# Momentum of intertia for a dihydrogen molecule

fab13
Homework Statement:
The rotational energy level of a symmetric molecule like H2 are given by :

##En = n(n + 1)h^{2}/(2J)##

where ##J## is the momentum of inertia of the molecule. Compute the energy of the ﬁrst rotational level in eV.

the following information is given : distance between the proton in H2: ##74.14 pm##
Relevant Equations:
I have used the following equation for momentum of inertia : ##J=MR^{2}## with ##M## the total mass and ##R## the radius of rotation.
I don't know if the value for distance between protons given in the homework is right (##d = 74.14 pm##).

Indeed, on the following link : https://brainly.in/question/7147660 , they take a distance equal to ##d = 4\times10^{-10} m##.

In all cases, the same formula is applied : ##J=2\,m_{p}\,(\dfrac{d}{2})^{2} = m_{p}\,d^{2}/2##

Which value for distance between the 2 protons have I to take ? ##74.14## pm or ##4\times10^{-10} m## ?