Amide I Isosbestic Point Super-radiance

An isosbestic point for an absorbance spectrum depending on temperature and frequency (or wavelength) is a frequency at which the absorbance is independent of temperature. In the work of Austin et al. the experimental plots of myoglobin amide absorbance vs. temperature show isosbestic points which are also inflection points in the graph. We show that pumping with intense coherent mid-IR light pulses, whose line width can be varied, that at the isosbestic point with narrow-band excitation that the amide I shows super-radiant fluoresence in the IR. We discuss how this surprising result can be understood quantum mechanically by a coupled ensemble of oscillators with no temperature dependence to their state levels.