Knowledge Bank

The fluorescence spectra of naphthalene-h $s$ and napthalene-d $s$ vapour in the 3100 {\AA} region have been photographed with a high speed spectrograph having a resolution of about $0.5cm-1$. Resonance fluorescence and fluorescence with added helium have been observed. Analysis of the vibronic bands has been attempted using the criterion previously $described1$ of a single maximum in the rotational contour of a band indicating long axis polarisation of the transition moment ($B20$, vibronic symmetry) and a double maximum indicating short axis polarisation ($B1u$ vibronic symmetry). The existence of two ground-state vibrations of frequencies $506cm-1$ ($b3g$) and $516cm-1$ ($ag$) in naphthalene-$hs$ and $490cm-1(b3g$) and $493cm-1$ ($ag$) in naphthalene-$dg$ will be discussed in relation to the fluorescence spectra.