Electronmicroscopical investigations of laser irradiated foils and particles

Wurster, R.; Haas, U.; Wieser, P.

doi:10.1007/bf00479625

Cited by 14 publications

(2 citation statements)

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“…Laser Focusing. The effects of laser focus position on ion intensity is discussed in only two references (10,11). Detailed results of considerable experimentation here investigating these effects will be discussed elsewhere (12).…”

Section: Sectionmentioning

confidence: 99%

Determination of carbon, nitrogen, and oxygen in solids by laser mass spectrometry

Zhao¹,

Conzemius²,

Svec³

1984

Anal. Chem.

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Carbon, nltrogen, and oxygen are measured directly In metal speclmens wlthout standards by laser mass spectrometry. Accuracy Is wlthln the uncertalnty of NBS standard reference materlals used to test the technique. The results lndlcate that parts-per-bllllon level measurements of these elements will be stralghtforward. Contrlbutlons due to lnteractlons of samples and resldual gases are negated by Increased rates of laser cleaning In relatlonshlp to the background gas pressure.Improved methods are needed for determining nonmetallic elements present in solid materials (1). More than 45 papers have been published (2) describing the analysis of gaseous impurities in solids and thin films by laser mass spectrometry (LMS) since Honig (3) introduced the laser ion source. There are some vital advantages gained by using a focused laser beam combined with mass spectrometry to determine gaseous impurities in solids:1. No background is introduced due to bulk heating of the sample as in methods, such as vacuum fusion, pulsed dc heating, etc.2. Very low concentrations can be detected, possibily in the parts-per-billion range.3. Only a few milligrams of sample is needed while most other methods require gram-sized samples.4. Local analysis is possibile when spatial resolutions down to tens of micrometers or less are used. 5.No special sample preparation is required. 6. The possibility exists for absolute measurements, i.e., determination without requiring standard samples ( 4 ) .Heretofore some, but not all, of these advantages have been demonstrated (2, 5). Here we introduce a method for determining C, N, and 0 in solids without standards in which the relative errors approach the confidence levels for the concentrations known in reference materials. EXPERIMENTAL SECTIONApparatus. The laser mass spectrometer has been described (6). Figure 1 gives a schematic diagram of the instrument. X-Y galvoscanning mirrors, located just above the objective lens and used to raster the laser beam, are not shown to simplify the layout.Laser. The laser system is a Model 255QT Nd-doped yttrium aluminum garnet (YAG) with an acoustooptic Q-switch manufactured by the Holobeam Corp. The ranges of beam parameters available with this system are given in Table I.Mass Spectrometer. A double focusing mass spectrometer constructed locally (7) based on Mattauch-Herzog (8) ion optics was used. The ion transmission through the energy limit slit was set to transmit -150 eV to the magnetic analyzer. The 150-eV slice of the beam was -40% of the beam transmitted by the electrostatic analyzer. The electrical detector consisted of a Faraday cup followed by ion signal amplification with a Cary Model 401 electrometer. A cryopump provides evacuation of the ion source chamber with a pumping speed of loo0 L/s, producing a clean vacuum and a rapid pump down of the chamber to 1 X torr within an hour.

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Section: Sectionmentioning

confidence: 99%

Determination of carbon, nitrogen, and oxygen in solids by laser mass spectrometry

Zhao¹,

Conzemius²,

Svec³

1984

Anal. Chem.

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show abstract

“…Cluster ion formation in laser ionization mass spectrometry may occur either by direct ionization of the sample by the pulsed laser beam or by a recombination of ions and neutral atoms or molecules in the laser-induced plasma formed above the sample surface. For example, cluster ions of Ag"Cum+, formed by recombination in the plasma, were observed by Wurster et al in laser mass spectra obtained from physically separated Cu/Ag sandwich foils (18). Recombination ions of Ag"Aum+ were present along with cationized species in positive ion spectra collected by Benninghoven and Anders when in- ducing Ag cationization of leucine on Au-Ag sandwich substrates (19).…”

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confidence: 97%