Tetsuo Nagata

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.

Ionic fragmentation following the 3d core excitation of Sn(CH3)4 by soft X-rays

Abstract Ionic fragmentation following the core-level photoionization of Sn(CH 3 ) 4 has been studied in the photon energy region between 400 and 600 eV by use of monochromatized synchrotron radiation and time-of-flight mass spectrometry. The production of small ionic fragments Sn + , CH m + ( m =0–2), and H + is strongly enhanced by Sn 3d photoionization above 500 eV. Fragmentation processes yielding such small ions are interpreted as decomposition of the multiply charged ion Sn(CH 3 ) 4 q + ( q = 3–5) produced by the vacancy cascade via Auger and/or Coster-Kronig transitions following the Sn 3d photoionization.

Single and double photoionisation of Ca atoms between 35 and 42 nm

Photoionisation of Ca atoms has been investigated by means of a time-of-flight mass spectrometer coupled with a source of monochromatised synchrotron radiation and an atomic Ca beam. Relative photoionisation cross sections (q+ for single photoionisation and q2+ for double photoionisation, as well as the ratio R=q2+/q+) have been measured in the wavelength range 35-42 nm with a 0.15 nm bandwidth. Comparison with the photoabsorption data of Mansfield and Newsom (1977) shows a good correspondence in the peak structure between the absorption resonance and the Ca2+ yield for proton energies above the lowest 3p ionisation limit. The variation of R with wavelength exhibits a step behaviour which correlates with some of the 3p ionisation limits.

Site-specific fragmentation following inner-core level excitation of Pb(CH3)4 in the vapor phase

Abstract Ionic fragmentation following inner-shell (Pb 5p and 4f, C 1 s) excitation of Pb (CH 3 ) 4 has been studied in the vapor phase by use of synchrotron radiation and time-of-flight mass spectrometry. The C 1 s ionization is followed by KVV Auger process, and the fragmentation proceeds by way of the doubly charged parent ion. The Pb 5p or 4f ionization is followed by a cascade of Auger events, and the fragmentation proceeds by way of the triply or higher multiply charged parent ions. The fragmentation pattern changes significantly depending on the site of the core electrons excited (Pb or C).

Charge Changing Collisions of Atomic Beams in Alkali-Metal Vapors. IV. Total Cross Sections for Single-Electron Capture by H+ Ion and H(1s) Atom

Total cross sections σ +0 and σ 0- for single-electron capture by H + ion and H(1s) atom during passage through vapors of Cs, Rb, K and Na have been measured by observing the growth of fast collision products in the projectile energy range 0.4–5.0 keV. The partial cross sections σ m and σ g (σ +0 =σ m +σ g ), which are the cross sections eventually leading to formation of H(2s) and H(1s), respectively, have also been determined with the aid of the metastable atom fraction f 2s data obtained previously. Each σ m curve has noticeable structure composed of two humps. The total cross sections σ +0 also have, although not noticeable, similar structure, indicating the existence of some secondary inferference effects between the charge exchange channel and other inelastic or elastic channel. In the case of Cs target, comparison with other experimental and theoretical data is made.

Relative counting efficiencies of ion charge-states by microchannel plate

Abstract Relative detection efficiencies D q + of ions with different charges and impact energies in single-ion counting mode with microchannel plates (MCP, Hamamatsu F1094-21S) have been examined for Li q + , Ar q + , Ba p + and Yb p + ions ( q =1, 2 and p =1, 2, 3). The incident ion energy ranges from 1.1 to 15 keV. The efficiencies D q + for a given atom, plotted as a function of incident ion energy E K , lie on a unique curve. This comes originally from the fact that the secondary electron emission at the input channel-wall of MCP is dominated mainly by kinetic emission processes and little by potential emission processes in the keV energy range. When ions with different charges but the same E K value of a given atomic species are detected, almost equal detection efficiencies are ensured as far as E K is larger than 4 keV. Nearly equal detection efficiencies for singly and doubly charged ions accelerated by the same voltage are attainable at higher acceleration voltages for heavier ions, e.g., 5 kV for Ar + and Ar 2+ ions and about 10 kV for Ba + and Ba 2+ ions.

New Window Resonances in the Potassium 3s Photoabsorption Spectrum

The photoion spectrum of atomic potassium was measured over the 3 s → n p excitation region with the photoion time-of-flight method and monochromatized synchrotron radiation. An unusual spectrum wi...

Ionic fragmentation of SiH4 following the L-shell excitation

Ionic photofragmentation of SiH4 has been studied in the vicinity of the Si: L-edge using synchrotron radiation and time-of-flight mass spectrometry. Relative ionization efficiencies for more then 10 ionic fragment species and pair-ionization efficiencies for the pairs H+ + SiHn+ (n=0, 1 and 2) have been obtained as a function of the photon energy from 100 to 200 eV from the photoelectron-photion and the photoion-photoion coincidence measurements. Ionic dissociation of the continuum Si: 2p hole states may occur mostly via double ionization of the parent molecule giving rise to two types of dissociation channels; (type A) SiH4++ → H+ + H+ + neutrals and (type B) SiH4++ → H+ + Si+ (or SiH+) + neutrals. The average kinetic-energy release given to H+ is much higher in the dissociation channel B than in the dissociation channel A suggesting temporal existence of localized and delocalized valence-two-hole states.

Total photoion yield of atomic chromium at the 2p threshold

The total photoion yield spectrum of atomic chromium has been determined in the range of the 2p thresholds. The experimental data are compared to Hartree-Fock calculations, which include the interaction between three configurations, and to a previously published electron energy loss spectrum of solid chromium.

4d-shell photoionization of Xe, Cs, Ba, Sm, Eu and Yb atoms studied by photoion-yield spectra

A comparative study of multiple photoionization in the 4d ionization region (78-270eV) of M = Xe, Cs, Ba, Sm, Eu and Yb atoms is reported. Partial photion-yield spectra for Mn+ (n = 1-4) ions have been measured by using synchrotron radiation as a light source. Main products in Xe, Cs and Ba are Mn2+ and M3+ ions due to the creation of a 4d vacancy. In Sm and Eu, a large fraction of M+ ions are populated via the 4d-4f resonant excitation and subsequent autoionization to the 4f ionization continuum, which is squeezing the population of multiply-charged ions to about 50%. In Yb, a large amount of M+ ions are also populated, but are due largely to the direct 4f ionization. In all of the atoms studied, an appreciable or considerable amount of M4+ ions are observed, indicating the existence of photoelectron and/or Auger shake-off processes.