Temperature effects on IR spectrum of pyrene and comparison with the experimental spectrum (black dots), which was measured using SPIRES (Wagner et al. 2000). The red curves represent the calculated anharmonic emission spectrum after absorbing a 5 eV photon. In order to compare the band profiles with the experimental data, the calculated spectrum in the top panel is convolved with Gaussian functions. The blue lines represent the fundamental and combination bands calculated at 0 K, i.e., without temperature effects considered in the calculations.