[netslavender]

Hi chemical forums,

I'm working on the well-known HCl-DCl IR vibrational/rotational spectroscopy, and am looking at the literature values for: "Q branch" (or where it should be), force constant k, rotational constant and equilbirium Be, correction term to rotational constant due to vibrations at equilibrium Alphae, and bond length at equilibrium.

I see the following: Q branch is higher by 6 cm^-1 for DCl, k is higher by 6N/m for DCl, Be is 5 cm^-1 for HCl, Alphae is 0.8 cm^-1 higher for DCl, and bond length is the same.

I'd like the explain the differences above, but I'm not sure which ones are significant (as opposed to random error), and if significant, why those changes arise, without detailed quantum mechanical explanations. Any pointers?