Odagiri Takeshi

The electron energy-loss spectra of H(2) in coincidence with H(2p) formation have been measured in the range just above the dissociation limit of H(ls) + H(2p) at the incident electron energies of 30 and 150 eV and the scattering angle of 2 degrees, The ordinary energy-loss spectra at the same incident energies and scattering angle have also been measured. It is clearly seen that optically-allowed states dominate in the ordinary energy-loss spectra while optically-forbidden states contribute noticeably to the coincident energy-loss spectrum at the 30 eV incident energy. The forbidden states predissociating into H(1s) + H(2p) are assigned and the branching ratio of the predissociation. the intensity ratio of the coincident energy-loss spectrum to the corresponding ordinary one, is obtained. The predissociation pathways into H(ls) + H(2p) from those forbidden states are discussed in detail.

The state-resolved isotope effect an the cross sections of 2p atom formation via precursor doubly excited states of H-2 and D-2 is obtained at 80 eV incident electron energy and 3 degrees scattering angle by means of coincident electron-energy-loss spectroscopy as well as theoretical fits based on the reflection approximation and the survival probability. It turns out that the degree of the isotope effect depends strongly on the precursor doubly excited states and hence is a significant character of them. The origin of this dependence is discussed.

The dissociative recombinations of (HeH+)-He-3, (HeH+)-He-4, (HeD+)-He-3 and (HeD+)-He-4 were studied with an extremely low-temperature electron beam of the order of 1 meV produced by a superconducting electron cooler at the storage ring TARN II. The dissociative recombination spectra show a fine new structure and a clear isotope dependence in the low-energy region. Those features are well reproduced by the theoretical calculations based on a multichannel quantum-defect theory including rotational motion and discretized dissociative states. According to the theory, the newly observed structure is evidence for a new indirect mechanism where the intermediate states are not vibrationally excited Rydberg states but virtual dissociative states.

The dissociative recombinations of 3HeHC, 4HeHC, 3HeDC and 4HeDC were studied with an extremely low-temperature electron beam of the order of 1 meV produced by a superconducting electron cooler at the storage ring TARN II. The dissociative recombination spectra show a fine new structure and a clear isotope dependence in the low-energy region. Those features are well reproduced by the theoretical calculations based on a multichannel quantum-defect theory including rotational motion and discretized dissociative states. According to the theory, the newly observed structure is evidence for a new indirect mechanism where the intermediate states are not vibrationally excited Rydberg states but virtual dissociative states.

A superconducting electron cooler with an adiabatic expansion factor of 100 was designed and constructed at the TARN II ring for high-precision experiments and high-speed cooling. The gun solenoid is a liquid-helium-free superconducting magnet with a 20-cm room-temperature bore, which can produce a high magnetic field of up to 3.5 T An electron beam is expanded from a diameter of 5 mm to 50 mm in a gradually decreasing solenoid field from 3.5 T to 0.035 T With this cooler it can be expected to reach an electron temperature on the order of 1 meV. The cooler first came into operation in November, 1996. The spectrum of the dissociative recombination, (HeH+)-He-3+e-->He-3+H, clearly showed a dramatic decrease in the electron-beam temperature compared with our previous data measured at an expansion factor of 10 with a normal-conducting solenoid.

水素分子のコインシデンス電子エネルギー損失スペクトルを測定し、電子衝突中の2電子励起状態のスペクトルを初めて測定した。理論で見つかっていない、未知の解離性禁制2電子励起状態F状態を見出した。

The doubly excited states of molecular hydrogen have been studied by means of electron-energy-loss spectroscopy in coincidence with the detection of H(2p) formation at 80 eV incident energy and 3 degrees scattering angle. This is the first observation of doubly excited states of H-2 in electron energy-loss spectra. It is shown that a forbidden doubly excited state makes a large contribution as well as allowed states. The measured spectrum has been analysed by theoretical fits based on the reflection approximation.

分子の中性解離フラグメントからの蛍光放出でタグ付けされた電子エネルギー損失スペクトル=コインシデンス電子エネルギー損失スペクトルの測定装置、手法を開発することに成功した。