Analytical multiphoton ionization mass spectrometry. Part I. Theory and instrumentation

Lubman, David M.

doi:10.1002/mas.1280070504

Cited by 56 publications

(14 citation statements)

References 116 publications

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“…Supersonic molecular beams are used in mass spectrometry predominantly in conjunction with laserinduced multi photon ionization followed by time-offlight mass analysis [9][10][11][12][13][14]. In these experiments the vibrational supercooling is used mostly to improve the wavelength selectivity in resonance-enhanced two or multiphoton ionization schemes.…”

Section: Relatively Nonvolatile Molecules Undergo Lengthymentioning

confidence: 99%

Electron impact mass spectrometry of alkanes in supersonic molecular beams

Dagan

Amirav

1995

J. Am. Soc. Mass Spectrom.

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The electron impact mass spectrometry of straight chain alkanes C8H18-C40H82, squalane, methylstearate, 1-chlorohexadecane, 1-bromohexadecane, and dioctylphthalate was studied by sampling them with supersonic molecular beams. A fly-through Brink-type electron impact ion source was used, utilizing a vacuum background ion filtration technique based on differences between the kinetic energy of the supersonic beam species and that of thermal molecules. The 70-eV electron impact mass spectra of all the alkanes were characterized by a pronounced or dominant molecular weight peak together with all the fragment ions normally exhibited by the standard thermal 70-eV EI mass spectra. In contrast, the NIST library of most of these molecules did not show any molecular weight peak. By eliminating tile intramolecular thermal vibrational energy we gained control over the degree of molecular ion fragmentation by the electron energy. At an electron energy of 18 eV the molecular ion dissociation was further reduced considerably, with only a small absolute reduction in the peak height by less than a factor of 2. The effect of vibrational cooling increased with the molecular size and number of atoms. Pronounced differences were observed between the mass spectra of the straight chain triacontane and its branched isomer squalane. Similar mass spectra of octacosane (C28H58) achieved with 70-eV EI in a supersonic molecular beam were obtained with a magnetic sector mass spectrometer by using an electron energy of 14 eV and an ion source temperature of 150 °C. However, this ion source temperature precluded the gas chromatography-mass spectrometry (GC-MS) of octacosane. The GC-MS of alkanes was studied with an ion trap gas chromatograph-mass spectrometer at an ion source temperature of 230 °C. Thermal peak tailing was observed for C20H42 and heavier alkanes, whereas for C28H58 and heavier alkanes the severe peak tailing made quantitative GC-MS impractical. In contrast, no peak tailing existed even with C40H82 for GC-MS in supersonic molecular beams. The minimum detected amount of eicosane (C20, H42) was shown to be 60 fg. This was demonstrated by using single ion monitoring with the quadrupole mass analyzer tuned to the molecular weight peak of 282 u. The coupling of electron impact mass spectrometry in supersonic molecular beams with hyperthermal surface ionization and a fast GC-MS inlet is briefly discussed.

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Section: Relatively Nonvolatile Molecules Undergo Lengthymentioning

confidence: 99%

Electron impact mass spectrometry of alkanes in supersonic molecular beams

Dagan

Amirav

1995

J. Am. Soc. Mass Spectrom.

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“…Laser-Induced Evaporation A very promising method for vaporizing both atomic solid samples and large biomolecules uses laser-induced evaporation (Lubman 1988a(Lubman , 1988bGrotemeyer and Schlag 1988;Hayes 1987;Coates and Wilkins 1987;Beavis et al 1988). In the case of atoms, the process requires focussing a high-powered pulsed laser to ablate the atoms from the solid, creating a plume that may consist of neutrals and ions.…”

Section: 54mentioning

confidence: 99%

“…Since most polyatomic molecules have broad unresolvable spectral features at room temperature, the SSJ method has been used to provide ultracold molecules with sharp spectral features for analysis (Hayes 1987, Lubman, 1987, 1988a, 1988b. This involves seeding a small percentage of the large polyatomic molecules in a large bath of a light carrier such as argon or helium and expanding through a pinhole orifice into vacuum.…”

Section: Gas Phase Molecular Fluorescencementioning

confidence: 99%

Laser Spectroscopy: Assessment of Research Needs for Laser Technologies Applied to Advanced Spectroscopic Methods

Hurst¹

1990

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“…[3][4][5][6][7][8] Laser ionization utilizes the resonanceenhanced multi-photon ionization (REMPI) method, which features molecular selectivity and enables fragment-free ionization. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] The authors of the present report have developed an online monitoring method using ultrasonic jet-type laser ionization TOFMS (time of flight mass spectrometry), and have confirmed the usefulness of this method with respect to PCBs. 8 Because an extremely large number of molecules exist in environmental gas, the requirement is for a method that is for relatively large molecular selectivity in a short time, so as to enable the rapid analysis of trace concentrations.…”

Section: Introductionmentioning

confidence: 99%