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Can Rf/microwaves Produce Negative Ion

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#1 chewylord389

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Posted 06 April 2017 - 06:24 PM

Hello everyone,

 

Firstly, I'm new to this forum and therefore please forigve me if I don't suond as scientific as I should, In any case, I had a question to ask. Many people claim that negative ions are very good for your health as they are supposed to increase seratonin, make you happier and what not. In fact, it's even become a therapy in some parts of the world. In any case here is my question: would it be possible for RF/microwaves to produce negative ions under certain frequencies?  Or do all electromagnetic waves only emit positive radiation?

 

Steven



#2 OceanBreeze

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Posted 08 April 2017 - 02:36 AM

Good question, Steven!

 

If, by rf/microwaves you mean electromagnetic waves at radio frequency (around 3 kHz to 300 GHz) then the answer is no; such waves are not energetic enough to cause ionization; that is, to cause the removal/addition of an electron from/to an electron shell of a neutral charge atom.

This is a consequence of quantization as evidenced by the photo-electric effect. Increasing the amplitude of the radio wave will not cause ionization, as it does not change the energy of the individual photons. Only by changing the frequency can the necessary energy be reached. That is, only very high frequency electromagnetic waves, such as X-rays and gamma rays can cause ionization. Such high frequency em radiation is not called radio waves.

As for creating negative ions, I don’t believe X and gamma rays can do that. These high-frequency em waves transfer energy to the atoms they interact with, thereby releasing electrons from the atoms, leaving behind positive ions.

As for biological effects, x and gamma rays are generally destructive to living cells as they can break apart DNA resulting in mutations, cancer and even cell death.

 

 

Edit: still trying to fix font size and some typos.


Edited by OceanBreeze, 08 April 2017 - 05:17 AM.


#3 exchemist

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Posted 08 April 2017 - 05:04 AM

I am interested in this topic, as I do not know what anions are allegedly produced in the commercial ion generators that one can buy. The Wiki article speaks of N₂⁻ and O₂⁻, (latter is the superoxide anion) but as these will be odd-electron species they would be pretty reactive and unpleasant to experience at high concentration, I should have thought.

 

I agree with OceanBreeze that while very energetic electromagnetic radiation  (UV or higher) can excite an electron sufficiently to drive it off the atom, leaving behind a +ve charged ion (a cation), the only way to produce a negatively charged ion (an anion) is by adding an electron to a neutral atom or molecule, and this electron has to come from somewhere, which radiation will not by itself provide. That "somewhere" could I suppose in principle be from a cation generated by EM ionisation, but my understanding is that commercial generators rely on electrostatically charged plates to add and remove electrons. 


Edited by exchemist, 08 April 2017 - 05:04 AM.


#4 OceanBreeze

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Posted 08 April 2017 - 05:23 AM

I am interested in this topic, as I do not know what anions are allegedly produced in the commercial ion generators that one can buy. The Wiki article speaks of N₂⁻ and O₂⁻, (latter is the superoxide anion) but as these will be odd-electron species they would be pretty reactive and unpleasant to experience at high concentration, I should have thought.

 

I agree with OceanBreeze that while very energetic electromagnetic radiation  (UV or higher) can excite an electron sufficiently to drive it off the atom, leaving behind a +ve charged ion (a cation), the only way to produce a negatively charged ion (an anion) is by adding an electron to a neutral atom or molecule, and this electron has to come from somewhere, which radiation will not by itself provide. That "somewhere" could I suppose in principle be from a cation generated by EM ionisation, but my understanding is that commercial generators rely on electrostatically charged plates to add and remove electrons. 

 

 

I don't think UV can cause ionization, only excitation.

 

from this source:

 

Excitation occurs when the radiation excites the motion of the atoms or molecules, or excites an electron from an occupied orbital into an empty, higher-energy orbital.

 

Ionization occurs when the radiation carries enough energy to remove an electron from an atom or molecule.

 

There is a chart there that indicates the dividing line is above UV, "radiation that forms ions is often assumed to be equal to the ionization of water: 1216 kJ/mol"



#5 OceanBreeze

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Posted 08 April 2017 - 05:30 AM

I was wrong. In re-reading my own source:

 

"The dividing line between ionizing and non-ionizing radiation in the electromagnetic spectrum falls in the ultraviolet portion of the spectrum. It is therefore useful to divide the UV spectrum into two categories: UVA and UVB. Radiation at the high-energy end of the UV spectrum can be as dangerous as x-rays or gammasma.gif-rays."



#6 exchemist

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Posted 08 April 2017 - 07:42 AM

I was wrong. In re-reading my own source:

 

"The dividing line between ionizing and non-ionizing radiation in the electromagnetic spectrum falls in the ultraviolet portion of the spectrum. It is therefore useful to divide the UV spectrum into two categories: UVA and UVB. Radiation at the high-energy end of the UV spectrum can be as dangerous as x-rays or gammasma.gif-rays."

Yes it's interesting. The Wiki article here: https://en.wikipedia...iki/Ultraviolet indeed claims that UV is "non-ionising", but then it gives, lower down, a table of photon energy ranges, in eV, for near, middle and far UV. 

 

The 1st ionisation energy of sodium, which admittedly is an alkali metal and thus is one of the most easily ionised elements, is about 5eV. This is well within the middle UV range. There is a table of these ionisation energies here: https://en.wikipedia...nization_energy

 

This shows that while most are of course higher than for the alkali metals, in many cases they are still arguably within the upper end of the UV ranges as defined in the Wiki energy table.

 

I have the impression that perhaps the standard use of the term "ionising radiation" has in mind the effect on body tissues, i.e. the risk of damage from exposure, and that what people often really mean- without perhaps realising it -  is radiation that can ionise the main elements found biochemistry: C, N, O, H.  All of these, you will notice, are above 10eV - double that of sodium. 

 

(Note for other readers: accounting for the periodicity of the 1st ionisation energy is one of the classic successes of atomic quantum theory and is something every 6th form chemist learns!) 


Edited by exchemist, 08 April 2017 - 10:24 AM.




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