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The proton yields from Si(111)7 × 7 and Si(100)2 × 1 reconstructed surfaces irradiated with slow ( v 0.25 v Bohr ) highly charged Xe ions are obtained. H 2 O molecules adsorbed over time on the surfaces at room temperature, under ultra-high vacuum can be detected as an increase of the proton yield. For the Si(100)2 × 1 surface, the proton yield with HCI-irradiation time is discussed based on temporal variation of the H 2 O coverage. The proton desorption efficiency with Xe 50 + is more than about ten times and twice as compared with Xe 29 + and Xe 44 + , respectively. For the Si(111)7 × 7 and Si(100)2 × 1 surfaces, the proton yield in each time increases with the charge states q to the power of 6 and 4, respectively, and is changed with time with the power laws held on.

The interaction of slow iodine highly charged ions (HCIs), I q + , with a hydrogen-terminated Si(1 1 1)-(1 × 1) surface was investigated for a wide range of q from 17 to 53 (fully stripped ion). The coincidence measurement for secondary ion emission reveals that correlated sputtering is enhanced toward higher q , that is, while Si + sputtering is anti-correlated with H + , multiple H + are simultaneously emitted. The direct observation of the HCI-bombarded surface with a scanning tunneling microscope supports the result of the multiple hydrogen emission. These results are discussed in consideration of the strong Coulomb interaction of incident HCIs with the surface and subsurface atoms.

Highly charged ions produced in an electron beam ion trap, I q + , q = 10–50, were transmitted through a tapered glass capillary having diameter of 50 μ m at the end. We found that for a particular beam current, there exists an optimum tilting angle of the capillary in which a steady output of ions is observed, while for smaller angles, the ion counts first rise, then gradually decay on a time scale of minutes. In the case of steady transmission, the charge state distribution is found to be slightly towards the lower side.

The electron beam ion trap (EBIT) in Tokyo was constructed about 10 years after the first EBIT at Lawrence Livermore National Laboratory was built, and has been being stably operated since then. In this paper, we present recent experimental activities at the Tokyo EBIT. In particular, experiments utilizing slow, very highly charged ion beams extracted from the EBIT are reported. PACS Nos.: 39.10.+j, 32.30.Rj, 34.50.Dy, 34.80.Kw

We have observed radiation effect in collision of slow highly charged ions with the following target materials; a SiO2 thin film, a Si(1 1 1)-(7 × 7) surface and a hydrogen terminated Si(1 1 1)-(1 × 1) surface. Secondary ion mass spectrometry and scanning tunneling microscopy revealed some features due to “potential sputtering”; (a) strong dependence of secondary particle emission on the surface condition, (b) high yield of positive ion emission including cluster fragments and (c) creation of nanometer sized surface structure. The mechanism for the potential sputtering is briefly discussed, based on the “Coulomb explosion” model.

Some results on surface modification of Si and graphite with highly charged ions (HCIs) are presented. Modified surfaces were observed using scanning tunneling microscopy. Crater-like structure with a diameter in nm region is formed on a Si(1 1 1)-(7 × 7) surface by the incidence of a single HCI. The protrusion structure is formed on a highly oriented pyrolytic graphite surface on the other hand, and the structure becomes an active site for molecular adsorption. A new, intense HCI source and an experimental apparatus are under development in order to process and observe aligned nanostructures created by the impact of collimated HCI beam.

Interference between radiative and dielectronic recombination in electron and highly charged Bi ion collisions has been studied by observing emitted x-rays with the Tokyo electron beam ion trap. The so-called Fano line shapes were fitted to the KLL DR resonant profiles observed as the enhancement of the x-ray counts. The shape parameters q have been determined similarly to the previous experiments for highly charged U [D A Knapp et al 1995 Phys. Rev. Lett. 74 54] and Hg ions [A J Gonzalez Martinez et al 2005 Phys. Rev. Lett. 94 20320]. The present results were compared to the previous results.

We present scanning tunneling microscope (STM) images, atomically resolved, of the nanostructures on various kinds of surfaces bombarded with highly charged ions (HCIs). In the STM image of a highly oriented pyrolytic graphite surface (Xe29+-impact), a protrusion structure was observed with √3 × √3 R30° surface reconstruction around the impact site. A crater-like structure was formed on a Si(111)-(7×7) surface by an I50+-HCI impact. An atomic image of ~0.1 nm in height was also observed around the missing topmost layers of the crater. In the case of a TiO2(110) surface, a typical nanostructure induced by a single I51+-HCI impact, relatively larger crater structure than that on the Si surface was observed; the height (~1 nm) was higher than the atomic step of the TiO2(110)-(1×1) surface (~0.3 nm) and the depth reached at least 1.5 nm. This implies that the degree of the HCI-radiation effect on the TiO2 surface is higher than that of the Si(111) case.

X-rays emitted in the collisions of highly charged ions with a surface have been measured to investigate dissipation schemes of their potential energies. While 8.1% of the potential energy was dissipated in the collisions of He-like I ions with a W surface, 29.1% has been dissipated in the case of He-like Bi ions. The x-ray emissions play significant roles in the dissipation of the potential energies in the interaction of highly charged heavy ions with the surface.

Recent activities at the Tokyo electron beam ion trap related to observations of resonant processes in the collisions of electrons with open-shell highly charged ions are reported. Extracted ion observations and high resolution x-ray spectroscopic observations have been applied to resolve the contribution from different charge states. In particular, dielectronic recombination (DR) of a H-like ion have been observed by high resolution x-ray spectroscopy for the first time. The DR satellite spectra obtained in the present experiment are compared with theoretical spectra.

We have observed surface chemical reactions which occur at the impact sites on a Si(1 1 1)-(7 × 7) surface and a highly oriented pyrolytic graphite (HOPG) surface bombarded by highly charged ions (HCIs) by using a scanning tunneling microscope (STM). Crater structures are formed on the Si(1 1 1)-(7 × 7) surface by single I50+-impacts. STM-observation for the early step of oxidation on the surface suggests that the impact site is so active that dangling bonds created by HCI impacts are immediately quenched by reaction with residual gas molecules. We show also the selective adsorption of organic molecules at a HCI-induced impact site on the HOPG surface.

Using scanning tunneling microscopy (STM) and time of flight secondary ion mass spectrometry (TOF/SIMS), we observed radiation effects on a Si(1 1 1)-(7 × 7) surface in the collision of a single highly charged ion (HCI) with a charge state q up to q = 50. The STM observation with atomic resolution revealed that a nanometer sized crater-like structure was created by a single HCI impact, where the size increased rapidly with q . The secondary ion yields also increased with q in which multiply charged Si ions (Si n + ) were clearly observed in higher q HCI-collisions. The sputtering mechanism is briefly discussed, based on the so-called Coulomb explosion model.

We have observed secondary particles and photons emitted from hydrogen terminated Si(1 1 1) 1 × 1 surfaces in the interactions with highly charged ions (HCIs) of iodine having a wide range of charge state, q, from I17+ up to I53+, fully stripped iodine ion. A TOF-SIMS (time-of-flight secondary ion mass spectrometry) apparatus has been used to investigate secondary emissions where protons are dominant signals in the TOF spectra. Measured yields of H+ and H 2 + show strong q-dependences, proportional to q3.4 and q5, respectively. For Si+, while the yield remains constant for q

We have investigated surface modification by highly charged ions (HCIs) on highly oriented pyrolytic graphite (HOPG) surfaces with Raman spectroscopy and scanning tunneling microscopy. The xenon-HCIs having various charges up to 48+ were incident on HOPG samples with an identical collision velocity (5 × 10 5 m/s). In Raman spectra, disorder induced peaks (D peak) appeared around 1355 cm −1 in addition to narrower, persistent peaks (G peak) at 1580 cm −1 which are characteristic of unirradiated HOPG. The intensity ratio of the D peak to the G peak is much larger than that of HOPG irradiated with singly charged ions (SCIs) at the same fluence. By the annealing treatment, the intensity of the D peak decreased as small as practically unobservable. In the microscopic observation, on the other hand, protrusion nanostructures induced by HCI impacts did not disappear completely although their volume decreased drastically. From such relaxation dynamics, it is made clear that not only point and dimmer vacancies which is created in common with SCI irradiation, but also “cluster vacancies” are formed at the surface and subsurface.

The adsorption, desorption and vibrational excitation dynamics of methane monolayer physisorbed on a Ag(1 1 1) surface was studied by LEED and HREELS measurements. For LEED observation, electron stimulated desorption of adsorbed CH4 was obvious even at a minimized incident electron current of 1 nA, and the result suggests the possibility of leftover of electron stimulated reaction on the substrate that cannot be identified by LEED nor desorb at raised temperature. Mode dependence of the width of energy loss peak was observed in the HREEL spectra. The excitation of the vibrational mode with sharper width is mainly associated with dipole scattering mechanism.

We have observed mass spectra of desorbed ions from a clean and a hydrogen terminated silicon surfaces by the impact of highly charged ions (Xe q + , q = 26, 34, 44 and 50). The released ions mainly consist of proton for both surfaces, and the quantum yield of proton desorption for hydrogen terminated surface exceeds unity. It is seemed that charge state dependence of ion yield roughly follows q 5 rule reported by Kuroki et al. in the experiments for lower charge states.

We have observed secondary particle emission in collision of HCI with Si and HOPG surfaces. For HOPG, we have measured the number of secondary electrons and the number of dot structures on the surface as the imprint of the incidence by STM. The single ion impact is surely observable with almost 100% efficiency by detecting an event of the secondary electron emission. For hydrogen terminated Si(1 1 1), H+, H 2 + , H 3 + , C+ and Si+ ions have been detected. The proton sputtering yield, which depends on the charge of HCI, has been examined.

We have observed positive secondary ion mass spectra from highly oriented pyrolytic graphite (HOPG) and hydrogen terminated Si (Si–H) surfaces irradiated with highly charged ions (HCIs). In the spectra from HOPG irradiated by HCIs of Xe q + , carbon clusters up to C 5 + were observed in addition to hydrogenated carbon cluster peaks. On the other hand, in the spectra from the Si(1 1 1)–H, peaks of H + and H 2 + were detected dominantly with weak signals for C + and Si + . Strong dependence of peak intensities of these spectra on q were also observed. It is shown that sputtering phenomena are closely related to deposition of potential energy of HCIs onto the surfaces and the HCI-probe can be applied to the high sensitivity surface analysis.

Double charge transfer spectra of NO2+ were observed using 1.5-keV H+ projectiles. The vibrational progression of the X 2 Σ + state was resolved. For the unresolved vibrational peaks of the A 2 Π state, peak-fitting procedures determined their energies and intensities. From the present observation, the ν=0 energy of the A 2 Π state given by threshold photoelectrons coincidence method was corrected, which confirmed the independent recent work by Eland et al. This correction was concluded from the smooth vibrational distributions, suggesting the Franck–Condon behavior. So Franck–Condon analyses were performed to deduce the bond lengths for the X 2 Σ + and A 2 Π states, in a similar manner developed for photoelectron spectroscopy. For the X 2 Σ + state, the error of the bond length thus estimated is 0.005 A compared with the rotational data. For another quantitative check, high-level ab initio calculations have also been done. The theoretical Franck–Condon profiles well reproduced the experimental spectra, verifying the validity of the Franck–Condon principle.

A single-crystal film of α-Al2O3 was grown on the Ru(0001) surface with thicknesses of 6.5, 12 and 30 A and a overlayer plasmon was found for 6.5 and 12 A thick films. The dispersion relation as a function of wavevector parallel to the surface was observed to have a negative gradient in the direction using angle-resolved electron-energy-loss spectroscopy (AREELS). This relation is as expected for the overlayer plasmon due to the collective motion of electrons in the oxide layer along the direction perpendicular to the surface. The energy of the overlayer plasmon is closely related to the interband transition energy: the latter plus depolarization shift equals the former. From the energy loss at the point and the dispersion relation we arrived at the conclusion that intrinsic bandgap narrowing occurred. AREELS measurements with τ = 12 and 30 A support that the overlayer plasmon leading to the bandgap narrowing is caused by a strong interaction of the excited electron and hole inside the thin film with the image dipole induced in the metal substrate.

In electron interactions with highly charged Fe ions, the X-ray spectra were theoretically analysed and compared with the experimental results at the Tokyo EBIT. In the present analysis, cross sections for dielectronic recombination, resonance excitation, resonance recombination, and direct excitation were calculated by use of the distorted wave method. Simulated spectra were obtained by convoluting the calculated cross sections with the experimental beam energy resolution and X-ray detector resolution, which are in close agreement with the experimental observations. Based on our calculations including polarization effects, we estimate the charge state balance: He-like Fe 24+ (74%), Li-like Fe 23+ (18%), and Be-like Fe 22+ (8%), and the ion density in the trap to be 6.5 ‐ 8.5 × 10 8 cm -3 . The present calculations were also compared with the previous high-resolution measurements of the KLL resonances in He-like

A Thomson scattering system has been installed at the Tokyo electron beam ion trap for probing characteristics of the electron beam. A YVO4 green laser beam was injected antiparallel to the electron beam. The image of the Thomson scattering light from the electron beam has been observed using a charged-coupled device camera. By using a combination of interference filters, the spectral distribution of the Thomson scattering light has been measured. The Doppler shift observed for the scattered light is consistent with the beam energy. The beam radius dependence was investigated as a function of the beam energy, the beam current, and the magnetic field at the trap region. The variation of the measured beam radius against the beam current and the magnetic field were similar to those in Herrmann’s prediction. The beam radius as a function of the beam energy was also similar to Herrmann’s prediction but seemed to become larger at low energy.

We have observed a vibrational progression of C2H22+ with double charge transfer (DCT) spectroscopy. From an exploratory calculation, the progression is assigned to the symmetric C–C stretching mode of the lowest singlet 1 Δ g state with linear geometry. The observed structure is well reproduced with the theoretical Franck–Condon (FC) factors obtained from the potential curves of the 1 Δ g and first-excited 1 Σ g + states along the normal C–C stretching coordinate. Multi-reference CI calculations reveal a predominant contribution of the 1 Δ g state. These results suggest that the DCT process can probe dicationic states of polyatomic molecules like acetylene with resort to the FC principle.

We have developed a double charge transfer (DCT) spectroscope to study doubly charged molecular ions (dications). In the course of the development, DCT spectra of N2, CO, and NO has been ob served with energy resolution of about 0.5 eV. The spectral profiles observed have shown the Franck-Condon (FC) behavior. We have made an effort to in crease the resolution up to about 140 meV, which is much better than those (1–1.5 eV) reported in previous works. In the present measurement, the vibrationally resolved DCT spectrum for N2++ could be obtained for the first time. The observed peak structures agree well with those calculated using FC factors, differing meaningfully from the spectra taken with Auger electron spectroscopy (AES) and thresh old photoelectrons coincidence (TPEsCO) spectroscopy. The DCT spectroscopy might be a powerful method to study the potential curves of short-lived dications.

A remarkable improvement of ab initio calculations was obtained for wavelengths of (3d4) J = 3 2 forbid den transition. Present calculations reduced the long-standing discrepancy from measurements down to less than 0.2% for most high-Z titanium-like ions. In the present calculations, a large extent of configuration space was included so that most important many-body effects were taken into account. To this end, the linearized second-order Brillouin-Wigner perturbation theory was employed with optimized spin-orbitals. Transition probability and atomic g-factor were also calculated with the improved atomic wave functions.

Doubly charged molecular ions (dications) of N 2 and CO have been studied using a double charge transfer (DCT) spectrometer capable of resolving vibrational levels. The vibrational structures of low-lying singlet states are observed in the translational energy spectra of H − ions produced by double electron capture collisions of H + projectiles. The observed spectra are well reproduced using the theoretical Franck–Condon (FC) profiles calculated from the best available ab initio potential curves. This suggests that the DCT process obeys the FC principle, i.e., the vertical transition from a neutral molecule to the corresponding dication.

The microwave spectrum of CsO has been observed and analyzed, not only in the ground vibrational state, but also in the v=1–3 excited vibrational states. The CsO radical was generated by the reaction of N2O with Cs vapor, which was produced by the reaction of Li metal with CsCl at 500–530 °C. The observed spectra were found to conform to those expected for a 2Σ diatomic molecule, thereby establishing the ground electronic state of CsO to be of 2Σ. The observed rotational and centrifugal distortion constants yielded the equilibrium bond length and the harmonic vibrational frequency to be 2.300 745 (16) A and 356.78 (11) cm−1, respectively, based on the Born–Oppenheimer approximation. A careful examination of the observed spectral pattern definitely concluded that the spin-rotation interaction constant was positive, at variance with the expectation from a simple 2Σ/2Π two-states interaction. This observation was interpreted by assuming positive contributions from higher excited electronic states which super...

The rotational spectra of 85RbO in the ground- and the first excited vibrational states and of 87RbO in the ground vibrational state were observed in the millimeter- and submillimeter-wave region. The RbO radical was generated in a high-temperature absorption cell by the reaction of N2O with Rb vapor, which was produced in the cell by heating a mixture of RbCl and lithium metal to 500–550 °C. Analysis of the observed spectra yielded the rotational and centrifugal distortion constants, spin–rotation interaction constants, and hyperfine interaction constants. The bond length and the vibrational frequency were calculated from the rotational and centrifugal distortion constants to be 2.254 193 1 (15) A and 387.22 (20) cm−1, respectively, for 85RbO. The ground electronic state of RbO was confirmed to be 2Σ, and the low-lying 2Π state was estimated to be located at 650–700 cm−1 above the ground state by using a second-order perturbation expression with the vibrational energy in the denominator for the spin–rota...

When highly charged ions were implanted on a graphite surface with monitoring of secondary electrons emitted at the point of incidence, dot structures on the surface, as the imprint of ion incidence, were observed by a scanning tunneling microscope (STM). The number of events of secondary electron emission and the number of imprints coincided, which indicates that a method of detecting incident events of ion implantation of almost 100% efficiency has been established by using highly charged ions.

We report on the first observation of surface second-harmonic generation (SHG) during the molecular beam epitaxy (MBE) growth of GaAs homoepitaxy on a GaAs(100) substrate. We used a specific optical arrangement which enabled us to observe the surface SHG and the reflection high-energy electron diffraction (RHEED) pattern simultaneously. We found that the surface SH intensity increased according to a change from an As-stabilized to a Ga-stabilized surface due to an interruption of the As flux while keeping the Ga flux constant. We show that the surface SH intensity has its maximum value when there is about 1 monolayer (ML) of excess Ga on the surface.

The fundamental vibrational band of the 7LiO radical in the ground electronic state X 2Πi was observed in a region from 720 to 850 cm−1 using a source frequency modulation infrared diode laser spectrometer. Radicals were generated in a high‐temperature cell by the reaction of lithium metal vapor with nitrous oxide. The observed spectrum was analyzed together with the radio‐frequency and microwave spectra already reported. It was found that the vibration‐rotation Hamiltonian employed in a previous paper was insufficient to fit all of the observed spectra simultaneously. The Hamiltonian was thus extended to include higher‐order corrections for the centrifugal distortion and Λ‐type doubling terms, and was used to derive molecular parameters.

We report on the first observation of the twofold rotational anisotropy of second-harmonic generation (SHG) in the reflected light from a noncentrosymmetric crystal surface of GaAs(001). We interpret this as meaning that the interference of surface SHG and dipole-allowed bulk SHG having fourfold symmetry results in twofold anisotropy. The degree of anisotropy changes according to the surface reconstruction.

This paper reports a systematic study of the dependence on atomic number of the dielectronic recombination resonance strengths for He-like, Li-like and Be-like ions. Recent measurements of dielectronic recombination resonance strengths for the KLL and KLM manifolds for iron, yttrium, iodine, holmium, and bismuth are also described. The resonance strengths were normalized to calculated electron impact ionization cross sections. The measured resonance strengths generally agree well with theoretical calculations using the distorted wave approximation. However, KLM resonance strength measurements on high atomic number open-shell ions gave higher values than those suggested by calculations. Using recently measured data, along with existing results, scaling laws have been generated as a function of atomic number for He-like, Li-like, and Be-like ions in the KLL and KLM manifolds.

The vibration—rotation transitions of aluminum monohydride were observed using an infrared diode laser spectrometer. Aluminum monohydride was generated by the reaction of heated aluminum metal with hydrogen gas. The observed spectra were combined with those for aluminum monodeuteride to determine mass-independent parameters and mass scaling coefficients.

Allyl radicals were generated by the photolysis of 1,5‐hexadiene at 193 nm and were detected by observing the ν11, i.e., CH2 symmetric wagging band by infrared diode laser kinetic spectroscopy. The observed spectrum showed clearly the effect of nuclear‐spin statistical weights, establishing the presence of a Cb2 axis in the molecule. The spin–rotation splitting was not resolved; only some high‐Ka lines were found broader than others, placing an upper limit for the eaa constant at about 200 MHz or less. The rotational constants derived from the observed spectrum indicate that the molecule is essentially planar. The C–C bond length and the CCC bond angle were calculated from the ground‐state rotational constants to be 1.3869 A and 123.96°, respectively, where structural parameters involving hydrogens were fixed to those of ab initio values.

Millimeter- and submillimeter-wave spectroscopy was applied to an alkali heterodimer molecule NaK. The NaK molecule was generated in a heated stainless steel pipe, which also served as an absorption cell. Rotational transitions of J = 14 to 69 were observed for the vibrational states of v = 0 to 6 in the ground electronic state. A set of Dunham coefficients which reproduced the observed transition frequencies within experimental errors were determined with much higher precision than in previous studies. The possibility of detecting NaK in the circumstellar atmosphere was briefly discussed.

Several techniques for injecting various metallic elements into an electron beam ion trap are presented. They have been developed by making use of a metal vapor vacuum are source, a wire probe, an alkali ion source, gaseous metallic compounds, and so on. These techniques are needed to systematically investigate highly charged ions along isoelectronic sequences. Merits and demerits of these methods are discussed.

The rotational spectrum of NaBH4 was observed in the millimeter‐wave region using a high temperature absorption cell. The observed spectrum of NaBH4 showed the pattern of a symmetric top molecule: Strong and weak for K=3n and 3n±1, respectively, because of the nuclear spin statistical weight for C3v symmetry. The rotational and centrifugal distortion constants for the 11B and 10B species were determined. The observed rotational constants of Na11BH4 and Na10BH4, combined with the assumption that r(B–Hb)−r(B−Ht)=0.04 A and θ (Hb–B–Ht)=111°, gave estimates for r(Na–B) and r(B–Hb) to be 2.308±0.006 A and 1.28±0.10 A, respectively, where the uncertainties are mainly due to those of the assumed values. This bond length obtained for Na–B is much shorter than the reported value in crystal: 3.08 A. The bond lengths derived indicate that NaBH4 has a tridentate molecular structure with three bridging hydrogens. This result agrees with those of ab initio calculations.

Fluorescence of an organic-dye thin film induced by the impact of individual slow iodine highly charged ions (HCIs) has been investigated for a wide range of charge states $q$ from 30 (V-like ion) to 52 (H-like ion). Combined analysis of emission yields of the visible and x-ray photons reveal that $L$ Auger electrons emitted in the neutralization process of the HCI play an important role in the electronic excitation of the target. It is also noted that, contrary to the energy dissipation of $L$ Auger electrons, x rays carry away a large fraction of the potential energy of a HCI with higher $q$ than the Ne-like ion.

A ${\text{TiO}}_{2}(110)$ surface was bombarded with slow iodine highly charged ions (HCIs), ${\text{I}}^{q+}$, having a wide range of charge states from Ni-like ${\text{I}}^{25+}$ to He-like ${\text{I}}^{51+}$. A scanning tunneling microscopic observation revealed that nanometer-sized hillock or crater structures were created by individual HCI impacts and the size of the structures increased with $q$. In time-of-flight secondary-ion mass spectrometry, a strong $q$ dependence of the secondary-ion yield of ${\text{O}}^{+}$, $Y({\text{O}}^{+})$ was observed; $Y({\text{O}}^{+})$ exceeded $Y({\text{Ti}}^{+})$ for $q\ensuremath{\sim}35$. We discuss that these secondary effects are the results of the strong coupling of HCIs with electrons in the valence band of the target.

Through the coincidence measurement of x rays with secondary electrons, x-ray spectra, and their yields have been measured in the interaction of H-like and bare highly charged ions (${\text{I}}^{52+}$ and ${\text{I}}^{53+}$) with different target materials (Be, C, Cu, and W). $K$ x-ray yields are independent of the material, where the $K$ vacancies are almost filled through $K$ x-ray emission. $L$ x-ray yields are affected by the electronic state of the targets and the interacting projectiles, because the states involved in the electron capture depend on the level structure of the projectile and the target and the possible number of electrons captured by the highly charged ions is different depending on the number of electrons in the target states $(2{n}^{2})$ which are resonant transferred to the projectile states in the dynamics of below-surface neutralization and deexcitation.

The millimeter-wave spectrum of the GeF + ion in the ground vibrational state was observed for four major isotopic species. The ion was generated in a free-space absorption cell by a hollow cathode discharge in GeF 4 mixed with Ar. The magnetic field effect was used to discriminate the absorption lines of the ion from those of neutral species; the intensity of the ion lines decreased markedly on applicatin of an axial magnetic field of about 170 G. The observed millimeter-wave spectrum was combined with a previously reported diode laser spectrum in an analysis to determine mass-independent Dunham coefficients. The equilibrium bond length is r e = 1.664821 A.

The rotational spectrum of the aluminum monoxide radical in the ground electronic state X 2Sigma(+) was observed in the millimeter- and submillimeter-wave region. Aluminum monoxide radicals were generated directly in a flow reactor absorption cell by the reaction of N2O with aluminum vaporized from a high-temperature crucible. The observed spectrum was analyzed to yield molecular constants including the rotational constant, centrifugal distortion constant, spin-rotation interaction constant, magnetic hyperfine interaction constants, and nuclear quadrupole coupling constant.

X-ray emission yields, which are defined as the total number of emitted x-ray photons per incident ion, and dissipated fractions of potential energies through x-ray emission have been measured for slow highly charged ions of I, Pr, Ho, and Bi colliding with a W surface. A larger amount of potential energy was consumed for the x-ray emission with increasing the atomic number and the charge state. The present measurements show that x-ray emission is one of the main decay channels of hollow atoms produced in collisions of very highly charged ions of heavy elements.

X-ray emission yields from highly charged iodine ions incident on a hydrogen terminated silicon surface were measured. It was found that the $K$ shell vacancies were filled through x-ray transitions with the probability of approximately 100%, while only about 20% of $L$ shell vacancies were filled through x-ray transitions and almost all the $M$ shell vacancies were filled nonradiatively. Dissipation of the potential energy ${E}_{p}$ of an incident ion through x-ray emissions increases gradually with the number of $L$ shell vacancies and amounts to 10% of ${E}_{p}$ for the He-like ${\mathrm{I}}^{51+}$ ion. 30 to 40 % of ${E}_{p}$ for ${\mathrm{I}}^{52+}$ and ${\mathrm{I}}^{53+}$ with $K$ shell vacancies was measured to be dissipated mainly by $K$ x-ray emissions.

The double-charge-transfer (DCT) spectrum of O{sub 2}{sup 2+} has been recorded at 140 meV resolution using 1.5 keV H{sup +} projectiles. Electronic bands of the low-lying triplet states, namely A {sup 3}{sigma}{sub u}{sup +}, W {sup 3}{delta}{sub u}, B {sup 3}{pi}{sub g}, and B{sup '} {sup 3}{sigma}{sub u}{sup -}, have been resolved. Assuming that the observed bands directly reflect the Franck-Condon (FC) profiles, potential-energy curves of the A {sup 3}{sigma}{sub u}{sup +}, W {sup 3}{delta}{sub u}, and B{sup '} {sup 3}{sigma}{sub u}{sup -} states within the FC region are determined based on the reflection approximation. For a quantitative check of the results, complete active space self-consistent-field and multireference configuration-interaction calculations have been performed to predict the potential-energy curves and the FC profiles. The calculated energy curves agree well with the experimentally derived ones. The theoretical FC profiles reproduced well the band shapes observed by both present DCT and previous Doppler-free kinetic-energy release methods. However, our results cast doubt on the previous assignment of luminescence to the O{sub 2}{sup 2+} B {sup 3}{pi}{sub g}{yields}A {sup 3}{sigma}{sub u}{sup +} transition and the observed bound level of the A {sup 3}{sigma}{sub u}{sup +} state by the previous threshold photoelectron coincidence experiment.

A simple pulse‐operated plasma gun, which is a combination of a pulsed‐solenoid valve and an electrode to induce an electric discharge in gas at the outlet is described. The performance of the pulsed‐plasma‐beam gun was tested by carrying out hydrogen‐plasma deoxidization of a GaAs wafer.

The symmetry properties of surface second-harmonic generation (SHG) have been studied for compound semiconductor materials, such as GaAs, in which the nonlinear susceptibility of the bulk does not vanish. The rotation-angle dependence (anisotropy) of the intensity of surface-reflection SHG for singular as well as vicinal surfaces, with and without surface tensor components, was examined and compared with the existing experimental results.