What Is the Notation \text{OH}(X^2\pi - A^2\Sigma^+) Used For in Chemistry?

[Saladsamurai]

Hi folks

I really was not sure where to put this, so I put it here since it gets the most traffic. My friend is doing some experimental research on the concentration of hydroxyl radicals in flames. In the literature, she keeps encountering the notation:

$$\text{OH}(X^2\pi - A^2\Sigma^+)$$

We have no idea what this means and are just trying to figure out what the notation is called so we have a place to start looking.

Any help is appreciated

 

[Saladsamurai]

Any thoughts on this?

 

[Clever-Name]

Out of context it can mean anything. Can you link us to a relevant paper where this term comes up? Maybe from the context someone could deduce its meaning