Fundamentals of Laser Desorption Ionization

Laser desorption ionization (LDI) of atomic, molecular, cluster, or particulate species are central methods for transferring an analyte from the condensed phase to the gas phase for subsequent mass spectrometric analysis. This chapter provides a basic introduction to the fundamental chemistry and physics of LDI including the most important experimental parameters and observables. It describes some of the advantages and challenges in LDI. The mechanism of LDI is highly dependent on the laser parameters as well as repetition rate and total number of laser shots. The simplest type of laser desorption is laser-induced thermal desorption of neutral molecules adsorbed on a metal substrate. The chapter discusses ultraviolet matrix-assisted laser desorption ionization (UV-MALDI) and infrared (IR) ablation. IR-MALDI has shown the ability to analyze large biomolecules such as antibodies with low fragmentation. The chapter also provides information on the applications of femtosecond laser ablation.