Takato Hirayama

Characteristics of the Tokyo Electron-Beam Ion Trap.

We have constructed a new Electron Beam Ion Trap (EBIT). Over recent months, we have operated this device and obtained some experimental results. In this paper, we show the performance of this EBIT by illustrating these results.

An overview of the Tokyo electron beam ion trap

A new Electron Beam Ion Trap has recently been completed in Tokyo. The general features of the apparatus, design and operation are given. This paper also surveys the planned and ongoing experimental program.

Energy partitioning in the dissociation reaction Ar3 + → Ar2 + + Ar

Threshold‐photoelectron photoion coincidence (TPEPICO) spectra of argon clusters ionized with synchrotron radiation have been observed, and the average kinetic energy of Ar2+, which originates from Ar3+, has been estimated. All the line shapes of the Ar2+ ion observed in the TPEPICO spectra have been appropriately simulated in terms of superposition of a sharp and a broad Gaussian function, where the sharp Gaussian function corresponds to ionization of the argon dimer Ar2. The observed line shapes agree very well with the simulated ones, implying that the excess energy in the Ar3 ionization is thermally or quasithermally partitioned to translational energy of the fragment species. From the average kinetic energies of Ar2+, it has been found that the percentage of excess energy in Ar3+, that is partitioned into the total translational energy of the fragment species, is dependent on the excitation energy. The percentage is slightly less than the value of 40% expected from statistical theory. It has also bee...

Electron stimulated desorption from the surface of solid Ne: kinetic energy and angular distributions of desorbed metastables

Abstract Electron stimulated desorption of metastable species from the surface of solid Ne was investigated. Ne metastables through various desorption channels were identified in the kinetic energy distributions which were obtained by time-of-flight measurement. The energy distribution is identical to that obtained by photo-stimulated desorption experiments. Two dominant species observed in the time-of-flight spectrum showed different characteristics in the angular distribution of desorption. The lower kinetic energy one, which has a kinetic energy of ∼ 0.18 eV and was attributed to a “cavity-ejection” mechanism, had a sharp angular distribution along the surface normal with FWHM of ∼ 30°. The other one, which has ∼ 1.4 eV and was attributed to a “excimer-dissociation” mechanism, did not show a preferential direction of desorption.

Electron impact ionization of O+, S+ and S2+ ions

Absolute cross sections for electron impact single ionization of O + , S + and S 2+ ions have been measured at an electron impact energy range from below threshold to 1000 eV, using the crossed beam technique. The measured cross sections for O + ions are reproduced quite well with the semiempirical Lotz formula over the whole energy range investigated. The measured cross sections for S + and S 2+ ions show a more rapid rise from the threshold to their peak than those expected from the Lotz formula. For S 2+ ions, another small bump beginning at 120 eV is observed, where no level exists that may contribute to any direct or indirect ionization processes.

Time-of-flight measurement of desorbed particles from solid rare gases using synchrotron radiation

Photo-desorbed species from a condensed layer of rare gas were analysed by Time-of-Flight (TOF) technique. The excitation source was monochromatized synchrotron radiation in the vuv region. TOF spectra were obtained by either chopping an incident radiation or applying pulse potential to the sample. Thickness and temperature of the condensed rare gas layers (Ar, Kr, and Xe) were 500–3000 atomic layers and 20 K, respectively. Desorbed ions from the surface of solid Kr and Xe mainly originated from residual gases (H2O, CO, and Ar) which possibly adsorbed on the rare gas matrix. The desorption yield of these species was enhanced around the optical absorption band of the matrix layers: 5–10 nm for Kr 3d and 10–12 nm for Xe 4d.

Characteristics of the beam line at the Tokyo electron beam ion trap

A new beam line has been constructed to make various experiments with highly charged ions produced in an electron beam ion trap. The characteristics of the beam line are reported. Ions are extracted upward into the beam line and are deflected horizontally and analyzed for the charge states by a double-focusing magnet. To obtain sufficient intensity, several electrostatic lenses are located. A quadrupole lens is used to correct the distorted beam shape before an entrance slit of the magnet. Ions are accelerated during the passing of the analyzing magnet to obtain the higher mass resolution. Trajectories were calculated by a ray-tracing program and matrix multiplication for lens actions. Preliminary results are shown here for investigation of characteristics of extracted ions.

The present status of the Tokyo electron beam ion trap

Recent progress of the Tokyo electron beam ion trap (Tokyo-EBIT) project is described. The Tokyo-EBIT is of an original design and construction with several features different from other EBITs in the world. The maximum energy and current of the electron beam are designed to be 340 keV and 300 mA with a magnetic field of 4.5 T. The ongoing and planned physics experiments are described and the results for the initial stage of operation of the Tokyo-EBIT are given.

Electron Impact Ionization of C + , N + and P + Ions

Absolute cross sections for electron impact ionization of C + , N + and P + ions have been measured for electron energies from threshold up to 1000 eV, using the crossed beam technique. The measured cross sections for both C + and N + ions are in good agreement with the semiempirical Lotz formula over the whole energy range investigated, and also with those previously reported except for near threshold. The results for P + ions show a more rapid rise from the threshold and larger values around the peak than those calculated with the Lotz formula.

Absolute yields of the exciton-induced desorption at the surface of solid rare gases

Absolute yields of the photo-induced desorption at the surface of solid rare gases are studied in the excitonic excitation region. Both metastable and total desorption yields depend strongly on excitation energy and film thickness of rare gas solids. The absolute desorption yields and their dependence on film thickness are quantitatively reproduced by a simulation based on the diffusion of excitons in the bulk and the kinetic energy release by a cavity ejection mechanism and an excimer dissociation mechanism followed by internal sputtering.