Influence of rotational degrees of freedom on gas phase stability of ions in CID

In mass spectrometry it is possible to determine the stability of an ion in the gas phase using e.g. collision induced dissociation (CID). In CID, we fragment an ion by colliding it with a neutral buffer gas. By gradually increasing the collision energy, it is thereby possible to get a relative measurement of the stability of the ion in the gas phase (so called survival yield analysis).


Now, I have the following question:


The picture below illustrates an effect that is commonly observed in CID namely that bigger ions tend to be more stable as they have more rotational degrees of freedom available to handle the collision energy transferred using CID. This can lead to counterintuitive effects, as for example in this case, one would expect acetic acid to be more acidic (and thus a more stable anion), than propanoic and decanoic acid, but it is the least stable.


[![enter image description here](https://i.stack.imgur.com/SaxXX.png)](https://i.stack.imgur.com/SaxXX.png)


In my work, I wanted to show that increasing chain lengths of the ligand increase the stability of a complex by weak interactions but I don't know how to factor in the effect that the increasing chain length has on the stabilization by the increased rotational freedom. Obviously I want to rule out that the increase in stability is due to the longer chains absorbing the collision energy better. How large could that effect be? Is there any systematic approach to take this effect into account? Is there any literature on the subject?


