High-resolution laser spectroscopy of the v₆ fundamental band of jet-cooled C₂F₆

The v₆ parallel band of C₂F₆ has been measured at high resolution by using diode laser absorption spectroscopy in a free jet expansion. A comparison of the rotational intensity distribution with simulated band profiles indicated a rotational temperature of between 2 and 3 K in the jet. In addition to the fundamental band, weak Q-branches of other bands were also found, both to the red and to the blue side of the v₆ fundamental Q-branch. The band origin of the v₆ mode was measured as 713.671 05(10) cm^-1. The B rotational constants were determined in different ways as described in the text. A preferred value of B₀ = 0.061 580 6(22) cm^-1 was selected for simulation purposes. This value is independent of the electron diffraction structure.