Temperature effects on IR spectrum of pyrene in 5–9 μm region and comparison with experimental data (blue curve in the top panel) (Cook et al. 1996). The red curve represents the calculated anharmonic emission spectrum after absorbing a 5 eV photon. The blue sticks are the fundamental and combination bands calculated at 0 K, i.e., without temperature effects considered in the calculations. The gray dashed lines show prominent bands observed on the experimental spectrum.