I'm currently studying IR but my mind is having trouble tying everything together. While I see that vibrational frequency is determined really by just reduced mass, I can see from the equation that vib equation is the same throughout energy levels and so does energy (bc that basically depends on reduced mass and frequency). However, I've seen IR and there's all sorts of crazy spikes and loops and I'm confused on how that ties it together? Like something can have the same frequency but the spikes will be all different? I've tried reading about IR from different sources and something just isn't clicking. I'd seriously appreciate it if someone can clear this up for me!