Gas-phase luminescence of aromatic carbonyl compounds in excited nitrogen at atmospheric pressure

Certain types of aroyl compounds such as benzaldehyde, acetophenone, benzop henone, and anthraquinone produce intense gas-phase luminescence in excited nitrogen at atmospheric pressure. This luminescence was measured in pressu re ranges of 1.00-1.67 atm and temperature ranges of 343-473 K. A novel, ra dioactively (Ni-63) stimulated, high-voltage (less than or equal to 1750 V/ mm), low-current (less than or equal to 35 nA) discharge in high-purity nit rogen was used for gas chromatographic detection and spectral excitation. T he gas-phase luminescence spectra of about sixty aroyl compounds - introduc ed as gas chromatographic peaks - could thus be measured and compared with literature spectra obtained by conventional excitation in condensed phases. Only a few gas-phase spectra are available from the Literature, and these did agree well with the spectra of this study. A speculative luminescence m echanism is proposed, in which ground-state N-2 becomes excited by collisio n with fast electrons. This is followed by efficient triplet-triplet energy transfer from N-2(A (3)Sigma(u)(+)) to the n-->pi* excited aroyl compound.