In my bachelor thesis, I compare simulated IR-spectra computed by different basis sets. The simulated spectra from sets like cc-pVTZ and cc-pVQZ are too similar to compare them by plotting them next to each other. That's why my supervisor asks me to create a differential spectrum from these spectra. I try to subtract one from the other, but the x-axes don't align, because I scaled them with different scaling factors. When I subtract them without scaling I get a similar result. In both cases, the miss alignment of the peaks results in a jump from positive to negative values and vice versa in the differential spectra.
I wonder if there is a way to create a differential spectrum from two simulated spectra computed with different basis sets.
To give you a better understanding of my problem I upload my spectra. All spectra are not scaled with scaling factors.
This spectrum (red) was computed with B3LYP/6-31G**.
This spectrum (blue) was computed with B3LYP/6-311++G**.
That was my try to subtract the blue spectrum from the red spectrum.
Here I divided the blue spectrum by the red spectrum like Cavenfish said.
I want to show how much higher or lower the intensity is in the red spectrum compared to the blue spectrum. In my understanding I should have intense peaks when the difference is high and peaks with low intensity when the difference between the peak intensities is small.