Molecular physics

Molecular physics is the study of how molecules behave and what they are made of. Molecules are tiny parts of everything around us, like the water in a glass or the air we breathe. Scientists who study molecular physics look at how these tiny parts move and change.

This area of science overlaps with other subjects like physical chemistry, chemical physics, and quantum chemistry. It is often thought of as a part of atomic, molecular, and optical physics. To understand molecules, scientists use ideas from both old and new physics, called classical and quantum mechanics.

They also study how light and other kinds of energy interact with molecules. Experiments in molecular physics often use special tools, such as spectroscopy and scattering, which help scientists see and measure the tiny actions of molecules. This research helps us learn more about the world and can lead to new technologies and medicines.

Molecular structure

In a molecule, both the tiny particles called electrons and the centers of atoms, known as nuclei, feel similar forces. But the nuclei stay mostly in one place, while the electrons move around a lot. This happens because nuclei are much heavier than electrons, so they don't move as much when the same force acts on them. Special experiments using neutron scattering have helped scientists confirm this view of molecules.

Molecular energy levels and spectra

When atoms come together to form molecules, some electrons stay close to their original atom, but others spread out around the whole molecule. These spreading electrons decide the energy levels of the molecule, and this can be explained using a theory called molecular orbital theory. Molecules have extra energy levels besides the ones atoms have, called vibrational and rotational levels. Vibrational levels are about movement of the atoms in the molecule, and rotational levels are about the molecule spinning. These different types of energy levels mean molecules can absorb and give off light at different colors and wavelengths, which scientists can measure.

Experiments

Scientists study molecules to learn about their shapes, sizes, and energy levels. They use special tools like rotational and vibrational spectra to measure distances between atoms in molecules. X-ray diffraction helps them see these distances directly, especially in molecules with heavier elements.

Researchers also use molecules to test important scientific ideas and explore new physics. Molecules might help in future technologies for processing information in new ways. By studying how energy moves within molecules, scientists learn more about their behavior.