# I Can resonance be used to split a molecule of CO2?

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1. May 9, 2017

### Sveral

Hello,
interested, if the posibility of splitting atoms by using resonance is possible, if so, wheather or not I can use it for something else, thanks in advance.

2. May 9, 2017

### Staff: Mentor

You mean to dissociate a molecule?

If so, what resonance are you thinking about?

3. May 9, 2017

### Sveral

Yes, exactly. Im thinking about the dissociation of the nucleus of, for example, CO2 into Carbon and oxygen. Hope it makes sense

4. May 9, 2017

### Staff: Mentor

You haven't said what resonance you are thinking about.

5. May 9, 2017

### Sveral

You mean, how I intend to create the resonance itself? Sound, very high frequency.

6. May 9, 2017

### Staff: Mentor

You can't use sound to break a molecule like CO2.

7. May 9, 2017

### Sveral

If the input frequency matches the frequency of self-oscillation of the bond between C and O, then, why not? Any ideas as to, where to find the frequencies of bonds between certain elements or how to calculate them?

8. May 9, 2017

9. May 9, 2017

### Staff: Mentor

Even if you could do that in theory, molecular vibrations are highly non-linear, so there isn't a single frequency you could excite at. And the link you gave talks about using laser light, which is not the same thing! Even then, simply vibrationally exciting a molecule at a single frequency won't work, but time-varying frequencies are needed.

At the molecular level, a sound wave simply corresponds to collisions between molecules. Regular chemistry applies.

10. May 9, 2017

### f95toli

There are several reasons. One is that frequencies involved in molecules are optical, i.e. a few THz at the very least. "Sound" in the usual sense of the word only goes up to a few MHz at most (for ultrasound). Note also that this neglects the (not so small) problem of how you would "convert" your (theoretical) sound into the energy needed to actually break the bond.
Also, just think of the wavelength of sound compared to the size of the molecule.

Note that both of the explanations above neglects a LOT of physics; I am merely trying to illustrate why it wouldn't work,

11. May 9, 2017

### Sveral

That is a point even one with my...knowledge can understand, well put.
Ok, but what about the link I posted? It should mean, that it is doable with light...

12. May 9, 2017

### Sveral

Much appreciated for the information. Thank you.

13. May 9, 2017

### Staff: Mentor

14. May 9, 2017

### Sveral

Ok, but any ideas as to how to calculate the resonant frequency of a bond of C-O? Also are there any DIY verions of wideband light generation chips or something?

15. May 9, 2017

### Staff: Mentor

The easiest is to look at the infra-red spectrum http://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Type=IR-SPEC&Index=1

I don't think that the equipment needed to do this is within reach of a layman.

16. May 9, 2017

### Sveral

17. May 9, 2017

### Sveral

Any ideas as to, how one can calculate the output frequency of a laser diode by knowing the type of semiconductors used?

18. May 9, 2017

### Ben Wilson

easier to measure it by observing the color of the laser light. Or more quantitatively, measuring the distance between fringes in an interference pattern

19. May 9, 2017

### Sveral

Solid answer, but seems like I need to specify the question. If I know everything about every component thatll be used for the building of the laser, how can I calculate the frequency using those numbers?

20. May 9, 2017

### Ben Wilson

Buy a laser where they tell you the frequency on the box. I think the calculations you want to do are very complex. But there may be simpler method that I've missed.

Last edited: May 9, 2017
21. May 10, 2017

### f95toli

You can't. The laser frequency will depend on the details of the device design and the choice of material is only one of several factors. Laser diodes are complex devices built up of many semiconductor layers with different composition; there are also many different ways to make a laser diode (a InGaAs based VCSEL is very different from the "classical" red Si based diode).
Hence, you need to either measure it or just read the datasheet.

22. May 10, 2017

### Sveral

A. K. A. It's far from simple or DIY...

23. May 10, 2017

### Nino MMP

You might enjoy looking up the HCl canon. It's a physical chemistry experiment with H2 and Cl2 in a container; it demonstres how a certain wavelength is needed to break a bond of diatomic chloride, forming HCl and a 'canon' effect.

E=h (nu) where nu is frequency and nu or sometimes f=v/lambda where v here would be the speed of light. Play with these and the energy of a CO2 bond (typically in kJ/mol - there's tables for it anywhere from google). That paired with the typical wavelength for sound help explain why that wouldn't really work. There are plenty of E/M wavelengths that will break the bond in question, though.

24. May 10, 2017

### Staff: Mentor

I would like to point out that in this case, the molecule dissociates due to electronic excitation, not vibrational excitation.

25. May 10, 2017

### Nino MMP

Oh okay, thank you for the correction DrClaude! Would atomic/optical books be best to read into this more? I am intrigued.