Determining the internal dynamics of individual molecules by utilizing UV femtosecond laser pulses have been achieved by physicists at Max Planck Institute of Quantum (MPQ).
The physicists at MPQ and Universität Freiburg, along with Prof. Tobias Schätz, have developed a new concept with single laser pulses by which the internal dynamics of a single molecular ion including a hydrogen atom and a magnesium ion can be resolved.
Light pulses consisting of numerous photons within a few fs range generate single molecule images prior to the detection of radiation damage. Focusing the beam diameter of the laser to the size of a molecule is necessary, followed by placing a single molecule within the laser pulse.
Since 20 years or more, ion traps had generated control capabilities for charged particles. The entry of numerous ions into the trap with their mutual repulsion yields a structured pattern, representing a solid state crystal.
The MPQ team has come up with a process wherein the molecules are embedded into a crystal produced by cooled atomic ions. Two ion traps are connected in series. The molecular ion in the first trap is formulated with magnesium and hydrogen, in a photochemical reaction. These molecular ions are then shifted into a second ion trap embedded with atomic magnesium ions. At a low temperature, the single molecule stops activating and replaces one of the atoms in the ion crystal. The atomic ions emanate light by fluorescence, and the lattice site remains dark. The molecular ion’s position can then be analyzed by detecting the adjacent fluorescence light with accuracy less than 1 µm.
The process of striking the single molecule with a femtosecond laser pulse is demonstrated as follows. The molecule is initially in a vibrational ground state. With a professed pump pulse, the molecules are activated into a state wherein both the hydrogen atom and the magnesium ion oscillate with a period of 30 fs. After 15 fs, the distance between the particles at the turning point of the oscillation, has attained its peak. The disappearance of a non fluorescing dark spot stimulates the breaking of the chemical bond.
Source: http://www.mpq.mpg.de/