# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: memoryerase1 on 31/12/2015 23:20:49

Title: Does the electron absorb only 1 photon to move up 1 energy band/shell?
Post by: memoryerase1 on 31/12/2015 23:20:49
Also at what rate does the absorption, and transmission process happen.
Does it take more than 1 photon to excite the electron to a higher energy band, or does it take several photons.
Is it one photon for every electron, or does it depend on the frequency of the light.
Title: Re: Does the electron absorb only 1 photon to move up 1 energy band/shell?
Post by: chiralSPO on 01/01/2016 06:43:06
Typically, one photon excites one atom or molecule (you can think of it as one electron per photon, but remember that it is the whole system that gets excited.)

It is possible to have multiphoton processes, but usually requires very high photon densities, as would be generated by a laser.
Title: Re: Does the electron absorb only 1 photon to move up 1 energy band/shell?
Post by: evan_au on 01/01/2016 09:19:17
To paraphrase a slightly different aspect of the question:
Quote
Does 1 photon to move an electron up only 1 energy band/shell?
An atom (eg Hydrogen) has a large number of energy levels, often called "n"; in theory there are an infinite number of them (n=1 to ∞), although in practice the energy of anything above n=10 is so close to each other that you could ignore it for practical purposes.

It is possible for 1 photon (of λ=121.57nm in the ultraviolet) to take 1 electron in 1 Hydrogen atom up 1 energy level from n=1 to n=2.
Similarly, 1 photon (of λ=656.3 in the visible violet) could move 1 electron from n=2 to n=3.
These are cases such as described in the question.

However, it is also possible for 1 photon (of λ=102.57nm in the ultraviolet) to take 1 electron up two levels from n=1 to n=3.

In theory, there are an infinite number of examples where an electron can skip 1 or more levels, but in practice you could say there are at least 100 important cases for Hydrogen.

Hydrogen is the easiest element to study, because each atom has just 1 electron, but the same principle applies to other atoms...
http://en.wikipedia.org/wiki/Hydrogen_spectral_series