Detection of the FO radical by CO2 laser magnetic resonance

Abstract

The fundamental vibrational band of the elusive free radical FO has been detected using the technique of CO2 laser magnetic resonance in the 1025–1043 cm−1 region. The FO was produced by a discharge in CF4 gas flowing in a fused quartz (SiO) tube, and the resulting spectra were strong enough to allow the resolution of saturated absorption dips and 19F nuclear hyperfine structure. Seven different CO2 laser lines were used to observe six vibration–rotation transitions, all belonging to the Ω = 3/2 component of the 2Π ground electronic state. The analysis of these observations yielded the first experimental determinations for FO of the rotational constant B, centrifugal distortion constant D, fine structure constant A, and axial hyperfine constant h, as well as the vibrational dependences of B and h. The bond length of FO was found to be re = 1.35789 ± 0.00025 Å, which is 1.5 to 2.7% larger than previous values given by ab initio calculations.