The observation of hot bands in the 288Â nm system of the FeCl2 radical

The 288 nm band system of FeCl2 has been recorded with a sample produced in a warmed, free-jet expansion at moderately high resolution (with a linewidth of 0.28 cm−1). Under these conditions, several hot bands are observed involving excitation of the symmetric and anti-symmetric stretching vibrations. The wavenumbers determined as a result for FeCl2 in its ground 5Δg,4 state are ν1″=352.34(12)cm-1 and ν3″=504.8(2)cm-1. No hot, sequence bands in the bending vibration ν2″ were observed. The most likely explanation is that the wavenumber for ν2 is essentially the same in both the electronic states involved (88 cm−1). Additional strong hot bands are observed that are unrelated to the previously assigned electronic transitions; they appear to emanate from a low-lying electronic state of FeCl2.