DYNAMICS OF HYDROGEN-BONDING AND ENERGY-TRANSFER IN MATRIX-ASSISTED LASER-DESORPTION

A molecular dynamics simulation of matrix-assisted laser desorption is presented for host and guest particles with internal structure. The l aser-induced phase transition is modeled in a hemispherical volume of pyridine-3-carboxylic acid matrix seeded with a leucine enkephalin gue st molecule. Following an instantaneous temperature jump to 1500 K, re presenting the laser excitation, the network of hydrogen bonds is disr upted in approximately 3 ps. After a 0.7 ps segregation period, the gu est molecule is entrained by the evaporating matrix molecules. The gue st lift-off velocity is estimated at approximate to 156 m/s, a value a bout a factor of two lower than measured for neutral matrix molecules in similar systems.