The fast dance of electron spins

October 04, 2019

When a molecule is hit by light, in many cases a so-called "photoinduced" reaction is initiated. This can be thought of as the interplay of electron motion and nuclear motion. First, the absorption of light energetically "excites" the electrons, which for instance can weaken some of the bonds. Subsequently, the much heavier nuclei start moving. If at a later point in time the nuclei assume a favorable constellation with respect to each other, the electrons can switch from one orbit to another one. Controlled by the physical effect of "spin-orbit coupling" the electron spin can flip in the same moment.

This interplay of motion is the reason why spin-flip processes in molecules typically take quite long. However, computer simulations have shown that this is not the case in some metal complexes. For example, in the examined rhenium complex the spin-flip process already takes place within ten femtoseconds, even though in this short time the nuclei are virtually stationary--even light moves only three thousandths of a millimeter within this time. This knowledge is particularly useful for the precise control of electron spins, as, e.g., in quantum computers.

Investigation is based on enormous computer power

One of the biggest difficulties during the investigation was the huge amount of computer power that was required for the simulations. Although for small organic molecules one can nowadays carry out very accurate simulations already with a modest amount of computational effort, metal complexes present a much bigger challenge. Among other reasons, this is due to the large number of atoms, electrons, and solvent molecules that need to be included in the simulations, but also because the electron spin can only be accurately described with equations from relativity theory. Altogether, the scientists from the Institute of Theoretical Chemistry spent almost one million computer hours at the Austrian super computer "Vienna Scientific Cluster" in the course of their study. This is equivalent to about 100 years of computer time on a typical personal computer.
Publication in Chemical Science: Mai, Sebastian; González, Leticia. Unconventional two-step spin relaxation dynamics of [Re(CO)3(im)(phen)]+ in aqueous solution. Chemical Science 2019. DOI: 10.1039/C9SC03671G

University of Vienna

Related Electrons Articles from Brightsurf:

One-way street for electrons
An international team of physicists, led by researchers of the Universities of Oldenburg and Bremen, Germany, has recorded an ultrafast film of the directed energy transport between neighbouring molecules in a nanomaterial.

Mystery solved: a 'New Kind of Electrons'
Why do certain materials emit electrons with a very specific energy?

Sticky electrons: When repulsion turns into attraction
Scientists in Vienna explain what happens at a strange 'border line' in materials science: Under certain conditions, materials change from well-known behaviour to different, partly unexplained phenomena.

Self-imaging of a molecule by its own electrons
Researchers at the Max Born Institute (MBI) have shown that high-resolution movies of molecular dynamics can be recorded using electrons ejected from the molecule by an intense laser field.

Electrons in the fast lane
Microscopic structures could further improve perovskite solar cells

Laser takes pictures of electrons in crystals
Microscopes of visible light allow to see tiny objects as living cells and their interior.

Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.

Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.

Researchers develop one-way street for electrons
The work has shown that these electron ratchets create geometric diodes that operate at room temperature and may unlock unprecedented abilities in the illusive terahertz regime.

Photons and electrons one on one
The dynamics of electrons changes ever so slightly on each interaction with a photon.

Read More: Electrons News and Electrons Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to