Laser magnetic resonance spectroscopy of the ν2 fundamental band of HCO at 9.25 μm

The ν2 bending fundamental (ν0=1080.76 cm−1) of the formyl radical, HCO, has been studied using CO2 laser magnetic resonance. Fluorine atoms from a discharge in CF4 were reacted with H2CO to form the short‐lived HCO, which then flowed through an absorption cell located between the pole faces of an electromagnet and within the optical cavity of a CO2 laser. By means of the Zeeman effect, HCO, vibration‐rotation transitions were tuned through resonance with the laser lines. Numerous resonances involving levels with 1⩽N⩽7 and 1⩽Ka⩽3 were assigned, and from analysis of the spectra accurate determinations of the band origin, rotational, centrifugal distortion, spin‐rotation, and Fermi interaction parameters for ν2 were made. Fairly large changes in the values of A, ΔK, eaa, and ηaaaa between the ground and v2=1 vibrational states were observed.