Atomic, Molecular & Optical Physics:

Introduction:

The study of matter-matter and light-matter interactions at scales of one or a few atoms and energies of a few electron volts is known as atomic, molecular, and optical physics (AMO). The relationships between the three are intricate. Classical, semi-classical, and quantum approaches are all included in AMO theory. These areas often include the theory and applications of optical properties of matter in general as well as emission, absorption, scattering, and spectroscopy of electromagnetic radiation (light) from excited atoms and molecules.

 

While molecular physics is the study of the physical characteristics of molecules, atomic physics is the branch of AMO that investigates atoms as a standalone system of electrons and an atomic nucleus. Due to the synonymous usage of the terms atomic and nuclear in standard English, the word "atomic physics" is frequently connected with nuclear energy and nuclear bombs. However, physicists make a distinction between nuclear physics, which only takes into account atomic nuclei, and atomic physics, which deals with the atom as a system made up of a nucleus and electrons. The different forms of spectroscopy are crucial experimental methods. While closely related to atomic physics, theoretical chemistry, physical chemistry, and chemical physics all share a lot in common with molecular physics.

 

Atomic, Molecular & Optical Physics

Electronic structure and the dynamical mechanisms through which these groupings change are the main topics of both subfields. This work typically makes use of quantum mechanics. This approach is known as quantum chemistry in molecular physics. One significant feature of molecular physics is the extension of the fundamental atomic orbital theory to the molecular orbital theory. In addition to focusing on atomic processes in molecules, molecular physics also considers influences brought on by the structure of the molecules.Moles can rotate and vibrate in addition to the electronic excitation states that are known from atoms. There are discrete energy levels and quantized rotations and vibrations. The far infrared area of the electromagnetic spectrum (between 30 and 150 m in wavelength) is where pure rotational spectra can be found since there are the smallest energy differences between the various rotational states. Near infrared (between 1 and 5 m) is where vibrational spectra are located, while the visible and ultraviolet spectrum is where electronic transition spectra are primarily found. It is possible to determine attributes of molecules, such as the distance between the nuclei, by measuring the rotational and vibrational spectra.

 

In atomic physics, as in many other scientific disciplines, rigorous demarcation is sometimes viewed in the broader perspective of atomic, molecular, and optical physics. Typically, physics research groups fall within this category.

 

The study of electromagnetic radiation's creation, its characteristics, and its interactions with matter, particularly its manipulation and control, is known as optical physics. Because it is concentrated on the study and use of novel phenomena, it varies from general optics and optical engineering. However, there is little difference between optical physics, applied optics, and optical engineering because basic research in optical physics leads to the creation of novel devices and applications whereas applied optics and optical engineering devices are required for that research.In many cases, the same individuals work on both fundamental research and the development of applicable technologies. Take, for instance, the experimental proof of electromagnetically induced transparency by S. E. Harris and the experimental proof of slow light by Harris and Lene Vestergaard Hau.

 

Microwaves to X-rays are just a few of the light sources that optical physics researchers utilize and create. Light generation and detection, linear and nonlinear optical processes, and spectroscopy are all included in this field. Optical science has been revolutionized by lasers and laser spectroscopy. Quantum optics, coherence, and femtosecond optics are further areas of focus in optical physics. Support is also given in optical physics for topics like the atom-cavity interaction at high fields, the nonlinear response of single atoms to strong, ultra-short electromagnetic fields, and the quantum characteristics of the electromagnetic field.

 

The creation of novel optical methods for nano-optical measurements, diffractive optics, low-coherence interferometry, optical coherence tomography, and near-field microscopy are other significant areas of study. Ultrafast optical science and technologies are a focus of optical physics research. Applications in communications, medical, industry, and even entertainment are made possible by optical physics.

 

Atomic, Molecular & Optical Physics

History:

The realization that everything is made up of atoms—terms, today's the fundamental unit of a chemical element—was one of the initial steps toward the development of atomic physics. In the 18th century, John Dalton created this theory. Although they could be broadly characterized and categorized by their visible qualities, which were eventually enumerated by John Newlands and Dmitri Mendeleyev in the mid- to late 19th century, it was still unclear what atoms were at this point.

 

Later, the discovery of spectral lines and attempts to explain the phenomenon—notably by Joseph von Fraunhofer, Fresnel, and others in the 19th century—made the relationship between atomic physics and optical physics evident.

 

Physicists were attempting to comprehend atomic spectra and blackbody radiation from that point until the 1920s. The Bohr atom model was one method used to explain hydrogen spectral lines.

 

Due to numerous factors, including the Bohr model's restriction to hydrogen and experiments involving electromagnetic radiation and matter (such as the photoelectric effect, Compton effect, and the spectra of sunlight), a brand-new mathematical model of matter and light, known as quantum mechanics, was developed.

 

According to the Paul Drude and Hendrik Lorentz model, early theories to explain the origin of the index of refraction regarded an electron in an atomic system conventionally. The idea was created in an effort to identify the source of a material's wavelength-dependent refractive index n. In this concept, an electron that was linked to an atom was made to oscillate by incident electromagnetic waves. The frequency of the incident electromagnetic wave and the oscillator's resonant frequencies would then be related to the oscillation's amplitude. The result of superimposing these waves from numerous oscillators would be a wave that moved more slowly.

 

Ernest Rutherford came to the conclusion that an atom had a core proton in 1911 based on the scattering of alpha particles. He further reasoned that Coulomb's law, which he had confirmed was still valid at small scales, would still cause an electron to be attracted to the proton. He consequently thought that electrons were revolving around the proton. In 1913, Niels Bohr merged Planck's thoughts on quantization with the Rutherford model of the atom. Only precise and well-defined electron orbits, which likewise don't emit light, may exist. According on the energy difference between the orbits, an electron in a jumping orbit would either emit or absorb light. The energy levels he predicted were then in agreement with what was observed.

 

These findings, which were based on a discrete collection of unique standing waves, clashed with the continuous classical oscillator theory.

 

The photoelectric effect, on which Albert Einstein's research focused in 1905, allowed for the correlation of a light wave's frequency with a photon's energy. By including the three stages of stimulated emission, spontaneous emission, and absorption in 1917, Einstein expanded on Bohrs' model (electromagnetic radiation).