Izumi Waki

Cooling and Mass-Analysis of Molecules Using Laser-Cooled Atoms

This paper presents the first sympathetic cooling of molecular ions using laser-cooled atomic ions. To this end, we developed a novel combination of sympathetic cooling and in situ mass spectroscopy that allows the use of laser-cooled atomic ions to detect sympathetically-cooled molecular ions non-destructively. We demonstrate this technique by cooling and mass-analysing ions of ultra-high-vacuum residual gas and externally introduced air in situ with less than 80 ions each, confined in a radio-frequency quadrupole (RFQ). This capability to detect and identify sympathetically-cooled molecules with potentially-high sensitivity in situ in an RFQ should be useful for molecular spectroscopy, chemical analysis and study of cold molecules and clusters.

Sensitive Monitoring of Volatile Chemical Warfare Agents in Air by Atmospheric Pressure Chemical Ionization Mass Spectrometry with Counter-Flow Introduction

A new method for sensitively and selectively detecting chemical warfare agents (CWAs) in air was developed using counter-flow introduction atmospheric pressure chemical ionization mass spectrometry (MS). Four volatile and highly toxic CWAs were examined, including the nerve gases sarin and tabun, and the blister agents mustard gas (HD) and Lewisite 1 (L1). Soft ionization was performed using corona discharge to form reactant ions, and the ions were sent in the direction opposite to the airflow by an electric field to eliminate the interfering neutral molecules such as ozone and nitrogen oxide. This resulted in efficient ionization of the target CWAs, especially in the negative ionization mode. Quadrupole MS (QMS) and ion trap tandem MS (ITMS) instruments were developed and investigated, which were movable on the building floor. For sarin, tabun, and HD, the protonated molecular ions and their fragment ions were observed in the positive ion mode. For L1, the chloride adduct ions of L1 hydrolysis products were observed in negative ion mode. The limit of detection (LOD) values in real-time or for a 1 s measurement monitoring the characteristic ions were between 1 and 8 μg/m(3) in QMS instrument. Collision-induced fragmentation patterns for the CWAs were observed in an ITMS instrument, and optimized combinations of the parent and daughter ion pairs were selected to achieve real-time detection with LOD values of around 1 μg/m(3). This is a first demonstration of sensitive and specific real-time detection of both positively and negatively ionizable CWAs by MS instruments used for field monitoring.

Chemical reaction of sympathetically laser-cooled molecular ions

We report an ion/neutral reaction of sympathetically laser-cooled molecular ions. Using laser-cooled fluorescence mass spectrometry, a reaction of about 100 sympathetically cooled H3O+ ions with NH3 were traced at 4 min interval as the reacting ions were kept within a radiofrequency-quadrupole ion trap. To obtain the reaction rate of the reaction molecular dynamical calculation was used to relate the fluorescence mass spectra to the quantity of the molecular ions.

Spectral shape of in situ mass spectra of sympathetically cooled molecular ions

We formulated a model to reproduce the spectral shape of in situ mass spectra of sympathetically cooled molecular ions trapped in a linear radio-frequency-quadrupole. The molecular ions are sympathetically cooled by laser cooled ions. The mass spectrum is obtained by observing fluorescence emitted from the laser-cooled ions as we excite the resonant motion of the sympathetically cooled molecular ions in the trap. The model, which uses a pseudopotential and space-charge approach, reproduces the mass spectra of molecules. The model suggests that the variation of the space-charge density of the laser-cooled ions can produce in-trap kinetic excitation without the loss of the excited ions from the trap.

Determination of the thickness and distribution of a Langmuir-Blodgett film using soft X-ray reflection

Abstract This paper reports the simultaneous observation of the thickness and distribution of XY-type Langmuir-Blodgett (LB) films by measurement of the reflectivity of soft X-rays using synchrotron radiation. The thickness and distribution are obtained by analysing the oscillation of the reflectivity, which is produced by varying the wavelength λ or grazing angle θ. The thickness obtained is compared with models of the XY-type deposition mechanism. It is shown that the molecular overturning model is the most satisfactory.

Higher-harmonics suppressor for soft x rays

We have developed an apparatus for suppressing higher harmonics contained in the soft x‐ray output beam of grazing‐incidence grating monochromators. It consists of eight pairs of total‐reflection mirrors. Each pair serves as a low‐pass filter with the cutoff energy different from one another. The eight pairs are designed to cover an energy range of 80–1600 eV with an efficiency of harmonic suppression better than 97%, while transmitting more than 50% of the fundamental photons. We have tested its preliminary performance on the soft x‐ray beamline BL‐8A at the Photon Factory. We present the observed transmission efficiencies and the effects of the harmonic suppressor on measurements of reflectivity and fluorescence spectra.

Laser-cooled fluorescence mass spectrometry using laser-cooled barium ions in a tandem linear ion trap

We report on a mass spectrometry that uses laser-cooled barium ions to optically detect sample ions in a linear radio-frequency-quadrupole ion trap. To obtain a mass spectrum, we observe the intensity modulation of laser-induced fluorescence emitted by the barium ions, as we electrically excite the secular motions of sample ions that are sympathetically cooled by the barium ions. In a fluorescence mass spectrum of sample xenon ions, we identified the major isotopes of xenon. To estimate the absolute amount of the sample ions that contribute to the mass spectrum, we detect the ions using an electron multiplier that is absolutely calibrated by crystallized laser-cooled barium ions. We enhance transfer efficiency to the electron multiplier using a linear radio-frequency-quadrupole ion guide that is placed in tandem with the ion trap. Typically 30 ions of xenon isotope 131Xe+ were detected with a signal-to-noise ratio of ∼30 in the fluorescence mass spectrum.

Design and performance of beamline BL-8 at the photon factory

Abstract We designed and constructed beamline BL-8 at the Photon Factory, the National Laboratory for High Energy Physics. The beamline has been in full operation since 1987–1988. On this beamline, one can utilize the synchrotron radiation from a bending magnet in the 40 eV to 35 keV energy range. The beamline has three branch beamlines (8A, 8B, and 8C) where one can perform a wide scope of researches: e.g., soft X-ray spectroscopy and photochemical reactions on 8A; XAFS on 8B; lithography, microscopy, and micro-tomography on 8C.

Soft x‐ray analysis system for reflection, secondary electron, and fluorescence spectroscopy

This article describes an UHV compatable soft x‐ray analysis system for reflection, secondary electron, and fluorescence spectroscopy. It is equipped with a reflectometer with an angular accuracy of 0.01°. This is achieved with rotary encoders directly coupled to the rotation axes. At the same time, the system is equipped with an electron multiplier, a cylindrical mirror analyzer, and a Si(Li) detector, each for measuring total secondary electrons, photo‐ and Auger electrons, and fluorescence. Furthermore, it is possible to form multilayer films and analyze them in situ. The performance of the reflectometer has been tested on the beamline BL‐8A at the Photon Factory. We present the results of reflectivity measurements for diamond‐cut copper mirrors and Langmuir–Blodgett films.

Precise EXAFS Analysis for High-Tc YBa2Cu3Ox

EXAFS oscillation caused by oxygen atoms around the Cu atoms in high-Tc orthorhombic YBa2Cu3Ox (Tc=90 K) is studied. Although the experimental EXAFS profile has been explained by the conventional analysis in which only one kind of Cu-O pairs is assumed to be present, this assumption is found to lead to a misunderstanding of the Cu-O structure. The Cu-O structure should be analyzed by taking into account the contributions from the individual Cu-O pairs based on the reported structure by the Rietveld analysis of the neutron diffraction data. Comparison of theoretical EXAFS with the experiment does not suggest trivalent Cu ions in orthorhombic YBa2Cu3Ox.