In IR spectroscopy, bonds vibrate and therefore there are moving charges and usually a changing dipole. If accelerating charges cause EM waves to be given off due to the changing electric field then shouldn't the vibrating bond be constantly emitting photons and therefore losing energy in a similar way to an electron moving around the nucleus? Doesn't this then make molecular vibrations impossible (well not impossible but inconsistent with them emitting single photons as they fall from a higher level to a lower level). I've also read that the infrared absorbed by molecules does not correspond to the frequency of the bond vibrations themselves but rather the difference in vibrational energy levels. If this is the case then what is the significance of the frequency of the molecular vibration when modeled as a spring?