Abstract

European Journal of Mass Spectrometry
Volume 15 Issue 2, Pages 189–198 (2009)
doi: 10.1255/ejms.960

Laser desorption/ablation plumes from capillary-like restricted volumes

Richard Knochenmuss
Novartis Institutes for Biomedical Research, WSJ 503.1104, 4052 Basel, Switzerland. E-mail: rknochenmuss@gmx.net

Laser desorption/ionization from structured surfaces has been the object of recently renewed interest. Conditions in the plume of material ablated from such surfaces may differ from those of a sample which is ablated in bulk. Since recombination and secondary ion–molecule reactions in the plume play a major role in determining the types and quantities of ions observed at the detector, these differences are analytically relevant. Desorption/ionization substrates with channels of high aspect ratio are modeled as capillary nozzles, from which free jets are emitted. A previously developed matrix-assisted laser desorption/ionization ablation/ionization model is adapted for these jets. More primary ions reach the detector when ablated from a capillary orifice, but fewer analye ions are created in secondary reactions. These differences in ion yield can persist for arrays of capillaries on the surface, depending on the ratio of their diameter to spacing.

Keywords: laser desorption/ionization, nanostructured surface, ionization mechanisms, plume expansion

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