# Quantum Chemistry [closed]

How to find the degeneracy of a given state in quantum mechanics? What is the formula?

• Welcome to Chem.SE. It is a policy of the site that when posting a homework problem you should demonstrate your attempt to find a solution. – Buck Thorn Jan 26 '19 at 11:21
• Sorry but I got my exams knocking on the door... It's a national level entrance exam for MSc, so I don't really have that much time to show the solution as well... really sorry... And it's not like I post a question without trying first. – user67074 Jan 27 '19 at 15:37

The energy is normally written as $$\displaystyle E=\ell(\ell+1)\frac{\hbar^2}{2I}$$ where $$\ell$$ is angular momentum and $$I$$ the moment of inertia. The multiplicity is $$2\ell+1$$ and in the absence of any perturbation this is the degeneracy. You can see that 9 is the correct answer if $$\ell=4$$