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Volume 38 (1990)
- Issue 6 Pages 269-
- Issue 5 Pages 241-
- Issue 4 Pages 151-
- Issue 3 Pages 95-
- Issue 2 Pages 65-
- Issue 1 Pages 1-
Volume 38, Issue 4
Displaying 1-6 of 6 articles from this issue
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INTEGRATED PAPERS
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Atsushi Shigihara, Hiroshi Ichikawa1990 Volume 38 Issue 4 Pages 151-163
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSThe equilibrium structures and fragmentations of the protonated butane, aminopropanol, formates, and acetates are studied by semi-empirical MINDO/3 MO method. The results obtained were discussed in relation with the role of the proton. Comparison in the energy barriers leads the following conclusions. 1) The H2 elimination easily occurs in the protonated hydrocarbons, while as for the protonated aminopropanol, H2O loss is favorable. 2) The fragmentations do not always occur from the most stable molecular protonated ion. 3) The olefin elimination from the protonated esters favors the stepwise process via intermediate ion A (HCOOH…H+…CH2=CHR) more than any other processes via ring transition states, resulting in good accord with the observed ratios of the hydrogen migrations in protonated propyl ester.View full abstractDownload PDF (738K) -
Akio Makishima1990 Volume 38 Issue 4 Pages 165-173
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSTanaka and Masuda1) first applied lanthanum-cerium isotope systematics to geochronology in 1982, using β-decay of 138La. In this systematics, it is necessary to measure cerium isotope ratio (ex. 138Ce/142Ce) with precision better than 0.01% because of long half life and low abundance of 138La. Many studies have been done to improve the precision and accuracy of the Ce isotope analysis. But there are some problems in the analysis, such as long data acquisition time and requirement of large amount of cerium. When the La-Ce systematics is used as a geochemical tracer or in geochronology, β-decay constant of 138La is a very important factor. However, the decay constant is still in controversy so that age dating results using the La-Ce isotope systematics are less convinced compared with those of Sm-Nd and Rb-Sr systematics.
In this paper, precise measurements of cerium isotope ratios and geochronological applications are reviewed and their problems are pointed out.View full abstractDownload PDF (654K)
REGULAR PAPERS
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Ryoji Nishio, Kazuki Tuchida, Masahiro Tohma, Kazumichi Suzuki1990 Volume 38 Issue 4 Pages 175-181
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSA sensitivity determination method for a quadrupole mass spectrometer using an electron impact ionization process was investigated to determine ion density from observed ion current. Theoretical expression of the relation among measured ion current, irradiated electron beam current and electron energy was obtained, in which direct ionization was assumed. Sensitivity was determined as a fitting factor of the calculated value to the measured ion current by the least square method.
Sensitivity was measured for argon under the condition that ionization processes except direct ionization were negligible. The dependence of measured ion current on the irradiated electron energy and current agreed with the theoretical prediction and the sensitivity was determined with an uncertainty of 6%. The same measurement was performed for uranium and the sensitivity was successfully determined.View full abstractDownload PDF (514K) -
Takahisa Yamada, Motohiro Naito, Youiti Yamamoto, Akinori Mogami1990 Volume 38 Issue 4 Pages 183-192
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSA double-focusing mass analyzer (γ=150 mm) with crossed electric and magnetic field is developed. A newly designed multielectrode is used to make the electric field in the narrow gap between the magnet pole pieces. Experimental results verify the following features of this mass analyzer as predicted theoretically; 1) much wider energy window of approximately 1 keV, 2) mass spectrum available by voltage scanning as well, 3) high mass resolution of 1,700 obtained with the wide main slit of 0.1 mm.View full abstractDownload PDF (612K) -
Takeru Yanagi1990 Volume 38 Issue 4 Pages 193-198
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSA new method of accurate determination of isotopic composition and concentration of a strontium-84 spike solution was devised for simultaneous determination of strontium contents and isotopic compositions in rocks and minerals by measuring strontium isotopic ratios in spiked samples. In this method, the isotopic composition of strontium in the spike were determined so as to minimize the sum of squares of deviations of spike strontium-84 concentrations which were calculated from measured isotopic ratios of strontium in five different mixtures of the spike and the standard solution. The method can eliminate all mass discriminations occurred during the measurement on a surface ionization mass spectometer. The results were tested by measuring 87Sr/86Sr ratios of Eimer and Amend SrCO3 and JB-1 geochemical reference material, and by determining the strontium content in JB-1. The measurements of strontium isotope ratios in spiked samples give average values of 0.708007 ± 0.000052 and 0.70417 ± 0.00004 for 87Sr/86Sr ratios of E and A SrCO3, and JB-1, respectively. The strontium content in JB-1 was estimated at 457.1±1.3 ppm. These values are very close to reported respective values.View full abstractDownload PDF (392K) -
Kimio Isa, Katsuhiko Nishioka, Akinobu Unishi, Yoshinori Hashimoto1990 Volume 38 Issue 4 Pages 199-208
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSThe CAD spectra of sulfur by electron ionization (70 eV) were measured by means of MS/MS (EBE type) method. In the CAD spectra of precursor ion, S8+, S7+ fragment ion could not be found. The S7+ ion is considered not to be the fragment ion of precursor ion, S8+, and S7+ was produced before the electron ionization. The fragment ion of S32+ (m/z 48) was found in the CAD spectra of precursor S42+ (m/z 64) ion. The precursor ions of m/z 64 contains S2+ and S42+ ion. Doubly charged ions of S42+ was first found in the present experiment and the structure of S42+ is considered to be straightly formed. Three-dimensional CAD spectra were shown for the understanding of Sn+ ions (n=8~2) more easily.View full abstractDownload PDF (562K)
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