n –π* Electronic Emission and Absorption Spectra of o -Fluorobenzaldehyde in Vapor Phase

The electronic emission and absorption spectra of o-fluorobenzaldehyde have been studied. The emission spectrum recorded on a Fuess glass and a medium quartz spectrograph lies in the region 26 668–17 862 cm⁻¹ and the absorption spectrum recorded on a Zeiss Q–24 medium quartz spectrograph lies in the region 30 995–24 610 cm⁻¹. The O—O band has been observed at 26 337 cm⁻¹. The C=O stretching frequency 1733 cm⁻¹ in the ground state and 1355 cm⁻¹ in the excited state is most intense and forms progressions of bands both in the emission and absorption spectra. The observed bands have been interpreted as combinations of the C=O stretching frequency and its multiples with other fundamentals. The transition involved is A‘–A’ (n–π*).