Peering through a viewport, I watch as a blob of
atoms absorbs photons of laser light and re-emits them at slightly higher energies, losing a bit of heat each time.
As
the atom absorbs photons, it will receive a barrage of momentum kicks in the direction that the light beam propagates.
Some might argue that the term «re-radiate» should be reserved for cases where a molecule or
atom absorbs a photon of a given energy, and later emits a photon of the same energy, as the excited state returns to normalcy.
Not exact matches
These rules predict, for example, how electrons orbit a nucleus in an
atom, and how an
atom can
absorb photons, particles of light.
According to quantum mechanics, an
atom can only
absorb a
photon of particular energies and colors as the electron within the
atom hops from a lower energy state to a higher energy state.
Photons that enter the crystal at one end bounce back and forth between these «mirrors» a few thousand times before they can escape, which increases their likelihood of getting
absorbed by an
atom along the way.
Generally, the bigger the chunk of crystal, the greater the chance that one of its
atoms will
absorb a
photon streaking through the material.
Instead of being knocked out, when an electron tightly bound to a neon
atom absorbs the lower energy
photon, it becomes loosely bound, causing the
atom to become «excited».
The rules of quantum mechanics give
atoms discrete ways to
absorb energy in collisions or lose it to
photons.
Ordinarily the
atom acts as a barrier to
photons from the probe beam because it would first
absorb them — going from its «ground» state to an «excited» state — and then shoot them back, that is, reflect them.
Instead, each particle of light, or
photon, is briefly
absorbed by an
atom in the material.
If an
atom absorbs a single
photon, its change in velocity is tiny compared with the average velocity of
atoms in a gas at room temperature.
Of course, for every
photon the
atom absorbs, it must emit one.
The
photon momentum has a component that is opposite to the atomic motion and, as a result, the momentum kick of the
absorbed photon slows the
atom down.
If
atoms are exposed to several laser beams with carefully chosen polarization and frequency values, then they preferentially
absorb photons from the forward hemisphere, where the
photon angular momentum and the atomic velocity are at an angle larger than 90 degrees.
Some of those
atoms vibrate sufficiently vigorously that their vibrational energy is roughly equal to the electronic energy (
photons)
absorbed from the sun — in essence, they are in resonance with the solar energy.
If an
atom is bombarded with a beam of light of a particular frequency, it will continuously
absorb and reemit
photons, the quanta of light.
An
atom can
absorb a
photon, or light particle, by boosting one of its electrons to a higher energy, but it's unstable in this state.
When an already excited
atom is hit by another
photon, however, it can't
absorb it; instead it releases a
photon of the same color, or frequency.
When such a
photon collides with a sodium
atom, the sodium's own peculiar properties allow it to
absorb the
photon's angular momentum.
But after soaking up the twisting of one
photon, an
atom can't
absorb any more and becomes «bleached» — invisible to the laser light.
On its 12 - billion - year journey, the light had passed through interstellar clouds of metals such as iron, nickel and chromium, and the researchers found these
atoms had
absorbed some of the
photons of quasar light — but not the ones they were expecting.
Ordinary
atoms can change their energy levels under the right conditions by either
absorbing or emitting a
photon.
Because dark
atoms would emit or
absorb dark
photons, the universe might be full of invisible, dark light that constantly interacts with clouds of dark
atoms, raising their temperature and puffing them up.
Vibrational modes in molecules with three or more
atoms (H2O, CO2, O3, N2O, CH4, CFCs, HFCs...) include bending motions that are easier to excite and so will
absorb and emit lower energy
photons which co-incide with the infrared radiation that the Earth emits.
Photons of sufficient energy are
absorbed by oxygen molecules and as a result the
atoms of the oxygen are «blown» apart.
All
atoms and molecules
absorb some waveband (s) of light, then they emit that
photon of light shortly thereafter.
If the
photon's frequency and energy is different by even a little, the
atom can not
absorb it (this is the basis of quantum theory).
When that
photon hits an
atom, that energy can be
absorbed.
If the
atom absorbs that
photon, the
atom will have more energy than before.