Energetics of gramicidin S after UV laser desorption from a ferulic acid matrix

Photoionization with coherent 118 nm vacuum ultraviolet light is applied to study kinetic energies of gramicidin S and ferulic acid molecules, laser desorbed from a ferulic acid matrix with 266 nm light. Analysis of the matrix photodecomposition products shows decarboxylation as a main photochemical pathway involved with desorption. Entrainment of the polypeptide by the matrix molecules is found under typical conditions. However, the velocity distributions are not particularly narrow, being at most borderline supersonic.