Researchers Develop Optical Method Controlling Chemical Reactions
13 May 2014
An optical technique ensuring precise control over certain chemical reactions with ultra-short bursts of energy has been developed by a team of German and Austrian scientists.
Researchers from the Institut für Physikalische Chemie der Friedrich-Schiller-Universität Jena in Germany developed the theory that by directing femtosecond laser pulses at some organic molecules, they can change the distribution of electrons in that molecule - and then determine output products in different ways from conventional chemical reactions.
This is possible because electrons have a relatively tiny mass compared with atomic nuclei and are influenced significantly by the laser pulse, while nuclei are hardly affected because they are heavier. The theory was tested and practical results were achieved at the Technical University of Vienna, Austria.
The scientists managed to direct the molecules with the first laser pulse, and then changed the relative angle at which a second laser hit the molecule to achieve selectivity in the dissociation process.
The first pulse lasts about 50 femtoseconds and makes the molecules rotate at different speeds until they become approximately aligned. Then the second, much shorter pulse is applied for 5 femtoseconds, managing to change the state of electrons and in some cases even removing electrons from a molecule.
Removing the right electrons causes the molecule to break at a specific position. For example, acetylene (C2H2) was broken into CH2+, CH+ or carbon ions, C+. Using this method, scientists were able for the first time to distinguish the various paths the reaction might take and select the outcome they desired.