François Légaré's team at the INRS Énergie Matériaux Télécommunications Research Centre Montreal, Quebec, Canada) has taken a high-resolution molecular movie of a chemical reaction with a spatial and temporal resolution greatly exceeding that obtained to date using microscopes. The team used a femtosecond laser source to image an acetylene molecule turning into vinylidene.1
Via multiphoton ionization caused by 266 nm ultrashort laser pulses, the tabletop system investigated two chemical reactions: proton migration, and carbon=carbon bond breaking. The results showed for the first time that multiple to-and-fro oscillations can occur between the two isomers acetylene and vinylidene.
"The approach we developed combines multiphoton ionization and Coulomb explosion imaging," says Heide Ibrahim, Banting postdoctoral fellow and primary author of the article. "With the significantly improved resolution of the image, we were able to reveal previously unknown details of this isomerization process and clarify the dynamics of proton migration. This form of imaging uses a compact laser source and is a simple option for studying the ultrafast molecular dynamics of other small organic molecules."
This isomerization process has already been observed using vacuum-ultraviolet (VUV) light from a large free-electron laser. However, the techniques most commonly employed to track nuclear rearrangement in a molecule were largely insensitive to the subtle and irregular changes that occur during a chemical reaction.
The experiments were designed by postdoctoral fellow Heide Ibrahim and professor François Légaré and conducted at INRS's Advanced Laser Light Source (ALLS) laboratory (Laboratoire de sources femtosecondes) in collaboration with the University of Waterloo, the National Research Council of Canada, and Université de Sherbrooke.
1. Heide Ibrahim et al., Nature Communications (2014); doi: 10.1038/ncomms5422