[P CHem] HCL/DCL r and p branch J value assignment

[Chickenpoxpie]

Homework Statement

Assign J values for P and R branches of H35cl, H37cl, d35cl, and d37cl compounds.

Homework Equations

The Attempt at a Solution

I have a fundamental IR spectra I did on and HCL/DCL compound. I'm extremely confused how to assign J values. I've been looking online and see R can be 0, 1, 2, 3, etc but P starts at 1,2,3, etc. How did they assign these values?

What I do know
I peaked picks so I know the wave numbers.
I can tell the P branch form the R because as the wave numbers get smaller they get more spread out.
I know the less intense peaks of the doublets are the H37CL or D37CL b/c it is a less common isotope and intensities are based on number of species.

 

[HOMO]

I'm stuck here too! How do you go from wave numbers to j values. What's the difference between j and j'?