Laser multiphoton and multistep photoionization of molecules and mass spectrometry

Антонов, В. Г.; Letokhov, V. S.

doi:10.1007/bf00902263

Cited by 92 publications

(21 citation statements)

References 70 publications

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“…In agreement with the above, 7,26,27 it was reported that for benzene and other molecules, fast relaxation processes (e.g. photo-dissociation) can compete with further photon excitation, a process which is highly wavelength selective.…”

Section: à2supporting

confidence: 69%

Time-of-flight mass spectrometry of aromatic molecules subjected to high intensity laser beams

Smith

Ledingham

Singhal

et al. 1998

Rapid Commun. Mass Spectrom.

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The recent introduction of femtosecond technology to pulsed lasers has led to the development of femtosecond laser mass spectrometry (FLMS). The present paper describes an FLMS investigation of the aromatic molecules, benzene, toluene and naphthalene. Wavelengths of 750 and 375 nm were used with beam intensities up to 4 Â 10 14 W cm À2 . Pulse widths were of the order of 50-90 fs. The laser system was coupled to a linear time-of-flight mass spectrometer. This experimental method of chemical analysis is gaining momentum, often replacing its nanosecond forerunner, resonant enhanced multiphoton ionization. For the said molecules, predominant parent ion production is found, making identification unambiguous. In fact this characteristic is being consistently attained in small to medium mass molecules irradiated under similar conditions, leading to the conclusion that a universal chemical detection system is a possibility. Such soft ionization is particularly evident at longer wavelengths ($750 nm) with less relative fragmentation, daughter ion formation, compared to results at shorter wavelengths ($375 nm). In terms of parent ion formation, similar numbers are produced with laser intensities around 10 14 W cm À2 for both wavelengths. It has also been shown that at a threshold of about 5 Â 10 13 W cm À2, double ionized molecules appear for the 750 nm wavelength. These interesting new mass spectra display intense single, double and even triple ionized peaks without significantly increased dissociation. Such effects are less pronounced at 375 nm.

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Section: à2supporting

confidence: 69%

Time-of-flight mass spectrometry of aromatic molecules subjected to high intensity laser beams

Smith

Ledingham

Singhal

et al. 1998

Rapid Commun. Mass Spectrom.

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“…To date, some profound papers have been published, reviewing the fundamentals of REMPI as well as REMPI-MS in detail [12][13][14]. In respect to the detailed information given in those publications, only a short overview is presented in this work.…”

Section: Introductionmentioning

confidence: 99%

Determination of Relative Ionization Cross Sections for Resonance Enhanced Multiphoton Ionization of Polycyclic Aromatic Hydrocarbons

et al. 2018

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Resonance enhanced multiphoton ionization (REMPI) is a powerful method for the sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in gaseous mixtures via mass spectrometry (MS). In REMPI, ions are produced by the absorption of at least two photons including defined electronic intermediate states. As a result—unlike other laser-based ionization techniques—spectroscopic selectivity is involved into the ionization process. Nevertheless, these wavelength-dependent ionization rates impede the quantification using REMPI. For this purpose, relative photoionization cross sections (relPICS) give an easy-to-use approach to quantify REMPI-MS measurements. Hereby, the ionization behavior of a single compound was compared to that of a reference substance of a given concentration. In this study, relPICS of selected single-core aromatics and PAHs at wavelengths of 266 nm and 248 nm were determined using two different time-of-flight mass spectrometric systems (TOFMS). For PAHs, relPICS were obtained which showed a strong dependence on the applied laser intensity. In contrast, for single-core aromatics, constant values of relPICS were determined. Deviations of relPICS between both TOFMS systems were found for small aromatics (e.g., benzene), which can be assigned to the differences in UV generation in the particular system. However, the relPICS of this study were found to be in good agreement with previous results and can be used for system-independent quantification.

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“…[1][2][3] Photons are directed to a selected chemical bond in a molecule to achieve a highefficiency energy coupling into a physical or chemical process. The purpose of the resonant excitation is to realize selective bond breaking and control reaction pathways.…”

Section: Introductionmentioning

confidence: 99%

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

Líu

Xie

Gao

et al. 2009

Journal of Applied Physics

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Wavelength-matched vibrational excitations of ethylene ͑C 2 H 4 ͒ molecules using a tunable carbon dioxide ͑CO 2 ͒ laser were employed to significantly enhance the chemical vapor deposition ͑CVD͒ of diamond in open air using a precursor gas mixture of C 2 H 4 , acetylene ͑C 2 H 2 ͒, and oxygen ͑O 2 ͒. The CH 2 -wag vibration mode ͑ 7 ͒ of the C 2 H 4 molecules was selected to achieve the resonant excitation in the CVD process. Both laser wavelengths of 10.591 and 10.532 m were applied to the CVD processes to compare the C 2 H 4 excitations and diamond depositions. Compared with 10.591 m produced by common CO 2 lasers, the laser wavelength of 10.532 m is much more effective to excite the C 2 H 4 molecules through the CH 2 -wag mode. Under the laser irradiation with a power of 800 W and a wavelength of 10.532 m, the grain size in the deposited diamond films was increased by 400% and the film thickness was increased by 300%. The quality of the diamond crystals was also significantly enhanced.

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Laser multiphoton and multistep photoionization of molecules and mass spectrometry

Cited by 92 publications

References 70 publications

Time-of-flight mass spectrometry of aromatic molecules subjected to high intensity laser beams

Time-of-flight mass spectrometry of aromatic molecules subjected to high intensity laser beams

Determination of Relative Ionization Cross Sections for Resonance Enhanced Multiphoton Ionization of Polycyclic Aromatic Hydrocarbons

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

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