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Volume 48 (2000)
- Issue 6 Pages 373-
- Issue 5 Pages 289-
- Issue 4 Pages 241-
- Issue 3 Pages 179-
- Issue 2 Pages 71-
- Issue 1 Pages 8-
Volume 48, Issue 4
Displaying 1-6 of 6 articles from this issue
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REGULAR PAPERS
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Naoaki SAITO, Kazuyoshi KOYAMA, Mitsumori TANIMOTO2000 Volume 48 Issue 4 Pages 241-247
Published: 2000
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSA time-of-flight mass spectrometer with a reflector has been constructed in a compact device (<1.8 m long). Neutral clusters are photoionized and accelerated by dc electric potential up to 25 kV. Positive and negative ion clusters are accelerated by a fast rising (<80 ns) pulsed electric potential up to ±10 kV. The ion clusters are detected by a two-stage multi-channel-plate and the detection signals are recorded by a microcomputer with a multi-stop time-to-digital converter. Both a high mass resolution up to 5,000 and a wide mass range from 1 u to more than 200,000 u are attained.View full abstractDownload PDF (697K) -
Mitsuo TAKAYAMA, Yuzuru HAYASHI2000 Volume 48 Issue 4 Pages 248-253
Published: 2000
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSThe precision or relative standard deviation (RSD) of measurements in a sector type mass spectrometer equipped with an electron ionization system is examined experimentally and theoretically. The observed RSD is obtained by the usual replication and the theoretical RSD is predicted from the probabilistic properties of the baseline noise by the uncertainty theory called the FUMI theory (Function of Mutual Information). By comparing the experimental and theoretical RSD, this paper identifies two kinds of error sources: (1) for small peaks, the major cause of the measurement uncertainty is the baseline noise originating mainly from the detection unit; (2) for large peaks, the measurement error is subject to ion/particles processes such as the fluctuation of gaseous sample concentration, electron ionization efficiency, and ion beam flux and there is a lower limit of the measurement RSD (≈3%). In case 1, the measurement RSD can successfully be predicted by the theory. In case 2, the observed RSD is even larger than the theoretical RSD, and the repeated measurements are necessary to estimate the measurement uncertainty. The peak corresponding to the limit of detection (RSD=33%) is demonstrated.View full abstractDownload PDF (651K) -
Yasumasa IKEZOE, Kazuya SUZUKI2000 Volume 48 Issue 4 Pages 254-262
Published: 2000
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSAmmoniated ammonium ions (NH4+·nNH3, n=0-6) were studied theoretically by molecular orbital calculations and experimentally by observing their formation and decomposition in a corona discharge-jet expansion process. Ab initio calculations were carried out by employing Gaussian 98 program, which gave optimized structures, binding energies, and wave numbers of the symmetric bending mode of the solvent ammonia molecule. Effects of the stagnation pressure of reactant gas and the diameter of the gas expanding pinhole were examined on the size distribution of NH4+·nNH3. It was found that the cluster size n in NH4+·nNH3 increased by one or remained unchanged in the jet expansion process. Effects of discharge current, the pinhole diameter and flight time were examined on the decomposition rate of the ammonia cluster ions. It was deduced that the internal energies of the cluster were mainly determined by the reactions involved in the cluster formation or decomposition.View full abstractDownload PDF (832K) -
Makoto FUJIWARA2000 Volume 48 Issue 4 Pages 263-269
Published: 2000
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSA three dimensional many particle model is proposed for computer simulation of Fourier transform ion cyclotron resonance (FT-ICR) mass spectra. The model is relatively simple and includes Coulomb interactions between ions in an FT-ICR cell. FT-ICR mass spectra of CO+ and C2H4+ mixtures are simulated at CO+:C2H4+=1:1, 2:1, and 1:2 for low, medium, and high ion density. The Coulomb interaction at CO+:C2H4+=1:1 appears to be the most significant from the results on peak coalescence phenomenon. The simulation performance is estimated through comparison with Mitchell's simulation model. Ion loss due to the space charge effect during detection period is investigated for ions of the same (C2H4+), two different (C2H4+: m/z 50.0=1:1) and two closely spaced (CO+:C2H4+=1:1) mass-to-charge ratios as a function of initial ion population. In the case of different m/z ions, particularly for closely spaced m/z ions, the ion loss ratio increases considerably with initial ion population. On the other hand, for the same m/z ions no significant ion loss occurs even at a large initial ion population.View full abstractDownload PDF (573K) -
Osamu SEKIGUCHI, Yutaka TAKAHASHI, Atsuyo FUJIZUKA, Satoshi NAKAJIMA, ...2000 Volume 48 Issue 4 Pages 270-274
Published: 2000
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSUnimolecular metastable decompositions of 1,1-dimethoxypropane (CH3CH2CH(OCH3)2, 1) and 2,2-dimethoxypropane ((CH3)2C(OCH3)2, 2) upon electron impact have been investigated by means of mass-analyzed ion kinetic energy (MIKE) spectrometry and D-labeling technique. The molecular ions of 1 and 2, even at 20eV electron energy, are formed with extremely low abundance. Sequential transfers of a methyl group and a hydrogen atom to an ether oxygen are observed during the decomposition of [1-H]+ (CH3CH2C(OCH3)=O+CH3, m/z 103), [2-CH3]+ (CH3C(OCH3)=O+CH3, m/z 89), and [1-C2H5]+ (CH(OCH3)=O+CH3, m/z 75) to protonated dimethyl ether (m/z 47). The relative importance of this process increases with decreasing the length of the alkyl chain, R, in RC(OCH3)=O+CH3 (R=C2H5, CH3, and H). On the other hand, the abundance of the ion (RCO+) generated by the loss of CH3OCH3 from these ions with transfer of only a methyl group increases with increasing R. The relative abundance of the ions in the MIKE spectra is rationalized with energetic consideration, i.e, the total heat of formation (ΣΔHf) of the ion plus the neutral fragment, or proton affinity (PA) of two components in an intermediate proton-bridged complex.View full abstractDownload PDF (379K) -
Tomoe HATAKEYAMA, Keiji HISAYOSHI, Mamoru MURATA, Hiroaki OZAWA, Takes ...2000 Volume 48 Issue 4 Pages 275-283
Published: 2000
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSThe isotopic ratios of lithium, 7Li/6Li, have been measured by a modified type surface ionization mass spectrometer whose ion source was newly designed. It needs no chemical preparation prior to the ionization, and makes an analysis of small portions of sample possible. We mainly analyzed the Murchison meteorite and compared with terrestrial laboratory standard samples, spodumene and lepidolite. Many kinds of isotope anomalies for Murchison have been reported, and these anomalies are considered to be originated from presolar events. Spallation reactions are thought to be one of the processes that produced lithium isotopes, and to synthesize 7Li and 6Li isotopes as almost the same quantities. If lithium isotopes produced by such reactions in the presolar stage have been maintained in meteorites, there may be an isotopic anomaly of lithium whose ratio, 7Li/6Li, is extremely lower than that for terrestrial standards. The mean isotopic ratio, 7Li/6Li, for one laboratory standard, spodumene, is 10.519±0.0004, and that for another one, lepidolite, is 11.329±0.0009. The discrepancy between these lithium isotopic ratios is estimated to be due to the different fractionation processes of these minerals. The isotopic ratios for Murchison are within a range from 10.056 to 11.356. This range of the scattering for Murchison is within those for previous works. The lithium isotopic ratios for Murchison analyzed so far gave no significant difference from those for terrestrial standards.View full abstractDownload PDF (713K)
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