Excimer laser desorption mass spectrometry of biomolecules at 248 and 193 nm

Laser desorption mass spectrometry (LD-MS) of various peptides has been performed with excimer laser nanosecond pulses of 248- and 193-nm wavelengths. Whereas the spectra obtained with 248 nm resemble those obtained earlier with quadrupled Nd:YAG lasers at 266 nm, the peptides show a quite different fragmentation and association behavior at 193 nm. These observations can help in understanding the desorption and ion formation process. They indicate a wavelength-dependent competition between photochemical ion formation and ion generation via a collective process of the strongly perturbed solid. They can also help to further optimize the analysis of given organic molecules by LD-MS.