Author Topic: If Xrays are in the KeV range and gmma MeV whats light and radio?  (Read 754 times)

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Offline Beamin

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Another adventure into the crazy world that is the EMF spectrum! (This topic always gets the girls excited try talking about this at bars when trying to get a date)  :=\

We know what happens when you smash electrons at metal at keV nd MeV energies: x and gamma rays, but what happens when you go lower does the same process make UV/light or IR? And I'm not talking through secondary heating: making black body glow, but spectral lines. What is this field of study called?


Can you have less then 1eV?


Designation: 7 of 9 of Unimatrix 0. Species: 475  Human; female. Origination: Grid 001. Your knowledge will be assimilated into the eevblog collective. We are Beamin. Foreplay is inefficient and unnecessary to precede copulation. Resistance is Futile. You will be assimilated.
 

Offline Canis Dirus Leidy

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #1 on: June 18, 2018, 11:57:56 pm »
We know what happens when you smash electrons at metal at keV nd MeV energies: x and gamma rays, but what happens when you go lower does the same process make UV/light or IR?
Yes. There is description (in Russian) of one such experiment. They used 1-15 keV ions and 600 eV electrons to bombard alkali-haloid crystals. In another experiment, electrons with energies of 10-1000 eV were used.
 

Online Kleinstein

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #2 on: June 19, 2018, 01:16:59 am »
Part of those effects at lower energy is the low energy electron diffraction (LEED) - though not looking at the excitations of the solid, but the electrons that bounce back. AFAIK one can go rather low in energy, though it adds extra complications to filter the electron energies to less than thermal energies.
 

Offline T3sl4co1l

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #3 on: June 19, 2018, 02:04:51 am »
LMGTFY, ;)
https://www.google.com/search?q=Planck+constant+*+100+megahertz+in+electron+volts

Edit: great, it thinks it knows better than I do, how to format a URL. :palm:

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Offline MatthewEveritt

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #4 on: June 20, 2018, 10:35:49 pm »
Try it with red light (430THz), you might recognise the result.
 

Offline NiHaoMike

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #5 on: June 20, 2018, 10:38:20 pm »
Isn't that how CRTs worked?
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Offline borjam

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #6 on: June 20, 2018, 10:59:54 pm »
Another adventure into the crazy world that is the EMF spectrum! (This topic always gets the girls excited try talking about this at bars when trying to get a date)  :=\
Sorry, but girls are living spectrum analyzers.

Exhibit one:

http://www.thedoghousediaries.com/1406

 
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Offline NiHaoMike

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #7 on: June 20, 2018, 11:44:10 pm »
Sorry, but girls are living spectrum analyzers.

Exhibit one:

http://www.thedoghousediaries.com/1406
There are some girls who see in 4 primaries instead of just 3 like normal people do, I don't think I know any but it's hard to tell when even they probably are not aware.
https://en.wikipedia.org/wiki/Tetrachromacy#Humans
Just imagine if they were involved in computer graphics - they'd insist on RYGB instead of RGB!
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Offline Nominal Animal

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #8 on: June 21, 2018, 01:22:11 am »
http://www.thedoghousediaries.com/1406
Related: actual XKCD survey results.

I think my favourite color is dunno. Or maybe baige or wtf; I'm not exactly sure.
 
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Online Circlotron

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #9 on: June 21, 2018, 10:08:09 am »
My understanding of X-rays when I read about it as a kid in the 60s was that you had to knock an electron from an inner shell, and then all the outer shell electrons moved in to fill the gap. The change in energy state when shifting orbital layers radiated X-rays. If that description is still accurate then there must be a lower limit of energy needed to dislodge that inner electron so you wouldn’t be able to produce lower and lower energy, longer and longer wavelength radiation. There must be a lower limit somewhere.
 

Offline T3sl4co1l

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #10 on: June 21, 2018, 01:37:28 pm »
There isn't a hard line between EUV (outer-orbital transitions of medium or heavy ions, that have been stripped of several electrons) and x-rays (inner orbital transitions of medium+ atoms).  In practical terms, XRF is difficult to do on light atoms (say, below aluminum).  Soft x-rays / EUV are also readily blocked by air, making them further inconvenient.

Further, there are many gamma rays with energy clearly in the x-ray (e.g., tritium decay ~5.7keV), and x-rays can be produced well into the gamma ray range (bremsstrahlung from semirelativistic+ electrons).  There's no need for a hard and fast distinction -- it's more a matter of how the waves are generated and used! :)

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Offline JohnnyMalaria

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #11 on: June 21, 2018, 01:46:11 pm »
Isn't that how CRTs worked?

Worked? Gosh, you must be a young'un. I'm watching my CRT TV as I type this :)
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Offline Nominal Animal

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #12 on: June 21, 2018, 02:05:04 pm »
There must be a lower limit somewhere.
That was just one way photons at different energies get emitted.

Another is simply knocking one of the (outermost) electrons into a higher energy state. When it returns to a lower energy state, a photon gets emitted with the wavelength corresponding to the energy difference. This covers phenomena like fluorescence and phosphorescence.

That also explains why quantum dots (QD) are so useful. Their size (which is relatively easy to control very precisely) defines their band gap (basically the step from filled electron states to the free electron states; corresponding to the wavelength most photons emitted would get, when the "outermost" electrons get kicked about). Energize them, and they emit light that very precisely depends on the size of the QDs. Shine light to them, and they absorb very specific wavelengths. Basically, you can precisely tune the color, and still use the exact same material. The only difference is how long you grow the nanocrystals in your vacuum deposition chamber. It isn't even expensive or hard to do, with current manufacturing technologies.


There are others, too. The surface phonon stuff is particularly interesting; there, the scattering effects have an energy range of about 0.001 eV to 1 eV.

On the other end, we get stuff like ultra-high-energy cosmic rays from space, with energies above 1 000 000 000 000 000 000 eV (1018 eV), and oddballs like Oh-My-God particles.
« Last Edit: June 21, 2018, 02:10:28 pm by Nominal Animal »
 
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Offline NiHaoMike

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #13 on: June 21, 2018, 02:21:22 pm »
Worked? Gosh, you must be a young'un. I'm watching my CRT TV as I type this :)
Is 30 years of age considered young? It has been about 7 years since I last used a CRT, which happened to be an old Tektronix scope used to visualize some data lines in a partly automated setup. There is a DSO in the setup but it was used by the testing software to measure stuff. The old boob tube was just to allow the operator to notice the DUT locking up before the timer in the software does.
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Offline IanMacdonald

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #14 on: June 22, 2018, 04:31:55 am »
Talking of particle energies, a surprising thing is that though hydrogen fusion requires enormous temperatures when thermal excitation is used (a few megakelvin for useful output) using electrical excitation it only requires quite modest  accelerating voltages. For example D-T fusion will take place with as little as 10keV. (Don't try it as it gives off very dangerous fast neutrons, one reason why this isn't a good choice)

The proton-boron reaction, arguably one of the best for power generation since it only creates alphas and no deep-penetrating radiation, can be made to work with an accelerating voltage of a few hundred kV (Or less of a multistage accelerator is used) but is virtually impossible to achieve by heating, requiring supernova-class temperatures.   

It's one of those paradoxes, that the smallest accelerator at CERN is actually more powerful than needed to do fusion. Yet, we can't seem to get a commercially viable fusion reactor going. This has a lot to do with the question of achieving breakeven, ie more energy out than in, and is determined by the capture cross-section, ie the number of times a collision will result in successful fusion.
 

Offline TimFox

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #15 on: June 22, 2018, 05:10:00 am »
This is only a question of nomenclature.
X rays are photons that are produced by electron processes: Bremsstrahlung (e.g., deceleration of electrons hitting the target in an X-ray tube) or electronic transitions in atoms.
Gamma rays are photons produced by nuclear reactions, such as radioactive decay.
The energy ranges of these photons have a substantial overlap.
The names refer to only the production process;  the photons themselves are identical to each other and to other named photons (radio, infrared, visible, ultraviolet, etc.) which are named for their wavelength.
 
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Offline Beamin

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #16 on: June 24, 2018, 07:32:07 am »
Sorry, but girls are living spectrum analyzers.

Exhibit one:

http://www.thedoghousediaries.com/1406


I can see colors in amazing detail I didn't notice this but I was able to match the paint codes on any car by eye at an old job. The paint guy didn't understand how I could figure out the paint code so fast so he tested me. His explanation was: "That's amazing". Trade off is I can't see in low light and have night blindness.


How did you (tim) figure out ev by using that google page? Or were sayin google was stupid?
There are some girls who see in 4 primaries instead of just 3 like normal people do, I don't think I know any but it's hard to tell when even they probably are not aware.
https://en.wikipedia.org/wiki/Tetrachromacy#Humans
Just imagine if they were involved in computer graphics - they'd insist on RYGB instead of RGB!
Designation: 7 of 9 of Unimatrix 0. Species: 475  Human; female. Origination: Grid 001. Your knowledge will be assimilated into the eevblog collective. We are Beamin. Foreplay is inefficient and unnecessary to precede copulation. Resistance is Futile. You will be assimilated.
 

Offline Beamin

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #17 on: June 24, 2018, 07:37:16 am »
My understanding of X-rays when I read about it as a kid in the 60s was that you had to knock an electron from an inner shell, and then all the outer shell electrons moved in to fill the gap. The change in energy state when shifting orbital layers radiated X-rays. If that description is still accurate then there must be a lower limit of energy needed to dislodge that inner electron so you wouldn’t be able to produce lower and lower energy, longer and longer wavelength radiation. There must be a lower limit somewhere.


I made a thread asking this same question: How are photons emitted at longer wave lengths then the shortest electron hop (some where in IR from a molecular bond I think) I was trying to figure out how photons are emitted from metal antennas and the area between far IR and mm waves. There should be a well defined cut off.
Designation: 7 of 9 of Unimatrix 0. Species: 475  Human; female. Origination: Grid 001. Your knowledge will be assimilated into the eevblog collective. We are Beamin. Foreplay is inefficient and unnecessary to precede copulation. Resistance is Futile. You will be assimilated.
 

Offline Nominal Animal

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Re: If Xrays are in the KeV range and gmma MeV whats light and radio?
« Reply #18 on: June 24, 2018, 06:32:38 pm »
I made a thread asking this same question: How are photons emitted at longer wave lengths then the shortest electron hop (some where in IR from a molecular bond I think) I was trying to figure out how photons are emitted from metal antennas and the area between far IR and mm waves. There should be a well defined cut off.

It is difficult to explain in everyday terms, because this area of physics starts to exhibit quantum phenomena that behave differently to everyday phenomena humans understand.  Simply put, it is in many ways nonintuitive.  Trying to explain it to someone without a suitable basis, is like trying to explain why bumblebees can actually fly to someone who has no idea about aerodynamics, and has no reason to believe what you say.

I won't be able to convince anyone about this either, but I'll try to explain it in terms that let you build a rough picture/understanding of the stuff involved, and if you are inclined to do so, research the details.



The first thing to understand is that metals in some ways behave as a single large molecule. That is, there are free electrons, or more properly, delocalized electrons in the lattice formed by the atoms. (Only the outermost electron or electrons of each atom are delocalized or "shared" this way.) In many ways, these electrons can be modelled as if they formed a gas, electron gas or Fermi gas.  Because of the regular lattice structure, there are a lot of states (corresponding to electron orbitals in molecules); so much so, that they're not even individually numbered, but described using a curve, density of states. The curve describes the number of states as a function of energy; and because the entire lattice of atoms is involved, it is (can be) continuous: the difference in energy between different states can be infinitesimally small.

When there is no external energy input, the electrons are at their base energy states, and they occupy all the lowest energy states. The states that are normally filled are called the valence band, and the states that are normally empty are called the conduction band. (The name "band" comes from them forming a band in the density of states graph. It is not a physical band like in geological strata or a nice strawberry cake.)

If the valence and conduction bands are right next to each other, you have a conductor.  If there is a large gap in between, with no electron states at all, you have an insulator. If the gap is small (less than 4 eV), you have a semiconductor.

When a semiconductor material is excited somehow (so it absorbs energy), some of the electrons jump from the valence band to the conduction band.  When they relax back, the electrons emit a photon with energy corresponding to the band gap size.  There is really no lower limit to the band gap; only when it is very small, the material properties blur between a conductor and semiconductor.

Conducting metals have no such band gap. The valence band and the conduction band are right next to each other in energy. So, there is no lower limit to the photon energy when an electron drops to a lower energy state in the Fermi gas, because the density of states can be continuous: that is, there is no lower limit between the energies of two different electron states.

This is a very simplified picture, mind you. The entire lattice itself can vibrate (acoustic waves, acoustic phonons), as can the electron "gas" (especially at the material surface). These all interact, for example in sonoluminescence (we just do not know exactly how).  Even the interactions in something as dull as a chunk of room-temperature iron are quite complex and very, very fascinating: not simple at all.  Water, on the other hand, is so complicated to model that it frustrates many a materials physicist/quantum chemist/quantum biologist every day.
 


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