# Why is the intensity of the IR spectra of IBr higher than that of ICl?

Why is the intensity of the IR spectra of $$\ce{IBr}$$ higher than that of $$\ce{ICl}$$?

I know that the IR spectra intensities are proportional to the derivative of the dipole moment with internuclear distance. However, how would one be able to deduce (without looking at the IR spectra) that the IR spectra for $$\ce{IBr}$$ is higher than $$\ce{ICl}$$ in the gas phase?

I would have thought it would be the other way around since $$\ce{Cl}$$ has the higher electronegativity.