Simulation of the infrared spectrum of ultrafast interconverting geometrical isomers

The effect of ultrafast interconversion of geometrical isomers on the infrared spectrum was obtained through molecular dynamics simulation. Arresting the interconversion by introduction of a very high barrier allowed exchange broadening in the absence of that barrier to be convincingly demonstrated. The spectra obtained could all be fitted very well with Bloch lineshapes and the lifetimes extracted in this way agreed well with those obtained directly from the simulation except in those cases where the interconversion rate was too slow or too fast.