Everything about Atomic Physics totally explained
Atomic physics (or
atom physics) is the field of
physics that studies atoms as an isolated system of
electrons and an
atomic nucleus. It is primarily concerned with the
arrangement of electrons around the nucleus andthe processes by which these arrangements change. This includes
ions as well as neutral atoms and, unless otherwise stated, for the purposes of this discussion it should be assumed that the term
atom includes ions.
The term
atomic physics is often associated with
nuclear power and
nuclear bombs, due to the
synonymous use of
atomic and
nuclear in
standard English. However, physicists distinguish between atomic physics—which deals with the atom as a system comprising of a nucleus and electrons, and
nuclear physics—which considers
atomic nuclei alone.
As with many scientific fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of
atomic, molecular, and optical physics. Physics research groups are usually so classified.
Isolated atoms
Atomic physics always considers atoms in
isolation. Atomic models will consist of a single nucleus which may be surrounded by one or more bound electrons. It is
not concerned with the formation of
molecules (although much of the physics is identical) nor does it examine atoms in a
solid state as
condensed matter. It
is concerned with processes such as
ionization and
excitation by photons or collisions with atomic particles.
While modelling atoms in isolation may not seem realistic, if one considers atoms in a
gas or
plasma then the time-scales for atom-atom interactions are huge in comparison to the atomic processes that we're concerned with. This means that the individual atoms can be treated as if each were in isolation because for the vast majority of the time they are. By this consideration atomic physics provides the underlying theory in
plasma physics and
atmospheric physics
even though both deal with huge numbers of atoms.
Electronic configuration
Electrons form notional
shells around the nucleus. These are naturally in a
ground state but can be excited
by the absorption of energy from light (
photons), magnetic fields, or interaction with a colliding particle (typically other electrons). The excited electron may still be bound to the nucleus
and should, after a certain period of time, decay back to the original ground state. The energy is released as a photon. There
are strict
selection rules as to the electronic configurations that can be reached by excitation by light—however there are no such rules for excitation by collision processes.
An electron may be sufficiently excited so that it breaks free of the nucleus and is no longer part of the atom. The remaining system is an
ion and the atom is said to have been
ionized having been left in a charged state.
History and developments
The majority of fields in physics can be divided between theoretical work and experimental work
and atomic physics is no exception. It is usually the case, but not always, that progress goes
in alternate cycles from an experimental observation, through to a theoretical explanation
followed by some predictions which may or may not be confirmed by experiment, and so on. Of course, the current state of technology at any given time can put limitations on what can be achieved experimentally and theoretically so it may take considerable time for theory to be refined.
Clearly the earliest steps towards atomic physics was the recognition that matter was composed
of
atoms, in the modern sense of the basic unit of a
chemical element. This theory was developed by the British chemist and physicist
John Dalton in the 18th century. At this stage, it wasn't clear what atoms were although they could be described and classified by their properties (in bulk) in a
periodic table.
The true beginning of atomic physics is marked by the discovery of
spectral lines and attempts to describe the phenomenon, most notably by
Joseph von Fraunhofer. The study of these lines led to the
Bohr atom model and to the birth of
quantum mechanics itself. In seeking to explain atomic spectra an entirely new mathematical model of matter was revealed. As far as atoms and their electron shells were concerned, not only did this yield a better overall description, for example the
atomic orbital model, but it also provided a new theoretical basis for
chemistry
(
quantum chemistry) and
spectroscopy.
Since the
Second World War, both theoretical and experimental fields have advanced at a great pace. This can be attributed to progress in computing technology which has allowed bigger and more sophisticated models of atomic structure and associated collision processes. Similar technological advances in accelerators, detectors, magnetic field generation and
lasers have greatly assisted experimental work.
Significant atomic physicists
Pre quantum mechanics
Further Information
Get more info on 'Atomic Physics'.
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