Tsuruji Iwai

Temperature Dependence of the Optical Absorption Edge of Tungsten Trioxide Single Crystal

The optical absorption edge of WO 3 single crystal has been measured with polarized light over the temperature range from -100°C to 900°C. From 0°C to about 700°C, the absorption edge shifts linearly toward red with increasing temperature, the temperature coefficients being -9.0×10 -4 ev/deg for the case of light polarized in the direction parallel to the a -axis( a -polarized light) and -6.5×10 -4 ev/deg for the case of light polarized in the direction parallel to the c -axis( c -polarized light), respectively. In the vicinity of -50°C, anomalous shift of the absorption edge takes place. This is attributed to the phase transition. In the low temperature phase, the extinction position is different from that in the high temperature phase. In addition, when the temperature is raised through 740°C, a sudden red shift takes place for the case of a -polarized light, the magnitude being about 0.35 ev, while no anomaly occurs for c -polarized light.

Landau-Zener model calculations of one-electron capture from He atoms by highly stripped ions at low energies

Cross sections for single electron capture from He atom by highly stripped, C q + , N q + , O q + , F q + , Ne q + ( q =4–9) and Kr q + ( q =10–25) ions have been calculated using the multichannel Landau-Zener model. The collision energy is 600 eV/amu except for Kr q + , whose energy is q ×1 keV. The selective electron capture into a single or at most two n -shells is predicted for the cases of q ≤9. The n -distributions obtained by the present calculation are quite consistent with our earlier observation and the total cross sections agree reasonably well with the measured data in spite of the simple model. In the case of Kr q + , where q is larger than 10, more and more shells can be populated and the total cross sections increase monotonically with the increase of q .

Absolute Measurements of Emission Cross-Sections for Dissociative Excitations of H2O by Electron-Impact with Crossed-Beam Apparatus and High Sensitive Quartz Spring Balance

Absolute measurements of the emission cross-sections for the A - X band-spectrum of OH and the H β line in the dissociative excitation processes of H 2 O by electron-impact have been carried out by means of the crossed-beam technique, with the aid of a high sensitive spring balance made of fused quartz. The spring has a tiny pan, which is surrounded by a specially designed trap of liquid nitrogen. The spring words well for direct intensity measurements of the water molecular beam, because the condensation coefficient of H 2 O on ice is large enough at lower temperatures. The following results have been obtained; (4.2±2.1)×10 -18 cm 2 for the H β transition, and (7.1±3.5)×10 -18 cm 2 for the OH ( A , 2 Σ + - X , \(^{2}\varPi\)) transition, at 300 eV respectively.

Experimental study of one-electron capture by ground and metastable Ar2+ ions from Na at 1.5 keV

The cross sections for one-electron capture by the ground-state Ar2+(3P) ions, sigma 21, and by the metastable Ar2+(1D) ions, sigma 21*, have been measured independently by an optical attenuation method (OAM). Both the cross-sections are of the order of 10-14 cm2 and sigma 21* is about 1.3 times as large as sigma 21. The metastable fraction in the primary-ion beam has been estimated at 0.29+or-0.16 from the OAM combined with the beam attenuation method. The OAM provides a useful means to determine one-electron capture cross sections for the ground and metastable ions, in particular when both the cross sections are nearly the same. The validity of the present method is discussed in detail.

Comparison between Crossed-Beam and Target-Gas Methods for Study on Optical Excitation Functions in Electron-Impact of H2O

The so-called “crossed-beam method” and “target-gas method” are applied to the same events of molecular collisions. It is shown that the former method gives reliable informations about the excitation functions for the OH band and the Balmer lines in dissociative and radiative collisions of H 2 O with electrons, while the latter does not, at least, in the range of lower energies of incident electrons.

Gain characteristics of a microchannel plate and a channel-electron multiplier for low energy multiply charged ions

Abstract Pulse height distribution are measured when multiply charged ions of S, Ne, F, O, N and C are incident on a microchannel plate of chevron type (MCP) and a channel electron multiplier (CEM) in the velocity range of 3–4.5 × 105 m/s. The pulse height distributions obtained with the CEM shows no significant dependence of the gain on the energy, mass and charge state of incident ions. On the other hand, for the case of the MCP, an increase of the gain is observed with an increase of the charge state of incident ions irrespectively of ionic species. Such behavior is discussed in connection with secondary electron emission yield at the input and electron multiplication mechanism iin the channels.

Dissociative Excitation of Water Molecule by Electron Impacts. I. General Survey and the Born Approximation

Emission cross sections are evaluated in the Born approximation for the dissociative excitation processes of H 2 O by electron impacts, accompanied by the OH violet band, or the Lyman-α emission. Wave functions are from the Hatano-Nomura-Tanaka basis set as well as the Lin-Duncan set. The choice of wave functions strongly affects the magnitude of the cross section, but hardly affects its dependence on the incident electron energy. For the OH band, main contribution comes from the transition 3 a 1 →4 a 1 , and the electron exchange collision should be considered. For the Lyman-α emission, to which a number of superexcited states may correlate, it is found that the contribution of the transition 1 b 2 →6 a 1 (=4 s a 1 ) is dominant, while ones 1 b 2 →3 d a 1 , 3 d a 2 and 3 d b 2 the next. The calculated cross section is different from the experimental one at low energies of the incident electron, but is in accord with the experimental one at high energies. Alternative comparison is made on the optical and ...

Electron capture processes of Iq+ ions with very high charge states (41⩾q⩾10) in collisions with He atoms

One-electron capture processes of iodine (Iq+) ions with very high charge q up to 41 in collisions with He atoms at low energies have been investigated using energy gain spectroscopy. It is found that total cross sections increase with increasing charge of ions q, and also increase roughly with the square of the crossing radius Rc of the diabatic potential curves in the quasi-molecules where the electron transfer takes place. This smooth variation, in contrast to that in ions with low charge where only few crossings play a role, can be understood from the fact that a number of the crossings closely located in a relatively narrow region of Rc contribute to the one-electron transfer processes in ions with high charge.

Observation of electron capture into selective state by fully stripped ions from He atom

Energy spectra of charge-changing projectile ions are measured for one-electron capture by fully stripped C and O ions from He atoms. The electron is selectively captured into a single level of principal quantum number n=3 of C5+ and n=4 of O7+, respectively, at a collision of 0.45 KeV amu-1.

Measurement of Relative Population between B2+(2s) and B2+(2p) in Electron Capture Collision of B3+with He

One-electron capture processes into B 2+ (2s) and B 2+ (2p) have been investigated in B 3+ –He collision at low velocities (1.3-2.3×10 7 cm/sec) using a translation energy spectroscopy. Energy dependence of the relative population between B 2+ (2s) and B 2+ (2p) is obtained and compared with the theoretical result of Shipsey et al.