# Does photon electromagnetic field “shake” charged particles and atoms?

Lets theoreticaly imagine completly stationary particle,like electron for example.Can photon,or photons shake it,or oscillate its position? By that I dont necesarily mean the center position must change,more like jumping up and down,cyclicaly attracted and repelled by electromagnetic field.

What I really want to know is,if there is plasma above solid surface,with charged atoms and electrons being in close proximity but not touching the surface,will photons from either coherent or incoherent light source smash them against the solid surface?

I know that in plasma due to thermal motion they are colliding with the solid surface all the time,but apart from this normal thermal motion,theoreticaly if it was near zero temperature plasma,will the photons grab the charged species with their EM field and smash them agaisnt the surface near the peaks of the EM field oscillation cycle?

If photons can indeed make the electrons shake with their oscillating EM field,is it only when they hit the electron or can electron start oscillating in this field without being directly hit with the photons just flying close to it?

How far away can the photons move the electron from its center position during the oscillating movement? Is it 1/4 of wavelenght? So 400nm photon could move it 100nm from center,is it more? Is it less? Does it depend on photon flux density?

If the electrons or charged atoms move around the photons,how fast they will go at the peak in eV units? Does it depends more on the number of photons or wavelenght of photons? Will for example a 10eV photons make the electron shake with peak speed of 10 eV?

• Your question is based on a large number of loose assumptions assigning a classical behavior to quantum objects. This is why it is difficult to answer without first taking your question apart. However I'd like to point out one thing that may give you one insight. The electromagnetic wave oscillates perpendicular to the direction of movement. Therefore photons cannot "push" electrons forward like little "balls". Also you need to separate the field (virtual photons) from the wave (real photons), as their interactions with electrons are very different. – safesphere Sep 23 '17 at 15:14
• I never mentioned any "push",it doesnt need to be front to back ,it can be up and down,left to right.Also push sounds like I am thinking the average or rest center position would move,but I dont think that,I dont mean moving permanently,I mean cyclical oscillations around center position.Anyway,I just want to know if electrons position in 3d space can oscillate when coherent photon beam is travelling nearby – wav scientist Sep 23 '17 at 15:53
• Then I would not bring photons into the question, but ask how a free stationary electron moves in a classical electromagnetic wave. I'd say, being stationary the electron would not feel the magnetic field, but move under the electric field. And then, since it moves, it would also feel the magnetic field a bit. However I'll leave this to the experts. You've confused @AnnaV into a quantum answer while your question is purely classical. – safesphere Sep 23 '17 at 16:19

As photons travel rather fast, I strongly doubt that the picture, that an electron is accelerated due to the E-field of the photon, makes sense. Just take your example and estimate

• Let's assume the interaction takes place over one wavelength. The time it takes the photon to travel one wavelength is $T = \lambda/c$.
• The acceleration would be by rearranging $s = \frac{1}{2} a t^2$ to get $a \sim 2 \lambda / T^2$.
• Now let's calc the energy in units of $mc^2$ \begin{align} \frac{E}{mc^2} &= \frac{F \cdot s}{mc^2} \sim \frac{F \cdot \frac{\lambda}{4}}{mc^2} \\ &= \frac{a \cdot \lambda}{4 c^2} = \frac{a\cdot \lambda}{4 \lambda^2/T^2} \\ &= \frac{2 \lambda/T^2\cdot \lambda}{4 \lambda^2/T^2} = 0.5 \end{align} So the energy would be just half the energy needed to create a second electron. Hence, this is huge.

However, you might want to look into the possibility of a photon "colliding" with an electron. This is called the Compton effect.

• But what if there isnt just single photon flying around,but train of photons? So the electron will be in the photon EM field all the time as long as the laser is switched on.Single photon or coherent photon stream from laser,it doesnt matter,I want to know if photons can vibrate,oscillate or move in any kind of way charged particle.Even if the center position doesnt change,but it jumps up and down,left to right,front to back or even starts circling,it doesnt matter,I just want to know if it will move. – wav scientist Sep 23 '17 at 15:43
• I also want to add,that I think this might depend on the group or phase velocity of the coherent laser beam,I think in certain combination it might keep the electron stationary while in other it will vibrate it in sine wave kind of way. – wav scientist Sep 23 '17 at 15:48
• If you ask whether or not an electron can temporarly change it's position due to the electric field of a visible photon (within the classical picture), the answer is yes. The change will be tiny and so it will not make sense in the qm picture. However, if you consider a resonator of a particle collider, the situation differs: The wavelength is much larger than $400nm$ so the period is much longer too. Hence, the electron will experience a significant acceleration. – Semoi Sep 23 '17 at 15:52
• What kind of interaction between photons and electron makes the electron vibrate? Photons can either fly nearby the electron,collide and reflect or collide and get absorbed,whitch of these is the one who will move it? – wav scientist Sep 24 '17 at 8:19
• a photon does not have a measurable electric field or a magnetic field. see the link above on the photon wave function. It is only in a superposition of innumerable photons that the classical fields appear. see motls.blogspot.com/2011/11/… – anna v Sep 24 '17 at 15:20

Photons are elementary particles in the standard model of physics, with zero mass, spin + or -1 to its direction of motion, and energy=h*nu. No electric or magnetic field there for individual photons.

The classical electromagnetic field with the varying electric and magnetic fields is an emergent phenomenon from the superposition of innumerable quantum mechanical photon wavefunctions.

In the wave function the electric and magnetic fields are there but photon-electron interactions are described by Feynman diagrams not by a classical "charged particle interaction with electric field", because one is in the quantum mechanical regime at photon particle interactions.

In conclusion, photon electron interaction has no oscillations as you envisage, there will be a scattering described by

when integrated it will give the probability of scattering a photon off an electron.

Classical em radiation is a different story , because the coherent ensemble of zillions of photons does build up a varying electric and magnetic field. After all that is the power of a laser beam, its coherence . Have a look at this .

In high-harmonic generation (HHG) the highly nonlinear interaction between high-intensity laser pulses and atoms generates odd harmonics of the frequency of the driving laser. Very high-order harmonics are possible — the harmonic order can reach several hundred — allowing the generation of coherent light at nanometre wavelengths with visible driving lasers. We study methods for increasing the generation efficiency as well as applications of high-harmonic beams, such as ultrafast, "lensless" X-ray imaging.

• But Semoi says photons can move electron,I believe he didnt mean that electron will absorb photon and increase its speed by the eV number of the photon. – wav scientist Sep 24 '17 at 8:50
• Something moving something means energy is transferred. For elementary particles, electronsand photons, it is the compton effect . If atoms are involved more complicated transfers can happen , see also my answer here physics.stackexchange.com/questions/358727/… . Photons have the electric field in the complex wave function, not measurable . only effect is in psi*psi, the probability. It is the superposition of innumerable photons that build the electric and magnetic field of the classical em radiation – anna v Sep 24 '17 at 14:52

Photons induce a small push on the electrons of a transparent material which slow down the peak of the electric part of the wave. Then, the electron return to it's rest position inducing the delayed peak of the magnetic part, 90 degrees compared to the wave mentioned above. Brief, photon wave is slowed down for the same reason an electric wave slows down in a coax cable : The cable is equivalent to an infinite number of inductors in series and capacitors in parallel. The inductors store then release current while the capacitors store then release voltage. The ohmic loss is negligeable so the wave travel with a delay but without wasting energy. The electron act as the capacitor when pushed away, then act like the inductor when it comes back to the rest position. Note: If the electromagnetic wave would be a continuous sinusoidal wave, we would not be able to distinguish the electric from the magnetic side since it is symmetrical on any 90 degrees increment. But photons are made of a single wave, so the first side that reach a peak is arbitrarily called electric and the electric wave oriented 90 degrees and delayed by 1/4 of a cycle is magnetic as it is reacting to a changing electric field.

• But what if the photon pushes the electron into some solid object? How fast is the electron moving when its being pushed? For example,if the stationary electron is pushed by 10 eV photon,does it at some point move at 10 eV velocity? Or does it move only so fast,as the energy that photon lost as ot temporarely slowed down during the interaction? – wav scientist Jul 24 '18 at 23:27