# Early plume and shock wave dynamics in atmospheric-pressure ultraviolet-laser ablation of different matrix-assisted laser ablation matrices

Author(s) Schmitz, Thomas A., Koch, Joachim, Günther, Detlef, Zenobi, Renato
Publication Type Journal Items, Publication Status: Published
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Title Early plume and shock wave dynamics in atmospheric-pressure ultraviolet-laser ablation of different matrix-assisted laser ablation matrices
Author(s) Schmitz, Thomas A.
Koch, Joachim
Günther, Detlef
Zenobi, Renato
Description 15 p.
Journal or Series Title Journal of applied physics
Volume Number 109
Issue Number 12
Start Page 123106
ISSN 0021-8979
1089-7550
Publisher American Institute of Physics
Publication Place Melville, NY
Publication Date 2011-06
Abstract Pulsed laser ablation of molecular solids is important for identification and quantification in (bio-)organic mass spectrometry, for example using matrix-assisted laser desorption/ionization (MALDI). Recently, there has been a major shift to using MALDI and related laser ablation/post-ionization methods at atmospheric pressure. However, the underlying laser ablation processes, in particular early plume formation and expansion, are still poorly understood. Here, we present a study of the early ablation processes on the ns-time scale in atmospheric pressure UV-laser ablation of anthracene as well as of different common MALDI matrices such as 2,5-dihydroxybenzoic acid (2,5-DHB), alpha-cyano-4-hydroxycinnamic acid and sinapinic acid. Material release as well as the formation and expansion of hemi-spherical shock waves were studied by shadowgraphy with high temporal resolution (similar to 5 ns). The applicability of the classical Taylor-Sedov model for expansion of strong shock waves ("point-blast model"), as well as the drag force model, were evaluated to mathematically describe the observed shock wave propagation. The time-and energy-dependent expansion of the shock waves could be described using a Taylor-Sedov scaling law of the form R proportional to t(q), when a q-exponent of similar to 0.5 instead of the theoretical value of q = 0.4 was found, indicating a faster expansion than expected. The deviations from the ideal value of q were attributed to the non-negligible influence of ambient pressure, a weak versus strong shock regime, and additional acceleration processes present in laser ablation that surpass the limit of the point-blast model. The onset of shock wave formation at a fluence of similar to 15-30 mJ/cm(2) for the compounds investigated coincides with the onset of bulk material release, whereas, pure desorption below this fluence threshold did not lead to features visible in shadowgraphy.
DOI 10.1063/1.3592651
Additional Notes Received 6 December 2010, Accepted 22 April 2011, Published online 22 June 2011
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03512
03430
Organisational Unit(s)
NEBIS System Number 000037502
Source Database ID WOS-000292331200007
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@article{Schmtz2011,
author = "Schmitz, Thomas A. and Koch, Joachim and G{\"{u}}nther, Detlef and Zenobi, Renato",
title = "{E}arly plume and shock wave dynamics in atmospheric-pressure ultraviolet-laser ablation of different matrix-assisted laser ablation matrices",
journal = "Journal of applied physics",
year = 2011,
volume = "109",
number = "12",
pages = "123106--",
month = jun,
}


E-Citations record created: Fri, 02 Sep 2011, 06:31:06 CET