H surface. The proton sputtering efficiency from a H–O–Si bond was extracted from measurements of the water-saturated surface, which was ∼8 times larger than the H–Si bond of the Si(1 0 0)2×1-H surface. An effective distance of the proton from its substrate was proposed to be the key parameter to govern the yield, which also influences the energy distributions of sputtered protons. These findings are consistently explained with a pair-wise bond-breaking model induced by a double electron capture, where the classical over barrier process plays an essential role.

We measured the emerging charge-state distribution of hydrogen-like 390 MeV/u Ar 17þ ions planar channeled in a silicon surface barrier detector for the DE measurement, and observed their energy deposition in the detector simultaneously. We simulated the energy loss spectrum of specific emerging charge state, and succeeded in reproducing it with an adjusting parameter for the cut-off momentum transfer between close and distant collisions. 2002 Elsevier Science B.V. All rights reserved.

K x rays emitted from 2.1 keV/uN{sup 6+} ions passed through a thin Ni microcapillary foil were measured in coincidence with the exit charge states. Ions with a K hole but with several electrons in outershells, i.e., hollow ions formed above a surface (in the first generation), were successfully extracted in vacuum. It was found that a considerable fraction of extracted hollow ions had extremely long lifetimes of the order of ns. {copyright} {ital 1997} {ital The American Physical Society}

Continuum x rays originated from radiative electron capture into continuum states (RECC) of relativistic Ne{sup 10+} ions have been observed. It has been found that the intensities of x rays decrease as their energy increases and the observed spectra show a clear edge which corresponds to the maximum energy transferred to free electrons under energetic projectile-ion collisions. The edge becomes dramatically sharp as the incident projectile energy decreases from 290 to 75 MeV/amu, indicating that the cross sections for RECC sharply increase at low projectile energies, which is in agreement with the theoretical expectation. {copyright} {ital 1997} {ital The American Physical Society}

The absolute cross section for the production of binary encounter electrons has been studied at zero degree for highly charged, clothed ions. Experimental and theoretical results for 1 MeV u-1 Auq+ (q=12-37) colliding with helium are presented. It is found experimentally that as the charge state of the incident ion is increased (1) the binary peak magnitude increases, (2) the electron energy at which the peak occurs decreases, and (3) the peak broadens. Classical trajectory Monte Carlo (CTMC) calculations are found to give good account for the magnitude and the shift to lower electron energy of the peak. The continuum distorted wave-eikonal initial state (CDW-EIS) approximation is shown to yield cross sections which are much smaller in magnitude than the experiments, but to reproduce well the relative magnitudes and shapes of the peaks for these ions. It is noted that the increase in the binary peak magnitude with increasing ionic charge state is in distinction to previous measurements which showed enhancement of the binary peak with decreasing charge state for clothed ions.

A potential sputtering mechanism of hydrogen has been studied for impact of slow highly charged Xeq+ ions (

Binary encounter electrons originating from collisions of 2 MeV/u F q+ , 4 MeV/u Si q+ and Ni q+ ions impact on a He target have been measured at zero degree with respect to the beam direction. The dependence of the binary encounter peak on the projectile charge states was studied. As earlier observed by Richard et al. [J. Phys. B23 (1990) L213] using fluorine ions, we found that the binary encounter electron production increased for decreasing charge state for the present ion species and energy. For fluorine ion impact, the enhancement of the binary encounter electron production becomes weaker at 2 MeV/u compared to the results of Richard et al. (1 and 1.5 MeV/u). A simple estimation based on potential screening and collision diameter for the enhancement is presented and the results reproduced the experimental values well.

Hydrogen atoms chemisorbed on and/or embedded under a surface are analyzed by the resonance nuclear reaction of 1 H( 15 N, αγ) 12 C. A monochromatized 15 N 2+ ion beam at 6.385 MeV is generated from a 5 MV tandem-type Van de Graaff accelerator. The amount of hydrogen is determined by measuring the γ-ray yield emitted in the nuclear reaction. Hydrogen atoms located at the interface between an amorphous Si layer of 35 A thick and a Si(001) surface are clearly distinguished from those adsorbed on the clean Si(001) surface.

In 89-MeV Sc{sup 8+}+He collisions, the light target atom He was used to ionize selectively the 2{ital p} shell of the scandium projectile. The subsequent {ital L}-shell Auger emission from Mg-like Sc{sup 9+} was measured with high resolution using the method of zero-degree Auger spectroscopy. The spectra are dominated by three peak groups that are attributed to transitions from the various initial states belonging to the configuration 1{ital s}{sup 2}2{ital s}{sup 2}2{ital p}{sup 5}3{ital s}{sup 2}3{ital p} to the final states 1{ital s}{sup 2}2{ital s}{sup 2}2{ital p}{sup 6}3{ital s} {sup 2}{ital S}, 1{ital s}{sup 2}2{ital s}{sup 2}2{ital p}{sup 6}3{ital p} {sup 2}{ital P}, and 1{ital s}{sup 2}2{ital s}{sup 2}2{ital p}{sup 6}3{ital d} {sup 2}{ital D}. The {sup 2}{ital P}{sub 1/2-}{sup 2}{ital P}{sub 3/2} fine-structure splitting was resolved for the final configuration 1{ital s}{sup 2}2{ital s}{sup 2}2{ital p}{sup 6}3{ital p}. The branching ratio for the transition to 1{ital s}{sup 2}2{ital s}{sup 2}2{ital p}{sup 6}3{ital d} {sup 2}{ital D}, which involves three electrons and, thus, must be ascribed to correlation, is compared to earlier results for the isoelectronic ions Al{sup +} and Ar{sup 6+}. Good agreement between observed and calculated branching ratios to the three final states is obtained by including onlymore » correlation in the initial state. A discrepancy for the branching to the 1{ital s}{sup 2}2{ital s}{sup 2}2{ital p}{sup 6}3{ital d} {sup 2}{ital D} term, which was observed already in the earlier investigation of Ar{sup 6+}, has been removed by including correlation in the {ital n}=2 shell in addition to the correlation in the {ital n}=3 shell, which was the only correlation introduced previously.« less

Binary encounter electrons originating from collisions between 56 MeV Si q + and He have been measured at zero degrees with respect to the beam direction. The dependence of the binary-encounter peak on the projectile charge state q =6, 12, 13 and 14 (fully stripped Si) was studied. As earlier observed by Richard et al . (J. Phys. B 23 (1990) L213) using fluorine ions, we found that the binary-encounter electron production increased for decreasing charge state. This dependence which reflects the importance of outer screening has recently been treated in several theoretical papers and the present results are compared to estimates by K. Taulbjerg (private communication).

Energy spectra of electrons emitted in the forward direction by antiproton and proton bombardments on carbon foil targets were measured in the incident energy region from 500 to 750 keV. In the spectra for antiproton impact, no sharp anticusp, which is expected in place of the cusp in the case of the proton impact, is recognized and a small bump is found at 50 eV below the cusp energy. The spectral profile in the equivelocity region, including smearing out of the anticusp, together with the energy and intensity of the bump, is consistent with a theoretical prediction for wake-riding electrons based on the classical trajectory Monte Carlo method.

Charge-state evolution of 2.0 MeV/u carbon, sulfur, and 1.0 MeV/u tungsten ions after carbon-foil penetration has been studied experimentally in the foil thickness range covering both pre- and after the equilibrium. It was observed for the first time that mean charge-states for Sq+ (q = 6-14) initial ions evolved to coincide in 12.3 at a target thickness of 6.9 μg/cm2, showing a "quasi-equilibrium," and further evolved simultaneously to a real equilibrium value of 12.68, whereas those for Sq+ (q = 15, 16) initial ions evolved directly to the real equilibrium, without through the "quasi-equilibrium," until the target thickness was increased to 100 μg/cm2. Such kind of shell-effect was observed also for C-ions, and could be qualitatively reproduced by some simulations.

Interactions of relativistic clothed heavy ions with solid targets have been studied for 390 MeV/u Ar17+ ions traversing carbon foils of various thicknesses through measurements of the convoy electrons. The electron energy spectra at 0° were obtained by a magnetic analyzer combined with a Si surface barrier detector with a depletion layer of 5 mm. The peak widths of the convoy electrons in the laboratory frame have been found to decrease as the target thickness is increased from 25 to about 500 µg/cm2, and broaden for thicker targets due to multiple scattering.

We measured the energy loss of charge-frozen clothed ions (i.e., partially stripped ions which maintain their charge states throughout the passage) in a Si solid employing a totally depleted silicon detector with 4.1 µm thickness as a target, to measure the energy deposition of 390 MeV/u Ar17+ directly. Under the present conditions, the probability of the electron loss is not so large, and that of the electron capture is negligibly small. Accordingly, the energy loss of charge-frozen Ar17+ ions in a rather thick target can be measured. Charge states of ions transmitted through the target were observed by a 2D-position sensitive detector in coincidence with the energy deposition. We have obtained an effective charge of Ar17+ ions for the stopping power, as Zeff = 17.36 (±0.03).

Channeling radiation from relativistic electrons channeled zone axis of the germanium single crystal is measured by using 1 MeV electron microscope. The energy of channeling radiations is accordance with the theoretical results although the intensity of X-rays is weak.

Time evolution of hydrogen coverage on a well defined tungsten surface detected by the nuclear reaction is discussed. A difference equation is proposed to describe a competition between the adsorption and desorption processes. Overshoot and oscillalion behaviors in the time variation of the hydrogen coverage are explained. A quantitative agreement between the experimental and theoretical results is observed.

Aluminum Kα X-ray spectra for equal velocity H+ and H2+ ions of 0.8–1.5 MeV/amu incident on thin aluminum and aluminum oxide films with the thicknesses 100–500 A were observed. The high resolution X-ray spectra were observed with a Bragg crystal spectrometer. From the Kα satellite intensity the L-shell ionization probability was investigated. The L-shell ionization probability for H2+ incident on Al films of thickness 100 A was about 8% larger than that for H+ incident. For Al films of thickness 300 and 500 A the enhancements were about 5%. Similar results were obtained for aluminum oxide films.

The X-ray spectra emitted during the radiative capture of target electrons into the projectile K shell have been measured under single collision conditions for a He gas target. The experiment was performed for 40–76 MeV F q + ( q = 8,9) and 120–175 MeV Cl q + ( q = 16,17) ions. The centroid energies of the radiative electron capture (K-REC) X-rays have been found to be in good agreement with the calculated ones. It is also confirmed that the widths of the K-REC X-ray distributions for Cl 17+ ion impact are in good agreement with the simple model calculations.

Energy spectra of the channeling radiation from 0.8 and 1.0 MeV electrons channeled along the 〈111〉 axis of a germanium crystal were measured using a high voltage electron microscope attached with a gas flow proportional counter. Subtracting the yield of the Ge L X-rays and bremsstrahlung, the contribution of the channeling radiation was obtained. Peak energy of the radiation at 0.8 and 1.0 MeV and the incident angle dependence of the channeling radiation intensity are in good agreement with calculated ones.

Charge states and angular distributions of 150 MeV Cl ions have been measured as a function of carbon target thickness (2.5–180 μg/cm 2 ). Evidence for the large shell effect under single collision conditions is found in the thinnest target. Transition energies in highly ionized Cl ions have been measured using a grazing incidence monochromator at the VUV region, and using a crystal spectrometer and a Doppler-tuned spectrometer at the X-ray region. The lifetimes have also been measured using the time of flight technique at the VUV and X-ray regions. Results of measurements are given and some are discussed in comparison with other data.

A Beam-foil study was made on highly ionized chlorine ions. Emission lines in the wavelength region from 170 A to 260 A were observed and most of the lines were due to the 2 s -2 p transitions belonging to Cl XII-Cl XIV. Two lines at ∼180 A and ∼206 A are newly identified as transitions between high n l levels of Cl XV and Cl XIV. The lifetimes of 2 s 2 p 1 P 1 and 2 p 2 1 D 2 levels in Cl XIV were determined from the intensity decay curve of 237.7 Aobtained with time-of-flight technique to be 0.14 nsec and 0.60 nsec, respectively.

Both charge states and scattering angles have been simultaneously measured using an electrostatic deflector and a two dimensional-position sensitive detector for 150-MeV 37Cl ions emerging from carbon foils of 2.5–360 μg/cm2. The increase of mean charges for foils of a few μg/cm2 is noticeable at larger scattering angles. Concerning charge distributions, marked variations are found for the shapes of distributions and distribution widths in the range of non-equilibrium to equilibrium thickness, and these show a weak dependence on the scattering angle.

Distributions of charge states and multiple scattering widths of angular distributions have been simultaneously measured using a two dimensional-position sensitive detector for 150 MeV 37Cl10+ ions emerging from carbon foils with thickness of 2.5–180 μg cm 2 . For thinner foils, the scattering angle dependence of mean charge states verifies the evidence for the so-called single violent and/or plural collisions

Using the crystal blocking technique, we have measured the emission distributions of protons near the 〈110〉 axis elastically scattered from a 7000 A thick single nickel crystal, at 5.65 and 6.50 MeV. These distributions are fitted by an analytic multiple string calculation of the blocking process which yields the time-dependent compound-nucleus decay probability curve. Shape- and compound-elastic cross sections are simultaneously determined in a reaction-model-independent way, as is the mean compound nucleus lifetime. The resulting decay curves for the delayed component are consistent with a single exponential at both energies and show no indication of the presence of level-level correlations. Use of such data in testing recent statistical theories is discussed.

The angular distribution and dip area of the planar blocking due to charged particles emerged from a crystal are calculated. The derived formulas are applied to the cases where the emitting atom is not on lattice plane and the compound nucleus is formed. The results show that the change of dip area is very sensitive to displacement of emitting atom from the lattice plane. The yield of the channelling part in the blocking pattern is also calculated. Numerical examples of angular distribution for various positions of the emitting atom are given for the {111} planar blocking of protons in germanium. Winkelverteilung und Bereich des Minimums des ebenen Sperrens durch geladene Teilchen, die aus dem Kristall austreten (Blocking), werden berechnet. Die abgeleiteten Formeln werden angewandt auf den Fall, das das emittierende Atom nicht in einer Gitterebene liegt und ein Compoundkern gebildet wird. Die Ergebnisse zeigen, das eine Anderung des Minimums durch Verschiebung des emittierenden Atoms aus der Gitterebene stark beeinflust wird. Der Anteil des Channelling im Blockingbild wird ebenfalls berechnet. Numerische Beispiele der Winkelverteilung fur verschiedene Lagen des emittierenden Atoms fur das Blocking von Protonen in der {111}-Ebene von Germanium werden angegeben.

The temperature dependence of minimum yield and dechanneling coefficient is studied for and axial channeling in germanium and silicon crystals. The observed minimum yield and the dechanneling coefficient are represented by linear relations of the mean square amplitude of thermal vibrations, and the results are compared with theory. For the minimum yield, the observed values are independent of energy and kind of particles and agree with theoretical values. The dechanneling coefficients show a poor agreement with theory. To find a reason for this discrepancy, the critical angle and the theoretical treatment are considered and discussed. A method to obtain the lattice disorder in a crystal doped with impurity atoms by measuring the dechanneling coefficient and minimum yield for protons and helium ions is presented. This method is applied to a silicon crystal containing arsenic atoms.

A method is presented to obtain density distribution and attenuation factor of foreign atoms inside a silicon crystal using backscattering spectra of a 2 MeV helium beam in the random and aligned directions. Experiments were performed on two silicon crystals, one including about 0.15 at% arsenic atoms obtained by the Czochralski method and the other with arsenic and phosphorus atoms doped by the diffusion method. Density distribution observed in the latter crystal is represented by the complementary error function except in the surface layer, where the attenuation factor is extremely large. Eine Methode zur Bestimmung der Dichteverteilung und des Schwachungsfaktors von Fremdatomen in einem Siliziumkristall mittels Ruckstreuungs-Spektren eines 2 MeV-Heliumstrahls in willkurlicher und gerichteter Anordnung wird mitgeteilt. Die Experimente wurden an zwei Siliziumkristallen, von denen der eine 0,15 At% Arsenatome enthielt und mit der Czochralski-Methode erhalten wurde und der andere mit Arsen und Phosphor durch Diffusion dotiert war, durchgefuhrt. Die im letzteren Kristall beobachtete Dichteverteilung wird durch die komplementare Fehlerfunktion dargestellt, auser im Oberflachenbereich, wo der Schwachungsfaktor extrem gros ist.

Previous work (Komaki et al., Phys. Lett.; 38B: 218(1972))-reported on lifetime measurements for the /sup 27/Al(p, alpha )/sup 24/Mg reaction. The alpha -particles were detected by celluloid films. The reaction times were determined from the ratio of the dip areas in the (111) and (111) planar blocking direction. In the present work, a study is reported of the effect of the reaction time on the minimum yield in the axial and planar blocking dips. (UK)

The temperature dependence of the dechanneling coefficient and the minimum yield is studied for 〈111〉 and 〈110〉 axial channeling of 1.0 and 1.5 Me V protons in a silicon crystal. The results show that the dechanneling coefficient is represented by A ϱ2⊥ + B, where ϱ⊥ is the mean amplitude of thermal vibrations normal to the crystal axis. The minimum yield is represented by C ϱ2⊥. The obtained values of A, B, and C are compared with theory. Die Temperaturabhangigkeit des Dechanneling-Koeffizienten und der minimalen Ausbeute wird fur axiale 〈111〉- und 〈110〉-Channeling-Prozesse von 1,0 und 1,5 Me V-Protonen in einem Si-Kistall untersucht. Die Ergebnisse zeigen, das der Dechanneling-Koeffizient in der Form A ϱ2⊥ + B von der mittleren Amplitude ϱ⊥ der thermischen Schwingungen senkrecht zur Kristallachse abhangt. Die minimale Ausbeute besitzt die Abhangigkeit C ϱ2⊥. Die erhaltenen Werte von A, B und C werden mit der Theorie verglichen.

The behaviour of the channeling peaks and blocking dips observed in the two-dimensional spectrum (energy and scattering angle) of the (111) planar blocking of protons transmitted through thin crystals of germanium and silicon is studied. The experimental results are compared with the calculations. The discrepancies between experiment and calculation are explained by the random scattering which smears out the blocking profile within the angular region estimated from the multiple Coulomb scattering. Das Verhalten von Kanalbildungsmaxima und Sperrminima wurde untersucht, die im zweidimensionalen Spektrum (Energie und Streuwinkel) der (111)-Flachensperrung von Protonen beobachtet wurden, die durch dunne Germanium- und Silziumkristalle gestrahlt wurden. Die experimentellen Ergebnisse werden mit Rechnungen verglichen. Die Differenzen zwischen Experiment und Rechnung werden mit statistischer Streuung erklart, die das Sperrprofil innerhalb des Winkelbereichs verschmiert, der aus der Coulomb-Mehrfachstreuung abgeschatzt wird.

Transverse energy levels of channeled electrons and photon energies due to the channeling radiation are calculated for major planes of silicon and germanium crystals. Results show a good agreement with photon energies observed in a silicon crystal. Number spectrum of photons and the effect of thermal vibrations on the photon energy are discussed.

Spectra of the channeling radiation emitted by 350 MeV (HO)-planar channeled electrons in silicon crystals were observed and the dechanneling length was obtained as 31 μm. A photon spectrum, only from channeled electrons, deduced from observed aligned and random photon spectra, was compared with that calculated quantum mechanically, taking account of the experimental conditions and the efficiency of the photon detector. The result showed good agreement for the absolute intensity.

The transverse energy levels of channeled electrons and the photon energies due to the channeling radiation are calculated for major planes of silicon and germanium crystals. The results show good agreement with photon energies observed in a silicon crystal. The number spectrum of photons and the effect of thermal vibrations on the photon energy are discussed.

The hydrogen concentration in amorphous carbon films prepared on silicon wafers by the rf-sputtering was measured by the elastic recoil detection technique (ERD) using a 12 MeV 12 C 3+ ion beam. During the measurements, it was observed that the hydrogen concentration decreased to a definite value. The decay rate and the final value of the hydrogen concentration depend on the initial amount of hydrogen and the chemical condition of carbon and hydrogen in the film. The variation in the chemical structure of the films was analysed by comparing IR absorption spectra before and after the ion bombardment. As results, it was found that dangling bonds were created by ion bombardment and that they make CC bonds with neighbors or CO bonds by capturing oxygen atoms in air.

A new method to measure reaction times by the use of the blocking effect of energetic particles in single crystals was applied to the 28Si(p, p′)28Si∗, 70Ge(p, p′)70Ge∗ and 72Ge(p, p′)72Ge∗ reactions. For germanium, reaction times of the order of 10−17 s were observed.

Coster-Kronig electrons from the autoionizing Rydberg states of 2 MeV/u silicon projectiles excited through a thin carbon foil were observed at zero degrees. The most prominent lines came from Si10+ 1s22p(2P°1/2) nl-1s22sl' and 1s22p(2P°3/2) nl-1s22sl' transitions, with n ranging from 9 to ~20. Other peaks and shoulders in the spectra were examined.

We have developed a parallel beam suitable for channeling experiments with relativistic heavy ions at HIMAC (Heavy Ion Medical Accelerator in Chiba). To observe channeling phenomena, we used a silicon surface barrier detector (SSD) as a sample crystal and as a detector for the energy loss in itself. Further, we measured the angular spread of the beam transmitted through the SSD by a position sensitive detector (PSD) placed downstream of the SSD. Under axial and (111), (220) and (004) planar channeling conditions, we observed that the energy loss of the channeled ions in the SSD became almost a half and their angular spread was also reduced.

We present a theoretical study of convoy electron emission resulting from transmission of relativistic 390 MeV/amu Ar17+ ions through carbon foils of various thicknesses. Our approach is based on a Langevin equation describing the random walk of the electron initially bound to the argon nucleus and later in the continuum. The calculated spectra of ejected electrons in the forward direction exhibit clear signatures of multiple scattering and are found to be in good agreement with recent experimental data.

The variations of dechanneling coefficient with temperature are studied on the 〈111〉 axial channeling of proton for silicon crystal. The result shows that the dechanneling coefficient is represented by Aϱ2 + B where ϱ is the mean amplitude of thermal vibrations.

The temperature dependence of the minimum yield in channeling phenomena along the 〈110〉 and 〈111〉 axes is measured in germanium and silicon crystals. The observed values agree well with those obtained by computer simulation.

Behavior of phosphorus and arsenic atoms diffused simultaneously into silicon crystals, in which the density of phosphorus at the surface is 1021 cm−3, was studied by random and aligned spectra of backscattered helium ions and radioactive analysis techniques. It was concluded that the phosphorus atoms enter substitutionally and arsenic atoms interstitially, indicating that interstitial atoms inhibit the generation of dislocations.

The temperature effects of the {111} and {110} planar channeling of 1.5 MeV protons for silicon thin crystal are investigated. the results show that the low loss component (channeling peak) in energy spectrum of transmitted protons decreases with increasing temperature and its energy value does not change. The half width of the channeling angle is almost independent of temperature.