[Timemachine1 (OP)]

Is it possible for any invisible EM waves, like radio waves, ultraviolet soft, or hard X- Rays, or gamma rays, to be combined with other types of EM waves to be able to move electrons in the carbon block, to a shell level that does not absorb visible light, like in glass.
So you mix invisible EM waves of different wavelengths, and frequencies together, you could mix four invisible EM waves as a single beam.
So you want the EM wave to pass through the block of carbon, while also the electrons absorb some of the invisible EM waves, so the electron moves to a shell level that does not absorb visible light.
So the mixed invisible EM waves are passing through the carbon, while some of the invisible EM waves are being absorbed, and moving the electrons to a shell level where they will not absorb visible light.
Like in glass, the electrons are in shell levels that do not absorb visible light
Thank you for your help, anything helps even a few words.

[chiralSPO]

I don't think that this would be effective in most cases. I will explain my thoughts below, but first, I will share some cases in for which it does work (sorta).

Transient absorption spectroscopy (TA or "pump-probe") is a technique in which a sample is illuminated by a brief and bright flash of light (either at a single frequency, or broad spectrum, usually from a laser, called a "pump") and then the absorbance spectrum of the sample is measured (called the "probe"), and compared with the same spectrum from before the flash. If the sample is photoactive, then the two spectra are different, and some useful information can be extracted from the difference. See more here: https://en.wikipedia.org/wiki/Time-resolved_spectroscopy#Transient-absorption_spectroscopy

One type of difference observed in TA spectroscopy is called a "bleach" which is an absorption signal that decreases after the initial flash of light perturbs the electronic structure of the sample--essentially there is a frequency of light that gets absorbed less intensely right after the flash than it was before the flash. In theory, a bleach could be strong enough that a material goes from colored to colorless.

The tricky part is that bleach is only very short lived. I mean anywhere from a few picoseconds (10^–12 seconds) to a few nanoseconds (10^–9 seconds). That is very short lived on any sort of human time-frame. I think we have to see something for at least 20 milliseconds (2x10^–2 seconds) for it to register subconsciously, and more than 50 milliseconds for it to register consciously, so you would have to flash the laser onto the sample more than a million times in a row for the bleach to be barely visibly noticeable... Or you could hold the sample under constant illumination, but that much optical pumping would deliver a huge amount of heat to the sample (likely vaporizing it before you could notice it was invisible).

In addition to this time-scale limitation, there is also the issue of how much sample the pump can actually reach. If the pump frequency interacts strongly with the sample (as it needs to for any significant effect on the sample) then it will also have only a limited penetration depth into the sample. You could turn up the power of the pump, but then again with the risk of vaporizing whatever you are trying to cloak...

Even if somehow we were able to avoid heating the sample up, we would still have to worry about it breaking down. Remember, it is the electronic structure of matter that holds stuff together--exciting electrons out of bonding orbitals (or bonding bands) will destabilize the material, and exciting electrons into different states will likely make the material much more chemically reactive.


Overall, and interesting idea, that might sorta work in some very specific cases, but nothing that could be useful or probably even noticeable. You would have made a very powerful death ray long before it could serve as even a pathetic cloaking device.