Benzene ν4 integrated band intensity versus temperature

The integrated band intensity of the ν4 band (around 15 μm) of benzene, AB, was determined experimentally at different temperatures ranging from 328 to 220 K. Contrary to theoretical predictions, AB appears to vary only slightly with T: it decreases by about 20% when T decreases from 328 to 220 K. In this range of temperatures AB follows the empirical law AB = (TT0)αf[1 − exp(−hcν̃kT)], with α = 12, f = 370.1 ± 8.6 cm−2 atm−1, and ν̃ = 674 cm−1.