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The rate at which molecules change shape may be slower than previously thought

Researchers from the Weizmann Institute found a way to measure the rate of change of shape of a molecule - and discovered that it may be slower than anything previously proposed

Illustration: pixabay.
Illustration: pixabay.

"...if we run fast, fast" - in the words of Yehiel Moher in the song about Lipa HaGalon - "then the whole business will break". Hence, slowness sometimes has an advantage. An example of this was recently discovered by scientists from the Weizmann Institute who studied molecular processes in outer space, which may affect the shape development and complexity of various molecules.

Molecules are often represented by models of "balls" and "sticks" reminiscent of children's toys; The balls represent the nuclei of the atoms, and the sticks - the bonds formed between them by the electrons. In these static models, the relative position of the sticks and spheres allows the shape of the molecule to be hypothesized. A more realistic model would show the nuclei vibrating around their "fixed" position and the entire molecule rotating. From time to time, the molecule undergoes a change and takes a different form than the initial one; In other words, it becomes an isomer of the original molecule. Answering a number of open questions in chemistry and physics depends on understanding the "isomerization" rate of the molecules, that is, how quickly - or slowly - they change their shape. Recently, Dr. Oded Haber, Dr. Koshik Shaha and their colleagues in the research group of Prof. Daniel Zeifman In the Department of Particle Physics and Astrophysics, a way to measure the rate of shape change - and they discovered that this rate can be significantly slower than anything previously proposed. These findings Were published Recently in the scientific journal Nature Communications..

"These findings may help in building models for the development of complex molecules in outer space"

Slower: How long it takes for a long carbon molecule to change shape from a chain to a ring after being bombarded with a laser. Source: Weizmann Institute magazine.
Slower: How long it takes for a long carbon molecule to change shape from a chain to a ring after being bombarded with a laser. Source: Weizmann Institute magazine.

Any change in the shape of a molecule substantially affects its properties. Therefore, understanding the isomerization process is essential for many fields of research. Dr. Haber explains that the measurement of the time it takes for a molecule to change its shape - assuming that all the necessary conditions for this are met (for example, a sufficient energy level) - has so far been based on estimates and measurements using two laser pulses at different times. The best estimate was based on the dynamics in the molecule - for example, measuring the rotation speed of the atomic nuclei. Typical rotation times of a molecule are on the order of one picosecond to hundreds of picoseconds, depending on the size of the molecule; Previous experiments have produced numerical results similar to these estimates.

However, Dr. Haber and his colleagues were able to measure the time period in which a molecule of ten carbon atoms - with one additional electron - undergoes isomerization from a chain form to a ring form. To carry out the change process, the researchers bombarded the molecule with a controlled laser pulse that caused the carbon molecule to be excited. The measurement showed that instead of picoseconds, the process lasted up to about a hundred microseconds. In other words, up to about a million times slower than what previous experiments have shown.

From the right: Dr. Oded Haber, Dr. Michael Rappaport, Dr. Koshik Shaha, Dr. Mark Iron and Prof. Daniel Zeifman. Source: Weizmann Institute magazine.
From the right: Dr. Oded Haber, Dr. Michael Rappaport, Dr. Koshik Shaha, Dr. Mark Iron and Prof. Daniel Zeifman. Source: Weizmann Institute magazine.

These findings may help in building models for the development of complex molecules in outer space. The presence of these molecules in areas where the density of matter is quite low - as shown by measuring the absorption and emission lines of light - poses an open question that fascinates astrophysicists in different parts of the world. Among other things, one of the assumptions is that such processes could have led to the formation of complex organic molecules, such as amino acids, which are the building blocks of proteins.

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