Lysine IR emission spectrum excited by moderately intense visible radiation

The excitation of IR emission is observed for thin films illuminated by continuous visible light in the absence of light absorption in the sample. The effect is demonstrated by the example of the lysine molecule and explained by the resonant combined action of optical photons with frequencies $\omega_i$ and $\omega_j$, whose differences $\omega_i-\omega_j=\Omega$ coincide with the frequencies of the lysine vibrational modes.