No abstract

Laser irradiation of absorbing materials can be used to generate acoustic pulses with extremely high amplitude and short pulse duration. Such acoustic pulses can transfer energy and momentum to atomic particles on solid surfaces to cause desorption of the particles. We report experimental observations of the effect of laser-induced acoustic desorption (LIAD) of electrons from metal film surfaces and hydrogen ions from the surface of palladium saturated with hydrogen. We believe LIAD can be used as a gentle technique to transfer analyte molecules and ions into gas phase for mass analysis and for other applications.

Sequencing of DNA fragments of 130 and 200 bp using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for DNA ladder detection was demonstrated. With further improvement in mass resolution and detection sensitivity, mass spectrometry shows great promise for routine DNA sequencing in the future.

Matrix-assisted laser desorption/ionization was used for the detection of four base short tandem repeats (STR) for clinical samples using a time-of-flight mass spectrometer. Since STR plays an important role in genetic disease and human identification, this work indicates that laser desorption mass spectrometry has the potential to achieve rapid DNA typing for both forensic applications and genetic disease diagnosis.

Laser desorption mass spectroscopy has been used to characterize both modern and ∼ 150-year-old daguerreotypes. Such investigations are a necessary prelude to attempts to clean them of tarnish and other contaminants by laser ablation of the surface layers. Both positive- and negative-ion time-of-flight spectra were obtained following YAG laser ablation/desorption at 1064, 532, and 355 nm. Major peaks obtained from several daguerreotypes reveal expected elements from the substrate (Ag, Cu) as well as the developing (Hg) and gilding (Au) processes. Silver clusters (Agn) may reflect surface desorption of molecules or, alternatively, aggregates formed in the ejection process. Silver sulfide molecules observed from old daguerreotypes are the signature of the tarnishing process.