摘要:

By using a combination of einzel lenses and deceleration grids, it is possible to inject cold molecular ions from a supersonic beam apparatus directly into the superconducting magnetic trap of a Fourier Transform Ion Cyclotron Resonance (FT-ICR) spectrometer1,2. The injection cycle may be repeated many times until the trap is “filled” with an adequate number of ions. Since the ion source is completely independent of the FT-ICR apparatus, and since the injection is mass-specific and nearly 100% efficient, these techniques may find wide application in the analysis and study of complicated molecules and clusters. Examples are given for the application of this new technique to the study of dissociative chemisorption on the surface of metal and semiconductor clusters, and to the study of the “soccerball” molecule, C60+, and its metal-substituted complex, C60La+.

ISSN:1073-9149    

DOI:10.1080/10739148808543664

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Lasers and mass spectrometers are combined to perform experiments on the study of cluster ions. Direct laser vaporization of a variety of solids is shown to be a simple and efficient means for the production of abundant high-mass cluster ions. Both time-of-flight and Fourier transform mass spectrometry are used for the detection and structural analysis of these cluster ions. The results exemplify the unique advantages of each mass spectrometric method.

ISSN:1073-9149    

DOI:10.1080/10739148808543665

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The present analytical capabilities of resonance ionization mass spectrometry (RIMS) are discussed. The chronology of the development of the method is described. Examples of RIMS instrumentation are given where possible. The advantages of this technique are presented, and the parameters that currently limit the applicability of RIMS are addressed. Directions for future studies are indicated.

ISSN:1073-9149    

DOI:10.1080/10739148808543666

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The application of laser resonance ionization mass spectrometry (RIMS) to the measurement of low abundance isotopes was investigated. The long-lived radionuclide129I was used to evaluate the present capabilities. Issues of sensitivity and selectivity were studied, as well as dynamic range limitations imposed by the low-duty-cycle pulsed ionization process.

ISSN:1073-9149    

DOI:10.1080/10739148808543667

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A novel apparatus was designed for the introduction of supersonic jets of supercritical CO2, N2O and high-pressure hot liquids such as methanol and water. The key features of this experiment are a pulsed injection source, which was designed with efficient liquid nitrogen cryopumping to operate at pressures of up to 380 atm and nearly 200°C. The reduction in duty cycle provided by a pulsed source has allowed the use of a 200 μm orifice, which significantly increases the on-axis density in the jet compared to continuous expansions where a 10 μm orifice is customarily used. Resonant two-photon ionization is then used to softly ionize the molecules in the beam for mass analysis and detection in a time-of-flight mass spectrometer.

ISSN:1073-9149    

DOI:10.1080/10739148808543668

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Techniques are described based on observing photodissociation of gas-phase ions as a function of wavelength. Photodissociation spectra, thresholds, two-photon dissociations, IR/visible two-laser processes, and slow near-threshold dissociations are discussed. The information obtained provides experimental access to questions of ion structure, rearrangements, electronic and vibrational properties, and thermochemistry, and provides a link between mass spectrometry and optical spectroscopy.

ISSN:1073-9149    

DOI:10.1080/10739148808543669

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The advantages of obtaining both neutral fragment scattering distributions and reionized mass spectra for investigating highly reactive and/or metastable species produced by the neutralization of a high velocity precursor ion beam is outlined. Practical applications of these techniques are illustrated by results obtained recently for the neon hydride and the methanium (CH5) radicals. In these studies a unique metastability for the ground state of NeH is identified and the previously observed metastability of CH5is shown to arise from the formation of high Rydberg levels of the radical rather than the ground state as first proposed. Future prospects for obtaining absorption spectra of unusual neutral species by combining optical spectroscopic techniques with those of neutralized ion beams are discussed.

ISSN:1073-9149    

DOI:10.1080/10739148808543670

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A series of N-alkylpyridinium salts was studied by laser desorption mass spectrometry. Laser desorption was shown to produce gaseous N-alkylpyridinium cations quite easily from the relatively nonvolatile salts. Gas-phase dissociation studies revealed that these cations dissociate by two different mechanisms involving either a direct C-N bond cleavage or a more complicated cleavage involving proton transfer.

ISSN:1073-9149    

DOI:10.1080/10739148808543671

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A new time-of-flight mass spectrometer for UV-excimer-laser desorption of neutrals, followed by resonant - or nonresonant postionization with a second excimer laser or excimer-dye-laser combination is described. The advantages of the technique are discussed and the performance of the instrument is demonstrated for a number of nonvolatile organic compounds.

ISSN:1073-9149    

DOI:10.1080/10739148808543672

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A linear time-of-flight mass spectrometer with static electrode voltages was developed for isotopic abundance measurements and showed good resolving power (620) for atomic ions. Positive ions, produced by multiphoton excitations, were detected by a microchannel plate detector that featured low noise and good pulse height distribution. Signal pulses were too fast for precise quantification by currently available transient digitizers. A gated pulse counter, which used AND logic circuitry to direct pulses for different isotopes into separate channels of a counter, was developed for quantification of the signal pulses and results for isotopic ratio measurements showed good precision, 0.3% to 1% relative standard deviation. The time-of-flight mass spectrometer with gated pulse counter was particularly well matched to pulsed laser ionization, because it could detect all isotopes of the selected element ionized in each laser pulse, and it did not impose a limit on the laser pulse repetition rate.

ISSN:1073-9149    

DOI:10.1080/10739148808543673

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor