The v7 parallel band of Fe(CO)5 has been measured in the 620 cm-1 region using high-resolution diode laser absorption spectroscopy in a free jet expansion. A comparison with simulated band profiles indicated a rotational temperature of between 2 and 3 K in the jet. At these temperatures the K-structure of the Q-branch is partly resolved. The following molecular parameters were obtained: v0 = 619.95747(12) cm-1, B7 = 0.026743(2) cm-1, A7 = 0.030721(1) cm-1. Approximate values of the quartic centrifugal distortion constants were also obtained from fitting the spectra. (C) 2000 Elsevier Science B.V.