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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.

Energy spectra of electrons ejected through autoionization decay of high-Rydberg states in high-energy collisions of Nq+ (q = 1–3) with He have been measured with high-resolution by using zero-degree electron spectroscopy. Several series of autoionizing lines were observed, corresponding to decays from N3+ 1s22p(2P)nl Rydberg states produced in N3+ + He collisions, from N2+ 1s22s2p(3P)nl Rydberg states produced in N2+ + He and from N+ 1s22s2p2(4P)nl Rydberg states produced in N+ + He, respectively. Angular momentum distributions for the first or second peak of three series of Coster–Kronig electron transitions for Nq+ (q = 1–3) projectiles are also discussed, where the highly excited states are formed by electron excitation.

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.

K X-rays emitted from 2.1 keV/u N ions transmitted through a thin Ni microcapillary foil were measured in coincidence with a final charge state qf, using a Si(Li) X-ray detector in the cases of incident charge states of qi = 7 and 6. It was found that (1) the coincidence X-ray yield for (qi, qf) = (7, 6) decreased faster than those for other (qi, qf) combinations, (2) the coincidence X-ray yields did not depend on the number of K-shell holes of the incident ions but on the final charge state qf.

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.

A new scheme to effectively and quickly cool highly charged ions (HCIs) is presented. The key item is the combination of high density electron plasma and cold positron plasma, which enables to realize a quick cooling (∼1 s) and at the same time the HCI loss due to recombination with electrons and residual gases is largely suppressed.

We measured charge state dependence and incident angle dependence of sputtering yields and two-dimensional (2D) position distributions for H+, Si+ and SiOH+ ions emitted from a water adsorbed Si(1 0 0) surface irradiated by a few keV Arq+ (q = 4–8). It was found that (1) H+ yield strongly depended on the charge state and increased with increasing incident angle, (2) Si+ and SiOH+ yields were independent of the charge state and increased with increasing incident angle.

X-rays emitted from Ar 17+ , Fe 24+ and Kr 35+ ions of about 400 MeV/u transmitting through a thin Si crystal of about 20 μm thickness have been measured in a planar channeling condition and compared with those in a random incident condition. We have found that the X-ray yield from Ar 17+ ions is larger for the channeling condition than for the random incidence, while those from Fe 24+ and Kr 35+ ions are rather smaller. Such tendencies are explained by considering the projectile dependences of excitation and ionization probabilities together with X-ray emission rates. A crude simulation has qualitatively reproduced these experimental results. When the crystal thickness is small, the X-ray yield is smaller in the channeling condition than in the random incident condition, because excitation is depressed. However, for thicker crystals, the X-ray yield is larger, since the survived population of projectile-bound electrons is larger due to small ionization probabilities under the channeling condition. This inversion occurs at a specific crystal thickness depending on projectile species. Whether the thickness of the used crystal is smaller or larger than the inversion thickness determines enhancement or depression of the X-ray yield in the channeling condition.

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.

Energetic ions traveling through a single crystal are excited by an oscillating crystal field produced by a periodic arrangement of the atomic strings/planes, which is called Resonant Coherent Excitation (RCE). We have observed enhancement of convoy electron yields associated with RCE of 1s electron to the n=2 excited states of 390 MeV/u hydrogen-like Ar17+ ions passing through a Si crystal in the (2 2 0) planar channeling condition. Lost electrons from projectile ions due to ionization contribute to convoy electrons emitted in the forward direction with the same velocity as the projectile ions. With combination of a magnet and a thick Si solid-state detector, we measured the energy spectra of convoy electrons of about 200 keV emitted at 0°. The convoy electron yield as a function of the transition energy, i.e. the resonance profile, has a similar structure to the resonance profile observed through the ionized fraction of the emerging ions. It is explained by the fact that both enhancements are due to increase in the fraction of the excited states from which electrons are more easily ionized by target electron impact in the crystal than from the ground state.

X-rays emitted from resonant coherently excited (RCE) n =2 states of 390 MeV/amu hydrogen-like Ar 17+ ions were observed under planar channeling in a Si crystal. The resonance profiles for X-ray emission consisting of two peaks for j =1/2 and j =3/2 are characterized by suppression of the j =1/2 peak. The degeneracy of the n =2 states are removed by Stark effect due to the static crystal field. The RCE probability of these Stark splitted substates differs, reflecting the polarization of the oscillating crystal field. However, the associated alignment was not clearly observed. It is explained by the fact that both polarization of the oscillating crystal field and the wave functions of Stark-mixed n =2 states depend on the distance from the channel center, and the X-ray emission is preferred in a channel center in a crystal.

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.

We have observed photons in the visible light range emitted from slow (2.0 keV/amu) highly charged Ar6+ ions which have captured one electron and transmitted through a Ni microcapillary target. Observed lines were identified by comparing with an ab initio calculation based on the multi-configuration Hartree-Fock method. (C) 2003 Elsevier Science B.V. All rights reserved.

Coster–Kronig (C–K) and Auger electron spectra from highly excited states produced by high-energy highly charged ions with a He target have been investigated using zero-degree electron spectroscopy. C–K and Auger electrons produced in 32 MeV Oq+ (q=3,4)+He collisions were measured, where the highly excited states of three-, four- and five-electron O ions were formed by electron excitation/ionization. It is found that the 1s22pnl states with relatively low angular momenta are excited in the O4+ ion collisions while the 1s22s2pnl states with higher angular momenta are excited in the O3+ ion collisions. K Auger spectra produced in Oq+ (q=3,4)+He collisions qualitatively agree with the previously measured results.

A system consisting of a superconducting solenoid, a multi-ring trap and a slow positron source has been built to prepare a cold highly charged ion (HCI) beam, which will be applied to study interactions with solids or gases, e.g. potential energy deposition scheme during interaction of slow HCIs with a surface. An electron plasma with density more than 1010 cm−3 has already been prepared to trap positrons.

To detect weak X-rays with a high-resolution spectrometer, a charge-coupled device was operated in a single X-ray photon detection mode. A procedure to effectively identify single X-ray was established. In the case of 2.3 keV/u N7+ and Ne9+ incidence, X-rays emitted from ions transmitted through a Ni microcapillary target were measured with the spectrometer using the procedure of the single event mode. The signal-to-noise ratio was improved by using the single photon counting method.

The resonant coherent excitation from a 1s state to n=2 states of 94 MeV/u Ar17+ ions channeling in the (2 2 0) plane of a Si crystal was observed as the decrease of the survival fraction of Ar17+. Three resonance dips of survival fraction were clearly seen. The resonance profile is attributed to the spin–orbital interaction, the position-dependent Stark effect, the position-dependent transition probability and the position-dependent ionization probability of excited states. The estimated experimental resolution of measurement of the resonance profile is comparable to the width of the narrowest resonance dip (∼1.5 eV FWHM) or less.

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.

Proton sputtering from H-terminated Si(1 0 0) surfaces bombarded with Xeq+ (q=4–12, E=2–5 keV) were experimentally studied. Proton sputtering yields and two-dimensional (2D) distribution of protons were measured employing a time-of-flight technique with a 2D position sensitive detector. It was found that the q dependence of the proton sputtering yield from Si(1 0 0)–(2×1)H surface with Xeq+ was the same (∼q5) as that from an untreated surface, although the absolute yield was about 1/30. The yield from Si(1 0 0)–(1×1)H surface was about 10 times larger than that from the Si(1 0 0)–(2×1)H surface. The mean energy of emitted protons from Si(1 0 0)–(2×1)H and Si(1 0 0)–(1×1)H surfaces were 1.2 and 5.9 eV, respectively.

X-rays emitted from 2.3 keV/u 15 N 7þ ions transmitted through a highly ordered Ni microcapillary were measured with a high-resolution soft X-ray spectrometer. The highly ordered microcapillary has recently become available employing a nano-lithographic technique. A transmission ratio and charge state distribution of ions through the microcapillary target were found to be consistent with theoretical predictions. A preliminary analysis showed that a series of X-rays from np–1s transitions with n as high as 8 were identified,which is consistent with the classical over barrier model. 2002 Elsevier Science B.V. All rights reserved.

Spectra for Coster–Kronig (C–K) transition 1s 2 2pð 2 P3=2Þ9l ! 1s 2 2sð 2 S1=2Þel 0 of Be-like S 12þ ions produced following penetration of 2.5 MeV/u S qþ ions (q ¼ 7, 10, 12, 13) through C-foil targets of various thickness (1–6.9 lg/cm 2 ) have been probed using zero-degree electron spectroscopy. It has been found that in collisions for S qþ (q ¼ 7, 10) ion incidence, in which the C–K electrons originate from the projectile bound electrons, a fraction of the angular momentum l ¼ 1 of the Rydberg state decreases, and fractions of higher ðl P 2Þ angular momenta increase, while the total intensity of the C–K electrons grows, as target foil thickness increases. The electron spectra for S qþ (q ¼ 13) incident ions, in which the autoionizing Be-like state is preferably formed by electron capture from the target continuum upon or near the exiting surface, do not change in l-distribution or intensity. The shift to higher l comes from the multiple collisions of electron with the target, in traveling at the same speed under the strong Coulomb potential of the projectile. The observed dependence of the l-distribution and the intensity of the Rydberg state on projectile initial charge and target thickness indicates the importance of transport phenomena for both the S 13þ core and the projectile-entrained electrons inside solid. 2002 Elsevier Science B.V. All rights reserved.

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.

The formation and relaxation processes of hollow atoms and related excited states of ions produced with a Ni microcapillary thin foil have been studied employing various experimental techniques. The first stage of the charge transfer from the surface to the ions was studied by using visible light measurements. On the other hand, X-ray measurements revealed the core electronic configurations of ions at the last moment of the hollow atom evolution. The overall feature of the electron capture processes in the capillary was given by the charge state distribution measurements.

Resonant coherent excitation (RCE) of 390 MeV/u hydrogen-like Ar 17a ions planar channeled in a Si crystal was investigated through measurements of the de-excitation X-rays as well as the charge state distribution of the transmitted ions. We observed enhancements of both the fraction of ionized Ar 18a ions and the intensity of the de-excitation X-rays under the RCE condition. The na 2 states of Ar 17a in the crystal are split into four energy levels due to spin‐orbit interaction and Stark eAect induced by the planar potential of the crystal. The intensities of the X-rays from the lower two levels were found to be smaller compared with those from the higher two levels, which is explained by the dominance of the 2s component not decaying via a single photon emission. The diAerence between the resonance profiles of the charge state and the X-ray reflects the nature of na 2 states in the crystal field. ” 2000 Elsevier Science B.V. All rights reserved.

Resonant coherent excitation of the 1s electron to na 2 states in a hydrogen-like ion was studied through measurements of the survived fraction of 390 MeV/u Ar 17a planar channeled in a Si crystal. Adopting a totally depleted Si surface barrier detector as a target crystal, the charge state of the individual emerged ion was measured in coincidence with the energy deposition in the target. By changing the incident direction along theO2 20 U ,O 004 U, andO1 11 Uplanes, a series of clear resonances were observed as the decrease in the survived charge fraction due to higher electron loss probability for the excited state. Each resonance profile reflects energy splitting of the na 2 manifold originated from l‐ s interaction and Stark eAect due to the crystal field. From the correlation between the energy loss and survived charge fraction, transition energy as a function of the ion trajectory amplitude is deduced which is in good agreement with calculated results. ” 1998 Elsevier Science B.V. All rights reserved.

We have succeeded in observing the channeling of 290 MeV/u C 6+ ions in a Si crystal. Under 〈1 1 0〉 axial, and (0 0 4), (2 2 0) and (1 1 1) planar channeling conditions, energy loss of the channeled ion in the Si crystal was observed. We also calculated the trajectory dependent stopping power for planar channeling ions, which employs mean and local electron densities evaluated adopting the Moliere potential. Calculated energy loss spectra were found to reproduce the experimental results quite well.

We observed resonant coherent excitation (RCE) of 1s electron to n=2 states in Ar17+ through measurements of the survived fraction of 390 MeV/u hydrogen-like Ar17+ channeled in a Si crystal. We adopted a totally depleted Si surface barrier detector as a target crystal as well as a probe of the energy deposition. The charge state of emerged ions was measured by a combination of a charge separation magnet and a 2D-position sensitive detector. We observed the RCE for planar channeled ions by tilting the target Si crystal from the direction of [1 1 0] axis in the (2 2 0) , (0 0 4) , and (1 1 1) planes. Prominent resonances at tilt angles under the resonance condition were observed. Moreover, each resonance profile is split into several lines due to the l·s interaction and the Stark effect originating in the static crystal field. The energy deposition in the crystal gives the information of the amplitude of the ion trajectory. The resonance peak position, intensity and width in the survived fraction of Ar17+ reflect the position dependent strength of the crystal field, the RCE and the electron loss probabilities. They are in good accord with our calculation of the transition energy and probability.

Swift heavy ions channeled in a crystal experience a variety of atomic processes which depend on the ion trajectory in the channel. Recent studies on the atomic processes such as slowing down of the ion, charge changing collision, excitation of bound electrons, and so on in connection with ion trajectories or impact parameter are reviewed. Resonant coherent excitation (RCE) is a composition of various atomic processes and has offered a new field in atomic physics and has been investigated experimentally and theoretically. Recent progress in this field is also reviewed.

Soft X-rays were measured in collision of 1‐3 keV/u Ar qa (qa 2‐14) ions on an amorphous C target. Ar L X-rays due to initial L-shell holes were successfully decomposed. It was found that L-shell vacancies of Ar were filled stepwise primarily via 3s‐2p transition for each step. ” 1998 Elsevier Science B.V.

High-resolution Coster–Kronig (C–K) electron emission spectra in collisions of 32 MeV O 3+ ions with a He gas target have been investigated using zero-degree electron spectroscopy. Zero-degree electron spectrum for the O 3+ projectiles exhibits a trident-like structure around the cusp peak, consisting of three clear peaks. The sharp peaks directly on either side of the cusp corresponded to autoionization lines from highly excited O 3+ ions produced in the collision with a He gas target, which are confirmed to be due to the configuration 1s 2 2s2p( 3 P)5s, where the C–K ejection energy is 0.014 eV. The C–K transitions in higher energy region are found to originate in 1s 2 2s2p( 3 P) nl –1s 2 2s 2 el ′ ( n = 5–11). For n = 5–7, a clear angular momentum distribution is observed, where the maximum intensity is attributed to the relatively high angular momentum l = 2 or 3.

Zero-degree electron spectra were measured with high resolution for 64 MeV Sq+ (q = 6, 11 to 13) ions on a He and C-foil target. Several peaks are observed in the electron energy range up to 2.5 eV for the 64 MeV S12+ + He collision, in addition to a series of autoionization electrons produced by the Coster-Kronig transition 1 s 2 2p( 2 P 3 2 )9l−1 s 2 2s ϵl′ . The charge state dependence of electron spectra for 64 MeV S11+.12+.13+ + He and S6+.12+.13+ + C were measured to identify the origin of the low energy electrons. No characteristic line is observed in the electron energy spectra following the 64 MeV S13+ beam excitation with He. This indicates that the electron excitation and capture process that could produce the Li- and Be-like initial configurations resulting in autoionizing Coster-Kronig transitions does not occur during a collision between 64 MeV S13+ ions and a He target at this collision energy. It is supposed that the electron spectra for S11+ shows a series of autoionizing Coster-Kronig transitions of 1s22p27l−1s22s2pϵl′, 1s22p29l−1s22s2pϵl′ and 1s22s2p9l−1s22s2ϵl′ for S11+ ions, which are energetically possible.

We investigated the exit charge, scattering angle and energy loss distribution of heavy ions (30 MeV carbon) planar channeled in a thin crystal. We measured, in a list mode, exit charge q ex , scattering angle θ ex with respect to the (110) channeling plane, and energy loss ΔE , for each heavy ion of incident charge q in and incident angle θ in , and obtained a distribution Y ( θ sc , q ex , ΔE ; θ in , q in ). As a single crystal, we adopted a thin totally depleted Si detector of 4 μm in thickness, and we measured the energy loss by the signal of the detector itself. After passing through the sample crystal, the exit charge and angle of the ions were measured with a 2D position sensitive detector coupled with a slit and an electrostatic deflector. Close correlations among the exit charge, energy loss and exit angle were found.

Projectile L X-rays are observed for 18–260 keV Ar q + ions ( q =7 − 14) bombarding Be and Al targets. X-ray yields are found to increase with the L-shell hole number for q ≥ 9. The X-rays are shown to be emitted stepwise, which allows to disintegrate the spectra into the individual steps. It is found that 3s-2p transition is dominant in each step. Transitions from higher angular momentum states like 3d-2p and those from higher principal quantum numbers are relatively weak.

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.

We have measured the effect of the orientation of the molecular axis on average numbers and number distributions of multiply emitted secondary electrons (MUSE) from a very thin (∼ 50 A) carbon foil both in the forward and backward directions resulting from the passage of 1 MeV/u He2+ molecular ions. MUSE was observed in coincidence with a pair of outgoing He2+ ions detected 3.5 m downstream from the carbon foil. Average numbers of MUSE in the forward and backward directions per incident projectile are 11.5 and 7.5, respectively, when the orientation of the molecular axis is disregarded. Number distributions of MUSE are much wider than the Poisson distribution in any case. They are compared with those which are calculated from the data for 1 MeV/u He+ ions. A negative correlation of the number distributions of MUSE in the forward and backward directions was observed. The average number of MUSE in the forward directions is larger when the molecular axis is parallel to the beam direction than when it is perpendicular, but no orientation dependence was observed in the backward direction.

Zero-degree electron spectra were measured with high resolution for 64 MeV S5+ ions on He and 64 MeV S12+ ions on He and C, and for 90 MeV Sc8+ ions on He. In 64 MeV S ion collisions, a series of intense lines have been observed, which are attributed to the Auger transitions from 1s22s22p53snl to 1s22s22p6 for S5+ ions on He, and to the Coster-Kronig transitions from 1 s 2 2 p nl to 1 s 2 2 s ϵ l l′ for S12+ ions on He or C foils. The angular-momentum (l) distribution of the S12+ ions in the Rydberg state with n = 9 has been obtained and it is found that the high-l components are significantly enhanced for the solid target. In 90 MeV Sc8+ +He collisions, three groups of intense lines have been observed, which are attributed to the transitions from 1s22s22p53s23p to 1s22s22p63s, 1s22s22p63p, and 1s22s22p63d. The last transition, in which three electrons are involved via electron correlation, is studied and compared with previous results for the isoelectronic ions Al+ and Ar6+.

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.

Electrons emitted from projectile ions were measured with high resolution in collisions of 64 MeV S 12+ ions with He atoms and C foils by 0° electron spectroscopy. A series of intense lines have been observed, which are attributed to the Coster-Kronig transitions of 1s 2 2p nl -1s 2 2sϵ l' with n = 9 to 19. The angular-momentum ( l ) distribution of ions in the autoionizing states of n = 9 has been obtained and evidence for high l enhancement has been found in C-foil targets.

Resonant coherent excitation and subsequent radiative de-excitation have been investigated for hydrogen-like heavy ions axially channeled in a gold single crystal. The intensity of the F8+ Kα X-ray has shown a clear increase at the third-order resonance for F8+ ions channeled along the 〈110〉 axis at an incident energy of 37.6 MeV. However, the energy dependence of the exit charge state distribution of hyperchanneled ions did not show a resonant behavior. In the case of hydrogen-like C ions penetrating the same crystal along the 〈111〉 axis, the fourth-order resonance was clearly observed in the exit charge-state distribution at the incident energy of 15.3 MeV. These results are explained by comparing the crystal channel size with the orbital radius of the excited electron.

The proportionality coefficient between hydrogen concentration and the integrated intensities of the infrared reflection-absorption spectrum (IRAS) for CHn bonds was determined in hydrogenated amorphous carbon films (a-C:H) and hydrogenated silicon carbide films (a-SiC: H). The hydrogen concentration in the films was measured by using elastic recoil detection (ERD) analysis. Since the absorption strength of the CHn band strongly depends on the chemical structure of the films, the proportionality coefficients were obtained by the band separation of the IR spectrum as A(CH) = 3.85 × 1021 atoms/cm2, A(CH2) = 3.85 × 1020 atoms/cm2 and A(CH3) = 3.65 × 1020 atoms/cm2. These values can be applicable universally to a-C:H and a-SiC:H films.

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.

Resonant coherent excitation and its radiative deexcitation were studied for hydrogen-like heavy ions axially channeled in a single crystal. The 6th order resonance for Ne 9+ ions along the 〈111〉 axis of a gold crystal was found at the incident energy of 88 MeV by measuring the charge state distribution after passing through the crystal. The intensity of the Ne 9+ Kα X-ray (1.02 keV) normalized to the Au M X-rays was measured for the 〈111〉-aligned and random directions of the incident beam. An enhancement in the Ne 9+ deexcitation X-rays at the resonance was detected for the first time.

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.

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.