# Is it possible to simulate Diffuse Interstellar Bands?

I recently saw this YouTube video about Diffuse Interstellar Bands (DIB) which describes the confirmation of a buckminsterfullerene as the source of one DIB.

Is it possible to simulate how a proposed molecule would interact with interstellar radiation in deep space conditions and emit light with such DIBs? If so, is it computationally intensive?

Could similar molecules result in similar DIBs? If so, this could be used to guide a search for a given DIB?

This answer provides several simulations applications. Is there a software that is capable of do this kind of simulation?

I also found Edwards & Leach (A&A, 1993) where the authors tried to simulate this, I couldn't understand the whole paper, but they seemed to advance a lot the understanding of C60 DIB emissions. They also seemed to require lots of data, can those data also be theoretically calculated or maybe approximated?

Is it possible to simulate how a proposed molecule would interact with interstellar radiation in deep space conditions and emit light with such DIBs? If so, is it computationally intensive?

So long as the molecule isn't too large, then yes, computational quantum chemistry approaches are generally able to say a fair deal about the interaction of your molecule with radiation. Typical fullerenes like $$\rm C_{60}$$ are on the largeish size for such methods, but they're still manageable.

The important thing to realize, though, is this:

• You don't need to simulate this. You can just go into the lab and measure it.

Molecules on Earth interact with radiation in exactly the same ways that they do in interstellar space. If you want to know the IR spectrum, just pop your molecule into a gas cell, (potentially spend a fair amount of money and effort making sure that the conditions are exactly the same as the interstellar medium you're interested in,) shine some light through it, and measure its interaction.

Computational physics often does pretty well on these things, but it's not yet infallible and experiment is the irreplaceable gold standard for quantities like this.

Could similar molecules result in similar DIBs?

Quite possibly. There's nothing for it but checking a whole lot of molecules and trying to rule them out. As more and more molecules are observed to be incompatible with your target spectrum, you gain increasing confidence in your prospective identification.

Is there a software that is capable of do this kind of simulation?

You may be interested in the Wikipedia page List of quantum chemistry and solid-state physics software.

• No doubt, lab measurements will always be ultimate answer. But if simulation is possible, it is probably much cheaper then creating such conditions in a lab, so it might be a good way to guide such discoveries – RSFalcon7 Oct 4 '18 at 17:58
• It is conceivable that future improvements to quantum chemistry methods will take simulations to a level where they're cheap and reliable enough to take a leading role for that class of applications (with experimental confirmation as an unskippable final stage). We're not there yet, though, and we probably won't be for the foreseeable future. – Emilio Pisanty Oct 4 '18 at 18:17