'Ultrafast Camera' Built to Watch Electron Motion

By combining two ultrashort laser pulses that meet from different directions, scientists have succeeded in creating three-dimensional optical fields.

According to Ambassador Arjan's report, citing the Nano Headquarters, this method not only provides physicists with a new tool to study the interaction of light and matter, but it can also open new paths to identify chiral structures and precisely control the quantum states of electrons.

This research was conducted under the supervision of Professor Matthias Wollenhaupt (Matthias Wollenhaupt) from the University of Oldenburg and its results were published in the scientific journal Physical Review Research in an article entitled "Multiphoton ionization with three-dimensional optical fields".

The main idea of the research is based on the use of two very short laser pulses. These pulses last only a few millionths of a billionth of a second and are classified as femtosecond laser pulses. By specially shaping these pulses and using two laser beams with different colors, the researchers interfered with each other in a vacuum chamber in such a way that a three-dimensional light field was formed at the point of impact.

In a normal optical field, changes in the field can be observed in certain directions; But in the new method, the created field oscillates in all three spatial directions. This feature allows researchers to adjust the shape and characteristics of the light field more accurately and use it to manipulate specific interactions between light and matter.

Darius Köhnke, one of the paper's two lead authors and a PhD student in the "Ultrafast Coherent Dynamics" group at the University of Oldenburg, explains that oscillating the field in all three spatial directions creates new opportunities to probe and control specific interactions between light and matter. According to the researchers, one of the most important features of this method is that with three-dimensional light fields, electrons can be brought to certain quantum states that were previously impossible to create in experiments.

To demonstrate the feasibility of this method, the researchers conducted their experiment on potassium atoms. Using a three-dimensional light field, they selectively moved the electrons of these atoms to higher energy levels, known as excited states, and then separated them from the atom.

But the importance of the experiment was not limited to creating these excited states. Scientists were able to simultaneously observe the changes in the state of electrons in very short time intervals. This feature made the new method resemble a kind of "ultra-fast camera" for observing quantum processes; It is as if scientists have recorded the successive stages of a very fast process by using successive flashes, and by putting these images together, they have made a movie of the evolution of different electron states.

Explaining the importance of this achievement, Wollenhaupt says that this method enables the creation of electron quantum states that were previously only described theoretically. On the other hand, researchers can now observe these states from a spatial point of view. In this way, the experimental toolbox of physicists for the study of light and matter has been expanded by adding a new type of three-dimensional optical fields.

One of the most interesting possible applications of this technology is the study of chiral molecules; Molecules that are very important in biology and medicine. A chiral molecule can be thought of in two different forms that are mirror images of each other, but they cannot be completely matched; Just like the left and right hands of humans, which look similar to each other, but do not match each other.

Chirality is found in many biological molecules, including amino acids, carbohydrates, and active pharmaceutical ingredients. The important thing is that two mirror forms of a molecule do not necessarily have the same behavior or effect, and sometimes the difference between them can have very important consequences for human health.

A well-known example of this is Thalidomide; The active substance of the medicine used in Contergan medicine. One form of this molecule was associated with the occurrence of congenital abnormalities during pregnancy, while the other form did not have such a harmful effect. This difference shows why the accurate diagnosis and separation of different forms of chiral molecules is very important in pharmaceutical and biomedical sciences.

However, it is not always easy to identify and distinguish the two mirror-image forms of a molecule. Therefore, researchers hope that three-dimensional light fields can create new horizons in the field of molecular chirality detection.

Wollenhaupt says theoretical studies have shown that three-dimensional light fields themselves can also have chiral properties. This feature raises the possibility of using such fields to check and control the chirality of molecules more precisely; A field that can become important in the future for the study of molecular structures and their complex interactions with light.

The importance of this research path has already been noticed by Olga Smirnova, a physicist at the Max Born Institute for Nonlinear Optics in Berlin. In an article titled "The New Era of Molecular Chirality" published in the Science magazine, he discussed the capabilities of three-dimensional light fields to investigate molecular chirality.

The researchers of the University of Oldenburg believe that the results of the new study can provide one of the necessary experimental bases for the development of such applications. From controlling the quantum states of electrons to directly observing their evolution and probing chiral structures, 3D optical fields offer a new perspective on how light can be used to control matter on a quantum scale.

This achievement finally shows that light is not the only tool for observing the world; By carefully designing optical fields, it can also be used as a tool to shape and control the behavior of particles on a quantum scale.