B What happens when ethane absorbs UV light?

[Lotto]

TL;DR Summary

I have a molecule of ethane and when I use UV light, the molecule absorb it, so ethane's electron excitates from HOMO to LUMO. But what happens to the molecule? Does the sigma bond C-C still exist?

Because when I have two carbon atoms, they create a single bond, so their two electrons are in one boding orbital, but I have also one anti-bonding orbital here. And when the electron excitates from $\sigma$ to $\sigma^*$, how can the bond between the carbon atoms exist? It has to disappear. But what happens next? Does the UV light affect also bonds C-H?

 

[Hyperfine]

Have you conducted a search of the literature? For example on the photodissociation of ethane.

 

[Lotto]

Have you conducted a search of the literature? For example on the photodissociation of ethane.

I found out that ethene can disintegrate into different particles, so my ideal should be right. And it is caused by the excitation of an electron of the molecule, so it can happen that electron in bonding orbital of C-H excitates into an anti-bonding orbital as well as an electron in C-C bonding orbital excitates.

But in general, when we use UV light, the molecule disintegrates and radicals can arise for instance.

 

[Hyperfine]

But in general, when we use UV light, the molecule disintegrates and radicals can arise for instance.

Indeed, radicals can arise! That fact has been well documented for many decades.

However, you must realize that the topic is very broad and certainly not lacking in complexity. The structure of the initial molecule is very important as is the phase (gas, liquid, solid) in which the process takes place. And then there is the question of the nature of the excited states that are populated. All due care should be taken in considering generalizations.

As but one illustrative example, Ahmed Zewail and his group at Cal Tech pursued detailed investigations of the photodissociation of I₂ in rare gas clusters utilizing femtosecond spectroscopic techniques. Who would have guessed that the dynamics would be dependent on the polarizabilty of the rare gas?

You have mentioned both ethane and ethene. Very different molecules with very different energy states. Which one of the two is particular interest to you?

 

[Lotto]

Indeed, radicals can arise! That fact has been well documented for many decades.

However, you must realize that the topic is very broad and certainly not lacking in complexity. The structure of the initial molecule is very important as is the phase (gas, liquid, solid) in which the process takes place. And then there is the question of the nature of the excited states that are populated. All due care should be taken in considering generalizations.

As but one illustrative example, Ahmed Zewail and his group at Cal Tech pursued detailed investigations of the photodissociation of I₂ in rare gas clusters utilizing femtosecond spectroscopic techniques. Who would have guessed that the dynamics would be dependent on the polarizabilty of the rare gas?

You have mentioned both ethane and ethene. Very different molecules with very different energy states. Which one of the two is particular interest to you?

That ethene was a mistake, I meant ethane.